draft-ietf-quic-transport-16.txt   draft-ietf-quic-transport-latest.txt 
QUIC Working Group J. Iyengar, Ed. QUIC Working Group J. Iyengar, Ed.
Internet-Draft Fastly Internet-Draft Fastly
Intended status: Standards Track M. Thomson, Ed. Intended status: Standards Track M. Thomson, Ed.
Expires: June 20, 2019 Mozilla Expires: June 21, 2019 Mozilla
December 17, 2018 December 18, 2018
QUIC: A UDP-Based Multiplexed and Secure Transport QUIC: A UDP-Based Multiplexed and Secure Transport
draft-ietf-quic-transport-16 draft-ietf-quic-transport-latest
Abstract Abstract
This document defines the core of the QUIC transport protocol. This This document defines the core of the QUIC transport protocol.
document describes connection establishment, packet format, Accompanying documents describe QUIC's loss detection and congestion
multiplexing, and reliability. Accompanying documents describe the control [QUIC-RECOVERY] and the use of TLS for key negotiation
cryptographic handshake and loss detection. [QUIC-TLS].
Note to Readers Note to Readers
Discussion of this draft takes place on the QUIC working group Discussion of this draft takes place on the QUIC working group
mailing list (quic@ietf.org), which is archived at mailing list (quic@ietf.org), which is archived at
<https://mailarchive.ietf.org/arch/search/?email_list=quic>. <https://mailarchive.ietf.org/arch/search/?email_list=quic>.
Working Group information can be found at <https://github.com/ Working Group information can be found at <https://github.com/
quicwg>; source code and issues list for this draft can be found at quicwg>; source code and issues list for this draft can be found at
<https://github.com/quicwg/base-drafts/labels/-transport>. <https://github.com/quicwg/base-drafts/labels/-transport>.
skipping to change at page 1, line 44 skipping to change at page 1, line 44
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Document Structure . . . . . . . . . . . . . . . . . . . 6 1.1. Document Structure . . . . . . . . . . . . . . . . . . . 6
1.2. Conventions and Definitions . . . . . . . . . . . . . . . 7 1.2. Terms and Definitions . . . . . . . . . . . . . . . . . . 7
1.3. Notational Conventions . . . . . . . . . . . . . . . . . 8 1.3. Notational Conventions . . . . . . . . . . . . . . . . . 8
2. Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2. Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1. Stream Identifiers . . . . . . . . . . . . . . . . . . . 9 2.1. Stream Types and Identifiers . . . . . . . . . . . . . . 9
2.2. Stream Concurrency . . . . . . . . . . . . . . . . . . . 10 2.2. Sending and Receiving Data . . . . . . . . . . . . . . . 10
2.3. Sending and Receiving Data . . . . . . . . . . . . . . . 11 2.3. Stream Prioritization . . . . . . . . . . . . . . . . . . 10
2.4. Stream Prioritization . . . . . . . . . . . . . . . . . . 11 3. Stream States . . . . . . . . . . . . . . . . . . . . . . . . 11
3. Stream States: Life of a Stream . . . . . . . . . . . . . . . 12 3.1. Send Stream States . . . . . . . . . . . . . . . . . . . 11
3.1. Send Stream States . . . . . . . . . . . . . . . . . . . 13 3.2. Receive Stream States . . . . . . . . . . . . . . . . . . 13
3.2. Receive Stream States . . . . . . . . . . . . . . . . . . 15 3.3. Permitted Frame Types . . . . . . . . . . . . . . . . . . 16
3.3. Permitted Frame Types . . . . . . . . . . . . . . . . . . 18 3.4. Bidirectional Stream States . . . . . . . . . . . . . . . 16
3.4. Bidirectional Stream States . . . . . . . . . . . . . . . 18 3.5. Solicited State Transitions . . . . . . . . . . . . . . . 17
3.5. Solicited State Transitions . . . . . . . . . . . . . . . 19 4. Flow Control . . . . . . . . . . . . . . . . . . . . . . . . 18
4. Flow Control . . . . . . . . . . . . . . . . . . . . . . . . 20 4.1. Data Flow Control . . . . . . . . . . . . . . . . . . . . 19
4.1. Handling of Stream Cancellation . . . . . . . . . . . . . 21 4.2. Flow Credit Increments . . . . . . . . . . . . . . . . . 20
4.2. Data Limit Increments . . . . . . . . . . . . . . . . . . 22 4.3. Handling Stream Cancellation . . . . . . . . . . . . . . 21
4.3. Stream Final Offset . . . . . . . . . . . . . . . . . . . 23 4.4. Stream Final Offset . . . . . . . . . . . . . . . . . . . 21
4.4. Flow Control for Cryptographic Handshake . . . . . . . . 24 4.5. Controlling Concurrency . . . . . . . . . . . . . . . . . 22
4.5. Stream Limit Increment . . . . . . . . . . . . . . . . . 24 5. Connections . . . . . . . . . . . . . . . . . . . . . . . . . 23
5. Connections . . . . . . . . . . . . . . . . . . . . . . . . . 24 5.1. Connection ID . . . . . . . . . . . . . . . . . . . . . . 23
5.1. Connection ID . . . . . . . . . . . . . . . . . . . . . . 24 5.1.1. Issuing Connection IDs . . . . . . . . . . . . . . . 24
5.1.1. Issuing Connection IDs . . . . . . . . . . . . . . . 25 5.1.2. Consuming and Retiring Connection IDs . . . . . . . . 25
5.1.2. Consuming and Retiring Connection IDs . . . . . . . . 26 5.2. Matching Packets to Connections . . . . . . . . . . . . . 25
5.2. Matching Packets to Connections . . . . . . . . . . . . . 27 5.2.1. Client Packet Handling . . . . . . . . . . . . . . . 26
5.2.1. Client Packet Handling . . . . . . . . . . . . . . . 27 5.2.2. Server Packet Handling . . . . . . . . . . . . . . . 26
5.2.2. Server Packet Handling . . . . . . . . . . . . . . . 27 5.3. Life of a QUIC Connection . . . . . . . . . . . . . . . . 27
5.3. Life of a QUIC Connection . . . . . . . . . . . . . . . . 28 6. Version Negotiation . . . . . . . . . . . . . . . . . . . . . 27
6. Version Negotiation . . . . . . . . . . . . . . . . . . . . . 28 6.1. Sending Version Negotiation Packets . . . . . . . . . . . 28
6.1. Sending Version Negotiation Packets . . . . . . . . . . . 29 6.2. Handling Version Negotiation Packets . . . . . . . . . . 28
6.2. Handling Version Negotiation Packets . . . . . . . . . . 29 6.3. Using Reserved Versions . . . . . . . . . . . . . . . . . 29
6.3. Using Reserved Versions . . . . . . . . . . . . . . . . . 30 7. Cryptographic and Transport Handshake . . . . . . . . . . . . 29
7. Cryptographic and Transport Handshake . . . . . . . . . . . . 31 7.1. Example Handshake Flows . . . . . . . . . . . . . . . . . 30
7.1. Example Handshake Flows . . . . . . . . . . . . . . . . . 32 7.2. Negotiating Connection IDs . . . . . . . . . . . . . . . 32
7.2. Negotiating Connection IDs . . . . . . . . . . . . . . . 33 7.3. Transport Parameters . . . . . . . . . . . . . . . . . . 33
7.3. Transport Parameters . . . . . . . . . . . . . . . . . . 34 7.3.1. Values of Transport Parameters for 0-RTT . . . . . . 34
7.3.1. Values of Transport Parameters for 0-RTT . . . . . . 35 7.3.2. New Transport Parameters . . . . . . . . . . . . . . 35
7.3.2. New Transport Parameters . . . . . . . . . . . . . . 36 7.3.3. Version Negotiation Validation . . . . . . . . . . . 35
7.3.3. Version Negotiation Validation . . . . . . . . . . . 36
8. Address Validation . . . . . . . . . . . . . . . . . . . . . 37 8. Address Validation . . . . . . . . . . . . . . . . . . . . . 37
8.1. Address Validation During Connection Establishment . . . 38 8.1. Address Validation During Connection Establishment . . . 37
8.1.1. Address Validation using Retry Packets . . . . . . . 38 8.1.1. Address Validation using Retry Packets . . . . . . . 38
8.1.2. Address Validation for Future Connections . . . . . . 39 8.1.2. Address Validation for Future Connections . . . . . . 38
8.1.3. Address Validation Token Integrity . . . . . . . . . 41 8.1.3. Address Validation Token Integrity . . . . . . . . . 40
8.2. Path Validation . . . . . . . . . . . . . . . . . . . . . 41 8.2. Path Validation . . . . . . . . . . . . . . . . . . . . . 41
8.3. Initiating Path Validation . . . . . . . . . . . . . . . 42 8.3. Initiating Path Validation . . . . . . . . . . . . . . . 41
8.4. Path Validation Responses . . . . . . . . . . . . . . . . 42 8.4. Path Validation Responses . . . . . . . . . . . . . . . . 42
8.5. Successful Path Validation . . . . . . . . . . . . . . . 42 8.5. Successful Path Validation . . . . . . . . . . . . . . . 42
8.6. Failed Path Validation . . . . . . . . . . . . . . . . . 43 8.6. Failed Path Validation . . . . . . . . . . . . . . . . . 43
9. Connection Migration . . . . . . . . . . . . . . . . . . . . 43 9. Connection Migration . . . . . . . . . . . . . . . . . . . . 43
9.1. Probing a New Path . . . . . . . . . . . . . . . . . . . 44 9.1. Probing a New Path . . . . . . . . . . . . . . . . . . . 44
9.2. Initiating Connection Migration . . . . . . . . . . . . . 45 9.2. Initiating Connection Migration . . . . . . . . . . . . . 44
9.3. Responding to Connection Migration . . . . . . . . . . . 45 9.3. Responding to Connection Migration . . . . . . . . . . . 45
9.3.1. Handling Address Spoofing by a Peer . . . . . . . . . 46 9.3.1. Peer Address Spoofing . . . . . . . . . . . . . . . . 45
9.3.2. Handling Address Spoofing by an On-path Attacker . . 46 9.3.2. On-Path Address Spoofing . . . . . . . . . . . . . . 46
9.4. Loss Detection and Congestion Control . . . . . . . . . . 47 9.3.3. Off-Path Packet Forwarding . . . . . . . . . . . . . 47
9.5. Privacy Implications of Connection Migration . . . . . . 48 9.4. Loss Detection and Congestion Control . . . . . . . . . . 48
9.6. Server's Preferred Address . . . . . . . . . . . . . . . 49 9.5. Privacy Implications of Connection Migration . . . . . . 49
9.6.1. Communicating A Preferred Address . . . . . . . . . . 49 9.6. Server's Preferred Address . . . . . . . . . . . . . . . 50
9.6.2. Responding to Connection Migration . . . . . . . . . 49 9.6.1. Communicating A Preferred Address . . . . . . . . . . 50
9.6.3. Interaction of Client Migration and Preferred Address 50 9.6.2. Responding to Connection Migration . . . . . . . . . 50
10. Connection Termination . . . . . . . . . . . . . . . . . . . 50 9.6.3. Interaction of Client Migration and Preferred Address 51
10. Connection Termination . . . . . . . . . . . . . . . . . . . 51
10.1. Closing and Draining Connection States . . . . . . . . . 51 10.1. Closing and Draining Connection States . . . . . . . . . 51
10.2. Idle Timeout . . . . . . . . . . . . . . . . . . . . . . 52 10.2. Idle Timeout . . . . . . . . . . . . . . . . . . . . . . 53
10.3. Immediate Close . . . . . . . . . . . . . . . . . . . . 52 10.3. Immediate Close . . . . . . . . . . . . . . . . . . . . 53
10.4. Stateless Reset . . . . . . . . . . . . . . . . . . . . 53 10.4. Stateless Reset . . . . . . . . . . . . . . . . . . . . 55
10.4.1. Detecting a Stateless Reset . . . . . . . . . . . . 56 10.4.1. Detecting a Stateless Reset . . . . . . . . . . . . 57
10.4.2. Calculating a Stateless Reset Token . . . . . . . . 56 10.4.2. Calculating a Stateless Reset Token . . . . . . . . 57
10.4.3. Looping . . . . . . . . . . . . . . . . . . . . . . 57 10.4.3. Looping . . . . . . . . . . . . . . . . . . . . . . 58
11. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 58 11. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 59
11.1. Connection Errors . . . . . . . . . . . . . . . . . . . 58 11.1. Connection Errors . . . . . . . . . . . . . . . . . . . 59
11.2. Stream Errors . . . . . . . . . . . . . . . . . . . . . 59 11.2. Stream Errors . . . . . . . . . . . . . . . . . . . . . 60
12. Packets and Frames . . . . . . . . . . . . . . . . . . . . . 59 12. Packets and Frames . . . . . . . . . . . . . . . . . . . . . 60
12.1. Protected Packets . . . . . . . . . . . . . . . . . . . 59 12.1. Protected Packets . . . . . . . . . . . . . . . . . . . 60
12.2. Coalescing Packets . . . . . . . . . . . . . . . . . . . 60 12.2. Coalescing Packets . . . . . . . . . . . . . . . . . . . 61
12.3. Packet Numbers . . . . . . . . . . . . . . . . . . . . . 61 12.3. Packet Numbers . . . . . . . . . . . . . . . . . . . . . 62
12.4. Frames and Frame Types . . . . . . . . . . . . . . . . . 62 12.4. Frames and Frame Types . . . . . . . . . . . . . . . . . 63
13. Packetization and Reliability . . . . . . . . . . . . . . . . 65 13. Packetization and Reliability . . . . . . . . . . . . . . . . 66
13.1. Packet Processing and Acknowledgment . . . . . . . . . . 66 13.1. Packet Processing and Acknowledgment . . . . . . . . . . 66
13.1.1. Sending ACK Frames . . . . . . . . . . . . . . . . . 66 13.1.1. Sending ACK Frames . . . . . . . . . . . . . . . . . 67
13.1.2. ACK Frames and Packet Protection . . . . . . . . . . 67 13.1.2. ACK Frames and Packet Protection . . . . . . . . . . 68
13.2. Retransmission of Information . . . . . . . . . . . . . 67 13.2. Retransmission of Information . . . . . . . . . . . . . 68
13.3. Explicit Congestion Notification . . . . . . . . . . . . 69 13.3. Explicit Congestion Notification . . . . . . . . . . . . 70
13.3.1. ECN Counters . . . . . . . . . . . . . . . . . . . . 70 13.3.1. ECN Counters . . . . . . . . . . . . . . . . . . . . 71
13.3.2. ECN Verification . . . . . . . . . . . . . . . . . . 70 13.3.2. ECN Verification . . . . . . . . . . . . . . . . . . 71
14. Packet Size . . . . . . . . . . . . . . . . . . . . . . . . . 71 14. Packet Size . . . . . . . . . . . . . . . . . . . . . . . . . 73
14.1. Path Maximum Transmission Unit . . . . . . . . . . . . . 72 14.1. Path Maximum Transmission Unit (PMTU) . . . . . . . . . 73
14.1.1. IPv4 PMTU Discovery . . . . . . . . . . . . . . . . 73 14.2. ICMP Packet Too Big Messages . . . . . . . . . . . . . . 74
14.2. Special Considerations for Packetization Layer PMTU 14.3. Datagram Packetization Layer PMTU Discovery . . . . . . 75
Discovery . . . . . . . . . . . . . . . . . . . . . . . 73 15. Versions . . . . . . . . . . . . . . . . . . . . . . . . . . 76
15. Versions . . . . . . . . . . . . . . . . . . . . . . . . . . 74 16. Variable-Length Integer Encoding . . . . . . . . . . . . . . 77
16. Variable-Length Integer Encoding . . . . . . . . . . . . . . 75 17. Packet Formats . . . . . . . . . . . . . . . . . . . . . . . 77
17. Packet Formats . . . . . . . . . . . . . . . . . . . . . . . 75 17.1. Packet Number Encoding and Decoding . . . . . . . . . . 78
17.1. Packet Number Encoding and Decoding . . . . . . . . . . 76 17.2. Long Header Packet . . . . . . . . . . . . . . . . . . . 79
17.2. Long Header Packet . . . . . . . . . . . . . . . . . . . 77 17.3. Short Header Packet . . . . . . . . . . . . . . . . . . 81
17.3. Short Header Packet . . . . . . . . . . . . . . . . . . 79 17.4. Version Negotiation Packet . . . . . . . . . . . . . . . 83
17.4. Version Negotiation Packet . . . . . . . . . . . . . . . 81 17.5. Initial Packet . . . . . . . . . . . . . . . . . . . . . 84
17.5. Initial Packet . . . . . . . . . . . . . . . . . . . . . 82 17.5.1. Starting Packet Numbers . . . . . . . . . . . . . . 86
17.5.1. Starting Packet Numbers . . . . . . . . . . . . . . 84 17.5.2. 0-RTT Packet Numbers . . . . . . . . . . . . . . . . 86
17.5.2. 0-RTT Packet Numbers . . . . . . . . . . . . . . . . 84 17.6. Handshake Packet . . . . . . . . . . . . . . . . . . . . 87
17.6. Handshake Packet . . . . . . . . . . . . . . . . . . . . 85 17.7. Retry Packet . . . . . . . . . . . . . . . . . . . . . . 87
17.7. Retry Packet . . . . . . . . . . . . . . . . . . . . . . 85 18. Transport Parameter Encoding . . . . . . . . . . . . . . . . 90
18. Transport Parameter Encoding . . . . . . . . . . . . . . . . 88 18.1. Transport Parameter Definitions . . . . . . . . . . . . 92
18.1. Transport Parameter Definitions . . . . . . . . . . . . 90 19. Frame Types and Formats . . . . . . . . . . . . . . . . . . . 94
19. Frame Types and Formats . . . . . . . . . . . . . . . . . . . 92 19.1. PADDING Frame . . . . . . . . . . . . . . . . . . . . . 95
19.1. PADDING Frame . . . . . . . . . . . . . . . . . . . . . 93 19.2. PING Frame . . . . . . . . . . . . . . . . . . . . . . . 95
19.2. RST_STREAM Frame . . . . . . . . . . . . . . . . . . . . 93 19.3. ACK Frames . . . . . . . . . . . . . . . . . . . . . . . 95
19.3. CONNECTION_CLOSE frame . . . . . . . . . . . . . . . . . 94 19.3.1. ACK Block Section . . . . . . . . . . . . . . . . . 97
19.4. APPLICATION_CLOSE frame . . . . . . . . . . . . . . . . 95 19.3.2. ECN section . . . . . . . . . . . . . . . . . . . . 99
19.5. MAX_DATA Frame . . . . . . . . . . . . . . . . . . . . . 95 19.4. RESET_STREAM Frame . . . . . . . . . . . . . . . . . . . 99
19.6. MAX_STREAM_DATA Frame . . . . . . . . . . . . . . . . . 96 19.5. STOP_SENDING Frame . . . . . . . . . . . . . . . . . . . 100
19.7. MAX_STREAM_ID Frame . . . . . . . . . . . . . . . . . . 97 19.6. CRYPTO Frame . . . . . . . . . . . . . . . . . . . . . . 101
19.8. PING Frame . . . . . . . . . . . . . . . . . . . . . . . 98 19.7. NEW_TOKEN Frame . . . . . . . . . . . . . . . . . . . . 102
19.9. BLOCKED Frame . . . . . . . . . . . . . . . . . . . . . 98 19.8. STREAM Frames . . . . . . . . . . . . . . . . . . . . . 102
19.10. STREAM_BLOCKED Frame . . . . . . . . . . . . . . . . . . 99 19.9. MAX_DATA Frame . . . . . . . . . . . . . . . . . . . . . 104
19.11. STREAM_ID_BLOCKED Frame . . . . . . . . . . . . . . . . 99 19.10. MAX_STREAM_DATA Frame . . . . . . . . . . . . . . . . . 104
19.12. NEW_CONNECTION_ID Frame . . . . . . . . . . . . . . . . 100 19.11. MAX_STREAMS Frames . . . . . . . . . . . . . . . . . . . 105
19.13. RETIRE_CONNECTION_ID Frame . . . . . . . . . . . . . . . 101 19.12. DATA_BLOCKED Frame . . . . . . . . . . . . . . . . . . . 106
19.14. STOP_SENDING Frame . . . . . . . . . . . . . . . . . . . 102 19.13. STREAM_DATA_BLOCKED Frame . . . . . . . . . . . . . . . 106
19.15. ACK Frame . . . . . . . . . . . . . . . . . . . . . . . 102 19.14. STREAMS_BLOCKED Frames . . . . . . . . . . . . . . . . . 107
19.15.1. ACK Block Section . . . . . . . . . . . . . . . . . 104 19.15. NEW_CONNECTION_ID Frame . . . . . . . . . . . . . . . . 108
19.15.2. ECN section . . . . . . . . . . . . . . . . . . . . 105 19.16. RETIRE_CONNECTION_ID Frame . . . . . . . . . . . . . . . 109
19.16. PATH_CHALLENGE Frame . . . . . . . . . . . . . . . . . . 106 19.17. PATH_CHALLENGE Frame . . . . . . . . . . . . . . . . . . 110
19.17. PATH_RESPONSE Frame . . . . . . . . . . . . . . . . . . 107 19.18. PATH_RESPONSE Frame . . . . . . . . . . . . . . . . . . 110
19.18. NEW_TOKEN frame . . . . . . . . . . . . . . . . . . . . 107 19.19. CONNECTION_CLOSE Frames . . . . . . . . . . . . . . . . 110
19.19. STREAM Frames . . . . . . . . . . . . . . . . . . . . . 107 19.20. Extension Frames . . . . . . . . . . . . . . . . . . . . 111
19.20. CRYPTO Frame . . . . . . . . . . . . . . . . . . . . . . 109
19.21. Extension Frames . . . . . . . . . . . . . . . . . . . . 110
20. Transport Error Codes . . . . . . . . . . . . . . . . . . . . 110
20.1. Application Protocol Error Codes . . . . . . . . . . . . 111
21. Security Considerations . . . . . . . . . . . . . . . . . . . 112
21.1. Handshake Denial of Service . . . . . . . . . . . . . . 112
21.2. Spoofed ACK Attack . . . . . . . . . . . . . . . . . . . 113
21.3. Optimistic ACK Attack . . . . . . . . . . . . . . . . . 113
21.4. Slowloris Attacks . . . . . . . . . . . . . . . . . . . 114
21.5. Stream Fragmentation and Reassembly Attacks . . . . . . 114
21.6. Stream Commitment Attack . . . . . . . . . . . . . . . . 114
21.7. Explicit Congestion Notification Attacks . . . . . . . . 115
21.8. Stateless Reset Oracle . . . . . . . . . . . . . . . . . 115
22. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 116
22.1. QUIC Transport Parameter Registry . . . . . . . . . . . 116
22.2. QUIC Frame Type Registry . . . . . . . . . . . . . . . . 117
22.3. QUIC Transport Error Codes Registry . . . . . . . . . . 118
23. References . . . . . . . . . . . . . . . . . . . . . . . . . 121
23.1. Normative References . . . . . . . . . . . . . . . . . . 121
23.2. Informative References . . . . . . . . . . . . . . . . . 122
Appendix A. Sample Packet Number Decoding Algorithm . . . . . . 123
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 124
B.1. Since draft-ietf-quic-transport-15 . . . . . . . . . . . 124
B.2. Since draft-ietf-quic-transport-14 . . . . . . . . . . . 124
B.3. Since draft-ietf-quic-transport-13 . . . . . . . . . . . 125
B.4. Since draft-ietf-quic-transport-12 . . . . . . . . . . . 126
B.5. Since draft-ietf-quic-transport-11 . . . . . . . . . . . 126
B.6. Since draft-ietf-quic-transport-10 . . . . . . . . . . . 127
B.7. Since draft-ietf-quic-transport-09 . . . . . . . . . . . 127
B.8. Since draft-ietf-quic-transport-08 . . . . . . . . . . . 128
B.9. Since draft-ietf-quic-transport-07 . . . . . . . . . . . 129
B.10. Since draft-ietf-quic-transport-06 . . . . . . . . . . . 130
B.11. Since draft-ietf-quic-transport-05 . . . . . . . . . . . 130
B.12. Since draft-ietf-quic-transport-04 . . . . . . . . . . . 130
B.13. Since draft-ietf-quic-transport-03 . . . . . . . . . . . 131
B.14. Since draft-ietf-quic-transport-02 . . . . . . . . . . . 131
B.15. Since draft-ietf-quic-transport-01 . . . . . . . . . . . 132
B.16. Since draft-ietf-quic-transport-00 . . . . . . . . . . . 134
B.17. Since draft-hamilton-quic-transport-protocol-01 . . . . . 134
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 134
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 135
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 135
1. Introduction
QUIC is a multiplexed and secure transport protocol that runs on top
of UDP. QUIC aims to provide a flexible set of features that allow
it to be a general-purpose secure transport for multiple
applications.
o Version negotiation 20. Transport Error Codes . . . . . . . . . . . . . . . . . . . . 112
20.1. Application Protocol Error Codes . . . . . . . . . . . . 113
21. Security Considerations . . . . . . . . . . . . . . . . . . . 113
21.1. Handshake Denial of Service . . . . . . . . . . . . . . 113
21.2. Spoofed ACK Attack . . . . . . . . . . . . . . . . . . . 115
21.3. Optimistic ACK Attack . . . . . . . . . . . . . . . . . 115
21.4. Slowloris Attacks . . . . . . . . . . . . . . . . . . . 115
21.5. Stream Fragmentation and Reassembly Attacks . . . . . . 116
21.6. Stream Commitment Attack . . . . . . . . . . . . . . . . 116
21.7. Explicit Congestion Notification Attacks . . . . . . . . 117
21.8. Stateless Reset Oracle . . . . . . . . . . . . . . . . . 117
22. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 117
22.1. QUIC Transport Parameter Registry . . . . . . . . . . . 118
22.2. QUIC Frame Type Registry . . . . . . . . . . . . . . . . 119
22.3. QUIC Transport Error Codes Registry . . . . . . . . . . 120
23. References . . . . . . . . . . . . . . . . . . . . . . . . . 123
23.1. Normative References . . . . . . . . . . . . . . . . . . 123
23.2. Informative References . . . . . . . . . . . . . . . . . 124
Appendix A. Sample Packet Number Decoding Algorithm . . . . . . 126
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 126
B.1. Since draft-ietf-quic-transport-16 . . . . . . . . . . . 126
B.2. Since draft-ietf-quic-transport-15 . . . . . . . . . . . 127
B.3. Since draft-ietf-quic-transport-14 . . . . . . . . . . . 128
B.4. Since draft-ietf-quic-transport-13 . . . . . . . . . . . 128
B.5. Since draft-ietf-quic-transport-12 . . . . . . . . . . . 129
B.6. Since draft-ietf-quic-transport-11 . . . . . . . . . . . 130
B.7. Since draft-ietf-quic-transport-10 . . . . . . . . . . . 130
B.8. Since draft-ietf-quic-transport-09 . . . . . . . . . . . 131
B.9. Since draft-ietf-quic-transport-08 . . . . . . . . . . . 131
B.10. Since draft-ietf-quic-transport-07 . . . . . . . . . . . 132
B.11. Since draft-ietf-quic-transport-06 . . . . . . . . . . . 133
B.12. Since draft-ietf-quic-transport-05 . . . . . . . . . . . 133
B.13. Since draft-ietf-quic-transport-04 . . . . . . . . . . . 133
B.14. Since draft-ietf-quic-transport-03 . . . . . . . . . . . 134
B.15. Since draft-ietf-quic-transport-02 . . . . . . . . . . . 134
B.16. Since draft-ietf-quic-transport-01 . . . . . . . . . . . 135
B.17. Since draft-ietf-quic-transport-00 . . . . . . . . . . . 137
B.18. Since draft-hamilton-quic-transport-protocol-01 . . . . . 137
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 138
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 138
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 138
o Low-latency connection establishment 1. Introduction
o Authenticated and encrypted header and payload QUIC is a multiplexed and secure general-purpose transport protocol
that provides:
o Stream multiplexing o Stream multiplexing
o Stream and connection-level flow control o Stream and connection-level flow control
o Low-latency connection establishment
o Connection migration and resilience to NAT rebinding o Connection migration and resilience to NAT rebinding
QUIC uses UDP as a substrate to avoid requiring changes in legacy o Authenticated and encrypted header and payload
QUIC uses UDP as a substrate to avoid requiring changes to legacy
client operating systems and middleboxes. QUIC authenticates all of client operating systems and middleboxes. QUIC authenticates all of
its headers and encrypts most of the data it exchanges, including its its headers and encrypts most of the data it exchanges, including its
signaling. This allows the protocol to evolve without incurring a signaling, to avoid incurring a dependency on middleboxes.
dependency on upgrades to middleboxes.
1.1. Document Structure 1.1. Document Structure
This document describes the core QUIC protocol, and is structured as This document describes the core QUIC protocol and is structured as
follows: follows.
o Streams are the basic service abstraction that QUIC provides. o Streams are the basic service abstraction that QUIC provides.
* Section 2 describes core concepts related to streams, * Section 2 describes core concepts related to streams,
* Section 3 provides a reference model for stream states, and * Section 3 provides a reference model for stream states, and
* Section 4 outlines the operation of flow control. * Section 4 outlines the operation of flow control.
o Connections are the context in which QUIC endpoints communicate. o Connections are the context in which QUIC endpoints communicate.
* Section 5 describes core concepts related to connections, * Section 5 describes core concepts related to connections,
* Section 6 describes version negotiation, * Section 6 describes version negotiation,
* Section 7 details the process for establishing connections, * Section 7 details the process for establishing connections,
* Section 8 specifies critical denial of service mitigation * Section 8 specifies critical denial of service mitigation
mechanisms, mechanisms,
* Section 9 describes how endpoints migrate a connection to use a * Section 9 describes how endpoints migrate a connection to a new
new network paths, and network path,
* Section 10 lists the options for terminating an open * Section 10 lists the options for terminating an open
connection. connection, and
* Section 11 provides general guidance for error handling.
o Packets and frames are the basic unit used by QUIC to communicate. o Packets and frames are the basic unit used by QUIC to communicate.
* Section 12 describes concepts related to packets and frames, * Section 12 describes concepts related to packets and frames,
* Section 13 defines models for the transmission, retransmission, * Section 13 defines models for the transmission, retransmission,
and acknowledgement of information, and and acknowledgement of data, and
* Section 14 contains a rules for managing the size of packets. * Section 14 specifies rules for managing the size of packets.
o Details of encoding of QUIC protocol elements is described in: o Finally, encoding details of QUIC protocol elements are described
in:
* Section 15 (Versions), * Section 15 (Versions),
* Section 16 (Integer Encoding),
* Section 17 (Packet Headers), * Section 17 (Packet Headers),
* Section 18 (Transport Parameters), * Section 18 (Transport Parameters),
* Section 19 (Frames), and * Section 19 (Frames), and
* Section 20 (Errors). * Section 20 (Errors).
Accompanying documents describe QUIC's loss detection and congestion Accompanying documents describe QUIC's loss detection and congestion
control [QUIC-RECOVERY], and the use of TLS 1.3 for key negotiation control [QUIC-RECOVERY], and the use of TLS for key negotiation
[QUIC-TLS]. [QUIC-TLS].
QUIC version 1 conforms to the protocol invariants in This document defines QUIC version 1, which conforms to the protocol
[QUIC-INVARIANTS]. invariants in [QUIC-INVARIANTS].
1.2. Conventions and Definitions 1.2. Terms and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
Definitions of terms that are used in this document: Commonly used terms in the document are described below.
Client: The endpoint initiating a QUIC connection. QUIC: The transport protocol described by this document. QUIC is a
name, not an acronym.
Server: The endpoint accepting incoming QUIC connections. QUIC packet: The smallest unit of QUIC that can be encapsulated in a
UDP datagram. Multiple QUIC packets can be encapsulated in a
single UDP datagram.
Endpoint: The client or server end of a connection. Endpoint: An entity that can participate in a QUIC connection by
generating, receiving, and processing QUIC packets. There are
only two types of endpoint in QUIC: client and server.
Stream: A logical unidirectional or bidirectional channel of ordered Client: The endpoint initiating a QUIC connection.
bytes within a QUIC connection.
Connection: A conversation between two QUIC endpoints with a single Server: The endpoint accepting incoming QUIC connections.
encryption context that multiplexes streams within it.
Connection ID: An opaque identifier that is used to identify a QUIC Connection ID: An opaque identifier that is used to identify a QUIC
connection at an endpoint. Each endpoint sets a value that its connection at an endpoint. Each endpoint sets a value for its
peer includes in packets. peer to include in packets sent towards the endpoint.
QUIC packet: The smallest unit of data that can be exchanged by QUIC Stream: A unidirectional or bidirectional channel of ordered bytes
endpoints. within a QUIC connection. A QUIC connection can carry multiple
simultaneous streams.
QUIC is a name, not an acronym. Application: An entity that uses QUIC to send and receive data.
1.3. Notational Conventions 1.3. Notational Conventions
Packet and frame diagrams use the format described in Section 3.1 of Packet and frame diagrams in this document use the format described
[RFC2360], with the following additional conventions: in Section 3.1 of [RFC2360], with the following additional
conventions:
[x] Indicates that x is optional [x]: Indicates that x is optional
x (A) Indicates that x is A bits long x (A): Indicates that x is A bits long
x (A/B/C) ... Indicates that x is one of A, B, or C bits long x (A/B/C) ...: Indicates that x is one of A, B, or C bits long
x (i) ... Indicates that x uses the variable-length encoding in x (i) ...: Indicates that x uses the variable-length encoding in
Section 16 Section 16
x (*) ... Indicates that x is variable-length x (*) ...: Indicates that x is variable-length
2. Streams 2. Streams
Streams in QUIC provide a lightweight, ordered byte-stream Streams in QUIC provide a lightweight, ordered byte-stream
abstraction. abstraction to an application. An alternative view of QUIC streams
is as an elastic "message" abstraction.
There are two basic types of stream in QUIC. Unidirectional streams
carry data in one direction: from the initiator of the stream to its
peer; bidirectional streams allow for data to be sent in both
directions. Different stream identifiers are used to distinguish
between unidirectional and bidirectional streams, as well as to
create a separation between streams that are initiated by the client
and server (see Section 2.1).
Either type of stream can be created by either endpoint, can
concurrently send data interleaved with other streams, and can be
cancelled.
Streams can be created by sending data. Other processes associated Streams can be created by sending data. Other processes associated
with stream management - ending, cancelling, and managing flow with stream management - ending, cancelling, and managing flow
control - are all designed to impose minimal overheads. For control - are all designed to impose minimal overheads. For
instance, a single STREAM frame (Section 19.19) can open, carry data instance, a single STREAM frame (Section 19.8) can open, carry data
for, and close a stream. Streams can also be long-lived and can last for, and close a stream. Streams can also be long-lived and can last
the entire duration of a connection. the entire duration of a connection.
Stream offsets allow for the octets on a stream to be placed in Streams can be created by either endpoint, can concurrently send data
order. An endpoint MUST be capable of delivering data received on a interleaved with other streams, and can be cancelled. Any stream can
stream in order. Implementations MAY choose to offer the ability to be initiated by either endpoint. QUIC does not provide any means of
deliver data out of order. There is no means of ensuring ordering ensuring ordering between bytes on different streams.
between octets on different streams.
Streams are individually flow controlled, allowing an endpoint to
limit memory commitment and to apply back pressure. The creation of
streams is also flow controlled, with each peer declaring the maximum
stream ID it is willing to accept at a given time.
An alternative view of QUIC streams is as an elastic "message" QUIC allows for an arbitrary number of streams to operate
abstraction, similar to the way ephemeral streams are used in SST concurrently and for an arbitrary amount of data to be sent on any
[SST], which may be a more appealing description for some stream, subject to flow control constraints (see Section 4) and
applications. stream limits.
2.1. Stream Identifiers 2.1. Stream Types and Identifiers
Streams are identified by an unsigned 62-bit integer, referred to as Streams can be unidirectional or bidirectional. Unidirectional
the Stream ID. Stream IDs are encoded as a variable-length integer streams carry data in one direction: from the initiator of the stream
(see Section 16). The least significant two bits of the Stream ID to its peer. Bidirectional streams allow for data to be sent in both
are used to identify the type of stream (unidirectional or directions.
bidirectional) and the initiator of the stream.
The least significant bit (0x1) of the Stream ID identifies the Streams are identified within a connection by a numeric value,
initiator of the stream. Clients initiate even-numbered streams referred to as the stream ID. Stream IDs are unique to a stream. A
(those with the least significant bit set to 0); servers initiate QUIC endpoint MUST NOT reuse a stream ID within a connection. Stream
odd-numbered streams (with the bit set to 1). Separation of the IDs are encoded as variable-length integers (see Section 16).
stream identifiers ensures that client and server are able to open
streams without the latency imposed by negotiating for an identifier.
If an endpoint receives a frame for a stream that it expects to The least significant bit (0x1) of the stream ID identifies the
initiate (i.e., odd-numbered for the client or even-numbered for the initiator of the stream. Client-initiated streams have even-numbered
server), but which it has not yet opened, it MUST close the stream IDs (with the bit set to 0), and server-initiated streams have
connection with error code STREAM_STATE_ERROR. odd-numbered stream IDs (with the bit set to 1).
The second least significant bit (0x2) of the Stream ID The second least significant bit (0x2) of the stream ID distinguishes
differentiates between unidirectional streams and bidirectional between bidirectional streams (with the bit set to 0) and
streams. Unidirectional streams always have this bit set to 1 and unidirectional streams (with the bit set to 1).
bidirectional streams have this bit set to 0.
The two type bits from a Stream ID therefore identify streams as The least significant two bits from a stream ID therefore identify a
summarized in Table 1. stream as one of four types, as summarized in Table 1.
+----------+----------------------------------+ +------+----------------------------------+
| Low Bits | Stream Type | | Bits | Stream Type |
+----------+----------------------------------+ +------+----------------------------------+
| 0x0 | Client-Initiated, Bidirectional | | 0x0 | Client-Initiated, Bidirectional |
| | | | | |
| 0x1 | Server-Initiated, Bidirectional | | 0x1 | Server-Initiated, Bidirectional |
| | | | | |
| 0x2 | Client-Initiated, Unidirectional | | 0x2 | Client-Initiated, Unidirectional |
| | | | | |
| 0x3 | Server-Initiated, Unidirectional | | 0x3 | Server-Initiated, Unidirectional |
+----------+----------------------------------+ +------+----------------------------------+
Table 1: Stream ID Types Table 1: Stream ID Types
The first bidirectional stream opened by the client is stream 0. Within each type, streams are created with numerically increasing
stream IDs. A stream ID that is used out of order results in all
A QUIC endpoint MUST NOT reuse a Stream ID. Streams of each type are streams of that type with lower-numbered stream IDs also being
created in numeric order. Streams that are used out of order result opened.
in opening all lower-numbered streams of the same type in the same
direction.
2.2. Stream Concurrency
QUIC allows for an arbitrary number of streams to operate The first bidirectional stream opened by the client has a stream ID
concurrently. An endpoint limits the number of concurrently active of 0.
incoming streams by limiting the maximum stream ID (see Section 4.5).
The maximum stream ID is specific to each endpoint and applies only 2.2. Sending and Receiving Data
to the peer that receives the setting. That is, clients specify the
maximum stream ID the server can initiate, and servers specify the
maximum stream ID the client can initiate. Each endpoint may respond
on streams initiated by the other peer, regardless of whether it is
permitted to initiate new streams.
Endpoints MUST NOT exceed the limit set by their peer. An endpoint STREAM frames (Section 19.8) encapsulate data sent by an application.
that receives a STREAM frame with an ID greater than the limit it has An endpoint uses the Stream ID and Offset fields in STREAM frames to
sent MUST treat this as a stream error of type STREAM_ID_ERROR place data in order.
(Section 11), unless this is a result of a change in the initial
limits (see Section 7.3.1).
A receiver cannot renege on an advertisement; that is, once a Endpoints MUST be able to deliver stream data to an application as an
receiver advertises a stream ID via a MAX_STREAM_ID frame, ordered byte-stream. Delivering an ordered byte-stream requires that
advertising a smaller maximum ID has no effect. A receiver MUST an endpoint buffer any data that is received out of order, up to the
ignore any MAX_STREAM_ID frame that does not increase the maximum advertised flow control limit.
stream ID.
2.3. Sending and Receiving Data QUIC makes no specific allowances for delivery of stream data out of
order. However, implementations MAY choose to offer the ability to
deliver data out of order to a receiving application.
Endpoints uses streams to send and receive data. Endpoints send An endpoint could receive data for a stream at the same stream offset
STREAM frames, which encapsulate data for a stream. STREAM frames multiple times. Data that has already been received can be
carry a flag that can be used to signal the end of a stream. discarded. The data at a given offset MUST NOT change if it is sent
multiple times; an endpoint MAY treat receipt of different data at
the same offset within a stream as a connection error of type
PROTOCOL_VIOLATION.
Streams are an ordered byte-stream abstraction with no other Streams are an ordered byte-stream abstraction with no other
structure that is visible to QUIC. STREAM frame boundaries are not structure that is visible to QUIC. STREAM frame boundaries are not
expected to preserved when data is transmitted, when data is expected to be preserved when data is transmitted, when data is
retransmitted after packet loss, or when data is delivered to the retransmitted after packet loss, or when data is delivered to the
application at the receiver. application at a receiver.
When new data is to be sent on a stream, a sender MUST set the
encapsulating STREAM frame's offset field to the stream offset of the
first octet of this new data. The first octet of data on a stream
has an offset of 0. An endpoint is expected to send every stream
octet. The largest offset delivered on a stream MUST be less than
2^62.
QUIC makes no specific allowances for partial reliability or delivery
of stream data out of order. Endpoints MUST be able to deliver
stream data to an application as an ordered byte-stream. Delivering
an ordered byte-stream requires that an endpoint buffer any data that
is received out of order, up to the advertised flow control limit.
An endpoint could receive the same octets multiple times; octets that
have already been received can be discarded. The value for a given
octet MUST NOT change if it is sent multiple times; an endpoint MAY
treat receipt of a changed octet as a connection error of type
PROTOCOL_VIOLATION.
An endpoint MUST NOT send data on any stream without ensuring that it An endpoint MUST NOT send data on any stream without ensuring that it
is within the data limits set by its peer. Flow control is described is within the flow control limits set by its peer. Flow control is
in detail in Section 4. described in detail in Section 4.
2.4. Stream Prioritization 2.3. Stream Prioritization
Stream multiplexing has a significant effect on application Stream multiplexing can have a significant effect on application
performance if resources allocated to streams are correctly performance if resources allocated to streams are correctly
prioritized. Experience with other multiplexed protocols, such as prioritized.
HTTP/2 [HTTP2], shows that effective prioritization strategies have a
significant positive impact on performance.
QUIC does not provide frames for exchanging prioritization QUIC does not provide frames for exchanging prioritization
information. Instead it relies on receiving priority information information. Instead it relies on receiving priority information
from the application that uses QUIC. Protocols that use QUIC are from the application that uses QUIC.
able to define any prioritization scheme that suits their application
semantics. A protocol might define explicit messages for signaling
priority, such as those defined in HTTP/2; it could define rules that
allow an endpoint to determine priority based on context; or it could
leave the determination to the application.
A QUIC implementation SHOULD provide ways in which an application can A QUIC implementation SHOULD provide ways in which an application can
indicate the relative priority of streams. When deciding which indicate the relative priority of streams. When deciding which
streams to dedicate resources to, QUIC SHOULD use the information streams to dedicate resources to, the implementation SHOULD use the
provided by the application. Failure to account for priority of information provided by the application.
streams can result in suboptimal performance.
Stream priority is most relevant when deciding which stream data will
be transmitted. Often, there will be limits on what can be
transmitted as a result of connection flow control or the current
congestion controller state.
Giving preference to the transmission of its own management frames
ensures that the protocol functions efficiently. That is,
prioritizing frames other than STREAM frames ensures that loss
recovery, congestion control, and flow control operate effectively.
CRYPTO frames SHOULD be prioritized over other streams prior to the
completion of the cryptographic handshake. This includes the
retransmission of the second flight of client handshake messages,
that is, the TLS Finished and any client authentication messages.
STREAM data in frames determined to be lost SHOULD be retransmitted
before sending new data, unless application priorities indicate
otherwise. Retransmitting lost stream data can fill in gaps, which
allows the peer to consume already received data and free up the flow
control window.
3. Stream States: Life of a Stream 3. Stream States
This section describes the two types of QUIC stream in terms of the This section describes streams in terms of their send or receive
states of their send or receive components. Two state machines are components. Two state machines are described: one for the streams on
described: one for streams on which an endpoint transmits data which an endpoint transmits data (Section 3.1), and another for
(Section 3.1); another for streams from which an endpoint receives streams on which an endpoint receives data (Section 3.2).
data (Section 3.2).
Unidirectional streams use the applicable state machine directly. Unidirectional streams use the applicable state machine directly.
Bidirectional streams use both state machines. For the most part, Bidirectional streams use both state machines. For the most part,
the use of these state machines is the same whether the stream is the use of these state machines is the same whether the stream is
unidirectional or bidirectional. The conditions for opening a stream unidirectional or bidirectional. The conditions for opening a stream
are slightly more complex for a bidirectional stream because the are slightly more complex for a bidirectional stream because the
opening of either send or receive sides causes the stream to open in opening of either send or receive sides causes the stream to open in
both directions. both directions.
An endpoint can open streams up to its maximum stream limit in any An endpoint MUST open streams of the same type in increasing order of
order, however endpoints SHOULD open the send side of streams for stream ID.
each type in order.
Note: These states are largely informative. This document uses Note: These states are largely informative. This document uses
stream states to describe rules for when and how different types stream states to describe rules for when and how different types
of frames can be sent and the reactions that are expected when of frames can be sent and the reactions that are expected when
different types of frames are received. Though these state different types of frames are received. Though these state
machines are intended to be useful in implementing QUIC, these machines are intended to be useful in implementing QUIC, these
states aren't intended to constrain implementations. An states aren't intended to constrain implementations. An
implementation can define a different state machine as long as its implementation can define a different state machine as long as its
behavior is consistent with an implementation that implements behavior is consistent with an implementation that implements
these states. these states.
3.1. Send Stream States 3.1. Send Stream States
Figure 1 shows the states for the part of a stream that sends data to Figure 1 shows the states for the part of a stream that sends data to
a peer. a peer.
o o
| Create Stream (Sending) | Create Stream (Sending)
| Create Bidirectional Stream (Receiving) | Peer Creates Bidirectional Stream
v v
+-------+ +-------+
| Ready | Send RST_STREAM | Ready | Send RESET_STREAM
| |-----------------------. | |-----------------------.
+-------+ | +-------+ |
| | | |
| Send STREAM / | | Send STREAM / |
| STREAM_BLOCKED | | STREAM_DATA_BLOCKED |
| | | |
| Create Bidirectional | | Peer Creates |
| Stream (Receiving) | | Bidirectional Stream |
v | v |
+-------+ | +-------+ |
| Send | Send RST_STREAM | | Send | Send RESET_STREAM |
| |---------------------->| | |---------------------->|
+-------+ | +-------+ |
| | | |
| Send STREAM + FIN | | Send STREAM + FIN |
v v v v
+-------+ +-------+ +-------+ +-------+
| Data | Send RST_STREAM | Reset | | Data | Send RESET_STREAM | Reset |
| Sent |------------------>| Sent | | Sent |------------------>| Sent |
+-------+ +-------+ +-------+ +-------+
| | | |
| Recv All ACKs | Recv ACK | Recv All ACKs | Recv ACK
v v v v
+-------+ +-------+ +-------+ +-------+
| Data | | Reset | | Data | | Reset |
| Recvd | | Recvd | | Recvd | | Recvd |
+-------+ +-------+ +-------+ +-------+
Figure 1: States for Send Streams Figure 1: States for Send Streams
The sending part of stream that the endpoint initiates (types 0 and 2 The sending part of stream that the endpoint initiates (types 0 and 2
for clients, 1 and 3 for servers) is opened by the application or for clients, 1 and 3 for servers) is opened by the application. The
application protocol. The "Ready" state represents a newly created "Ready" state represents a newly created stream that is able to
stream that is able to accept data from the application. Stream data accept data from the application. Stream data might be buffered in
might be buffered in this state in preparation for sending. this state in preparation for sending.
Sending the first STREAM or STREAM_BLOCKED frame causes a send stream Sending the first STREAM or STREAM_DATA_BLOCKED frame causes a send
to enter the "Send" state. An implementation might choose to defer stream to enter the "Send" state. An implementation might choose to
allocating a Stream ID to a send stream until it sends the first defer allocating a stream ID to a send stream until it sends the
frame and enters this state, which can allow for better stream first frame and enters this state, which can allow for better stream
prioritization. prioritization.
The sending part of a bidirectional stream initiated by a peer (type The sending part of a bidirectional stream initiated by a peer (type
0 for a server, type 1 for a client) enters the "Ready" state then 0 for a server, type 1 for a client) enters the "Ready" state then
immediately transitions to the "Send" state if the receiving part immediately transitions to the "Send" state if the receiving part
enters the "Recv" state. enters the "Recv" state (Section 3.2).
In the "Send" state, an endpoint transmits - and retransmits as In the "Send" state, an endpoint transmits - and retransmits as
necessary - data in STREAM frames. The endpoint respects the flow necessary - stream data in STREAM frames. The endpoint respects the
control limits of its peer, accepting MAX_STREAM_DATA frames. An flow control limits set by its peer, and continues to accept and
endpoint in the "Send" state generates STREAM_BLOCKED frames if it process MAX_STREAM_DATA frames. An endpoint in the "Send" state
encounters flow control limits. generates STREAM_DATA_BLOCKED frames if it is blocked from sending by
stream or connection flow control limits Section 4.1.
After the application indicates that stream data is complete and a After the application indicates that all stream data has been sent
STREAM frame containing the FIN bit is sent, the send stream enters and a STREAM frame containing the FIN bit is sent, the send stream
the "Data Sent" state. From this state, the endpoint only enters the "Data Sent" state. From this state, the endpoint only
retransmits stream data as necessary. The endpoint no longer needs retransmits stream data as necessary. The endpoint does not need to
to track flow control limits or send STREAM_BLOCKED frames for a send check flow control limits or send STREAM_DATA_BLOCKED frames for a
stream in this state. The endpoint can ignore any MAX_STREAM_DATA send stream in this state. MAX_STREAM_DATA frames might be received
frames it receives from its peer in this state; MAX_STREAM_DATA until the peer receives the final stream offset. The endpoint can
frames might be received until the peer receives the final stream safely ignore any MAX_STREAM_DATA frames it receives from its peer
offset. for a stream in this state.
Once all stream data has been successfully acknowledged, the send Once all stream data has been successfully acknowledged, the send
stream enters the "Data Recvd" state, which is a terminal state. stream enters the "Data Recvd" state, which is a terminal state.
From any of the "Ready", "Send", or "Data Sent" states, an From any of the "Ready", "Send", or "Data Sent" states, an
application can signal that it wishes to abandon transmission of application can signal that it wishes to abandon transmission of
stream data. Similarly, the endpoint might receive a STOP_SENDING stream data. Alternatively, an endpoint might receive a STOP_SENDING
frame from its peer. In either case, the endpoint sends a RST_STREAM frame from its peer. In either case, the endpoint sends a
frame, which causes the stream to enter the "Reset Sent" state. RESET_STREAM frame, which causes the stream to enter the "Reset Sent"
state.
An endpoint MAY send a RST_STREAM as the first frame on a send An endpoint MAY send a RESET_STREAM as the first frame on a send
stream; this causes the send stream to open and then immediately stream; this causes the send stream to open and then immediately
transition to the "Reset Sent" state. transition to the "Reset Sent" state.
Once a packet containing a RST_STREAM has been acknowledged, the send Once a packet containing a RESET_STREAM has been acknowledged, the
stream enters the "Reset Recvd" state, which is a terminal state. send stream enters the "Reset Recvd" state, which is a terminal
state.
3.2. Receive Stream States 3.2. Receive Stream States
Figure 2 shows the states for the part of a stream that receives data Figure 2 shows the states for the part of a stream that receives data
from a peer. The states for a receive stream mirror only some of the from a peer. The states for a receive stream mirror only some of the
states of the send stream at the peer. A receive stream doesn't states of the send stream at the peer. A receive stream does not
track states on the send stream that cannot be observed, such as the track states on the send stream that cannot be observed, such as the
"Ready" state; instead, receive streams track the delivery of data to "Ready" state. Instead, receive streams track the delivery of data
the application or application protocol some of which cannot be to the application, some of which cannot be observed by the sender.
observed by the sender.
o o
| Recv STREAM / STREAM_BLOCKED / RST_STREAM | Recv STREAM / STREAM_DATA_BLOCKED / RESET_STREAM
| Create Bidirectional Stream (Sending) | Create Bidirectional Stream (Sending)
| Recv MAX_STREAM_DATA | Recv MAX_STREAM_DATA / STOP_SENDING (Bidirectional)
| Create Higher-Numbered Stream | Create Higher-Numbered Stream
v v
+-------+ +-------+
| Recv | Recv RST_STREAM | Recv | Recv RESET_STREAM
| |-----------------------. | |-----------------------.
+-------+ | +-------+ |
| | | |
| Recv STREAM + FIN | | Recv STREAM + FIN |
v | v |
+-------+ | +-------+ |
| Size | Recv RST_STREAM | | Size | Recv RESET_STREAM |
| Known |---------------------->| | Known |---------------------->|
+-------+ | +-------+ |
| | | |
| Recv All Data | | Recv All Data |
v v v v
+-------+ Recv RST_STREAM +-------+ +-------+ Recv RESET_STREAM +-------+
| Data |--- (optional) --->| Reset | | Data |--- (optional) --->| Reset |
| Recvd | Recv All Data | Recvd | | Recvd | Recv All Data | Recvd |
+-------+<-- (optional) ----+-------+ +-------+<-- (optional) ----+-------+
| | | |
| App Read All Data | App Read RST | App Read All Data | App Read RST
v v v v
+-------+ +-------+ +-------+ +-------+
| Data | | Reset | | Data | | Reset |
| Read | | Read | | Read | | Read |
+-------+ +-------+ +-------+ +-------+
Figure 2: States for Receive Streams Figure 2: States for Receive Streams
The receiving part of a stream initiated by a peer (types 1 and 3 for The receiving part of a stream initiated by a peer (types 1 and 3 for
a client, or 0 and 2 for a server) are created when the first STREAM, a client, or 0 and 2 for a server) is created when the first STREAM,
STREAM_BLOCKED, RST_STREAM, or MAX_STREAM_DATA (bidirectional only, STREAM_DATA_BLOCKED, or RESET_STREAM is received for that stream.
see below) is received for that stream. The initial state for a For bidirectional streams initiated by a peer, receipt of a
receive stream is "Recv". Receiving a RST_STREAM frame causes the MAX_STREAM_DATA or STOP_SENDING frame for the sending part of the
receive stream to immediately transition to the "Reset Recvd". stream also creates the receiving part. The initial state for a
receive stream is "Recv".
The receive stream enters the "Recv" state when the sending part of a The receive stream enters the "Recv" state when the sending part of a
bidirectional stream initiated by the endpoint (type 0 for a client, bidirectional stream initiated by the endpoint (type 0 for a client,
type 1 for a server) enters the "Ready" state. type 1 for a server) enters the "Ready" state.
A bidirectional stream also opens when a MAX_STREAM_DATA frame is An endpoint opens a bidirectional stream when a MAX_STREAM_DATA or
received. Receiving a MAX_STREAM_DATA frame implies that the remote STOP_SENDING frame is received from the peer for that stream.
peer has opened the stream and is providing flow control credit. A
MAX_STREAM_DATA frame might arrive before a STREAM or STREAM_BLOCKED
frame if packets are lost or reordered.
Before creating a stream, all lower-numbered streams of the same type Receiving a MAX_STREAM_DATA frame for an unopened stream indicates
MUST be created. That means that receipt of a frame that would open that the remote peer has opened the stream and is providing flow
a stream causes all lower-numbered streams of the same type to be control credit. Receiving a STOP_SENDING frame for an unopened
opened in numeric order. This ensures that the creation order for stream indicates that the remote peer no longer wishes to receive
streams is consistent on both endpoints. data on this stream. Either frame might arrive before a STREAM or
STREAM_DATA_BLOCKED frame if packets are lost or reordered.
In the "Recv" state, the endpoint receives STREAM and STREAM_BLOCKED Before creating a stream, all streams of the same type with lower-
frames. Incoming data is buffered and can be reassembled into the numbered stream IDs MUST be created. This ensures that the creation
correct order for delivery to the application. As data is consumed order for streams is consistent on both endpoints.
by the application and buffer space becomes available, the endpoint
sends MAX_STREAM_DATA frames to allow the peer to send more data.
When a STREAM frame with a FIN bit is received, the final offset (see In the "Recv" state, the endpoint receives STREAM and
Section 4.3) is known. The receive stream enters the "Size Known" STREAM_DATA_BLOCKED frames. Incoming data is buffered and can be
reassembled into the correct order for delivery to the application.
As data is consumed by the application and buffer space becomes
available, the endpoint sends MAX_STREAM_DATA frames to allow the
peer to send more data.
When a STREAM frame with a FIN bit is received, the final offset is
known (see Section 4.4). The receive stream enters the "Size Known"
state. In this state, the endpoint no longer needs to send state. In this state, the endpoint no longer needs to send
MAX_STREAM_DATA frames, it only receives any retransmissions of MAX_STREAM_DATA frames, it only receives any retransmissions of
stream data. stream data.
Once all data for the stream has been received, the receive stream Once all data for the stream has been received, the receive stream
enters the "Data Recvd" state. This might happen as a result of enters the "Data Recvd" state. This might happen as a result of
receiving the same STREAM frame that causes the transition to "Size receiving the same STREAM frame that causes the transition to "Size
Known". In this state, the endpoint has all stream data. Any STREAM Known". In this state, the endpoint has all stream data. Any STREAM
or STREAM_BLOCKED frames it receives for the stream can be discarded. or STREAM_DATA_BLOCKED frames it receives for the stream can be
discarded.
The "Data Recvd" state persists until stream data has been delivered The "Data Recvd" state persists until stream data has been delivered
to the application or application protocol. Once stream data has to the application. Once stream data has been delivered, the stream
been delivered, the stream enters the "Data Read" state, which is a enters the "Data Read" state, which is a terminal state.
terminal state.
Receiving a RST_STREAM frame in the "Recv" or "Size Known" states Receiving a RESET_STREAM frame in the "Recv" or "Size Known" states
causes the stream to enter the "Reset Recvd" state. This might cause causes the stream to enter the "Reset Recvd" state. This might cause
the delivery of stream data to the application to be interrupted. the delivery of stream data to the application to be interrupted.
It is possible that all stream data is received when a RST_STREAM is It is possible that all stream data is received when a RESET_STREAM
received (that is, from the "Data Recvd" state). Similarly, it is is received (that is, from the "Data Recvd" state). Similarly, it is
possible for remaining stream data to arrive after receiving a possible for remaining stream data to arrive after receiving a
RST_STREAM frame (the "Reset Recvd" state). An implementation is RESET_STREAM frame (the "Reset Recvd" state). An implementation is
able to manage this situation as they choose. Sending RST_STREAM free to manage this situation as it chooses. Sending RESET_STREAM
means that an endpoint cannot guarantee delivery of stream data; means that an endpoint cannot guarantee delivery of stream data;
however there is no requirement that stream data not be delivered if however there is no requirement that stream data not be delivered if
a RST_STREAM is received. An implementation MAY interrupt delivery a RESET_STREAM is received. An implementation MAY interrupt delivery
of stream data, discard any data that was not consumed, and signal of stream data, discard any data that was not consumed, and signal
the existence of the RST_STREAM immediately. Alternatively, the the receipt of the RESET_STREAM immediately. Alternatively, the
RST_STREAM signal might be suppressed or withheld if stream data is RESET_STREAM signal might be suppressed or withheld if stream data is
completely received. In the latter case, the receive stream completely received and is buffered to be read by the application.
effectively transitions to "Data Recvd" from "Reset Recvd". In the latter case, the receive stream transitions from "Reset Recvd"
to "Data Recvd".
Once the application has been delivered the signal indicating that Once the application has been delivered the signal indicating that
the receive stream was reset, the receive stream transitions to the the receive stream was reset, the receive stream transitions to the
"Reset Read" state, which is a terminal state. "Reset Read" state, which is a terminal state.
3.3. Permitted Frame Types 3.3. Permitted Frame Types
The sender of a stream sends just three frame types that affect the The sender of a stream sends just three frame types that affect the
state of a stream at either sender or receiver: STREAM state of a stream at either sender or receiver: STREAM
(Section 19.19), STREAM_BLOCKED (Section 19.10), and RST_STREAM (Section 19.8), STREAM_DATA_BLOCKED (Section 19.13), and RESET_STREAM
(Section 19.2). (Section 19.4).
A sender MUST NOT send any of these frames from a terminal state A sender MUST NOT send any of these frames from a terminal state
("Data Recvd" or "Reset Recvd"). A sender MUST NOT send STREAM or ("Data Recvd" or "Reset Recvd"). A sender MUST NOT send STREAM or
STREAM_BLOCKED after sending a RST_STREAM; that is, in the "Reset STREAM_DATA_BLOCKED after sending a RESET_STREAM; that is, in the
Sent" state in addition to the terminal states. A receiver could terminal states and in the "Reset Sent" state. A receiver could
receive any of these frames in any state, but only due to the receive any of these three frames in any state, due to the
possibility of delayed delivery of packets carrying them. possibility of delayed delivery of packets carrying them.
The receiver of a stream sends MAX_STREAM_DATA (Section 19.6) and The receiver of a stream sends MAX_STREAM_DATA (Section 19.10) and
STOP_SENDING frames (Section 19.14). STOP_SENDING frames (Section 19.5).
The receiver only sends MAX_STREAM_DATA in the "Recv" state. A The receiver only sends MAX_STREAM_DATA in the "Recv" state. A
receiver can send STOP_SENDING in any state where it has not received receiver can send STOP_SENDING in any state where it has not received
a RST_STREAM frame; that is states other than "Reset Recvd" or "Reset a RESET_STREAM frame; that is states other than "Reset Recvd" or
Read". However there is little value in sending a STOP_SENDING frame "Reset Read". However there is little value in sending a
after all stream data has been received in the "Data Recvd" state. A STOP_SENDING frame in the "Data Recvd" state, since all stream data
sender could receive these frames in any state as a result of delayed has been received. A sender could receive either of these two frames
delivery of packets. in any state as a result of delayed delivery of packets.
3.4. Bidirectional Stream States 3.4. Bidirectional Stream States
A bidirectional stream is composed of a send stream and a receive A bidirectional stream is composed of a send stream and a receive
stream. Implementations may represent states of the bidirectional stream. Implementations may represent states of the bidirectional
stream as composites of send and receive stream states. The simplest stream as composites of send and receive stream states. The simplest
model presents the stream as "open" when either send or receive model presents the stream as "open" when either send or receive
stream is in a non-terminal state and "closed" when both send and stream is in a non-terminal state and "closed" when both send and
receive streams are in a terminal state. receive streams are in a terminal state.
skipping to change at page 19, line 50 skipping to change at page 18, line 4
Note (*1): A stream is considered "idle" if it has not yet been Note (*1): A stream is considered "idle" if it has not yet been
created, or if the receive stream is in the "Recv" state without created, or if the receive stream is in the "Recv" state without
yet having received any frames. yet having received any frames.
3.5. Solicited State Transitions 3.5. Solicited State Transitions
If an endpoint is no longer interested in the data it is receiving on If an endpoint is no longer interested in the data it is receiving on
a stream, it MAY send a STOP_SENDING frame identifying that stream to a stream, it MAY send a STOP_SENDING frame identifying that stream to
prompt closure of the stream in the opposite direction. This prompt closure of the stream in the opposite direction. This
typically indicates that the receiving application is no longer typically indicates that the receiving application is no longer
reading data it receives from the stream, but is not a guarantee that reading data it receives from the stream, but it is not a guarantee
incoming data will be ignored. that incoming data will be ignored.
STREAM frames received after sending STOP_SENDING are still counted STREAM frames received after sending STOP_SENDING are still counted
toward the connection and stream flow-control windows, even though toward connection and stream flow control, even though these frames
these frames will be discarded upon receipt. This avoids potential will be discarded upon receipt.
ambiguity about which STREAM frames count toward flow control.
A STOP_SENDING frame requests that the receiving endpoint send a A STOP_SENDING frame requests that the receiving endpoint send a
RST_STREAM frame. An endpoint that receives a STOP_SENDING frame RESET_STREAM frame. An endpoint that receives a STOP_SENDING frame
MUST send a RST_STREAM frame for that stream, and can use an error MUST send a RESET_STREAM frame for that stream. An endpoint SHOULD
code of STOPPING. If the STOP_SENDING frame is received on a send copy the error code from the STOP_SENDING frame, but MAY use any
stream that is already in the "Data Sent" state, a RST_STREAM frame application error code. The endpoint that sends a STOP_SENDING frame
MAY still be sent in order to cancel retransmission of previously- can ignore the error code carried in any RESET_STREAM frame it
sent STREAM frames. receives.
If the STOP_SENDING frame is received on a send stream that is
already in the "Data Sent" state, an endpoint that wishes to cease
retransmission of previously-sent STREAM frames on that stream MUST
first send a RESET_STREAM frame.
STOP_SENDING SHOULD only be sent for a receive stream that has not STOP_SENDING SHOULD only be sent for a receive stream that has not
been reset. STOP_SENDING is most useful for streams in the "Recv" or been reset. STOP_SENDING is most useful for streams in the "Recv" or
"Size Known" states. "Size Known" states.
An endpoint is expected to send another STOP_SENDING frame if a An endpoint is expected to send another STOP_SENDING frame if a
packet containing a previous STOP_SENDING is lost. However, once packet containing a previous STOP_SENDING is lost. However, once
either all stream data or a RST_STREAM frame has been received for either all stream data or a RESET_STREAM frame has been received for
the stream - that is, the stream is in any state other than "Recv" or the stream - that is, the stream is in any state other than "Recv" or
"Size Known" - sending a STOP_SENDING frame is unnecessary. "Size Known" - sending a STOP_SENDING frame is unnecessary.
An endpoint that wishes to terminate both directions of a
bidirectional stream can terminate one direction by sending a
RESET_STREAM, and it can encourage prompt termination in the opposite
direction by sending a STOP_SENDING frame.
4. Flow Control 4. Flow Control
It is necessary to limit the amount of data that a sender may have It is necessary to limit the amount of data that a receiver could
outstanding at any time, so as to prevent a fast sender from buffer, to prevent a fast sender from overwhelming a slow receiver,
overwhelming a slow receiver, or to prevent a malicious sender from or to prevent a malicious sender from consuming a large amount of
consuming significant resources at a receiver. To this end, QUIC memory at a receiver. To enable a receiver to limit memory
employs a credit-based flow-control scheme similar to that in HTTP/2 commitment to a connection and to apply back pressure on the sender,
[HTTP2]. A receiver advertises the number of octets it is prepared streams are flow controlled both individually and as an aggregate. A
to receive on a given stream and for the entire connection. This QUIC receiver controls the maximum amount of data the sender can send
leads to two levels of flow control in QUIC: on a stream at any time, as described in Section 4.1 and Section 4.2
Similarly, to limit concurrency within a connection, a QUIC endpoint
controls the maximum cumulative number of streams that its peer can
initiate, as described in Section 4.5.
Data sent in CRYPTO frames is not flow controlled in the same way as
stream data. QUIC relies on the cryptographic protocol
implementation to avoid excessive buffering of data, see [QUIC-TLS].
The implementation SHOULD provide an interface to QUIC to tell it
about its buffering limits so that there is not excessive buffering
at multiple layers.
4.1. Data Flow Control
QUIC employs a credit-based flow-control scheme similar to that in
HTTP/2 [HTTP2], where a receiver advertises the number of bytes it is
prepared to receive on a given stream and for the entire connection.
This leads to two levels of data flow control in QUIC:
o Stream flow control, which prevents a single stream from consuming o Stream flow control, which prevents a single stream from consuming
the entire receive buffer for a connection. the entire receive buffer for a connection by limiting the amount
of data that can be sent on any stream.
o Connection flow control, which prevents senders from exceeding a o Connection flow control, which prevents senders from exceeding a
receiver's buffer capacity for the connection, and receiver's buffer capacity for the connection, by limiting the
total bytes of stream data sent in STREAM frames on all streams.
A data receiver sets initial credits for all streams by sending
transport parameters during the handshake (Section 7.3).
A data receiver sends MAX_STREAM_DATA or MAX_DATA frames to the A receiver sets initial credits for all streams by sending transport
sender to advertise additional credit. MAX_STREAM_DATA frames send parameters during the handshake (Section 7.3). A receiver sends
the maximum absolute byte offset of a stream, while MAX_DATA frames MAX_STREAM_DATA (Section 19.10) or MAX_DATA (Section 19.9) frames to
send the maximum of the sum of the absolute byte offsets of all the sender to advertise additional credit.
streams.
A receiver advertises credit for a stream by sending a A receiver advertises credit for a stream by sending a
MAX_STREAM_DATA frame with the Stream ID set appropriately. A MAX_STREAM_DATA frame with the Stream ID field set appropriately. A
receiver could use the current offset of data consumed to determine MAX_STREAM_DATA frame indicates the maximum absolute byte offset of a
the flow control offset to be advertised. A receiver MAY send stream. A receiver could use the current offset of data consumed to
MAX_STREAM_DATA frames in multiple packets in order to make sure that determine the flow control offset to be advertised. A receiver MAY
the sender receives an update before running out of flow control send MAX_STREAM_DATA frames in multiple packets in order to make sure
that the sender receives an update before running out of flow control
credit, even if one of the packets is lost. credit, even if one of the packets is lost.
Connection flow control is a limit to the total bytes of stream data A receiver advertises credit for a connection by sending a MAX_DATA
sent in STREAM frames on all streams. A receiver advertises credit frame, which indicates the maximum of the sum of the absolute byte
for a connection by sending a MAX_DATA frame. A receiver maintains a offsets of all streams. A receiver maintains a cumulative sum of
cumulative sum of bytes received on all contributing streams, which bytes received on all streams, which is used to check for flow
are used to check for flow control violations. A receiver might use control violations. A receiver might use a sum of bytes consumed on
a sum of bytes consumed on all streams to determine the maximum data all streams to determine the maximum data limit to be advertised.
limit to be advertised.
A receiver MAY advertise a larger offset at any point by sending A receiver can advertise a larger offset by sending MAX_STREAM_DATA
MAX_STREAM_DATA or MAX_DATA frames. A receiver cannot renege on an or MAX_DATA frames at any time during the connection. A receiver
advertisement; that is, once a receiver advertises an offset, cannot renege on an advertisement however. That is, once a receiver
advertising a smaller offset has no effect. A sender MUST therefore advertises an offset, it MAY advertise a smaller offset, but this has
ignore any MAX_STREAM_DATA or MAX_DATA frames that do not increase no effect.
flow control limits.
A receiver MUST close the connection with a FLOW_CONTROL_ERROR error A receiver MUST close the connection with a FLOW_CONTROL_ERROR error
(Section 11) if the peer violates the advertised connection or stream (Section 11) if the sender violates the advertised connection or
data limits. stream data limits.
A sender SHOULD send STREAM_BLOCKED or BLOCKED frames to indicate it
has data to write but is blocked by flow control limits. These
frames are expected to be sent infrequently in common cases, but they
are considered useful for debugging and monitoring purposes.
A similar method is used to control the number of open streams (see
Section 4.5 for details).
4.1. Handling of Stream Cancellation
There are some edge cases which must be considered when dealing with
stream and connection level flow control. Given enough time, both
endpoints must agree on flow control state. If one end believes it
can send more than the other end is willing to receive, the
connection will be torn down when too much data arrives. Conversely
if a sender believes it is blocked, while endpoint B expects more
data can be received, then the connection can be in a deadlock, with
the sender waiting for a MAX_STREAM_DATA or MAX_DATA frame which will
never come.
On receipt of a RST_STREAM frame, an endpoint will tear down state
for the matching stream and ignore further data arriving on that
stream. This could result in the endpoints getting out of sync,
since the RST_STREAM frame may have arrived out of order and there
may be further bytes in flight. The data sender would have counted
the data against its connection level flow control budget, but a
receiver that has not received these bytes would not know to include
them as well. The receiver must learn the number of bytes that were
sent on the stream to make the same adjustment in its connection flow
controller.
To ensure that endpoints maintain a consistent connection-level flow A sender MUST ignore any MAX_STREAM_DATA or MAX_DATA frames that do
control state, the RST_STREAM frame (Section 19.2) includes the not increase flow control limits.
largest offset of data sent on the stream. On receiving a RST_STREAM
frame, a receiver definitively knows how many bytes were sent on that
stream before the RST_STREAM frame, and the receiver MUST use the
final offset to account for all bytes sent on the stream in its
connection level flow controller.
RST_STREAM terminates one direction of a stream abruptly. Whether If a sender runs out of flow control credit, it will be unable to
any action or response can or should be taken on the data already send new data and is considered blocked. A sender SHOULD send
received is application specific. STREAM_DATA_BLOCKED or DATA_BLOCKED frames to indicate it has data to
write but is blocked by flow control limits. These frames are
expected to be sent infrequently in common cases, but they are
considered useful for debugging and monitoring purposes.
For a bidirectional stream, RST_STREAM has no effect on data flow in A sender sends a single STREAM_DATA_BLOCKED or DATA_BLOCKED frame
the opposite direction. The RST_STREAM sender can send a only once when it reaches a data limit. A sender SHOULD NOT send
STOP_SENDING frame to encourage prompt termination. Both endpoints multiple STREAM_DATA_BLOCKED or DATA_BLOCKED frames for the same data
MUST maintain state for the stream in the unterminated direction limit, unless the original frame is determined to be lost. Another
until that direction enters a terminal state, or either side sends STREAM_DATA_BLOCKED or DATA_BLOCKED frame can be sent after the data
CONNECTION_CLOSE or APPLICATION_CLOSE. limit is increased.
4.2. Data Limit Increments 4.2. Flow Credit Increments
This document leaves when and how many bytes to advertise in a This document leaves when and how many bytes to advertise in a
MAX_DATA or MAX_STREAM_DATA to implementations, but offers a few MAX_STREAM_DATA or MAX_DATA frame to implementations, but offers a
considerations. These frames contribute to connection overhead. few considerations. These frames contribute to connection overhead.
Therefore frequently sending frames with small changes is Therefore frequently sending frames with small changes is
undesirable. At the same time, larger increments to limits are undesirable. At the same time, larger increments to limits are
necessary to avoid blocking if updates are less frequent, requiring necessary to avoid blocking if updates are less frequent, requiring
larger resource commitments at the receiver. Thus there is a trade- larger resource commitments at the receiver. Thus there is a trade-
off between resource commitment and overhead when determining how off between resource commitment and overhead when determining how
large a limit is advertised. large a limit is advertised.
A receiver MAY use an autotuning mechanism to tune the frequency and A receiver MAY use an autotuning mechanism to tune the frequency and
amount that it increases data limits based on a round-trip time amount of advertised additional credit based on a round-trip time
estimate and the rate at which the receiving application consumes estimate and the rate at which the receiving application consumes
data, similar to common TCP implementations. data, similar to common TCP implementations.
If a sender runs out of flow control credit, it will be unable to If a sender runs out of flow control credit, it will be unable to
send new data. That is, the sender is blocked. A blocked sender send new data and is considered blocked. It is generally considered
SHOULD send a STREAM_BLOCKED or BLOCKED frame. A receiver uses these best to not let the sender become blocked. To avoid blocking a
frames for debugging purposes. A receiver MUST NOT wait for a sender, and to reasonably account for the possibility of loss, a
STREAM_BLOCKED or BLOCKED frame before sending MAX_STREAM_DATA or receiver should send a MAX_DATA or MAX_STREAM_DATA frame at least two
MAX_DATA, since doing so will mean that a sender will be blocked for round trips before it expects the sender to get blocked.
an entire round trip and the peer may never send a STREAM_BLOCKED or
BLOCKED frame.
It is generally considered best to not let the sender go into A receiver MUST NOT wait for a STREAM_DATA_BLOCKED or DATA_BLOCKED
quiescence if avoidable. To avoid blocking a sender, and to frame before sending MAX_STREAM_DATA or MAX_DATA, since doing so will
reasonably account for the possibility of loss, a receiver should mean that a sender will be blocked for at least an entire round trip,
send a MAX_DATA or MAX_STREAM_DATA frame at least two round trips and potentially for longer if the peer chooses to not send
before it expects the sender to get blocked. STREAM_DATA_BLOCKED or DATA_BLOCKED frames.
A sender sends a single BLOCKED or STREAM_BLOCKED frame only once 4.3. Handling Stream Cancellation
when it reaches a data limit. A sender SHOULD NOT send multiple
BLOCKED or STREAM_BLOCKED frames for the same data limit, unless the
original frame is determined to be lost. Another BLOCKED or
STREAM_BLOCKED frame can be sent after the data limit is increased.
4.3. Stream Final Offset Endpoints need to eventually agree on the amount of flow control
credit that has been consumed, to avoid either exceeding flow control
limits or deadlocking.
The final offset is the count of the number of octets that are On receipt of a RESET_STREAM frame, an endpoint will tear down state
for the matching stream and ignore further data arriving on that
stream. If a RESET_STREAM frame is reordered with stream data for
the same stream, the receiver's estimate of the number of bytes
received on that stream can be lower than the sender's estimate of
the number sent. As a result, the two endpoints could disagree on
the number of bytes that count towards connection flow control.
To remedy this issue, a RESET_STREAM frame (Section 19.4) includes
the final offset of data sent on the stream. On receiving a
RESET_STREAM frame, a receiver definitively knows how many bytes were
sent on that stream before the RESET_STREAM frame, and the receiver
MUST use the final offset to account for all bytes sent on the stream
in its connection level flow controller.
RESET_STREAM terminates one direction of a stream abruptly. For a
bidirectional stream, RESET_STREAM has no effect on data flow in the
opposite direction. Both endpoints MUST maintain flow control state
for the stream in the unterminated direction until that direction
enters a terminal state, or until one of the endpoints sends
CONNECTION_CLOSE.
4.4. Stream Final Offset
The final offset is the count of the number of bytes that are
transmitted on a stream. For a stream that is reset, the final transmitted on a stream. For a stream that is reset, the final
offset is carried explicitly in a RST_STREAM frame. Otherwise, the offset is carried explicitly in a RESET_STREAM frame. Otherwise, the
final offset is the offset of the end of the data carried in a STREAM final offset is the offset of the end of the data carried in a STREAM
frame marked with a FIN flag, or 0 in the case of incoming frame marked with a FIN flag, or 0 in the case of incoming
unidirectional streams. unidirectional streams.
An endpoint will know the final offset for a stream when the receive An endpoint will know the final offset for a stream when the receive
stream enters the "Size Known" or "Reset Recvd" state. stream enters the "Size Known" or "Reset Recvd" state (Section 3).
An endpoint MUST NOT send data on a stream at or beyond the final An endpoint MUST NOT send data on a stream at or beyond the final
offset. offset.
Once a final offset for a stream is known, it cannot change. If a Once a final offset for a stream is known, it cannot change. If a
RST_STREAM or STREAM frame causes the final offset to change for a RESET_STREAM or STREAM frame is received indicating a change in the
stream, an endpoint SHOULD respond with a FINAL_OFFSET_ERROR error final offset for the stream, an endpoint SHOULD respond with a
(see Section 11). A receiver SHOULD treat receipt of data at or FINAL_OFFSET_ERROR error (see Section 11). A receiver SHOULD treat
beyond the final offset as a FINAL_OFFSET_ERROR error, even after a receipt of data at or beyond the final offset as a FINAL_OFFSET_ERROR
stream is closed. Generating these errors is not mandatory, but only error, even after a stream is closed. Generating these errors is not
because requiring that an endpoint generate these errors also means mandatory, but only because requiring that an endpoint generate these
that the endpoint needs to maintain the final offset state for closed errors also means that the endpoint needs to maintain the final
streams, which could mean a significant state commitment. offset state for closed streams, which could mean a significant state
commitment.
4.4. Flow Control for Cryptographic Handshake 4.5. Controlling Concurrency
Data sent in CRYPTO frames is not flow controlled in the same way as An endpoint limits the cumulative number of incoming streams a peer
STREAM frames. QUIC relies on the cryptographic protocol can open. Only streams with a stream ID less than (max_stream * 4 +
implementation to avoid excessive buffering of data, see [QUIC-TLS]. initial_stream_id_for_type) can be opened (see Table 5). Initial
The implementation SHOULD provide an interface to QUIC to tell it limits are set in the transport parameters (see Section 18.1) and
about its buffering limits so that there is not excessive buffering subsequently limits are advertised using MAX_STREAMS frames
at multiple layers. (Section 19.11). Separate limits apply to unidirectional and
bidirectional streams.
4.5. Stream Limit Increment Endpoints MUST NOT exceed the limit set by their peer. An endpoint
that receives a STREAM frame with a stream ID exceeding the limit it
has sent MUST treat this as a stream error of type STREAM_LIMIT_ERROR
(Section 11).
An endpoint limits the number of concurrently active incoming streams A receiver cannot renege on an advertisement. That is, once a
by limiting the maximum stream ID. An initial value is set in the receiver advertises a stream limit using the MAX_STREAMS frame,
transport parameters (see Section 18.1) and is subsequently increased advertising a smaller limit has no effect. A receiver MUST ignore
by MAX_STREAM_ID frames (see Section 19.7). any MAX_STREAMS frame that does not increase the stream limit.
As with stream and connection flow control, this document leaves when As with stream and connection flow control, this document leaves when
and how many streams to make available to a peer via MAX_STREAM_ID to and how many streams to advertise to a peer via MAX_STREAMS to
implementations, but offers a few considerations. MAX_STREAM_ID implementations. Implementations might choose to increase limits as
frames constitute minimal overhead, while withholding MAX_STREAM_ID streams close to keep the number of streams available to peers
frames can prevent the peer from using the available parallelism. roughly consistent.
The STREAM_ID_BLOCKED frame (Section 19.11) can be used to signal a An endpoint that is unable to open a new stream due to the peer's
shortage of available streams. Implementations will likely want to limits SHOULD send a STREAMS_BLOCKED frame (Section 19.14). This
increase the maximum stream ID as peer-initiated streams close. signal is considered useful for debugging. An endpoint MUST NOT wait
to receive this signal before advertising additional credit, since
doing so will mean that the peer will be blocked for at least an
entire round trip, and potentially for longer if the peer chooses to
not send STREAMS_BLOCKED frames.
5. Connections 5. Connections
A QUIC connection is a single conversation between two QUIC QUIC's connection establishment combines version negotiation with the
endpoints. QUIC's connection establishment combines version cryptographic and transport handshakes to reduce connection
negotiation with the cryptographic and transport handshakes to reduce establishment latency, as described in Section 7. Once established,
connection establishment latency, as described in Section 7. Once a connection may migrate to a different IP or port at either endpoint
established, a connection may migrate to a different IP or port at as described in Section 9. Finally, a connection may be terminated
either endpoint as described in Section 9. Finally, a connection may by either endpoint, as described in Section 10.
be terminated by either endpoint, as described in Section 10.
5.1. Connection ID 5.1. Connection ID
Each connection possesses a set of connection identifiers, or Each connection possesses a set of connection identifiers, or
connection IDs, each of which can be identify the connection. connection IDs, each of which can identify the connection.
Connection IDs are independently selected by endpoints; each endpoint Connection IDs are independently selected by endpoints; each endpoint
selects the connection IDs that its peer uses. selects the connection IDs that its peer uses.
The primary function of a connection ID is to ensure that changes in The primary function of a connection ID is to ensure that changes in
addressing at lower protocol layers (UDP, IP, and below) don't cause addressing at lower protocol layers (UDP, IP) don't cause packets for
packets for a QUIC connection to be delivered to the wrong endpoint. a QUIC connection to be delivered to the wrong endpoint. Each
Each endpoint selects connection IDs using an implementation-specific endpoint selects connection IDs using an implementation-specific (and
(and perhaps deployment-specific) method which will allow packets perhaps deployment-specific) method which will allow packets with
with that connection ID to be routed back to the endpoint and that connection ID to be routed back to the endpoint and identified
identified by the endpoint upon receipt. by the endpoint upon receipt.
Connection IDs MUST NOT contain any information that can be used to Connection IDs MUST NOT contain any information that can be used by
correlate them with other connection IDs for the same connection. As an external observer to correlate them with other connection IDs for
a trivial example, this means the same connection ID MUST NOT be the same connection. As a trivial example, this means the same
issued more than once on the same connection. connection ID MUST NOT be issued more than once on the same
connection.
Packets with long headers include Source Connection ID and Packets with long headers include Source Connection ID and
Destination Connection ID fields. These fields are used to set the Destination Connection ID fields. These fields are used to set the
connection IDs for new connections, see Section 7.2 for details. connection IDs for new connections, see Section 7.2 for details.
Packets with short headers (Section 17.3) only include the Packets with short headers (Section 17.3) only include the
Destination Connection ID and omit the explicit length. The length Destination Connection ID and omit the explicit length. The length
of the Destination Connection ID field is expected to be known to of the Destination Connection ID field is expected to be known to
endpoints. Endpoints using a load balancer that routes based on endpoints. Endpoints using a load balancer that routes based on
connection ID could agree with the load balancer on a fixed length connection ID could agree with the load balancer on a fixed length
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needed for routing and the address/port tuple of packets is needed for routing and the address/port tuple of packets is
sufficient to identify a connection. An endpoint whose peer has sufficient to identify a connection. An endpoint whose peer has
selected a zero-length connection ID MUST continue to use a zero- selected a zero-length connection ID MUST continue to use a zero-
length connection ID for the lifetime of the connection and MUST NOT length connection ID for the lifetime of the connection and MUST NOT
send packets from any other local address. send packets from any other local address.
When an endpoint has requested a non-zero-length connection ID, it When an endpoint has requested a non-zero-length connection ID, it
needs to ensure that the peer has a supply of connection IDs from needs to ensure that the peer has a supply of connection IDs from
which to choose for packets sent to the endpoint. These connection which to choose for packets sent to the endpoint. These connection
IDs are supplied by the endpoint using the NEW_CONNECTION_ID frame IDs are supplied by the endpoint using the NEW_CONNECTION_ID frame
(Section 19.12). (Section 19.15).
5.1.1. Issuing Connection IDs 5.1.1. Issuing Connection IDs
Each Connection ID has an associated sequence number to assist in Each Connection ID has an associated sequence number to assist in
deduplicating messages. The initial connection ID issued by an deduplicating messages. The initial connection ID issued by an
endpoint is sent in the Source Connection ID field of the long packet endpoint is sent in the Source Connection ID field of the long packet
header (Section 17.2) during the handshake. The sequence number of header (Section 17.2) during the handshake. The sequence number of
the initial connection ID is 0. If the preferred_address transport the initial connection ID is 0. If the preferred_address transport
parameter is sent, the sequence number of the supplied connection ID parameter is sent, the sequence number of the supplied connection ID
is 1. is 1.
Additional connection IDs are communicated to the peer using Additional connection IDs are communicated to the peer using
NEW_CONNECTION_ID frames (Section 19.12). The sequence number on NEW_CONNECTION_ID frames (Section 19.15). The sequence number on
each newly-issued connection ID MUST increase by 1. The connection each newly-issued connection ID MUST increase by 1. The connection
ID randomly selected by the client in the Initial packet and any ID randomly selected by the client in the Initial packet and any
connection ID provided by a Reset packet are not assigned sequence connection ID provided by a Retry packet are not assigned sequence
numbers unless a server opts to retain them as its initial connection numbers unless a server opts to retain them as its initial connection
ID. ID.
When an endpoint issues a connection ID, it MUST accept packets that When an endpoint issues a connection ID, it MUST accept packets that
carry this connection ID for the duration of the connection or until carry this connection ID for the duration of the connection or until
its peer invalidates the connection ID via a RETIRE_CONNECTION_ID its peer invalidates the connection ID via a RETIRE_CONNECTION_ID
frame (Section 19.13). frame (Section 19.16).
Endpoints store received connection IDs for future use. An endpoint
that receives excessive connection IDs MAY discard those it cannot
store without sending a RETIRE_CONNECTION_ID frame. An endpoint that
issues connection IDs cannot expect its peer to store and use all
issued connection IDs.
An endpoint SHOULD ensure that its peer has a sufficient number of An endpoint SHOULD ensure that its peer has a sufficient number of
available and unused connection IDs. While each endpoint available and unused connection IDs. While each endpoint
independently chooses how many connection IDs to issue, endpoints independently chooses how many connection IDs to issue, endpoints
SHOULD provide and maintain at least eight connection IDs. The SHOULD provide and maintain at least eight connection IDs. The
endpoint can do this by always supplying a new connection ID when a endpoint SHOULD do this by always supplying a new connection ID when
connection ID is retired by its peer or when the endpoint receives a a connection ID is retired by its peer or when the endpoint receives
packet with a previously unused connection ID. Endpoints that a packet with a previously unused connection ID. Endpoints that
initiate migration and require non-zero-length connection IDs SHOULD initiate migration and require non-zero-length connection IDs SHOULD
provide their peers with new connection IDs before migration, or risk provide their peers with new connection IDs before migration, or risk
the peer closing the connection. the peer closing the connection.
5.1.2. Consuming and Retiring Connection IDs 5.1.2. Consuming and Retiring Connection IDs
An endpoint can change the connection ID it uses for a peer to An endpoint can change the connection ID it uses for a peer to
another available one at any time during the connection. An endpoint another available one at any time during the connection. An endpoint
consumes connection IDs in response to a migrating peer, see consumes connection IDs in response to a migrating peer, see
Section 9.5 for more. Section 9.5 for more.
An endpoint maintains a set of connection IDs received from its peer, An endpoint maintains a set of connection IDs received from its peer,
any of which it can use when sending packets. When the endpoint any of which it can use when sending packets. When the endpoint
wishes to remove a connection ID from use, it sends a wishes to remove a connection ID from use, it sends a
RETIRE_CONNECTION_ID frame to its peer, indicating that the peer RETIRE_CONNECTION_ID frame to its peer. Sending a
might bring a new connection ID into circulation using the RETIRE_CONNECTION_ID frame indicates that the connection ID won't be
NEW_CONNECTION_ID frame. used again and requests that the peer replace it with a new
connection ID using a NEW_CONNECTION_ID frame.
An endpoint that retires a connection ID can retain knowledge of that
connection ID for a period of time after sending the
RETIRE_CONNECTION_ID frame, or until that frame is acknowledged.
As discussed in Section 9.5, each connection ID MUST be used on As discussed in Section 9.5, each connection ID MUST be used on
packets sent from only one local address. An endpoint that migrates packets sent from only one local address. An endpoint that migrates
away from a local address SHOULD retire all connection IDs used on away from a local address SHOULD retire all connection IDs used on
that address once it no longer plans to use that address. that address once it no longer plans to use that address.
5.2. Matching Packets to Connections 5.2. Matching Packets to Connections
Incoming packets are classified on receipt. Packets can either be Incoming packets are classified on receipt. Packets can either be
associated with an existing connection, or - for servers - associated with an existing connection, or - for servers -
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than one connection ID can be associated with a connection; see than one connection ID can be associated with a connection; see
Section 5.1. Section 5.1.
If the Destination Connection ID is zero length and the packet If the Destination Connection ID is zero length and the packet
matches the address/port tuple of a connection where the host did not matches the address/port tuple of a connection where the host did not
require connection IDs, QUIC processes the packet as part of that require connection IDs, QUIC processes the packet as part of that
connection. Endpoints MUST drop packets with zero-length Destination connection. Endpoints MUST drop packets with zero-length Destination
Connection ID fields if they do not correspond to a single Connection ID fields if they do not correspond to a single
connection. connection.
Endpoints SHOULD send a Stateless Reset (Section 10.4) for any Endpoints can send a Stateless Reset (Section 10.4) for any packets
packets that cannot be attributed to an existing connection. that cannot be attributed to an existing connection. A stateless
reset allows a peer to more quickly identify when a connection
becomes unusable.
Packets that are matched to an existing connection, but for which the Packets that are matched to an existing connection, but for which the
endpoint cannot remove packet protection, are discarded. endpoint cannot remove packet protection, are discarded.
5.2.1. Client Packet Handling 5.2.1. Client Packet Handling
Valid packets sent to clients always include a Destination Connection Valid packets sent to clients always include a Destination Connection
ID that matches a value the client selects. Clients that choose to ID that matches a value the client selects. Clients that choose to
receive zero-length connection IDs can use the address/port tuple to receive zero-length connection IDs can use the address/port tuple to
identify a connection. Packets that don't match an existing identify a connection. Packets that don't match an existing
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multiple QUIC versions SHOULD pad the first packet they send to the multiple QUIC versions SHOULD pad the first packet they send to the
largest of the minimum packet sizes across all versions they support. largest of the minimum packet sizes across all versions they support.
This ensures that the server responds if there is a mutually This ensures that the server responds if there is a mutually
supported version. supported version.
6.1. Sending Version Negotiation Packets 6.1. Sending Version Negotiation Packets
If the version selected by the client is not acceptable to the If the version selected by the client is not acceptable to the
server, the server responds with a Version Negotiation packet (see server, the server responds with a Version Negotiation packet (see
Section 17.4). This includes a list of versions that the server will Section 17.4). This includes a list of versions that the server will
accept. accept. An endpoint MUST NOT send a Version Negotiation packet in
response to receiving a Version Negotiation packet.
This system allows a server to process packets with unsupported This system allows a server to process packets with unsupported
versions without retaining state. Though either the Initial packet versions without retaining state. Though either the Initial packet
or the Version Negotiation packet that is sent in response could be or the Version Negotiation packet that is sent in response could be
lost, the client will send new packets until it successfully receives lost, the client will send new packets until it successfully receives
a response or it abandons the connection attempt. a response or it abandons the connection attempt.
A server MAY limit the number of Version Negotiation packets it A server MAY limit the number of Version Negotiation packets it
sends. For instance, a server that is able to recognize packets as sends. For instance, a server that is able to recognize packets as
0-RTT might choose not to send Version Negotiation packets in 0-RTT might choose not to send Version Negotiation packets in
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reserved version numbers in the Version Negotiation Packet and in its reserved version numbers in the Version Negotiation Packet and in its
transport parameters. transport parameters.
A client MAY send a packet using a reserved version number. This can A client MAY send a packet using a reserved version number. This can
be used to solicit a list of supported versions from a server. be used to solicit a list of supported versions from a server.
7. Cryptographic and Transport Handshake 7. Cryptographic and Transport Handshake
QUIC relies on a combined cryptographic and transport handshake to QUIC relies on a combined cryptographic and transport handshake to
minimize connection establishment latency. QUIC uses the CRYPTO minimize connection establishment latency. QUIC uses the CRYPTO
frame Section 19.20 to transmit the cryptographic handshake. Version frame Section 19.6 to transmit the cryptographic handshake. Version
0x00000001 of QUIC uses TLS 1.3 as described in [QUIC-TLS]; a 0x00000001 of QUIC uses TLS as described in [QUIC-TLS]; a different
different QUIC version number could indicate that a different QUIC version number could indicate that a different cryptographic
cryptographic handshake protocol is in use. handshake protocol is in use.
QUIC provides reliable, ordered delivery of the cryptographic QUIC provides reliable, ordered delivery of the cryptographic
handshake data. QUIC packet protection ensures confidentiality and handshake data. QUIC packet protection is used to encrypt as much of
integrity protection that meets the requirements of the cryptographic the handshake protocol as possible. The cryptographic handshake MUST
handshake protocol: provide the following properties:
o authenticated key exchange, where o authenticated key exchange, where
* a server is always authenticated, * a server is always authenticated,
* a client is optionally authenticated, * a client is optionally authenticated,
* every connection produces distinct and unrelated keys, * every connection produces distinct and unrelated keys,
* keying material is usable for packet protection for both 0-RTT * keying material is usable for packet protection for both 0-RTT
and 1-RTT packets, and and 1-RTT packets, and
* 1-RTT keys have forward secrecy * 1-RTT keys have forward secrecy
o authenticated values for the transport parameters of the peer (see o authenticated values for the transport parameters of the peer (see
Section 7.3) Section 7.3)
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o authenticated negotiation of an application protocol (TLS uses o authenticated negotiation of an application protocol (TLS uses
ALPN [RFC7301] for this purpose) ALPN [RFC7301] for this purpose)
The first CRYPTO frame from a client MUST be sent in a single packet. The first CRYPTO frame from a client MUST be sent in a single packet.
Any second attempt that is triggered by address validation (see Any second attempt that is triggered by address validation (see
Section 8.1) MUST also be sent within a single packet. This avoids Section 8.1) MUST also be sent within a single packet. This avoids
having to reassemble a message from multiple packets. having to reassemble a message from multiple packets.
The first client packet of the cryptographic handshake protocol MUST The first client packet of the cryptographic handshake protocol MUST
fit within a 1232 octet QUIC packet payload. This includes overheads fit within a 1232 byte QUIC packet payload. This includes overheads
that reduce the space available to the cryptographic handshake that reduce the space available to the cryptographic handshake
protocol. protocol.
An endpoint can verify support for Explicit Congestion Notification
(ECN) in the first packets it sends, as described in Section 13.3.2.
The CRYPTO frame can be sent in different packet number spaces. The The CRYPTO frame can be sent in different packet number spaces. The
sequence numbers used by CRYPTO frames to ensure ordered delivery of sequence numbers used by CRYPTO frames to ensure ordered delivery of
cryptographic handshake data start from zero in each packet number cryptographic handshake data start from zero in each packet number
space. space.
7.1. Example Handshake Flows 7.1. Example Handshake Flows
Details of how TLS is integrated with QUIC are provided in Details of how TLS is integrated with QUIC are provided in
[QUIC-TLS], but some examples are provided here. An extension of [QUIC-TLS], but some examples are provided here. An extension of
this exchange to support client address validation is shown in this exchange to support client address validation is shown in
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used to establish the connection ID that each endpoint uses. Each used to establish the connection ID that each endpoint uses. Each
endpoint uses the Source Connection ID field to specify the endpoint uses the Source Connection ID field to specify the
connection ID that is used in the Destination Connection ID field of connection ID that is used in the Destination Connection ID field of
packets being sent to them. Upon receiving a packet, each endpoint packets being sent to them. Upon receiving a packet, each endpoint
sets the Destination Connection ID it sends to match the value of the sets the Destination Connection ID it sends to match the value of the
Source Connection ID that they receive. Source Connection ID that they receive.
When an Initial packet is sent by a client which has not previously When an Initial packet is sent by a client which has not previously
received a Retry packet from the server, it populates the Destination received a Retry packet from the server, it populates the Destination
Connection ID field with an unpredictable value. This MUST be at Connection ID field with an unpredictable value. This MUST be at
least 8 octets in length. Until a packet is received from the least 8 bytes in length. Until a packet is received from the server,
server, the client MUST use the same value unless it abandons the the client MUST use the same value unless it abandons the connection
connection attempt and starts a new one. The initial Destination attempt and starts a new one. The initial Destination Connection ID
Connection ID is used to determine packet protection keys for Initial is used to determine packet protection keys for Initial packets.
packets.
The final version used for a connection might be different from the
version of the first Initial from the client. To enable consistent
routing through the handshake, a client SHOULD select an initial
Destination Connection ID length long enough to fulfill the minimum
size for every QUIC version it supports.
The client populates the Source Connection ID field with a value of The client populates the Source Connection ID field with a value of
its choosing and sets the SCIL field to match. its choosing and sets the SCIL field to match.
The Destination Connection ID field in the server's Initial packet The Destination Connection ID field in the server's Initial packet
contains a connection ID that is chosen by the recipient of the contains a connection ID that is chosen by the recipient of the
packet (i.e., the client); the Source Connection ID includes the packet (i.e., the client); the Source Connection ID includes the
connection ID that the sender of the packet wishes to use (see connection ID that the sender of the packet wishes to use (see
Section 5.1). The server MUST use consistent Source Connection IDs Section 5.1). The server MUST use consistent Source Connection IDs
during the handshake. during the handshake.
On first receiving an Initial or Retry packet from the server, the On first receiving an Initial or Retry packet from the server, the
client uses the Source Connection ID supplied by the server as the client uses the Source Connection ID supplied by the server as the
Destination Connection ID for subsequent packets. That means that a Destination Connection ID for subsequent packets. That means that a
client might change the Destination Connection ID twice during client might change the Destination Connection ID twice during
connection establishment. Once a client has received an Initial connection establishment, once in response to a Retry and once in
packet from the server, it MUST discard any packet it receives with a response to the first Initial packet from the server. Once a client
different Source Connection ID. has received an Initial packet from the server, it MUST discard any
packet it receives with a different Source Connection ID.
A client MUST only change the value it sends in the Destination A client MUST only change the value it sends in the Destination
Connection ID in response to the first packet of each type it Connection ID in response to the first packet of each type it
receives from the server (Retry or Initial); a server MUST set its receives from the server (Retry or Initial); a server MUST set its
value based on the Initial packet. Any additional changes are not value based on the Initial packet. Any additional changes are not
permitted; if subsequent packets of those types include a different permitted; if subsequent packets of those types include a different
Source Connection ID, they MUST be discarded. This avoids problems Source Connection ID, they MUST be discarded. This avoids problems
that might arise from stateless processing of multiple Initial that might arise from stateless processing of multiple Initial
packets producing different connection IDs. packets producing different connection IDs.
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be validated (see Section 7.3.3) before the connection establishment be validated (see Section 7.3.3) before the connection establishment
is considered properly complete. is considered properly complete.
Definitions for each of the defined transport parameters are included Definitions for each of the defined transport parameters are included
in Section 18.1. Any given parameter MUST appear at most once in a in Section 18.1. Any given parameter MUST appear at most once in a
given transport parameters extension. An endpoint MUST treat receipt given transport parameters extension. An endpoint MUST treat receipt
of duplicate transport parameters as a connection error of type of duplicate transport parameters as a connection error of type
TRANSPORT_PARAMETER_ERROR. TRANSPORT_PARAMETER_ERROR.
A server MUST include the original_connection_id transport parameter A server MUST include the original_connection_id transport parameter
(Section 18.1) if it sent a Retry packet. (Section 18.1) if it sent a Retry packet to enable validation of the
Retry, as described in Section 17.7.
7.3.1. Values of Transport Parameters for 0-RTT 7.3.1. Values of Transport Parameters for 0-RTT
A client that attempts to send 0-RTT data MUST remember the transport A client that attempts to send 0-RTT data MUST remember the transport
parameters used by the server. The transport parameters that the parameters used by the server. The transport parameters that the
server advertises during connection establishment apply to all server advertises during connection establishment apply to all
connections that are resumed using the keying material established connections that are resumed using the keying material established
during that handshake. Remembered transport parameters apply to the during that handshake. Remembered transport parameters apply to the
new connection until the handshake completes and new transport new connection until the handshake completes and new transport
parameters from the server can be provided. parameters from the server can be provided.
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A server can remember the transport parameters that it advertised, or A server can remember the transport parameters that it advertised, or
store an integrity-protected copy of the values in the ticket and store an integrity-protected copy of the values in the ticket and
recover the information when accepting 0-RTT data. A server uses the recover the information when accepting 0-RTT data. A server uses the
transport parameters in determining whether to accept 0-RTT data. transport parameters in determining whether to accept 0-RTT data.
A server MAY accept 0-RTT and subsequently provide different values A server MAY accept 0-RTT and subsequently provide different values
for transport parameters for use in the new connection. If 0-RTT for transport parameters for use in the new connection. If 0-RTT
data is accepted by the server, the server MUST NOT reduce any limits data is accepted by the server, the server MUST NOT reduce any limits
or alter any values that might be violated by the client with its or alter any values that might be violated by the client with its
0-RTT data. In particular, a server that accepts 0-RTT data MUST NOT 0-RTT data. In particular, a server that accepts 0-RTT data MUST NOT
set values for initial_max_data, initial_max_stream_data_bidi_local, set values for the following parameters (Section 18.1) that are
initial_max_stream_data_bidi_remote, initial_max_stream_data_uni, smaller than the remembered value of those parameters.
initial_max_bidi_streams, or initial_max_uni_streams (Section 18.1)
that are smaller than the remembered value of those parameters. o initial_max_data
o initial_max_stream_data_bidi_local
o initial_max_stream_data_bidi_remote
o initial_max_stream_data_uni
o initial_max_streams_bidi
o initial_max_streams_uni
Omitting or setting a zero value for certain transport parameters can Omitting or setting a zero value for certain transport parameters can
result in 0-RTT data being enabled, but not usable. The applicable result in 0-RTT data being enabled, but not usable. The applicable
subset of transport parameters that permit sending of application subset of transport parameters that permit sending of application
data SHOULD be set to non-zero values for 0-RTT. This includes data SHOULD be set to non-zero values for 0-RTT. This includes
initial_max_data and either initial_max_bidi_streams and initial_max_data and either initial_max_streams_bidi and
initial_max_stream_data_bidi_remote, or initial_max_uni_streams and initial_max_stream_data_bidi_remote, or initial_max_streams_uni and
initial_max_stream_data_uni. initial_max_stream_data_uni.
The value of the server's previous preferred_address MUST NOT be used The value of the server's previous preferred_address MUST NOT be used
when establishing a new connection; rather, the client should wait to when establishing a new connection; rather, the client should wait to
observe the server's new preferred_address value in the handshake. observe the server's new preferred_address value in the handshake.
A server MUST reject 0-RTT data or even abort a handshake if the A server MUST either reject 0-RTT data or abort a handshake if the
implied values for transport parameters cannot be supported. implied values for transport parameters cannot be supported.
7.3.2. New Transport Parameters 7.3.2. New Transport Parameters
New transport parameters can be used to negotiate new protocol New transport parameters can be used to negotiate new protocol
behavior. An endpoint MUST ignore transport parameters that it does behavior. An endpoint MUST ignore transport parameters that it does
not support. Absence of a transport parameter therefore disables any not support. Absence of a transport parameter therefore disables any
optional protocol feature that is negotiated using the parameter. optional protocol feature that is negotiated using the parameter.
New transport parameters can be registered according to the rules in New transport parameters can be registered according to the rules in
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Connection establishment implicitly provides address validation for Connection establishment implicitly provides address validation for
both endpoints. In particular, receipt of a packet protected with both endpoints. In particular, receipt of a packet protected with
Handshake keys confirms that the client received the Initial packet Handshake keys confirms that the client received the Initial packet
from the server. Once the server has successfully processed a from the server. Once the server has successfully processed a
Handshake packet from the client, it can consider the client address Handshake packet from the client, it can consider the client address
to have been validated. to have been validated.
Prior to validating the client address, servers MUST NOT send more Prior to validating the client address, servers MUST NOT send more
than three times as many bytes as the number of bytes they have than three times as many bytes as the number of bytes they have
received. This limits the magnitude of any amplification attack that received. This limits the magnitude of any amplification attack that
can be mounted using spoofed source addresses. can be mounted using spoofed source addresses. In determining this
limit, servers only count the size of successfully processed packets.
To ensure that the server is not overly constrained by this Clients MUST pad UDP datagrams that contain only Initial packets to
restriction, clients MUST send UDP datagrams with at least 1200 1200 bytes. Once a client has received an acknowledgment for a
octets of payload until the server has completed address validation, Handshake packet it MAY send smaller datagrams. Sending padded
see Section 14. datagrams ensures that the server is not overly constrained by the
amplification restriction.
In order to prevent a handshake deadlock as a result of the server In order to prevent a handshake deadlock as a result of the server
being unable to send, clients SHOULD send a packet upon a handshake being unable to send, clients SHOULD send a packet upon a handshake
timeout, as described in [QUIC-RECOVERY]. If the client has no data timeout, as described in [QUIC-RECOVERY]. If the client has no data
to retransmit and does not have Handshake keys, it SHOULD send an to retransmit and does not have Handshake keys, it SHOULD send an
Initial packet in a UDP datagram of at least 1200 octets. If the Initial packet in a UDP datagram of at least 1200 bytes. If the
client has Handshake keys, it SHOULD send a Handshake packet. client has Handshake keys, it SHOULD send a Handshake packet.
A server might wish to validate the client address before starting A server might wish to validate the client address before starting
the cryptographic handshake. Client addresses can be verified using the cryptographic handshake. QUIC uses a token in the Initial packet
an address validation token. This token is delivered during to provide address validation prior to completing the handshake.
connection establishment with a Retry packet (see Section 8.1.1) or This token is delivered to the client during connection establishment
in a previous connection using the NEW_TOKEN frame (see with a Retry packet (see Section 8.1.1) or in a previous connection
Section 8.1.2). using the NEW_TOKEN frame (see Section 8.1.2).
8.1.1. Address Validation using Retry Packets 8.1.1. Address Validation using Retry Packets
QUIC uses token-based address validation during connection
establishment. Any time the server wishes to validate a client
address, it provides the client with a token. As long as it is not
possible for an attacker to generate a valid token for its own
address (see Section 8.1.3) and the client is able to return that
token, it proves to the server that it received the token.
Upon receiving the client's Initial packet, the server can request Upon receiving the client's Initial packet, the server can request
address validation by sending a Retry packet (Section 17.7) address validation by sending a Retry packet (Section 17.7)
containing a token. This token is repeated by the client in an containing a token. This token MUST be repeated by the client in all
Initial packet after it receives the Retry packet. In response to Initial packets it sends after it receives the Retry packet. In
receiving a token in an Initial packet, a server can either abort the response to processing an Initial containing a token, a server can
connection or permit it to proceed. either abort the connection or permit it to proceed.
As long as it is not possible for an attacker to generate a valid
token for its own address (see Section 8.1.3) and the client is able
to return that token, it proves to the server that it received the
token.
A server can also use a Retry packet to defer the state and A server can also use a Retry packet to defer the state and
processing costs of connection establishment. By giving the client a processing costs of connection establishment. By giving the client a
different connection ID to use, a server can cause the connection to different connection ID to use, a server can cause the connection to
be routed to a server instance with more resources available for new be routed to a server instance with more resources available for new
connections. connections.
A flow showing the use of a Retry packet is shown in Figure 6. A flow showing the use of a Retry packet is shown in Figure 6.
Client Server Client Server
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Figure 6: Example Handshake with Retry Figure 6: Example Handshake with Retry
8.1.2. Address Validation for Future Connections 8.1.2. Address Validation for Future Connections
A server MAY provide clients with an address validation token during A server MAY provide clients with an address validation token during
one connection that can be used on a subsequent connection. Address one connection that can be used on a subsequent connection. Address
validation is especially important with 0-RTT because a server validation is especially important with 0-RTT because a server
potentially sends a significant amount of data to a client in potentially sends a significant amount of data to a client in
response to 0-RTT data. response to 0-RTT data.
The server uses the NEW_TOKEN frame Section 19.18 to provide the The server uses the NEW_TOKEN frame Section 19.7 to provide the
client with an address validation token that can be used to validate client with an address validation token that can be used to validate
future connections. The client may then use this token to validate future connections. The client includes this token in Initial
future connections by including it in the Initial packet's header. packets to provide address validation in a future connection. The
The client MUST NOT use the token provided in a Retry for future client MUST include the token in all Initial packets it sends, unless
connections. a Retry replaces the token with a newer token. The client MUST NOT
use the token provided in a Retry for future connections. Servers
MAY discard any Initial packet that does not carry the expected
token.
Unlike the token that is created for a Retry packet, there might be Unlike the token that is created for a Retry packet, there might be
some time between when the token is created and when the token is some time between when the token is created and when the token is
subsequently used. Thus, a resumption token SHOULD include an subsequently used. Thus, a resumption token SHOULD include an
expiration time. The server MAY include either an explicit expiration time. The server MAY include either an explicit
expiration time or an issued timestamp and dynamically calculate the expiration time or an issued timestamp and dynamically calculate the
expiration time. It is also unlikely that the client port number is expiration time. It is also unlikely that the client port number is
the same on two different connections; validating the port is the same on two different connections; validating the port is
therefore unlikely to be successful. therefore unlikely to be successful.
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If the client has a token received in a NEW_TOKEN frame on a previous If the client has a token received in a NEW_TOKEN frame on a previous
connection to what it believes to be the same server, it can include connection to what it believes to be the same server, it can include
that value in the Token field of its Initial packet. that value in the Token field of its Initial packet.
A token allows a server to correlate activity between the connection A token allows a server to correlate activity between the connection
where the token was issued and any connection where it is used. where the token was issued and any connection where it is used.
Clients that want to break continuity of identity with a server MAY Clients that want to break continuity of identity with a server MAY
discard tokens provided using the NEW_TOKEN frame. Tokens obtained discard tokens provided using the NEW_TOKEN frame. Tokens obtained
in Retry packets MUST NOT be discarded. in Retry packets MUST NOT be discarded.
A client SHOULD NOT reuse a token. Reusing a token allows A client SHOULD NOT reuse a token in different connections. Reusing
connections to be linked by entities on the network path (see a token allows connections to be linked by entities on the network
Section 9.5). A client MUST NOT reuse a token if it believes that path (see Section 9.5). A client MUST NOT reuse a token if it
its point of network attachment has changed since the token was last believes that its point of network attachment has changed since the
used; that is, if there is a change in its local IP address or token was last used; that is, if there is a change in its local IP
network interface. A client needs to start the connection process address or network interface. A client needs to start the connection
over if it migrates prior to completing the handshake. process over if it migrates prior to completing the handshake.
When a server receives an Initial packet with an address validation When a server receives an Initial packet with an address validation
token, it SHOULD attempt to validate it. If the token is invalid token, it SHOULD attempt to validate it, unless it has already
then the server SHOULD proceed as if the client did not have a completed address validation. If the token is invalid then the
validated address, including potentially sending a Retry. If the server SHOULD proceed as if the client did not have a validated
validation succeeds, the server SHOULD then allow the handshake to address, including potentially sending a Retry. If the validation
proceed. succeeds, the server SHOULD then allow the handshake to proceed.
Note: The rationale for treating the client as unvalidated rather Note: The rationale for treating the client as unvalidated rather
than discarding the packet is that the client might have received than discarding the packet is that the client might have received
the token in a previous connection using the NEW_TOKEN frame, and the token in a previous connection using the NEW_TOKEN frame, and
if the server has lost state, it might be unable to validate the if the server has lost state, it might be unable to validate the
token at all, leading to connection failure if the packet is token at all, leading to connection failure if the packet is
discarded. A server MAY encode tokens provided with NEW_TOKEN discarded. A server MAY encode tokens provided with NEW_TOKEN
frames and Retry packets differently, and validate the latter more frames and Retry packets differently, and validate the latter more
strictly. strictly.
In a stateless design, a server can use encrypted and authenticated In a stateless design, a server can use encrypted and authenticated
tokens to pass information to clients that the server can later tokens to pass information to clients that the server can later
recover and use to validate a client address. Tokens are not recover and use to validate a client address. Tokens are not
integrated into the cryptographic handshake and so they are not integrated into the cryptographic handshake and so they are not
authenticated. For instance, a client might be able to reuse a authenticated. For instance, a client might be able to reuse a
token. To avoid attacks that exploit this property, a server can token. To avoid attacks that exploit this property, a server can
limit its use of tokens to only the information needed validate limit its use of tokens to only the information needed validate
client addresses. client addresses.
Attackers could replay tokens to use servers as amplifiers in DDoS
attacks. To protect against such attacks, servers SHOULD ensure that
tokens sent in Retry packets are only accepted for a short time.
Tokens that are provided in NEW_TOKEN frames (see Section 19.7) need
to be valid for longer, but SHOULD NOT be accepted multiple times in
a short period. Servers are encouraged to allow tokens to be used
only once, if possible.
8.1.3. Address Validation Token Integrity 8.1.3. Address Validation Token Integrity
An address validation token MUST be difficult to guess. Including a An address validation token MUST be difficult to guess. Including a
large enough random value in the token would be sufficient, but this large enough random value in the token would be sufficient, but this
depends on the server remembering the value it sends to clients. depends on the server remembering the value it sends to clients.
A token-based scheme allows the server to offload any state A token-based scheme allows the server to offload any state
associated with validation to the client. For this design to work, associated with validation to the client. For this design to work,
the token MUST be covered by integrity protection against the token MUST be covered by integrity protection against
modification or falsification by clients. Without integrity modification or falsification by clients. Without integrity
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For path validation to be successful, a PATH_RESPONSE frame MUST be For path validation to be successful, a PATH_RESPONSE frame MUST be
received from the same remote address to which the corresponding received from the same remote address to which the corresponding
PATH_CHALLENGE was sent. If a PATH_RESPONSE frame is received from a PATH_CHALLENGE was sent. If a PATH_RESPONSE frame is received from a
different remote address than the one to which the PATH_CHALLENGE was different remote address than the one to which the PATH_CHALLENGE was
sent, path validation is considered to have failed, even if the data sent, path validation is considered to have failed, even if the data
matches that sent in the PATH_CHALLENGE. matches that sent in the PATH_CHALLENGE.
Additionally, the PATH_RESPONSE frame MUST be received on the same Additionally, the PATH_RESPONSE frame MUST be received on the same
local address from which the corresponding PATH_CHALLENGE was sent. local address from which the corresponding PATH_CHALLENGE was sent.
An endpoint considers the path to be valid when a PATH_RESPONSE frame
is received on the same path with the same payload as the
PATH_CHALLENGE frame.
If a PATH_RESPONSE frame is received on a different local address If a PATH_RESPONSE frame is received on a different local address
than the one from which the PATH_CHALLENGE was sent, path validation than the one from which the PATH_CHALLENGE was sent, path validation
is considered to have failed, even if the data matches that sent in is not considered to be successful, even if the data matches the
the PATH_CHALLENGE. Thus, the endpoint considers the path to be PATH_CHALLENGE. This doesn't result in path validation failure, as
valid when a PATH_RESPONSE frame is received on the same path with it might be a result of a forwarded packet (see Section 9.3.3) or
the same payload as the PATH_CHALLENGE frame. misrouting.
8.6. Failed Path Validation 8.6. Failed Path Validation
Path validation only fails when the endpoint attempting to validate Path validation only fails when the endpoint attempting to validate
the path abandons its attempt to validate the path. the path abandons its attempt to validate the path.
Endpoints SHOULD abandon path validation based on a timer. When Endpoints SHOULD abandon path validation based on a timer. When
setting this timer, implementations are cautioned that the new path setting this timer, implementations are cautioned that the new path
could have a longer round-trip time than the original. could have a longer round-trip time than the original. A value of
three times the current Retransmittion Timeout (RTO) as defined in
[QUIC-RECOVERY] is RECOMMENDED.
Note that the endpoint might receive packets containing other frames Note that the endpoint might receive packets containing other frames
on the new path, but a PATH_RESPONSE frame with appropriate data is on the new path, but a PATH_RESPONSE frame with appropriate data is
required for path validation to succeed. required for path validation to succeed.
When an endpoint abandons path validation, it determines that the When an endpoint abandons path validation, it determines that the
path is unusable. This does not necessarily imply a failure of the path is unusable. This does not necessarily imply a failure of the
connection - endpoints can continue sending packets over other paths connection - endpoints can continue sending packets over other paths
as appropriate. If no paths are available, an endpoint can wait for as appropriate. If no paths are available, an endpoint can wait for
a new path to become available or close the connection. a new path to become available or close the connection.
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new outgoing IP address for a flow. NAT rebinding is not connection new outgoing IP address for a flow. NAT rebinding is not connection
migration as defined in this section, though an endpoint SHOULD migration as defined in this section, though an endpoint SHOULD
perform path validation (Section 8.2) if it detects a change in the perform path validation (Section 8.2) if it detects a change in the
IP address of its peer. IP address of its peer.
This document limits migration of connections to new client This document limits migration of connections to new client
addresses, except as described in Section 9.6. Clients are addresses, except as described in Section 9.6. Clients are
responsible for initiating all migrations. Servers do not send non- responsible for initiating all migrations. Servers do not send non-
probing packets (see Section 9.1) toward a client address until they probing packets (see Section 9.1) toward a client address until they
see a non-probing packet from that address. If a client receives see a non-probing packet from that address. If a client receives
packets from an unknown server address, the client MAY discard these packets from an unknown server address, the client MUST discard these
packets. packets.
9.1. Probing a New Path 9.1. Probing a New Path
An endpoint MAY probe for peer reachability from a new local address An endpoint MAY probe for peer reachability from a new local address
using path validation Section 8.2 prior to migrating the connection using path validation Section 8.2 prior to migrating the connection
to the new local address. Failure of path validation simply means to the new local address. Failure of path validation simply means
that the new path is not usable for this connection. Failure to that the new path is not usable for this connection. Failure to
validate a path does not cause the connection to end unless there are validate a path does not cause the connection to end unless there are
no valid alternative paths available. no valid alternative paths available.
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After changing the address to which it sends non-probing packets, an After changing the address to which it sends non-probing packets, an
endpoint could abandon any path validation for other addresses. endpoint could abandon any path validation for other addresses.
Receiving a packet from a new peer address might be the result of a Receiving a packet from a new peer address might be the result of a
NAT rebinding at the peer. NAT rebinding at the peer.
After verifying a new client address, the server SHOULD send new After verifying a new client address, the server SHOULD send new
address validation tokens (Section 8) to the client. address validation tokens (Section 8) to the client.
9.3.1. Handling Address Spoofing by a Peer 9.3.1. Peer Address Spoofing
It is possible that a peer is spoofing its source address to cause an It is possible that a peer is spoofing its source address to cause an
endpoint to send excessive amounts of data to an unwilling host. If endpoint to send excessive amounts of data to an unwilling host. If
the endpoint sends significantly more data than the spoofing peer, the endpoint sends significantly more data than the spoofing peer,
connection migration might be used to amplify the volume of data that connection migration might be used to amplify the volume of data that
an attacker can generate toward a victim. an attacker can generate toward a victim.
As described in Section 9.3, an endpoint is required to validate a As described in Section 9.3, an endpoint is required to validate a
peer's new address to confirm the peer's possession of the new peer's new address to confirm the peer's possession of the new
address. Until a peer's address is deemed valid, an endpoint MUST address. Until a peer's address is deemed valid, an endpoint MUST
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per estimated round-trip time (kMinimumWindow, as defined in per estimated round-trip time (kMinimumWindow, as defined in
[QUIC-RECOVERY]). In the absence of this limit, an endpoint risks [QUIC-RECOVERY]). In the absence of this limit, an endpoint risks
being used for a denial of service attack against an unsuspecting being used for a denial of service attack against an unsuspecting
victim. Note that since the endpoint will not have any round-trip victim. Note that since the endpoint will not have any round-trip
time measurements to this address, the estimate SHOULD be the default time measurements to this address, the estimate SHOULD be the default
initial value (see [QUIC-RECOVERY]). initial value (see [QUIC-RECOVERY]).
If an endpoint skips validation of a peer address as described in If an endpoint skips validation of a peer address as described in
Section 9.3, it does not need to limit its sending rate. Section 9.3, it does not need to limit its sending rate.
9.3.2. Handling Address Spoofing by an On-path Attacker 9.3.2. On-Path Address Spoofing
An on-path attacker could cause a spurious connection migration by An on-path attacker could cause a spurious connection migration by
copying and forwarding a packet with a spoofed address such that it copying and forwarding a packet with a spoofed address such that it
arrives before the original packet. The packet with the spoofed arrives before the original packet. The packet with the spoofed
address will be seen to come from a migrating connection, and the address will be seen to come from a migrating connection, and the
original packet will be seen as a duplicate and dropped. After a original packet will be seen as a duplicate and dropped. After a
spurious migration, validation of the source address will fail spurious migration, validation of the source address will fail
because the entity at the source address does not have the necessary because the entity at the source address does not have the necessary
cryptographic keys to read or respond to the PATH_CHALLENGE frame cryptographic keys to read or respond to the PATH_CHALLENGE frame
that is sent to it even if it wanted to. that is sent to it even if it wanted to.
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MUST close the connection silently by discarding all connection MUST close the connection silently by discarding all connection
state. This results in new packets on the connection being handled state. This results in new packets on the connection being handled
generically. For instance, an endpoint MAY send a stateless reset in generically. For instance, an endpoint MAY send a stateless reset in
response to any further incoming packets. response to any further incoming packets.
Note that receipt of packets with higher packet numbers from the Note that receipt of packets with higher packet numbers from the
legitimate peer address will trigger another connection migration. legitimate peer address will trigger another connection migration.
This will cause the validation of the address of the spurious This will cause the validation of the address of the spurious
migration to be abandoned. migration to be abandoned.
9.3.3. Off-Path Packet Forwarding
An off-path attacker that can observe packets might forward copies of
genuine packets to endpoints. If the copied packet arrives before
the genuine packet, this will appear as a NAT rebinding. Any genuine
packet will be discarded as a duplicate. If the attacker is able to
continue forwarding packets, it might be able to cause migration to a
path via the attacker. This places the attacker on path, giving it
the ability to observe or drop all subsequent packets.
Unlike the attack described in Section 9.3.2, the attacker can ensure
that the new path is successfully validated.
This style of attack relies on the attacker using a path that is
approximately as fast as the direct path between endpoints. The
attack is more reliable if relatively few packets are sent or if
packet loss coincides with the attempted attack.
A non-probing packet received on the original path that increases the
maximum received packet number will cause the endpoint to move back
to that path. Eliciting packets on this path increases the
likelihood that the attack is unsuccessful. Therefore, mitigation of
this attack relies on triggering the exchange of packets.
In response to an apparent migration, endpoints MUST validate the
previously active path using a PATH_CHALLENGE frame. This induces
the sending of new packets on that path. If the path is no longer
viable, the validation attempt will time out and fail; if the path is
viable, but no longer desired, the validation will succeed, but only
results in probing packets being sent on the path.
An endpoint that receives a PATH_CHALLENGE on an active path SHOULD
send a non-probing packet in response. If the non-probing packet
arrives before any copy made by an attacker, this results in the
connection being migrated back to the original path. Any subsequent
migration to another path restarts this entire process.
This defense is imperfect, but this is not considered a serious
problem. If the path via the attack is reliably faster than the
original path despite multiple attempts to use that original path, it
is not possible to distinguish between attack and an improvement in
routing.
An endpoint could also use heuristics to improve detection of this
style of attack. For instance, NAT rebinding is improbable if
packets were recently received on the old path, similarly rebinding
is rare on IPv6 paths. Endpoints can also look for duplicated
packets. Conversely, a change in connection ID is more likely to
indicate an intentional migration rather than an attack.
9.4. Loss Detection and Congestion Control 9.4. Loss Detection and Congestion Control
The capacity available on the new path might not be the same as the The capacity available on the new path might not be the same as the
old path. Packets sent on the old path SHOULD NOT contribute to old path. Packets sent on the old path SHOULD NOT contribute to
congestion control or RTT estimation for the new path. congestion control or RTT estimation for the new path.
On confirming a peer's ownership of its new address, an endpoint On confirming a peer's ownership of its new address, an endpoint
SHOULD immediately reset the congestion controller and round-trip SHOULD immediately reset the congestion controller and round-trip
time estimator for the new path. time estimator for the new path.
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appropriately. appropriately.
There may be apparent reordering at the receiver when an endpoint There may be apparent reordering at the receiver when an endpoint
sends data and probes from/to multiple addresses during the migration sends data and probes from/to multiple addresses during the migration
period, since the two resulting paths may have different round-trip period, since the two resulting paths may have different round-trip
times. A receiver of packets on multiple paths will still send ACK times. A receiver of packets on multiple paths will still send ACK
frames covering all received packets. frames covering all received packets.
While multiple paths might be used during connection migration, a While multiple paths might be used during connection migration, a
single congestion control context and a single loss recovery context single congestion control context and a single loss recovery context
(as described in [QUIC-RECOVERY]) may be adequate. A sender can make (as described in [QUIC-RECOVERY]) may be adequate. For instance, an
exceptions for probe packets so that their loss detection is endpoint might delay switching to a new congestion control context
independent and does not unduly cause the congestion controller to until it is confirmed that an old path is no longer needed (such as
reduce its sending rate. An endpoint might set a separate timer when the case in Section 9.3.3).
a PATH_CHALLENGE is sent, which is cancelled when the corresponding
PATH_RESPONSE is received. If the timer fires before the A sender can make exceptions for probe packets so that their loss
PATH_RESPONSE is received, the endpoint might send a new detection is independent and does not unduly cause the congestion
controller to reduce its sending rate. An endpoint might set a
separate timer when a PATH_CHALLENGE is sent, which is cancelled when
the corresponding PATH_RESPONSE is received. If the timer fires
before the PATH_RESPONSE is received, the endpoint might send a new
PATH_CHALLENGE, and restart the timer for a longer period of time. PATH_CHALLENGE, and restart the timer for a longer period of time.
9.5. Privacy Implications of Connection Migration 9.5. Privacy Implications of Connection Migration
Using a stable connection ID on multiple network paths allows a Using a stable connection ID on multiple network paths allows a
passive observer to correlate activity between those paths. An passive observer to correlate activity between those paths. An
endpoint that moves between networks might not wish to have their endpoint that moves between networks might not wish to have their
activity correlated by any entity other than their peer, so different activity correlated by any entity other than their peer, so different
connection IDs are used when sending from different local addresses, connection IDs are used when sending from different local addresses,
as discussed in Section 5.1. For this to be effective endpoints need as discussed in Section 5.1. For this to be effective endpoints need
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10.1. Closing and Draining Connection States 10.1. Closing and Draining Connection States
The closing and draining connection states exist to ensure that The closing and draining connection states exist to ensure that
connections close cleanly and that delayed or reordered packets are connections close cleanly and that delayed or reordered packets are
properly discarded. These states SHOULD persist for three times the properly discarded. These states SHOULD persist for three times the
current Retransmission Timeout (RTO) interval as defined in current Retransmission Timeout (RTO) interval as defined in
[QUIC-RECOVERY]. [QUIC-RECOVERY].
An endpoint enters a closing period after initiating an immediate An endpoint enters a closing period after initiating an immediate
close (Section 10.3). While closing, an endpoint MUST NOT send close (Section 10.3). While closing, an endpoint MUST NOT send
packets unless they contain a CONNECTION_CLOSE or APPLICATION_CLOSE packets unless they contain a CONNECTION_CLOSE frame (see
frame (see Section 10.3 for details). An endpoint retains only Section 10.3 for details). An endpoint retains only enough
enough information to generate a packet containing a closing frame information to generate a packet containing a CONNECTION_CLOSE frame
and to identify packets as belonging to the connection. The and to identify packets as belonging to the connection. The
connection ID and QUIC version is sufficient information to identify connection ID and QUIC version is sufficient information to identify
packets for a closing connection; an endpoint can discard all other packets for a closing connection; an endpoint can discard all other
connection state. An endpoint MAY retain packet protection keys for connection state. An endpoint MAY retain packet protection keys for
incoming packets to allow it to read and process a closing frame. incoming packets to allow it to read and process a CONNECTION_CLOSE
frame.
The draining state is entered once an endpoint receives a signal that The draining state is entered once an endpoint receives a signal that
its peer is closing or draining. While otherwise identical to the its peer is closing or draining. While otherwise identical to the
closing state, an endpoint in the draining state MUST NOT send any closing state, an endpoint in the draining state MUST NOT send any
packets. Retaining packet protection keys is unnecessary once a packets. Retaining packet protection keys is unnecessary once a
connection is in the draining state. connection is in the draining state.
An endpoint MAY transition from the closing period to the draining An endpoint MAY transition from the closing period to the draining
period if it can confirm that its peer is also closing or draining. period if it can confirm that its peer is also closing or draining.
Receiving a closing frame is sufficient confirmation, as is receiving Receiving a CONNECTION_CLOSE frame is sufficient confirmation, as is
a stateless reset. The draining period SHOULD end when the closing receiving a stateless reset. The draining period SHOULD end when the
period would have ended. In other words, the endpoint can use the closing period would have ended. In other words, the endpoint can
same end time, but cease retransmission of the closing packet. use the same end time, but cease retransmission of the closing
packet.
Disposing of connection state prior to the end of the closing or Disposing of connection state prior to the end of the closing or
draining period could cause delayed or reordered packets to be draining period could cause delayed or reordered packets to be
handled poorly. Endpoints that have some alternative means to ensure handled poorly. Endpoints that have some alternative means to ensure
that late-arriving packets on the connection do not create QUIC that late-arriving packets on the connection do not create QUIC
state, such as those that are able to close the UDP socket, MAY use state, such as those that are able to close the UDP socket, MAY use
an abbreviated draining period which can allow for faster resource an abbreviated draining period which can allow for faster resource
recovery. Servers that retain an open socket for accepting new recovery. Servers that retain an open socket for accepting new
connections SHOULD NOT exit the closing or draining period early. connections SHOULD NOT exit the closing or draining period early.
skipping to change at page 52, line 39 skipping to change at page 53, line 39
PADDING frames are not acknowledged until an endpoint has other PADDING frames are not acknowledged until an endpoint has other
frames to send, so they could prevent the timeout from being frames to send, so they could prevent the timeout from being
refreshed. refreshed.
The value for an idle timeout can be asymmetric. The value The value for an idle timeout can be asymmetric. The value
advertised by an endpoint is only used to determine whether the advertised by an endpoint is only used to determine whether the
connection is live at that endpoint. An endpoint that sends packets connection is live at that endpoint. An endpoint that sends packets
near the end of the idle timeout period of a peer risks having those near the end of the idle timeout period of a peer risks having those
packets discarded if its peer enters the draining state before the packets discarded if its peer enters the draining state before the
packets arrive. If a peer could timeout within an RTO (see packets arrive. If a peer could timeout within an RTO (see
Section 4.3.3 of [QUIC-RECOVERY]), it is advisable to test for Section 5.3.3 of [QUIC-RECOVERY]), it is advisable to test for
liveness before sending any data that cannot be retried safely. liveness before sending any data that cannot be retried safely.
10.3. Immediate Close 10.3. Immediate Close
An endpoint sends a closing frame (CONNECTION_CLOSE or An endpoint sends a CONNECTION_CLOSE frame (Section 19.19) to
APPLICATION_CLOSE) to terminate the connection immediately. Any terminate the connection immediately. A CONNECTION_CLOSE frame
closing frame causes all streams to immediately become closed; open causes all streams to immediately become closed; open streams can be
streams can be assumed to be implicitly reset. assumed to be implicitly reset.
After sending a closing frame, endpoints immediately enter the After sending a CONNECTION_CLOSE frame, endpoints immediately enter
closing state. During the closing period, an endpoint that sends a the closing state. During the closing period, an endpoint that sends
closing frame SHOULD respond to any packet that it receives with a CONNECTION_CLOSE frame SHOULD respond to any packet that it
another packet containing a closing frame. To minimize the state receives with another packet containing a CONNECTION_CLOSE frame. To
that an endpoint maintains for a closing connection, endpoints MAY minimize the state that an endpoint maintains for a closing
send the exact same packet. However, endpoints SHOULD limit the connection, endpoints MAY send the exact same packet. However,
number of packets they generate containing a closing frame. For endpoints SHOULD limit the number of packets they generate containing
instance, an endpoint could progressively increase the number of a CONNECTION_CLOSE frame. For instance, an endpoint could
packets that it receives before sending additional packets or progressively increase the number of packets that it receives before
increase the time between packets. sending additional packets or increase the time between packets.
Note: Allowing retransmission of a packet contradicts other advice Note: Allowing retransmission of a packet contradicts other advice
in this document that recommends the creation of new packet in this document that recommends the creation of new packet
numbers for every packet. Sending new packet numbers is primarily numbers for every packet. Sending new packet numbers is primarily
of advantage to loss recovery and congestion control, which are of advantage to loss recovery and congestion control, which are
not expected to be relevant for a closed connection. not expected to be relevant for a closed connection.
Retransmitting the final packet requires less state. Retransmitting the final packet requires less state.
After receiving a closing frame, endpoints enter the draining state. New packets from unverified addresses could be used to create an
An endpoint that receives a closing frame MAY send a single packet amplification attack (see Section 8). To avoid this, endpoints MUST
containing a closing frame before entering the draining state, using either limit transmission of CONNECTION_CLOSE frames to validated
a CONNECTION_CLOSE frame and a NO_ERROR code if appropriate. An addresses or drop packets without response if the response would be
endpoint MUST NOT send further packets, which could result in a more than three times larger than the received packet.
constant exchange of closing frames until the closing period on
either peer ended. After receiving a CONNECTION_CLOSE frame, endpoints enter the
draining state. An endpoint that receives a CONNECTION_CLOSE frame
MAY send a single packet containing a CONNECTION_CLOSE frame before
entering the draining state, using a CONNECTION_CLOSE frame and a
NO_ERROR code if appropriate. An endpoint MUST NOT send further
packets, which could result in a constant exchange of
CONNECTION_CLOSE frames until the closing period on either peer
ended.
An immediate close can be used after an application protocol has An immediate close can be used after an application protocol has
arranged to close a connection. This might be after the application arranged to close a connection. This might be after the application
protocols negotiates a graceful shutdown. The application protocol protocols negotiates a graceful shutdown. The application protocol
exchanges whatever messages that are needed to cause both endpoints exchanges whatever messages that are needed to cause both endpoints
to agree to close the connection, after which the application to agree to close the connection, after which the application
requests that the connection be closed. The application protocol can requests that the connection be closed. The application protocol can
use an APPLICATION_CLOSE message with an appropriate error code to use an CONNECTION_CLOSE frame with an appropriate error code to
signal closure. signal closure.
If the connection has been successfully established, endpoints MUST If the connection has been successfully established, endpoints MUST
send any closing frames in a 1-RTT packet. Prior to connection send any CONNECTION_CLOSE frames in a 1-RTT packet. Prior to
establishment a peer might not have 1-RTT keys, so endpoints SHOULD connection establishment a peer might not have 1-RTT keys, so
send closing frames in a Handshake packet. If the endpoint does not endpoints SHOULD send CONNECTION_CLOSE frames in a Handshake packet.
have Handshake keys, or it is not certain that the peer has Handshake If the endpoint does not have Handshake keys, or it is not certain
keys, it MAY send closing frames in an Initial packet. If multiple that the peer has Handshake keys, it MAY send CONNECTION_CLOSE frames
packets are sent, they can be coalesced (see Section 12.2) to in an Initial packet. If multiple packets are sent, they can be
facilitate retransmission. coalesced (see Section 12.2) to facilitate retransmission.
10.4. Stateless Reset 10.4. Stateless Reset
A stateless reset is provided as an option of last resort for an A stateless reset is provided as an option of last resort for an
endpoint that does not have access to the state of a connection. A endpoint that does not have access to the state of a connection. A
crash or outage might result in peers continuing to send data to an crash or outage might result in peers continuing to send data to an
endpoint that is unable to properly continue the connection. An endpoint that is unable to properly continue the connection. A
endpoint that wishes to communicate a fatal connection error MUST use stateless reset is not appropriate for signaling error conditions.
a closing frame if it has sufficient state to do so. An endpoint that wishes to communicate a fatal connection error MUST
use a CONNECTION_CLOSE frame if it has sufficient state to do so.
To support this process, a token is sent by endpoints. The token is To support this process, a token is sent by endpoints. The token is
carried in the NEW_CONNECTION_ID frame sent by either peer, and carried in the NEW_CONNECTION_ID frame sent by either peer, and
servers can specify the stateless_reset_token transport parameter servers can specify the stateless_reset_token transport parameter
during the handshake (clients cannot because their transport during the handshake (clients cannot because their transport
parameters don't have confidentiality protection). This value is parameters don't have confidentiality protection). This value is
protected by encryption, so only client and server know this value. protected by encryption, so only client and server know this value.
Tokens sent via NEW_CONNECTION_ID frames are invalidated when their Tokens are invalidated when their associated connection ID is retired
associated connection ID is retired via a RETIRE_CONNECTION_ID frame via a RETIRE_CONNECTION_ID frame (Section 19.16).
(Section 19.13).
An endpoint that receives packets that it cannot process sends a An endpoint that receives packets that it cannot process sends a
packet in the following layout: packet in the following layout:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
|0|K|1|1|0|0|0|0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Random Octets (160..) ... |0|1| Random Bits (182..) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
| | | |
+ Stateless Reset Token (128) + + Stateless Reset Token (128) +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Stateless Reset Packet Figure 7: Stateless Reset Packet
This design ensures that a stateless reset packet is - to the extent This design ensures that a stateless reset packet is - to the extent
possible - indistinguishable from a regular packet with a short possible - indistinguishable from a regular packet with a short
header. header.
The message consists of a header octet, followed by an arbitrary A stateless reset uses an entire UDP datagram, starting with the
number of random octets, followed by a Stateless Reset Token. first two bits of the packet header. The remainder of the first byte
and an arbitrary number of random bytes following it are set to
unpredictable values. The last 16 bytes of the datagram contain a
Stateless Reset Token.
A stateless reset will be interpreted by a recipient as a packet with A stateless reset will be interpreted by a recipient as a packet with
a short header. For the packet to appear as valid, the Random Octets a short header. For the packet to appear as valid, the Random Bits
field needs to include at least 20 octets of random or unpredictable field needs to include at least 182 bits of random or unpredictable
values. This is intended to allow for a destination connection ID of values (or 24 bytes, less the two fixed bits). This is intended to
the maximum length permitted, a packet number, and minimal payload. allow for a destination connection ID of the maximum length
The Stateless Reset Token corresponds to the minimum expansion of the permitted, with a minimal packet number, and payload. The Stateless
packet protection AEAD. More random octets might be necessary if the Reset Token corresponds to the minimum expansion of the packet
protection AEAD. More random bytes might be necessary if the
endpoint could have negotiated a packet protection scheme with a endpoint could have negotiated a packet protection scheme with a
larger minimum AEAD expansion. larger minimum AEAD expansion.
An endpoint SHOULD NOT send a stateless reset that is significantly An endpoint SHOULD NOT send a stateless reset that is significantly
larger than the packet it receives. Endpoints MUST discard packets larger than the packet it receives. Endpoints MUST discard packets
that are too small to be valid QUIC packets. With the set of AEAD that are too small to be valid QUIC packets. With the set of AEAD
functions defined in [QUIC-TLS], packets less than 19 octets long are functions defined in [QUIC-TLS], packets that are smaller than 21
never valid. bytes are never valid.
An endpoint MAY send a stateless reset in response to a packet with a An endpoint MAY send a stateless reset in response to a packet with a
long header. This would not be effective if the stateless reset long header. This would not be effective if the stateless reset
token was not yet available to a peer. In this QUIC version, packets token was not yet available to a peer. In this QUIC version, packets
with a long header are only used during connection establishment. with a long header are only used during connection establishment.
Because the stateless reset token is not available until connection Because the stateless reset token is not available until connection
establishment is complete or near completion, ignoring an unknown establishment is complete or near completion, ignoring an unknown
packet with a long header might be more effective. packet with a long header might be more effective.
An endpoint cannot determine the Source Connection ID from a packet An endpoint cannot determine the Source Connection ID from a packet
with a short header, therefore it cannot set the Destination with a short header, therefore it cannot set the Destination
Connection ID in the stateless reset packet. The Destination Connection ID in the stateless reset packet. The Destination
Connection ID will therefore differ from the value used in previous Connection ID will therefore differ from the value used in previous
packets. A random Destination Connection ID makes the connection ID packets. A random Destination Connection ID makes the connection ID
appear to be the result of moving to a new connection ID that was appear to be the result of moving to a new connection ID that was
provided using a NEW_CONNECTION_ID frame (Section 19.12). provided using a NEW_CONNECTION_ID frame (Section 19.15).
Using a randomized connection ID results in two problems: Using a randomized connection ID results in two problems:
o The packet might not reach the peer. If the Destination o The packet might not reach the peer. If the Destination
Connection ID is critical for routing toward the peer, then this Connection ID is critical for routing toward the peer, then this
packet could be incorrectly routed. This might also trigger packet could be incorrectly routed. This might also trigger
another Stateless Reset in response, see Section 10.4.3. A another Stateless Reset in response, see Section 10.4.3. A
Stateless Reset that is not correctly routed is ineffective in Stateless Reset that is not correctly routed is an ineffective
causing errors to be quickly detected and recovered. In this error detection and recovery mechanism. In this case, endpoints
case, endpoints will need to rely on other methods - such as will need to rely on other methods - such as timers - to detect
timers - to detect that the connection has failed. that the connection has failed.
o The randomly generated connection ID can be used by entities other o The randomly generated connection ID can be used by entities other
than the peer to identify this as a potential stateless reset. An than the peer to identify this as a potential stateless reset. An
endpoint that occasionally uses different connection IDs might endpoint that occasionally uses different connection IDs might
introduce some uncertainty about this. introduce some uncertainty about this.
Finally, the last 16 octets of the packet are set to the value of the Finally, the last 16 bytes of the packet are set to the value of the
Stateless Reset Token. Stateless Reset Token.
A stateless reset is not appropriate for signaling error conditions.
An endpoint that wishes to communicate a fatal connection error MUST
use a CONNECTION_CLOSE or APPLICATION_CLOSE frame if it has
sufficient state to do so.
This stateless reset design is specific to QUIC version 1. An This stateless reset design is specific to QUIC version 1. An
endpoint that supports multiple versions of QUIC needs to generate a endpoint that supports multiple versions of QUIC needs to generate a
stateless reset that will be accepted by peers that support any stateless reset that will be accepted by peers that support any
version that the endpoint might support (or might have supported version that the endpoint might support (or might have supported
prior to losing state). Designers of new versions of QUIC need to be prior to losing state). Designers of new versions of QUIC need to be
aware of this and either reuse this design, or use a portion of the aware of this and either reuse this design, or use a portion of the
packet other than the last 16 octets for carrying data. packet other than the last 16 bytes for carrying data.
10.4.1. Detecting a Stateless Reset 10.4.1. Detecting a Stateless Reset
An endpoint detects a potential stateless reset when a packet with a An endpoint detects a potential stateless reset when a packet with a
short header either cannot be decrypted or is marked as a duplicate short header either cannot be decrypted or is marked as a duplicate
packet. The endpoint then compares the last 16 octets of the packet packet. The endpoint then compares the last 16 bytes of the packet
with the Stateless Reset Token provided by its peer, either in a with the Stateless Reset Token provided by its peer, either in a
NEW_CONNECTION_ID frame or the server's transport parameters. If NEW_CONNECTION_ID frame or the server's transport parameters. If
these values are identical, the endpoint MUST enter the draining these values are identical, the endpoint MUST enter the draining
period and not send any further packets on this connection. If the period and not send any further packets on this connection. If the
comparison fails, the packet can be discarded. comparison fails, the packet can be discarded.
10.4.2. Calculating a Stateless Reset Token 10.4.2. Calculating a Stateless Reset Token
The stateless reset token MUST be difficult to guess. In order to The stateless reset token MUST be difficult to guess. In order to
create a Stateless Reset Token, an endpoint could randomly generate create a Stateless Reset Token, an endpoint could randomly generate
skipping to change at page 56, line 38 skipping to change at page 57, line 44
might lose state. Stateless reset specifically exists to handle the might lose state. Stateless reset specifically exists to handle the
case where state is lost, so this approach is suboptimal. case where state is lost, so this approach is suboptimal.
A single static key can be used across all connections to the same A single static key can be used across all connections to the same
endpoint by generating the proof using a second iteration of a endpoint by generating the proof using a second iteration of a
preimage-resistant function that takes a static key and the preimage-resistant function that takes a static key and the
connection ID chosen by the endpoint (see Section 5.1) as input. An connection ID chosen by the endpoint (see Section 5.1) as input. An
endpoint could use HMAC [RFC2104] (for example, HMAC(static_key, endpoint could use HMAC [RFC2104] (for example, HMAC(static_key,
connection_id)) or HKDF [RFC5869] (for example, using the static key connection_id)) or HKDF [RFC5869] (for example, using the static key
as input keying material, with the connection ID as salt). The as input keying material, with the connection ID as salt). The
output of this function is truncated to 16 octets to produce the output of this function is truncated to 16 bytes to produce the
Stateless Reset Token for that connection. Stateless Reset Token for that connection.
An endpoint that loses state can use the same method to generate a An endpoint that loses state can use the same method to generate a
valid Stateless Reset Token. The connection ID comes from the packet valid Stateless Reset Token. The connection ID comes from the packet
that the endpoint receives. that the endpoint receives.
This design relies on the peer always sending a connection ID in its This design relies on the peer always sending a connection ID in its
packets so that the endpoint can use the connection ID from a packet packets so that the endpoint can use the connection ID from a packet
to reset the connection. An endpoint that uses this design MUST to reset the connection. An endpoint that uses this design MUST
either use the same connection ID length for all connections or either use the same connection ID length for all connections or
skipping to change at page 57, line 40 skipping to change at page 58, line 45
in packets eventually being too small to trigger a response. in packets eventually being too small to trigger a response.
An endpoint can remember the number of Stateless Reset packets that An endpoint can remember the number of Stateless Reset packets that
it has sent and stop generating new Stateless Reset packets once a it has sent and stop generating new Stateless Reset packets once a
limit is reached. Using separate limits for different remote limit is reached. Using separate limits for different remote
addresses will ensure that Stateless Reset packets can be used to addresses will ensure that Stateless Reset packets can be used to
close connections when other peers or connections have exhausted close connections when other peers or connections have exhausted
limits. limits.
Reducing the size of a Stateless Reset below the recommended minimum Reducing the size of a Stateless Reset below the recommended minimum
size of 37 octets could mean that the packet could reveal to an size of 37 bytes could mean that the packet could reveal to an
observer that it is a Stateless Reset. Conversely, refusing to send observer that it is a Stateless Reset. Conversely, refusing to send
a Stateless Reset in response to a small packet might result in a Stateless Reset in response to a small packet might result in
Stateless Reset not being useful in detecting cases of broken Stateless Reset not being useful in detecting cases of broken
connections where only very small packets are sent; such failures connections where only very small packets are sent; such failures
might only be detected by other means, such as timers. might only be detected by other means, such as timers.
An endpoint can increase the odds that a packet will trigger a An endpoint can increase the odds that a packet will trigger a
Stateless Reset if it cannot be processed by padding it to at least Stateless Reset if it cannot be processed by padding it to at least
38 octets. 38 bytes.
11. Error Handling 11. Error Handling
An endpoint that detects an error SHOULD signal the existence of that An endpoint that detects an error SHOULD signal the existence of that
error to its peer. Both transport-level and application-level errors error to its peer. Both transport-level and application-level errors
can affect an entire connection (see Section 11.1), while only can affect an entire connection (see Section 11.1), while only
application-level errors can be isolated to a single stream (see application-level errors can be isolated to a single stream (see
Section 11.2). Section 11.2).
The most appropriate error code (Section 20) SHOULD be included in The most appropriate error code (Section 20) SHOULD be included in
the frame that signals the error. Where this specification the frame that signals the error. Where this specification
identifies error conditions, it also identifies the error code that identifies error conditions, it also identifies the error code that
is used. is used.
A stateless reset (Section 10.4) is not suitable for any error that A stateless reset (Section 10.4) is not suitable for any error that
can be signaled with a CONNECTION_CLOSE, APPLICATION_CLOSE, or can be signaled with a CONNECTION_CLOSE or RESET_STREAM frame. A
RST_STREAM frame. A stateless reset MUST NOT be used by an endpoint stateless reset MUST NOT be used by an endpoint that has the state
that has the state necessary to send a frame on the connection. necessary to send a frame on the connection.
11.1. Connection Errors 11.1. Connection Errors
Errors that result in the connection being unusable, such as an Errors that result in the connection being unusable, such as an
obvious violation of protocol semantics or corruption of state that obvious violation of protocol semantics or corruption of state that
affects an entire connection, MUST be signaled using a affects an entire connection, MUST be signaled using a
CONNECTION_CLOSE or APPLICATION_CLOSE frame (Section 19.3, CONNECTION_CLOSE frame (Section 19.19). An endpoint MAY close the
Section 19.4). An endpoint MAY close the connection in this manner connection in this manner even if the error only affects a single
even if the error only affects a single stream. stream.
Application protocols can signal application-specific protocol errors Application protocols can signal application-specific protocol errors
using the APPLICATION_CLOSE frame. Errors that are specific to the using the application-specific variant of the CONNECTION_CLOSE frame.
transport, including all those described in this document, are Errors that are specific to the transport, including all those
carried in a CONNECTION_CLOSE frame. Other than the type of error described in this document, are carried the QUIC-specific variant of
code they carry, these frames are identical in format and semantics. the CONNECTION_CLOSE frame.
A CONNECTION_CLOSE or APPLICATION_CLOSE frame could be sent in a A CONNECTION_CLOSE frame could be sent in a packet that is lost. An
packet that is lost. An endpoint SHOULD be prepared to retransmit a endpoint SHOULD be prepared to retransmit a packet containing
packet containing either frame type if it receives more packets on a containing a CONNECTION_CLOSE frame if it receives more packets on a
terminated connection. Limiting the number of retransmissions and terminated connection. Limiting the number of retransmissions and
the time over which this final packet is sent limits the effort the time over which this final packet is sent limits the effort
expended on terminated connections. expended on terminated connections.
An endpoint that chooses not to retransmit packets containing An endpoint that chooses not to retransmit packets containing a
CONNECTION_CLOSE or APPLICATION_CLOSE risks a peer missing the first CONNECTION_CLOSE frame risks a peer missing the first such packet.
such packet. The only mechanism available to an endpoint that The only mechanism available to an endpoint that continues to receive
continues to receive data for a terminated connection is to use the data for a terminated connection is to use the stateless reset
stateless reset process (Section 10.4). process (Section 10.4).
An endpoint that receives an invalid CONNECTION_CLOSE or An endpoint that receives an invalid CONNECTION_CLOSE frame MUST NOT
APPLICATION_CLOSE frame MUST NOT signal the existence of the error to signal the existence of the error to its peer.
its peer.
11.2. Stream Errors 11.2. Stream Errors
If an application-level error affects a single stream, but otherwise If an application-level error affects a single stream, but otherwise
leaves the connection in a recoverable state, the endpoint can send a leaves the connection in a recoverable state, the endpoint can send a
RST_STREAM frame (Section 19.2) with an appropriate error code to RESET_STREAM frame (Section 19.4) with an appropriate error code to
terminate just the affected stream. terminate just the affected stream.
Other than STOPPING (Section 3.5), RST_STREAM MUST be instigated by RESET_STREAM MUST be instigated by the protocol using QUIC, either
the application and MUST carry an application error code. Resetting directly or through the receipt of a STOP_SENDING frame from a peer.
a stream without knowledge of the application protocol could cause RESET_STREAM carries an application error code. Resetting a stream
the protocol to enter an unrecoverable state. Application protocols without knowledge of the application protocol could cause the
protocol to enter an unrecoverable state. Application protocols
might require certain streams to be reliably delivered in order to might require certain streams to be reliably delivered in order to
guarantee consistent state between endpoints. guarantee consistent state between endpoints.
12. Packets and Frames 12. Packets and Frames
QUIC endpoints communicate by exchanging packets. Packets are QUIC endpoints communicate by exchanging packets. Packets are
carried in UDP datagrams (see Section 12.2) and have confidentiality carried in UDP datagrams (see Section 12.2) and have confidentiality
and integrity protection (see Section 12.1). and integrity protection (see Section 12.1).
This version of QUIC uses the long packet header (see Section 17.2) This version of QUIC uses the long packet header (see Section 17.2)
skipping to change at page 62, line 12 skipping to change at page 63, line 17
keys). If the packet number for sending reaches 2^62 - 1, the sender keys). If the packet number for sending reaches 2^62 - 1, the sender
MUST close the connection without sending a CONNECTION_CLOSE frame or MUST close the connection without sending a CONNECTION_CLOSE frame or
any further packets; an endpoint MAY send a Stateless Reset any further packets; an endpoint MAY send a Stateless Reset
(Section 10.4) in response to further packets that it receives. (Section 10.4) in response to further packets that it receives.
A receiver MUST discard a newly unprotected packet unless it is A receiver MUST discard a newly unprotected packet unless it is
certain that it has not processed another packet with the same packet certain that it has not processed another packet with the same packet
number from the same packet number space. Duplicate suppression MUST number from the same packet number space. Duplicate suppression MUST
happen after removing packet protection for the reasons described in happen after removing packet protection for the reasons described in
Section 9.3 of [QUIC-TLS]. An efficient algorithm for duplicate Section 9.3 of [QUIC-TLS]. An efficient algorithm for duplicate
suppression can be found in Section 3.4.3 of [RFC2406]. suppression can be found in Section 3.4.3 of [RFC4303].
Packet number encoding at a sender and decoding at a receiver are Packet number encoding at a sender and decoding at a receiver are
described in Section 17.1. described in Section 17.1.
12.4. Frames and Frame Types 12.4. Frames and Frame Types
The payload of QUIC packets, after removing packet protection, The payload of QUIC packets, after removing packet protection,
commonly consists of a sequence of frames, as shown in Figure 8. commonly consists of a sequence of frames, as shown in Figure 8.
Version Negotiation, Stateless Reset, and Retry packets do not Version Negotiation, Stateless Reset, and Retry packets do not
contain frames. contain frames.
skipping to change at page 64, line 10 skipping to change at page 65, line 10
The frame types defined in this specification are listed in Table 3. The frame types defined in this specification are listed in Table 3.
The Frame Type in STREAM frames is used to carry other frame-specific The Frame Type in STREAM frames is used to carry other frame-specific
flags. For all other frames, the Frame Type field simply identifies flags. For all other frames, the Frame Type field simply identifies
the frame. These frames are explained in more detail in Section 19. the frame. These frames are explained in more detail in Section 19.
+-------------+----------------------+----------------+ +-------------+----------------------+----------------+
| Type Value | Frame Type Name | Definition | | Type Value | Frame Type Name | Definition |
+-------------+----------------------+----------------+ +-------------+----------------------+----------------+
| 0x00 | PADDING | Section 19.1 | | 0x00 | PADDING | Section 19.1 |
| | | | | | | |
| 0x01 | RST_STREAM | Section 19.2 | | 0x01 | PING | Section 19.2 |
| | | |
| 0x02 | CONNECTION_CLOSE | Section 19.3 |
| | | | | | | |
| 0x03 | APPLICATION_CLOSE | Section 19.4 | | 0x02 - 0x03 | ACK | Section 19.3 |
| | | | | | | |
| 0x04 | MAX_DATA | Section 19.5 | | 0x04 | RESET_STREAM | Section 19.4 |
| | | | | | | |
| 0x05 | MAX_STREAM_DATA | Section 19.6 | | 0x05 | STOP_SENDING | Section 19.5 |
| | | | | | | |
| 0x06 | MAX_STREAM_ID | Section 19.7 | | 0x06 | CRYPTO | Section 19.6 |
| | | | | | | |
| 0x07 | PING | Section 19.8 | | 0x07 | NEW_TOKEN | Section 19.7 |
| | | | | | | |
| 0x08 | BLOCKED | Section 19.9 | | 0x08 - 0x0f | STREAM | Section 19.8 |
| | | | | | | |
| 0x09 | STREAM_BLOCKED | Section 19.10 | | 0x10 | MAX_DATA | Section 19.9 |
| | | | | | | |
| 0x0a | STREAM_ID_BLOCKED | Section 19.11 | | 0x11 | MAX_STREAM_DATA | Section 19.10 |
| | | | | | | |
| 0x0b | NEW_CONNECTION_ID | Section 19.12 | | 0x12 - 0x13 | MAX_STREAMS | Section 19.11 |
| | | | | | | |
| 0x0c | STOP_SENDING | Section 19.14 | | 0x14 | DATA_BLOCKED | Section 19.12 |
| | | | | | | |
| 0x0d | RETIRE_CONNECTION_ID | Section 19.13 | | 0x15 | STREAM_DATA_BLOCKED | Section 19.13 |
| | | | | | | |
| 0x0e | PATH_CHALLENGE | Section 19.16 | | 0x16 - 0x17 | STREAMS_BLOCKED | Section 19.14 |
| | | | | | | |
| 0x0f | PATH_RESPONSE | Section 19.17 | | 0x18 | NEW_CONNECTION_ID | Section 19.15 |
| | | | | | | |
| 0x10 - 0x17 | STREAM | Section 19.19 | | 0x19 | RETIRE_CONNECTION_ID | Section 19.16 |
| | | | | | | |
| 0x18 | CRYPTO | Section 19.20 | | 0x1a | PATH_CHALLENGE | Section 19.17 |
| | | | | | | |
| 0x19 | NEW_TOKEN | Section 19.18 | | 0x1b | PATH_RESPONSE | Section 19.18 |
| | | | | | | |
| 0x1a - 0x1b | ACK | Section 19.15 | | 0x1c - 0x1d | CONNECTION_CLOSE | Section 19.19 |
+-------------+----------------------+----------------+ +-------------+----------------------+----------------+
Table 3: Frame Types Table 3: Frame Types
All QUIC frames are idempotent. That is, a valid frame does not All QUIC frames are idempotent. That is, a valid frame does not
cause undesirable side effects or errors when received more than cause undesirable side effects or errors when received more than
once. once.
The Frame Type field uses a variable length integer encoding (see The Frame Type field uses a variable length integer encoding (see
Section 16) with one exception. To ensure simple and efficient Section 16) with one exception. To ensure simple and efficient
implementations of frame parsing, a frame type MUST use the shortest implementations of frame parsing, a frame type MUST use the shortest
possible encoding. Though a two-, four- or eight-octet encoding of possible encoding. Though a two-, four- or eight-byte encoding of
the frame types defined in this document is possible, the Frame Type the frame types defined in this document is possible, the Frame Type
field for these frames is encoded on a single octet. For instance, field for these frames is encoded on a single byte. For instance,
though 0x4007 is a legitimate two-octet encoding for a variable- though 0x4007 is a legitimate two-byte encoding for a variable-length
length integer with a value of 7, PING frames are always encoded as a integer with a value of 7, PING frames are always encoded as a single
single octet with the value 0x07. An endpoint MUST treat the receipt byte with the value 0x07. An endpoint MAY treat the receipt of a
of a frame type that uses a longer encoding than necessary as a frame type that uses a longer encoding than necessary as a connection
connection error of type PROTOCOL_VIOLATION. error of type PROTOCOL_VIOLATION.
13. Packetization and Reliability 13. Packetization and Reliability
A sender bundles one or more frames in a QUIC packet (see A sender bundles one or more frames in a QUIC packet (see
Section 12.4). Section 12.4).
A sender can minimize per-packet bandwidth and computational costs by A sender can minimize per-packet bandwidth and computational costs by
bundling as many frames as possible within a QUIC packet. A sender bundling as many frames as possible within a QUIC packet. A sender
MAY wait for a short period of time to bundle multiple frames before MAY wait for a short period of time to bundle multiple frames before
sending a packet that is not maximally packed, to avoid sending out sending a packet that is not maximally packed, to avoid sending out
skipping to change at page 66, line 26 skipping to change at page 67, line 20
13.1.1. Sending ACK Frames 13.1.1. Sending ACK Frames
To avoid creating an indefinite feedback loop, an endpoint MUST NOT To avoid creating an indefinite feedback loop, an endpoint MUST NOT
send an ACK frame in response to a packet containing only ACK or send an ACK frame in response to a packet containing only ACK or
PADDING frames, even if there are packet gaps which precede the PADDING frames, even if there are packet gaps which precede the
received packet. The endpoint MUST however acknowledge packets received packet. The endpoint MUST however acknowledge packets
containing only ACK or PADDING frames when sending ACK frames in containing only ACK or PADDING frames when sending ACK frames in
response to other packets. response to other packets.
While PADDING frames do not elicit an ACK frame from a receiver, they Packets containing PADDING frames are considered to be in flight for
are considered to be in flight for congestion control purposes congestion control purposes [QUIC-RECOVERY]. Sending only PADDING
[QUIC-RECOVERY]. Sending only PADDING frames might cause the sender frames might cause the sender to become limited by the congestion
to become limited by the congestion controller (as described in controller (as described in [QUIC-RECOVERY]) with no acknowledgments
[QUIC-RECOVERY]) with no acknowledgments forthcoming from the forthcoming from the receiver. Therefore, a sender should ensure
receiver. Therefore, a sender should ensure that other frames are that other frames are sent in addition to PADDING frames to elicit
sent in addition to PADDING frames to elicit acknowledgments from the acknowledgments from the receiver.
receiver.
An endpoint MUST NOT send more than one packet containing only an ACK An endpoint MUST NOT send more than one packet containing only an ACK
frame per received packet that contains frames other than ACK and frame per received packet that contains frames other than ACK and
PADDING frames. PADDING frames.
The receiver's delayed acknowledgment timer SHOULD NOT exceed the The receiver's delayed acknowledgment timer SHOULD NOT exceed the
current RTT estimate or the value it indicates in the "max_ack_delay" current RTT estimate or the value it indicates in the "max_ack_delay"
transport parameter. This ensures an acknowledgment is sent at least transport parameter. This ensures an acknowledgment is sent at least
once per RTT when packets needing acknowledgement are received. The once per RTT when packets needing acknowledgement are received. The
sender can use the receiver's "max_ack_delay" value in determining sender can use the receiver's "max_ack_delay" value in determining
skipping to change at page 67, line 35 skipping to change at page 68, line 29
acknowledged in packets that are also protected with 1-RTT keys. acknowledged in packets that are also protected with 1-RTT keys.
Packets that a client sends with 0-RTT packet protection MUST be Packets that a client sends with 0-RTT packet protection MUST be
acknowledged by the server in packets protected by 1-RTT keys. This acknowledged by the server in packets protected by 1-RTT keys. This
can mean that the client is unable to use these acknowledgments if can mean that the client is unable to use these acknowledgments if
the server cryptographic handshake messages are delayed or lost. the server cryptographic handshake messages are delayed or lost.
Note that the same limitation applies to other data sent by the Note that the same limitation applies to other data sent by the
server protected by the 1-RTT keys. server protected by the 1-RTT keys.
Endpoints SHOULD send acknowledgments for packets containing CRYPTO Endpoints SHOULD send acknowledgments for packets containing CRYPTO
frames with a reduced delay; see Section 4.3.1 of [QUIC-RECOVERY]. frames with a reduced delay; see Section 5.3.1 of [QUIC-RECOVERY].
13.2. Retransmission of Information 13.2. Retransmission of Information
QUIC packets that are determined to be lost are not retransmitted QUIC packets that are determined to be lost are not retransmitted
whole. The same applies to the frames that are contained within lost whole. The same applies to the frames that are contained within lost
packets. Instead, the information that might be carried in frames is packets. Instead, the information that might be carried in frames is
sent again in new frames as needed. sent again in new frames as needed.
New frames and packets are used to carry information that is New frames and packets are used to carry information that is
determined to have been lost. In general, information is sent again determined to have been lost. In general, information is sent again
when a packet containing that information is determined to be lost when a packet containing that information is determined to be lost
and sending ceases when a packet containing that information is and sending ceases when a packet containing that information is
acknowledged. acknowledged.
o Data sent in CRYPTO frames is retransmitted according to the rules o Data sent in CRYPTO frames is retransmitted according to the rules
in [QUIC-RECOVERY], until all data has been acknowledged. in [QUIC-RECOVERY], until all data has been acknowledged.
o Application data sent in STREAM frames is retransmitted in new o Application data sent in STREAM frames is retransmitted in new
STREAM frames unless the endpoint has sent a RST_STREAM for that STREAM frames unless the endpoint has sent a RESET_STREAM for that
stream. Once an endpoint sends a RST_STREAM frame, no further stream. Once an endpoint sends a RESET_STREAM frame, no further
STREAM frames are needed. STREAM frames are needed.
o The most recent set of acknowledgments are sent in ACK frames. An o The most recent set of acknowledgments are sent in ACK frames. An
ACK frame SHOULD contain all unacknowledged acknowledgments, as ACK frame SHOULD contain all unacknowledged acknowledgments, as
described in Section 13.1.1. described in Section 13.1.1.
o Cancellation of stream transmission, as carried in a RST_STREAM o Cancellation of stream transmission, as carried in a RESET_STREAM
frame, is sent until acknowledged or until all stream data is frame, is sent until acknowledged or until all stream data is
acknowledged by the peer (that is, either the "Reset Recvd" or acknowledged by the peer (that is, either the "Reset Recvd" or
"Data Recvd" state is reached on the send stream). The content of "Data Recvd" state is reached on the send stream). The content of
a RST_STREAM frame MUST NOT change when it is sent again. a RESET_STREAM frame MUST NOT change when it is sent again.
o Similarly, a request to cancel stream transmission, as encoded in o Similarly, a request to cancel stream transmission, as encoded in
a STOP_SENDING frame, is sent until the receive stream enters a STOP_SENDING frame, is sent until the receive stream enters
either a "Data Recvd" or "Reset Recvd" state, see Section 3.5. either a "Data Recvd" or "Reset Recvd" state, see Section 3.5.
o Connection close signals, including those that use o Connection close signals, including packets that contain
CONNECTION_CLOSE and APPLICATION_CLOSE frames, are not sent again CONNECTION_CLOSE frames, are not sent again when packet loss is
when packet loss is detected, but as described in Section 10. detected, but as described in Section 10.
o The current connection maximum data is sent in MAX_DATA frames. o The current connection maximum data is sent in MAX_DATA frames.
An updated value is sent in a MAX_DATA frame if the packet An updated value is sent in a MAX_DATA frame if the packet
containing the most recently sent MAX_DATA frame is declared lost, containing the most recently sent MAX_DATA frame is declared lost,
or when the endpoint decides to update the limit. Care is or when the endpoint decides to update the limit. Care is
necessary to avoid sending this frame too often as the limit can necessary to avoid sending this frame too often as the limit can
increase frequently and cause an unnecessarily large number of increase frequently and cause an unnecessarily large number of
MAX_DATA frames to be sent. MAX_DATA frames to be sent.
o The current maximum stream data offset is sent in MAX_STREAM_DATA o The current maximum stream data offset is sent in MAX_STREAM_DATA
frames. Like MAX_DATA, an updated value is sent when the packet frames. Like MAX_DATA, an updated value is sent when the packet
containing the most recent MAX_STREAM_DATA frame for a stream is containing the most recent MAX_STREAM_DATA frame for a stream is
lost or when the limit is updated, with care taken to prevent the lost or when the limit is updated, with care taken to prevent the
frame from being sent too often. An endpoint SHOULD stop sending frame from being sent too often. An endpoint SHOULD stop sending
MAX_STREAM_DATA frames when the receive stream enters a "Size MAX_STREAM_DATA frames when the receive stream enters a "Size
Known" state. Known" state.
o The maximum stream ID for a stream of a given type is sent in o The limit on streams of a given type is sent in MAX_STREAMS
MAX_STREAM_ID frames. Like MAX_DATA, an updated value is sent frames. Like MAX_DATA, an updated value is sent when a packet
when a packet containing the most recent MAX_STREAM_ID for a containing the most recent MAX_STREAMS for a stream type frame is
stream type frame is declared lost or when the limit is updated, declared lost or when the limit is updated, with care taken to
with care taken to prevent the frame from being sent too often. prevent the frame from being sent too often.
o Blocked signals are carried in BLOCKED, STREAM_BLOCKED, and o Blocked signals are carried in DATA_BLOCKED, STREAM_DATA_BLOCKED,
STREAM_ID_BLOCKED frames. BLOCKED streams have connection scope, and STREAMS_BLOCKED frames. DATA_BLOCKED streams have connection
STREAM_BLOCKED frames have stream scope, and STREAM_ID_BLOCKED scope, STREAM_DATA_BLOCKED frames have stream scope, and
frames are scoped to a specific stream type. New frames are sent STREAMS_BLOCKED frames are scoped to a specific stream type. New
if packets containing the most recent frame for a scope is lost, frames are sent if packets containing the most recent frame for a
but only while the endpoint is blocked on the corresponding limit. scope is lost, but only while the endpoint is blocked on the
These frames always include the limit that is causing blocking at corresponding limit. These frames always include the limit that
the time that they are transmitted. is causing blocking at the time that they are transmitted.
o A liveness or path validation check using PATH_CHALLENGE frames is o A liveness or path validation check using PATH_CHALLENGE frames is
sent periodically until a matching PATH_RESPONSE frame is received sent periodically until a matching PATH_RESPONSE frame is received
or until there is no remaining need for liveness or path or until there is no remaining need for liveness or path
validation checking. PATH_CHALLENGE frames include a different validation checking. PATH_CHALLENGE frames include a different
payload each time they are sent. payload each time they are sent.
o Responses to path validation using PATH_RESPONSE frames are sent o Responses to path validation using PATH_RESPONSE frames are sent
just once. A new PATH_CHALLENGE frame will be sent if another just once. A new PATH_CHALLENGE frame will be sent if another
PATH_RESPONSE frame is needed. PATH_RESPONSE frame is needed.
o New connection IDs are sent in NEW_CONNECTION_ID frames and o New connection IDs are sent in NEW_CONNECTION_ID frames and
retransmitted if the packet containing them is lost. retransmitted if the packet containing them is lost.
Retransmissions of this frame carry the same sequence number Retransmissions of this frame carry the same sequence number
value. Likewise, retired connection IDs are sent in value. Likewise, retired connection IDs are sent in
RETIRE_CONNECTION_ID frames and retransmitted if the packet RETIRE_CONNECTION_ID frames and retransmitted if the packet
containing them is lost. containing them is lost.
o PADDING frames contain no information, so lost PADDING frames do o PING and PADDING frames contain no information, so lost PING or
not require repair. PADDING frames do not require repair.
Endpoints SHOULD prioritize retransmission of data over sending new
data, unless priorities specified by the application indicate
otherwise (see Section 2.3).
Upon detecting losses, a sender MUST take appropriate congestion Upon detecting losses, a sender MUST take appropriate congestion
control action. The details of loss detection and congestion control control action. The details of loss detection and congestion control
are described in [QUIC-RECOVERY]. are described in [QUIC-RECOVERY].
13.3. Explicit Congestion Notification 13.3. Explicit Congestion Notification
QUIC endpoints use Explicit Congestion Notification (ECN) [RFC3168] QUIC endpoints use Explicit Congestion Notification (ECN) [RFC3168]
to detect and respond to network congestion. ECN allows a network to detect and respond to network congestion. ECN allows a network
node to indicate congestion in the network by setting a codepoint in node to indicate congestion in the network by setting a codepoint in
skipping to change at page 70, line 7 skipping to change at page 71, line 7
To use ECN, QUIC endpoints first determine whether a path supports To use ECN, QUIC endpoints first determine whether a path supports
ECN marking and the peer is able to access the ECN codepoint in the ECN marking and the peer is able to access the ECN codepoint in the
IP header. A network path does not support ECN if ECN marked packets IP header. A network path does not support ECN if ECN marked packets
get dropped or ECN markings are rewritten on the path. An endpoint get dropped or ECN markings are rewritten on the path. An endpoint
verifies the path, both during connection establishment and when verifies the path, both during connection establishment and when
migrating to a new path (see Section 9). migrating to a new path (see Section 9).
13.3.1. ECN Counters 13.3.1. ECN Counters
On receiving a packet with an ECT or CE codepoint, an endpoint that On receiving a QUIC packet with an ECT or CE codepoint, an endpoint
can access the IP ECN codepoints increases the corresponding ECT(0), that can access the ECN codepoints from the enclosing IP packet
ECT(1), or CE count, and includes these counters in subsequent (see increases the corresponding ECT(0), ECT(1), or CE count, and includes
Section 13.1) ACK frames (see Section 19.15). these counters in subsequent ACK frames (see Section 13.1 and
Section 19.3).
A packet detected by a receiver as a duplicate does not affect the A packet detected by a receiver as a duplicate does not affect the
receiver's local ECN codepoint counts; see (Section 21.7) for receiver's local ECN codepoint counts; see (Section 21.7) for
relevant security concerns. relevant security concerns.
If an endpoint receives a packet without an ECT or CE codepoint, it If an endpoint receives a QUIC packet without an ECT or CE codepoint
responds per Section 13.1 with an ACK frame. If an endpoint does not in the IP packet header, it responds per Section 13.1 with an ACK
have access to received ECN codepoints, it acknowledges received frame without increasing any ECN counters. Similarly, if an endpoint
packets per Section 13.1 with an ACK frame. does not have access to received ECN codepoints, it does not increase
ECN counters.
Coalesced packets (see Section 12.2) mean that several packets can
share the same IP header. The ECN counter for the ECN codepoint
received in the associated IP header are incremented once for each
QUIC packet, not per enclosing IP packet or UDP datagram.
Each packet number space maintains separate acknowledgement state and
separate ECN counters. For example, if one each of an Initial,
0-RTT, Handshake, and 1-RTT QUIC packet are coalesced, the
corresponding counters for the Initial and Handshake packet number
space will be incremented by one and the counters for the 1-RTT
packet number space will be increased by two.
13.3.2. ECN Verification 13.3.2. ECN Verification
Each endpoint independently verifies and enables use of ECN by Each endpoint independently verifies and enables use of ECN by
setting the IP header ECN codepoint to ECN Capable Transport (ECT) setting the IP header ECN codepoint to ECN Capable Transport (ECT)
for the path from it to the other peer. Even if ECN is not used on for the path from it to the other peer. Even if ECN is not used on
the path to the peer, the endpoint MUST provide feedback about ECN the path to the peer, the endpoint MUST provide feedback about ECN
markings received (if accessible). markings received (if accessible).
To verify both that a path supports ECN and the peer can provide ECN To verify both that a path supports ECN and the peer can provide ECN
feedback, an endpoint MUST set the ECT(0) codepoint in the IP header feedback, an endpoint MUST set the ECT(0) codepoint in the IP header
of all outgoing packets [RFC8311]. of all outgoing packets [RFC8311].
If an ECT codepoint set in the IP header is not corrupted by a If an ECT codepoint set in the IP header is not corrupted by a
network device, then a received packet contains either the codepoint network device, then a received packet contains either the codepoint
sent by the peer or the Congestion Experienced (CE) codepoint set by sent by the peer or the Congestion Experienced (CE) codepoint set by
a network device that is experiencing congestion. a network device that is experiencing congestion.
If a packet sent with an ECT codepoint is newly acknowledged by the If a QUIC packet sent with an ECT codepoint is newly acknowledged by
peer in an ACK frame without ECN feedback, the endpoint stops setting the peer in an ACK frame without ECN feedback, the endpoint stops
ECT codepoints in subsequent packets, with the expectation that setting ECT codepoints in subsequent IP packets, with the expectation
either the network or the peer no longer supports ECN. that either the network path or the peer no longer supports ECN.
To protect the connection from arbitrary corruption of ECN codepoints To reduce the risk of non-standard compliant ECN markings affecting
by the network, an endpoint verifies the following when an ACK frame the operation of an endpoint, an endpoint verifies the counts it
is received: receives when it receives new acknowledgements:
o The increase in ECT(0) and ECT(1) counters MUST be at least the o The increase in ECT(0) and ECT(1) counters MUST be at least the
number of packets newly acknowledged that were sent with the number of QUIC packets newly acknowledged that were sent with the
corresponding codepoint. corresponding codepoint minus the increase in the CE counter.
This detects network remarking between ECT(0) and ECT(1).
o The total increase in ECT(0), ECT(1), and CE counters reported in o The total increase in ECT(0), ECT(1), and CE counters reported in
the ACK frame MUST be at least the total number of packets newly the ACK frame MUST be at least the total number of QUIC packets
acknowledged in this ACK frame. newly acknowledged in this ACK frame. This detects if the network
changes ECT(0), ECT(1) or CE to Not-ECT.
This validation is only performed if the ACK frame increases the
largest received packet number. Reordered acknowledgments could have
lower counter values and might not be successfully validated as a
result.
These counts might be inflated if acknowledgments are never received
for packets that were successfully delivered. If validation
succeeds, an endpoint MUST increase its expected counter values to
those it receives.
An endpoint could miss acknowledgements for a packet when ACK frames An endpoint could miss acknowledgements for a packet when ACK frames
are lost. It is therefore possible for the total increase in ECT(0), are lost. It is therefore possible for the total increase in ECT(0),
ECT(1), and CE counters to be greater than the number of packets ECT(1), and CE counters to be greater than the number of packets
acknowledged in an ACK frame. When this happens, the local reference acknowledged in an ACK frame. When this happens, the local reference
counts MUST be increased to match the counters in the ACK frame. counts MUST be increased to match the counters in the ACK frame.
Upon successful verification, an endpoint continues to set ECT Upon successful verification, an endpoint continues to set ECT
codepoints in subsequent packets with the expectation that the path codepoints in subsequent packets with the expectation that the path
is ECN-capable. is ECN-capable.
If verification fails, then the endpoint ceases setting ECT If verification fails, then the endpoint ceases setting ECT
codepoints in subsequent packets with the expectation that either the codepoints in subsequent IP packets with the expectation that either
network or the peer does not support ECN. the network path or the peer does not support ECN.
If an endpoint sets ECT codepoints on outgoing packets and encounters If an endpoint sets ECT codepoints on outgoing IP packets and
a retransmission timeout due to the absence of acknowledgments from encounters a retransmission timeout due to the absence of
the peer (see [QUIC-RECOVERY]), or if an endpoint has reason to acknowledgments from the peer (see [QUIC-RECOVERY]), or if an
believe that a network element might be corrupting ECN codepoints, endpoint has reason to believe that an element on the network path
the endpoint MAY cease setting ECT codepoints in subsequent packets. might be corrupting ECN codepoints, the endpoint MAY cease setting
Doing so allows the connection to traverse network elements that drop ECT codepoints in subsequent packets. Doing so allows the connection
or corrupt ECN codepoints in the IP header. to traverse network elements that drop IP packets with ECT or CE
markings or corrupt ECN codepoints in the IP header.
14. Packet Size 14. Packet Size
The QUIC packet size includes the QUIC header and integrity check, The QUIC packet size includes the QUIC header and protected payload,
but not the UDP or IP header. but not the UDP or IP header.
Clients MUST ensure that the first Initial packet they send is sent Clients MUST ensure they send the first Initial packet in a UDP
in a UDP datagram that is at least 1200 octets. Padding the Initial datagram that is at least 1200 bytes. The payload of a UDP datagram
packet or including a 0-RTT packet in the same datagram are ways to carrying the Initial packet MUST be expanded to at least 1200 bytes,
meet this requirement. Sending a UDP datagram of this size ensures by adding PADDING frames to the Initial packet and/or by combining
that the network path supports a reasonable Maximum Transmission Unit the Initial packet with a 0-RTT packet (see Section 12.2). Sending a
(MTU), and helps reduce the amplitude of amplification attacks caused UDP datagram of this size ensures that the network path supports a
by server responses toward an unverified client address, see reasonable Maximum Transmission Unit (MTU), and helps reduce the
Section 8. amplitude of amplification attacks caused by server responses toward
an unverified client address, see Section 8.
The payload of a UDP datagram carrying the Initial packet MUST be
expanded to at least 1200 octets, by adding PADDING frames to the
Initial packet and/or by combining the Initial packet with a 0-RTT
packet (see Section 12.2).
The datagram containing the first Initial packet from a client MAY The datagram containing the first Initial packet from a client MAY
exceed 1200 octets if the client believes that the Path Maximum exceed 1200 bytes if the client believes that the Path Maximum
Transmission Unit (PMTU) supports the size that it chooses. Transmission Unit (PMTU) supports the size that it chooses.
A server MAY send a CONNECTION_CLOSE frame with error code A server MAY send a CONNECTION_CLOSE frame with error code
PROTOCOL_VIOLATION in response to the first Initial packet it PROTOCOL_VIOLATION in response to the first Initial packet it
receives from a client if the UDP datagram is smaller than 1200 receives from a client if the UDP datagram is smaller than 1200
octets. It MUST NOT send any other frame type in response, or bytes. It MUST NOT send any other frame type in response, or
otherwise behave as if any part of the offending packet was processed otherwise behave as if any part of the offending packet was processed
as valid. as valid.
The server MUST also limit the number of bytes it sends before The server MUST also limit the number of bytes it sends before
validating the address of the client, see Section 8. validating the address of the client, see Section 8.
14.1. Path Maximum Transmission Unit 14.1. Path Maximum Transmission Unit (PMTU)
The Path Maximum Transmission Unit (PMTU) is the maximum size of the The PMTU is the maximum size of the entire IP packet including the IP
entire IP header, UDP header, and UDP payload. The UDP payload header, UDP header, and UDP payload. The UDP payload includes the
includes the QUIC packet header, protected payload, and any QUIC packet header, protected payload, and any authentication fields.
authentication fields. The PMTU can depend upon the current path characteristics.
Therefore, the current largest UDP payload an implementation will
send is referred to as the QUIC maximum packet size.
All QUIC packets SHOULD be sized to fit within the estimated PMTU to QUIC depends on a PMTU of at least 1280 bytes. This is the IPv6
avoid IP fragmentation or packet drops. To optimize bandwidth minimum size [RFC8200] and is also supported by most modern IPv4
efficiency, endpoints SHOULD use Packetization Layer PMTU Discovery networks. All QUIC packets (except for PMTU probe packets) SHOULD be
([PLPMTUD]). Endpoints MAY use PMTU Discovery ([PMTUDv4], [PMTUDv6]) sized to fit within the maximum packet size to avoid the packet being
for detecting the PMTU, setting the PMTU appropriately, and storing fragmented or dropped [RFC8085].
the result of previous PMTU determinations.
In the absence of these mechanisms, QUIC endpoints SHOULD NOT send IP An endpoint SHOULD use Datagram Packetization Layer PMTU Discovery
packets larger than 1280 octets. Assuming the minimum IP header ([DPLPMTUD]) or implement Path MTU Discovery (PMTUD) [RFC1191]
size, this results in a QUIC packet size of 1232 octets for IPv6 and [RFC8201] to determine whether the path to a destination will support
1252 octets for IPv4. Some QUIC implementations MAY be more a desired message size without fragmentation.
conservative in computing allowed QUIC packet size given unknown
tunneling overheads or IP header options.
QUIC endpoints that implement any kind of PMTU discovery SHOULD In the absence of these mechanisms, QUIC endpoints SHOULD NOT send IP
maintain an estimate for each combination of local and remote IP packets larger than 1280 bytes. Assuming the minimum IP header size,
addresses. Each pairing of local and remote addresses could have a this results in a QUIC maximum packet size of 1232 bytes for IPv6 and
different maximum MTU in the path. 1252 bytes for IPv4. A QUIC implementation MAY be more conservative
in computing the QUIC maximum packet size to allow for unknown tunnel
overheads or IP header options/extensions.
QUIC depends on the network path supporting an MTU of at least 1280 Each pair of local and remote addresses could have a different PMTU.
octets. This is the IPv6 minimum MTU and therefore also supported by QUIC implementations that implement any kind of PMTU discovery
most modern IPv4 networks. An endpoint MUST NOT reduce its MTU below therefore SHOULD maintain a maximum packet size for each combination
this number, even if it receives signals that indicate a smaller of local and remote IP addresses.
limit might exist.
If a QUIC endpoint determines that the PMTU between any pair of local If a QUIC endpoint determines that the PMTU between any pair of local
and remote IP addresses has fallen below 1280 octets, it MUST and remote IP addresses has fallen below the size needed to support
immediately cease sending QUIC packets on the affected path. This the smallest allowed maximum packet size, it MUST immediately cease
could result in termination of the connection if an alternative path sending QUIC packets on the affected path. An endpoint MAY terminate
cannot be found. the connection if an alternative path cannot be found.
14.1.1. IPv4 PMTU Discovery 14.2. ICMP Packet Too Big Messages
Traditional ICMP-based path MTU discovery in IPv4 [PMTUDv4] is PMTU discovery [RFC1191] [RFC8201] relies on reception of ICMP
potentially vulnerable to off-path attacks that successfully guess messages (e.g., IPv6 Packet Too Big messages) that indicate when a
the IP/port 4-tuple and reduce the MTU to a bandwidth-inefficient packet is dropped because it is larger than the local router MTU.
value. TCP connections mitigate this risk by using the (at minimum) DPLPMTUD can also optionally use these messages. This use of ICMP
8 bytes of transport header echoed in the ICMP message to validate messages is potentially vulnerable to off-path attacks that
the TCP sequence number as valid for the current connection. successfully guess the IP address 3-tuple and reduce the PMTU to a
However, as QUIC operates over UDP, in IPv4 the echoed information bandwidth-inefficient value.
could consist only of the IP and UDP headers, which usually has
insufficient entropy to mitigate off-path attacks.
As a result, endpoints that implement PMTUD in IPv4 SHOULD take steps An endpoint MUST ignore an ICMP message that claims the PMTU has
to mitigate this risk. For instance, an application could: decreased below 1280 bytes.
o Set the IPv4 Don't Fragment (DF) bit on a small proportion of QUIC endpoints SHOULD provide validation to protect from off-path
packets, so that most invalid ICMP messages arrive when there are injection of ICMP messages as specified in [RFC8201] and Section 5.2
no DF packets outstanding, and can therefore be identified as of [RFC8085]. This uses the quoted packet supplied in the payload of
spurious. an ICMP message, which, when present, can be used to associate the
message with a corresponding transport connection [DPLPMTUD].
o Store additional information from the IP or UDP headers from DF The requirements for generating ICMP ([RFC1812], [RFC4443]) state
packets (for example, the IP ID or UDP checksum) to further that the quoted packet should contain as much of the original packet
authenticate incoming Datagram Too Big messages. as possible without exceeding the minimum MTU for the IP version.
The size of the quoted packet can actually be smaller, or the
information unintelligible, as described in Section 1.1 of
[DPLPMTUD].
o Any reduction in PMTU due to a report contained in an ICMP packet When a randomized source port is used for a QUIC connection, this can
is provisional until QUIC's loss detection algorithm determines provide some protection from off path attacks that forge ICMP
that the packet is actually lost. messages. The source port in a quoted packet can be checked for UDP
transports [RFC8085] such as QUIC. When used, a stack will only pass
ICMP messages to a QUIC endpoint where the port information in quoted
packet within the ICMP payload matches a port used by QUIC.
14.2. Special Considerations for Packetization Layer PMTU Discovery As a part of ICMP validation, QUIC endpoints SHOULD validate that
connection ID information corresponds to an active session.
The PADDING frame provides a useful option for PMTU probe packets. Further validation can also be provided:
PADDING frames generate acknowledgements, but they need not be
delivered reliably. As a result, the loss of PADDING frames in probe
packets does not require delay-inducing retransmission. However,
PADDING frames do consume congestion window, which may delay the
transmission of subsequent application data.
When implementing the algorithm in Section 7.2 of [PLPMTUD], the o An IPv4 endpoint could set the Don't Fragment (DF) bit on a small
initial value of search_low SHOULD be consistent with the IPv6 proportion of packets, so that most invalid ICMP messages arrive
minimum packet size. Paths that do not support this size cannot when there are no DF packets outstanding, and can therefore be
deliver Initial packets, and therefore are not QUIC-compliant. identified as spurious.
Section 7.3 of [PLPMTUD] discusses trade-offs between small and large o An endpoint could store additional information from the IP or UDP
increases in the size of probe packets. As QUIC probe packets need headers to use for validation (for example, the IP ID or UDP
not contain application data, aggressive increases in probe size checksum).
carry fewer consequences.
The endpoint SHOULD ignore all ICMP messages that are not validated
or do not carry sufficient quoted packet payload to perform
validation. Any reduction in the QUIC maximum packet size MAY be
provisional until QUIC's loss detection algorithm determines that the
quoted packet has actually been lost.
14.3. Datagram Packetization Layer PMTU Discovery
Section 6.4 of [DPLPMTUD] provides considerations for implementing
Datagram Packetization Layer PMTUD (DPLPMTUD) with QUIC.
When implementing the algorithm in Section 5.3 of [DPLPMTUD], the
initial value of BASE_PMTU SHOULD be consistent with the minimum QUIC
packet size (1232 bytes for IPv6 and 1252 bytes for IPv4).
PING and PADDING frames can be used to generate PMTU probe packets.
These frames might not be retransmitted if a probe packet containing
them is lost. However, these frames do consume congestion window,
which could delay the transmission of subsequent application data.
A PING frame can be included in a PMTU probe to ensure that a valid
probe is acknowledged.
The considerations for processing ICMP messages in the previous
section also apply if these messages are used by DPLPMTUD.
15. Versions 15. Versions
QUIC versions are identified using a 32-bit unsigned number. QUIC versions are identified using a 32-bit unsigned number.
The version 0x00000000 is reserved to represent version negotiation. The version 0x00000000 is reserved to represent version negotiation.
This version of the specification is identified by the number This version of the specification is identified by the number
0x00000001. 0x00000001.
Other versions of QUIC might have different properties to this Other versions of QUIC might have different properties to this
skipping to change at page 74, line 26 skipping to change at page 76, line 26
[QUIC-INVARIANTS]. [QUIC-INVARIANTS].
Version 0x00000001 of QUIC uses TLS as a cryptographic handshake Version 0x00000001 of QUIC uses TLS as a cryptographic handshake
protocol, as described in [QUIC-TLS]. protocol, as described in [QUIC-TLS].
Versions with the most significant 16 bits of the version number Versions with the most significant 16 bits of the version number
cleared are reserved for use in future IETF consensus documents. cleared are reserved for use in future IETF consensus documents.
Versions that follow the pattern 0x?a?a?a?a are reserved for use in Versions that follow the pattern 0x?a?a?a?a are reserved for use in
forcing version negotiation to be exercised. That is, any version forcing version negotiation to be exercised. That is, any version
number where the low four bits of all octets is 1010 (in binary). A number where the low four bits of all bytes is 1010 (in binary). A
client or server MAY advertise support for any of these reserved client or server MAY advertise support for any of these reserved
versions. versions.
Reserved version numbers will probably never represent a real Reserved version numbers will probably never represent a real
protocol; a client MAY use one of these version numbers with the protocol; a client MAY use one of these version numbers with the
expectation that the server will initiate version negotiation; a expectation that the server will initiate version negotiation; a
server MAY advertise support for one of these versions and can expect server MAY advertise support for one of these versions and can expect
that clients ignore the value. that clients ignore the value.
[[RFC editor: please remove the remainder of this section before [[RFC editor: please remove the remainder of this section before
skipping to change at page 75, line 9 skipping to change at page 77, line 9
transport-13 would be identified as 0xff00000D. transport-13 would be identified as 0xff00000D.
Implementors are encouraged to register version numbers of QUIC that Implementors are encouraged to register version numbers of QUIC that
they are using for private experimentation on the GitHub wiki at they are using for private experimentation on the GitHub wiki at
<https://github.com/quicwg/base-drafts/wiki/QUIC-Versions>. <https://github.com/quicwg/base-drafts/wiki/QUIC-Versions>.
16. Variable-Length Integer Encoding 16. Variable-Length Integer Encoding
QUIC packets and frames commonly use a variable-length encoding for QUIC packets and frames commonly use a variable-length encoding for
non-negative integer values. This encoding ensures that smaller non-negative integer values. This encoding ensures that smaller
integer values need fewer octets to encode. integer values need fewer bytes to encode.
The QUIC variable-length integer encoding reserves the two most The QUIC variable-length integer encoding reserves the two most
significant bits of the first octet to encode the base 2 logarithm of significant bits of the first byte to encode the base 2 logarithm of
the integer encoding length in octets. The integer value is encoded the integer encoding length in bytes. The integer value is encoded
on the remaining bits, in network byte order. on the remaining bits, in network byte order.
This means that integers are encoded on 1, 2, 4, or 8 octets and can This means that integers are encoded on 1, 2, 4, or 8 bytes and can
encode 6, 14, 30, or 62 bit values respectively. Table 4 summarizes encode 6, 14, 30, or 62 bit values respectively. Table 4 summarizes
the encoding properties. the encoding properties.
+------+--------+-------------+-----------------------+ +------+--------+-------------+-----------------------+
| 2Bit | Length | Usable Bits | Range | | 2Bit | Length | Usable Bits | Range |
+------+--------+-------------+-----------------------+ +------+--------+-------------+-----------------------+
| 00 | 1 | 6 | 0-63 | | 00 | 1 | 6 | 0-63 |
| | | | | | | | | |
| 01 | 2 | 14 | 0-16383 | | 01 | 2 | 14 | 0-16383 |
| | | | | | | | | |
| 10 | 4 | 30 | 0-1073741823 | | 10 | 4 | 30 | 0-1073741823 |
| | | | | | | | | |
| 11 | 8 | 62 | 0-4611686018427387903 | | 11 | 8 | 62 | 0-4611686018427387903 |
+------+--------+-------------+-----------------------+ +------+--------+-------------+-----------------------+
Table 4: Summary of Integer Encodings Table 4: Summary of Integer Encodings
For example, the eight octet sequence c2 19 7c 5e ff 14 e8 8c (in For example, the eight byte sequence c2 19 7c 5e ff 14 e8 8c (in
hexadecimal) decodes to the decimal value 151288809941952652; the hexadecimal) decodes to the decimal value 151288809941952652; the
four octet sequence 9d 7f 3e 7d decodes to 494878333; the two octet four byte sequence 9d 7f 3e 7d decodes to 494878333; the two byte
sequence 7b bd decodes to 15293; and the single octet 25 decodes to sequence 7b bd decodes to 15293; and the single byte 25 decodes to 37
37 (as does the two octet sequence 40 25). (as does the two byte sequence 40 25).
Error codes (Section 20) and versions Section 15 are described using Error codes (Section 20) and versions Section 15 are described using
integers, but do not use this encoding. integers, but do not use this encoding.
17. Packet Formats 17. Packet Formats
All numeric values are encoded in network byte order (that is, big- All numeric values are encoded in network byte order (that is, big-
endian) and all field sizes are in bits. Hexadecimal notation is endian) and all field sizes are in bits. Hexadecimal notation is
used for describing the value of fields. used for describing the value of fields.
17.1. Packet Number Encoding and Decoding 17.1. Packet Number Encoding and Decoding
Packet numbers in long and short packet headers are encoded as Packet numbers in long and short packet headers are encoded in 1 to 4
follows. The number of bits required to represent the packet number bytes. The number of bits required to represent the packet number is
is first reduced by including only a variable number of the least reduced by including the least significant bits of the packet number.
significant bits of the packet number. One or two of the most
significant bits of the first octet are then used to represent how
many bits of the packet number are provided, as shown in Table 5.
+---------------------+----------------+--------------+
| First octet pattern | Encoded Length | Bits Present |
+---------------------+----------------+--------------+
| 0b0xxxxxxx | 1 octet | 7 |
| | | |
| 0b10xxxxxx | 2 | 14 |
| | | |
| 0b11xxxxxx | 4 | 30 |
+---------------------+----------------+--------------+
Table 5: Packet Number Encodings for Packet Headers
Note that these encodings are similar to those in Section 16, but use
different values.
Finally, the encoded packet number is protected as described in The encoded packet number is protected as described in Section 5.4 of
Section 5.3 of [QUIC-TLS]. [QUIC-TLS].
The sender MUST use a packet number size able to represent more than The sender MUST use a packet number size able to represent more than
twice as large a range than the difference between the largest twice as large a range than the difference between the largest
acknowledged packet and packet number being sent. A peer receiving acknowledged packet and packet number being sent. A peer receiving
the packet will then correctly decode the packet number, unless the the packet will then correctly decode the packet number, unless the
packet is delayed in transit such that it arrives after many higher- packet is delayed in transit such that it arrives after many higher-
numbered packets have been received. An endpoint SHOULD use a large numbered packets have been received. An endpoint SHOULD use a large
enough packet number encoding to allow the packet number to be enough packet number encoding to allow the packet number to be
recovered even if the packet arrives after packets that are sent recovered even if the packet arrives after packets that are sent
afterwards. afterwards.
As a result, the size of the packet number encoding is at least one As a result, the size of the packet number encoding is at least one
more than the base 2 logarithm of the number of contiguous bit more than the base-2 logarithm of the number of contiguous
unacknowledged packet numbers, including the new packet. unacknowledged packet numbers, including the new packet.
For example, if an endpoint has received an acknowledgment for packet For example, if an endpoint has received an acknowledgment for packet
0x6afa2f, sending a packet with a number of 0x6b2d79 requires a 0xabe8bc, sending a packet with a number of 0xac5c02 requires a
packet number encoding with 14 bits or more; whereas the 30-bit packet number encoding with 16 bits or more; whereas the 24-bit
packet number encoding is needed to send a packet with a number of packet number encoding is needed to send a packet with a number of
0x6bc107. 0xace8fe.
At a receiver, protection of the packet number is removed prior to At a receiver, protection of the packet number is removed prior to
recovering the full packet number. The full packet number is then recovering the full packet number. The full packet number is then
reconstructed based on the number of significant bits present, the reconstructed based on the number of significant bits present, the
value of those bits, and the largest packet number received on a value of those bits, and the largest packet number received on a
successfully authenticated packet. Recovering the full packet number successfully authenticated packet. Recovering the full packet number
is necessary to successfully remove packet protection. is necessary to successfully remove packet protection.
Once packet number protection is removed, the packet number is Once header protection is removed, the packet number is decoded by
decoded by finding the packet number value that is closest to the finding the packet number value that is closest to the next expected
next expected packet. The next expected packet is the highest packet. The next expected packet is the highest received packet
received packet number plus one. For example, if the highest number plus one. For example, if the highest successfully
successfully authenticated packet had a packet number of 0xaa82f30e, authenticated packet had a packet number of 0xa82f30ea, then a packet
then a packet containing a 14-bit value of 0x9b3 will be decoded as containing a 16-bit value of 0x9b32 will be decoded as 0xa82f9b32.
0xaa8309b3. Example pseudo-code for packet number decoding can be Example pseudo-code for packet number decoding can be found in
found in Appendix A. Appendix A.
17.2. Long Header Packet 17.2. Long Header Packet
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|1| Type (7) | |1|1|T T|R R|P P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version (32) | | Version (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|DCIL(4)|SCIL(4)| |DCIL(4)|SCIL(4)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Connection ID (0/32..144) ... | Destination Connection ID (0/32..144) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Connection ID (0/32..144) ... | Source Connection ID (0/32..144) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (i) ... | Length (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Packet Number (8/16/32) | | Packet Number (8/16/24/32) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload (*) ... | Payload (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: Long Header Packet Format Figure 10: Long Header Packet Format
Long headers are used for packets that are sent prior to the Long headers are used for packets that are sent prior to the
completion of version negotiation and establishment of 1-RTT keys. completion of version negotiation and establishment of 1-RTT keys.
Once both conditions are met, a sender switches to sending packets Once both conditions are met, a sender switches to sending packets
using the short header (Section 17.3). The long form allows for using the short header (Section 17.3). The long form allows for
special packets - such as the Version Negotiation packet - to be special packets - such as the Version Negotiation packet - to be
represented in this uniform fixed-length packet format. Packets that represented in this uniform fixed-length packet format. Packets that
use the long header contain the following fields: use the long header contain the following fields:
Header Form: The most significant bit (0x80) of octet 0 (the first Header Form: The most significant bit (0x80) of byte 0 (the first
octet) is set to 1 for long headers. byte) is set to 1 for long headers.
Long Packet Type: The remaining seven bits of octet 0 contain the Fixed Bit: The next bit (0x40) of byte 0 is set to 1. Packets
packet type. This field can indicate one of 128 packet types. containing a zero value for this bit are not valid packets in this
The types specified for this version are listed in Table 6. version and MUST be discarded.
Version: The QUIC Version is a 32-bit field that follows the Type. Long Packet Type (T): The next two bits (those with a mask of 0x30)
This field indicates which version of QUIC is in use and of byte 0 contain a packet type. Packet types are listed in
Table 5.
Reserved Bits (R): The next two bits (those with a mask of 0x0c) of
byte 0 are reserved. These bits are protected using header
protection (see Section 5.4 of [QUIC-TLS]). The value included
prior to protection MUST be set to 0. An endpoint MUST treat
receipt of a packet that has a non-zero value for these bits after
removing protection as a connection error of type
PROTOCOL_VIOLATION.
Packet Number Length (P): The least significant two bits (those with
a mask of 0x03) of byte 0 contain the length of the packet number,
encoded as an unsigned, two-bit integer that is one less than the
length of the packet number field in bytes. That is, the length
of the packet number field is the value of this field, plus one.
These bits are protected using header protection (see Section 5.4
of [QUIC-TLS]).
Version: The QUIC Version is a 32-bit field that follows the first
byte. This field indicates which version of QUIC is in use and
determines how the rest of the protocol fields are interpreted. determines how the rest of the protocol fields are interpreted.
DCIL and SCIL: The octet following the version contains the lengths DCIL and SCIL: The byte following the version contains the lengths
of the two connection ID fields that follow it. These lengths are of the two connection ID fields that follow it. These lengths are
encoded as two 4-bit unsigned integers. The Destination encoded as two 4-bit unsigned integers. The Destination
Connection ID Length (DCIL) field occupies the 4 high bits of the Connection ID Length (DCIL) field occupies the 4 high bits of the
octet and the Source Connection ID Length (SCIL) field occupies byte and the Source Connection ID Length (SCIL) field occupies the
the 4 low bits of the octet. An encoded length of 0 indicates 4 low bits of the byte. An encoded length of 0 indicates that the
that the connection ID is also 0 octets in length. Non-zero connection ID is also 0 bytes in length. Non-zero encoded lengths
encoded lengths are increased by 3 to get the full length of the are increased by 3 to get the full length of the connection ID,
connection ID, producing a length between 4 and 18 octets producing a length between 4 and 18 bytes inclusive. For example,
inclusive. For example, an octet with the value 0x50 describes an an byte with the value 0x50 describes an 8-byte Destination
8-octet Destination Connection ID and a zero-length Source Connection ID and a zero-length Source Connection ID.
Connection ID.
Destination Connection ID: The Destination Connection ID field Destination Connection ID: The Destination Connection ID field
follows the connection ID lengths and is either 0 octets in length follows the connection ID lengths and is either 0 bytes in length
or between 4 and 18 octets. Section 7.2 describes the use of this or between 4 and 18 bytes. Section 7.2 describes the use of this
field in more detail. field in more detail.
Source Connection ID: The Source Connection ID field follows the Source Connection ID: The Source Connection ID field follows the
Destination Connection ID and is either 0 octets in length or Destination Connection ID and is either 0 bytes in length or
between 4 and 18 octets. Section 7.2 describes the use of this between 4 and 18 bytes. Section 7.2 describes the use of this
field in more detail. field in more detail.
Length: The length of the remainder of the packet (that is, the Length: The length of the remainder of the packet (that is, the
Packet Number and Payload fields) in octets, encoded as a Packet Number and Payload fields) in bytes, encoded as a variable-
variable-length integer (Section 16). length integer (Section 16).
Packet Number: The packet number field is 1, 2, or 4 octets long. Packet Number: The packet number field is 1 to 4 bytes long. The
The packet number has confidentiality protection separate from packet number has confidentiality protection separate from packet
packet protection, as described in Section 5.3 of [QUIC-TLS]. The protection, as described in Section 5.4 of [QUIC-TLS]. The length
length of the packet number field is encoded in the plaintext of the packet number field is encoded in the plaintext packet
packet number. See Section 17.1 for details. number. See Section 17.1 for details.
Payload: The payload of the packet. Payload: The payload of the packet.
The following packet types are defined: The following packet types are defined:
+------+-----------------+---------------+ +------+-----------------+---------------+
| Type | Name | Section | | Type | Name | Section |
+------+-----------------+---------------+ +------+-----------------+---------------+
| 0x7F | Initial | Section 17.5 | | 0x0 | Initial | Section 17.5 |
| | | | | | | |
| 0x7E | Retry | Section 17.7 | | 0x1 | 0-RTT Protected | Section 12.1 |
| | | | | | | |
| 0x7D | Handshake | Section 17.6 | | 0x2 | Handshake | Section 17.6 |
| | | | | | | |
| 0x7C | 0-RTT Protected | Section 12.1 | | 0x3 | Retry | Section 17.7 |
+------+-----------------+---------------+ +------+-----------------+---------------+
Table 6: Long Header Packet Types Table 5: Long Header Packet Types
The header form, type, connection ID lengths octet, destination and The header form bit, connection ID lengths byte, Destination and
source connection IDs, and version fields of a long header packet are Source Connection ID fields, and Version fields of a long header
version-independent. The packet number and values for packet types packet are version-independent. The other fields in the first byte,
defined in Table 6 are version-specific. See [QUIC-INVARIANTS] for plus the Length and Packet Number fields are version-specific. See
details on how packets from different versions of QUIC are [QUIC-INVARIANTS] for details on how packets from different versions
interpreted. of QUIC are interpreted.
The interpretation of the fields and the payload are specific to a The interpretation of the fields and the payload are specific to a
version and packet type. Type-specific semantics for this version version and packet type. Type-specific semantics for this version
are described in the following sections. are described in the following sections.
The end of the packet is determined by the Length field. The Length The end of the packet is determined by the Length field. The Length
field covers both the Packet Number and Payload fields, both of which field covers both the Packet Number and Payload fields, both of which
are confidentiality protected and initially of unknown length. The are confidentiality protected and initially of unknown length. The
size of the Payload field is learned once the packet number length of the Payload field is learned once header protection is
protection is removed. The Length field enables packet coalescing removed. The Length field enables packet coalescing (Section 12.2).
(Section 12.2).
17.3. Short Header Packet 17.3. Short Header Packet
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|0|K|1|1|0|R R R| |0|1|S|R|R|K|P P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Connection ID (0..144) ... | Destination Connection ID (0..144) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Packet Number (8/16/32) ... | Packet Number (8/16/24/32) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protected Payload (*) ... | Protected Payload (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: Short Header Packet Format Figure 11: Short Header Packet Format
The short header can be used after the version and 1-RTT keys are The short header can be used after the version and 1-RTT keys are
negotiated. Packets that use the short header contain the following negotiated. Packets that use the short header contain the following
fields: fields:
Header Form: The most significant bit (0x80) of octet 0 is set to 0 Header Form: The most significant bit (0x80) of byte 0 is set to 0
for the short header. for the short header.
Key Phase Bit: The second bit (0x40) of octet 0 indicates the key Fixed Bit: The next bit (0x40) of byte 0 is set to 1. Packets
phase, which allows a recipient of a packet to identify the packet containing a zero value for this bit are not valid packets in this
protection keys that are used to protect the packet. See version and MUST be discarded.
[QUIC-TLS] for details.
[[Editor's Note: this section should be removed and the bit
definitions changed before this draft goes to the IESG.]]
Third Bit: The third bit (0x20) of octet 0 is set to 1.
[[Editor's Note: this section should be removed and the bit
definitions changed before this draft goes to the IESG.]]
Fourth Bit: The fourth bit (0x10) of octet 0 is set to 1. Spin Bit (S): The sixth bit (0x20) of byte 0 is the Latency Spin
Bit, set as described in [SPIN].
[[Editor's Note: this section should be removed and the bit Reserved Bits (R): The next two bits (those with a mask of 0x18) of
definitions changed before this draft goes to the IESG.]] byte 0 are reserved. These bits are protected using header
protection (see Section 5.4 of [QUIC-TLS]). The value included
prior to protection MUST be set to 0. An endpoint MUST treat
receipt of a packet that has a non-zero value for these bits after
removing protection as a connection error of type
PROTOCOL_VIOLATION.
Google QUIC Demultiplexing Bit: The fifth bit (0x8) of octet 0 is Key Phase (K): The next bit (0x04) of byte 0 indicates the key
set to 0. This allows implementations of Google QUIC to phase, which allows a recipient of a packet to identify the packet
distinguish Google QUIC packets from short header packets sent by protection keys that are used to protect the packet. See
a client because Google QUIC servers expect the connection ID to [QUIC-TLS] for details. This bit is protected using header
always be present. The special interpretation of this bit SHOULD protection (see Section 5.4 of [QUIC-TLS]).
be removed from this specification when Google QUIC has finished
transitioning to the new header format.
Reserved: The sixth, seventh, and eighth bits (0x7) of octet 0 are Packet Number Length (P): The least significant two bits (those with
reserved for experimentation. Endpoints MUST ignore these bits on a mask of 0x03) of byte 0 contain the length of the packet number,
packets they receive unless they are participating in an encoded as an unsigned, two-bit integer that is one less than the
experiment that uses these bits. An endpoint not actively using length of the packet number field in bytes. That is, the length
these bits SHOULD set the value randomly on packets they send to of the packet number field is the value of this field, plus one.
protect against unwanted inference about particular values. These bits are protected using header protection (see Section 5.4
of [QUIC-TLS]).
Destination Connection ID: The Destination Connection ID is a Destination Connection ID: The Destination Connection ID is a
connection ID that is chosen by the intended recipient of the connection ID that is chosen by the intended recipient of the
packet. See Section 5.1 for more details. packet. See Section 5.1 for more details.
Packet Number: The packet number field is 1, 2, or 4 octets long. Packet Number: The packet number field is 1 to 4 bytes long. The
The packet number has confidentiality protection separate from packet number has confidentiality protection separate from packet
packet protection, as described in Section 5.3 of [QUIC-TLS]. The protection, as described in Section 5.4 of [QUIC-TLS]. The length
length of the packet number field is encoded in the plaintext of the packet number field is encoded in Packet Number Length
packet number. See Section 17.1 for details. field. See Section 17.1 for details.
Protected Payload: Packets with a short header always include a Protected Payload: Packets with a short header always include a
1-RTT protected payload. 1-RTT protected payload.
The header form and connection ID field of a short header packet are The header form bit and the connection ID field of a short header
version-independent. The remaining fields are specific to the packet are version-independent. The remaining fields are specific to
selected QUIC version. See [QUIC-INVARIANTS] for details on how the selected QUIC version. See [QUIC-INVARIANTS] for details on how
packets from different versions of QUIC are interpreted. packets from different versions of QUIC are interpreted.
17.4. Version Negotiation Packet 17.4. Version Negotiation Packet
A Version Negotiation packet is inherently not version-specific, and A Version Negotiation packet is inherently not version-specific, and
does not use the long packet header (see Section 17.2). Upon receipt does not use the long packet header (see Section 17.2). Upon receipt
by a client, it will appear to be a packet using the long header, but by a client, it will appear to be a packet using the long header, but
will be identified as a Version Negotiation packet based on the will be identified as a Version Negotiation packet based on the
Version field having a value of 0. Version field having a value of 0.
skipping to change at page 82, line 35 skipping to change at page 84, line 30
The Version Negotiation packet does not include the Packet Number and The Version Negotiation packet does not include the Packet Number and
Length fields present in other packets that use the long header form. Length fields present in other packets that use the long header form.
Consequently, a Version Negotiation packet consumes an entire UDP Consequently, a Version Negotiation packet consumes an entire UDP
datagram. datagram.
See Section 6 for a description of the version negotiation process. See Section 6 for a description of the version negotiation process.
17.5. Initial Packet 17.5. Initial Packet
An Initial packet uses long headers with a type value of 0x7F. It An Initial packet uses long headers with a type value of 0x0. It
carries the first CRYPTO frames sent by the client and server to carries the first CRYPTO frames sent by the client and server to
perform key exchange, and carries ACKs in either direction. perform key exchange, and carries ACKs in either direction.
In order to prevent tampering by version-unaware middleboxes, Initial In order to prevent tampering by version-unaware middleboxes, Initial
packets are protected with connection- and version-specific keys packets are protected with connection- and version-specific keys
(Initial keys) as described in [QUIC-TLS]. This protection does not (Initial keys) as described in [QUIC-TLS]. This protection does not
provide confidentiality or integrity against on-path attackers, but provide confidentiality or integrity against on-path attackers, but
provides some level of protection against off-path attackers. provides some level of protection against off-path attackers.
An Initial packet (shown in Figure 13) has two additional header An Initial packet (shown in Figure 13) has two additional header
fields that are added to the Long Header before the Length field. fields that are added to the Long Header before the Length field.
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|1| 0x7f | |1|1| 0 |R R|P P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version (32) | | Version (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|DCIL(4)|SCIL(4)| |DCIL(4)|SCIL(4)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Connection ID (0/32..144) ... | Destination Connection ID (0/32..144) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Connection ID (0/32..144) ... | Source Connection ID (0/32..144) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token Length (i) ... | Token Length (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Token (*) ... | Token (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (i) ... | Length (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Packet Number (8/16/32) | | Packet Number (8/16/24/32) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload (*) ... | Payload (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: Initial Packet Figure 13: Initial Packet
These fields include the token that was previously provided in a These fields include the token that was previously provided in a
Retry packet or NEW_TOKEN frame: Retry packet or NEW_TOKEN frame:
Token Length: A variable-length integer specifying the length of the Token Length: A variable-length integer specifying the length of the
skipping to change at page 85, line 19 skipping to change at page 87, line 19
to use a longer packet number encoding. to use a longer packet number encoding.
A client SHOULD instead generate a fresh cryptographic handshake A client SHOULD instead generate a fresh cryptographic handshake
message and start packet numbers from 0. This ensures that new 0-RTT message and start packet numbers from 0. This ensures that new 0-RTT
packets will not use the same keys, avoiding any risk of key and packets will not use the same keys, avoiding any risk of key and
nonce reuse; this also prevents 0-RTT packets from previous handshake nonce reuse; this also prevents 0-RTT packets from previous handshake
attempts from being accepted as part of the connection. attempts from being accepted as part of the connection.
17.6. Handshake Packet 17.6. Handshake Packet
A Handshake packet uses long headers with a type value of 0x7D. It A Handshake packet uses long headers with a type value of 0x3. It is
is used to carry acknowledgments and cryptographic handshake messages used to carry acknowledgments and cryptographic handshake messages
from the server and client. from the server and client.
Once a client has received a Handshake packet from a server, it uses Once a client has received a Handshake packet from a server, it uses
Handshake packets to send subsequent cryptographic handshake messages Handshake packets to send subsequent cryptographic handshake messages
and acknowledgments to the server. and acknowledgments to the server.
The Destination Connection ID field in a Handshake packet contains a The Destination Connection ID field in a Handshake packet contains a
connection ID that is chosen by the recipient of the packet; the connection ID that is chosen by the recipient of the packet; the
Source Connection ID includes the connection ID that the sender of Source Connection ID includes the connection ID that the sender of
the packet wishes to use (see Section 7.2). the packet wishes to use (see Section 7.2).
The first Handshake packet sent by a server contains a packet number The first Handshake packet sent by a server contains a packet number
of 0. Handshake packets are their own packet number space. Packet of 0. Handshake packets are their own packet number space. Packet
numbers are incremented normally for other Handshake packets. numbers are incremented normally for other Handshake packets.
The payload of this packet contains CRYPTO frames and could contain The payload of this packet contains CRYPTO frames and could contain
PADDING, or ACK frames. Handshake packets MAY contain PADDING, or ACK frames. Handshake packets MAY contain
CONNECTION_CLOSE or APPLICATION_CLOSE frames. Endpoints MUST treat CONNECTION_CLOSE frames. Endpoints MUST treat receipt of Handshake
receipt of Handshake packets with other frames as a connection error. packets with other frames as a connection error.
17.7. Retry Packet 17.7. Retry Packet
A Retry packet uses a long packet header with a type value of 0x7E. A Retry packet uses a long packet header with a type value of 0x3.
It carries an address validation token created by the server. It is It carries an address validation token created by the server. It is
used by a server that wishes to perform a stateless retry (see used by a server that wishes to perform a stateless retry (see
Section 8.1). Section 8.1).
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
|1| 0x7e | |1|1| 3 |ODCIL(4|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version (32) | | Version (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|DCIL(4)|SCIL(4)| |DCIL(4)|SCIL(4)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Connection ID (0/32..144) ... | Destination Connection ID (0/32..144) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Connection ID (0/32..144) ... | Source Connection ID (0/32..144) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ODCIL(8) | Original Destination Connection ID (*) | | Original Destination Connection ID (0/32..144) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retry Token (*) ... | Retry Token (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: Retry Packet Figure 14: Retry Packet
A Retry packet (shown in Figure 14) only uses the invariant portion A Retry packet (shown in Figure 14) only uses the invariant portion
of the long packet header [QUIC-INVARIANTS]; that is, the fields up of the long packet header [QUIC-INVARIANTS]; that is, the fields up
to and including the Destination and Source Connection ID fields. A to and including the Destination and Source Connection ID fields. A
Retry packet does not contain any protected fields. Like Version Retry packet does not contain any protected fields. Like Version
Negotiation, a Retry packet contains the long header including the Negotiation, a Retry packet contains the long header including the
connection IDs, but omits the Length, Packet Number, and Payload connection IDs, but omits the Length, Packet Number, and Payload
fields. These are replaced with: fields. These are replaced with:
ODCIL: The length of the Original Destination Connection ID field. ODCIL: The four least-significant bits of the first byte of a Retry
The length is encoded in the least significant 4 bits of the packet are not protected as they are for other packets with the
octet, using the same encoding as the DCIL and SCIL fields. The long header, because Retry packets don't contain a protected
most significant 4 bits of this octet are reserved. Unless a use payload. These bits instead encode the length of the Original
for these bits has been negotiated, endpoints SHOULD send Destination Connection ID field. The length uses the same
randomized values and MUST ignore any value that it receives. encoding as the DCIL and SCIL fields.
Original Destination Connection ID: The Original Destination Original Destination Connection ID: The Original Destination
Connection ID contains the value of the Destination Connection ID Connection ID contains the value of the Destination Connection ID
from the Initial packet that this Retry is in response to. The from the Initial packet that this Retry is in response to. The
length of this field is given in ODCIL. length of this field is given in ODCIL.
Retry Token: An opaque token that the server can use to validate the Retry Token: An opaque token that the server can use to validate the
client's address. client's address.
The server populates the Destination Connection ID with the The server populates the Destination Connection ID with the
skipping to change at page 87, line 39 skipping to change at page 89, line 39
A client sets the Destination Connection ID field of this Initial A client sets the Destination Connection ID field of this Initial
packet to the value from the Source Connection ID in the Retry packet to the value from the Source Connection ID in the Retry
packet. Changing Destination Connection ID also results in a change packet. Changing Destination Connection ID also results in a change
to the keys used to protect the Initial packet. It also sets the to the keys used to protect the Initial packet. It also sets the
Token field to the token provided in the Retry. The client MUST NOT Token field to the token provided in the Retry. The client MUST NOT
change the Source Connection ID because the server could include the change the Source Connection ID because the server could include the
connection ID as part of its token validation logic (see connection ID as part of its token validation logic (see
Section 8.1.2). Section 8.1.2).
All subsequent Initial packets from the client MUST use the The next Initial packet from the client uses the connection ID and
connection ID and token values from the Retry packet. Aside from token values from the Retry packet (see Section 7.2). Aside from
this, the Initial packet sent by the client is subject to the same this, the Initial packet sent by the client is subject to the same
restrictions as the first Initial packet. A client can either reuse restrictions as the first Initial packet. A client can either reuse
the cryptographic handshake message or construct a new one at its the cryptographic handshake message or construct a new one at its
discretion. discretion.
A client MAY attempt 0-RTT after receiving a Retry packet by sending A client MAY attempt 0-RTT after receiving a Retry packet by sending
0-RTT packets to the connection ID provided by the server. A client 0-RTT packets to the connection ID provided by the server. A client
that sends additional 0-RTT packets without constructing a new that sends additional 0-RTT packets without constructing a new
cryptographic handshake message MUST NOT reset the packet number to 0 cryptographic handshake message MUST NOT reset the packet number to 0
after a Retry packet, see Section 17.5.2. after a Retry packet, see Section 17.5.2.
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18. Transport Parameter Encoding 18. Transport Parameter Encoding
The format of the transport parameters is the TransportParameters The format of the transport parameters is the TransportParameters
struct from Figure 15. This is described using the presentation struct from Figure 15. This is described using the presentation
language from Section 3 of [TLS13]. language from Section 3 of [TLS13].
uint32 QuicVersion; uint32 QuicVersion;
enum { enum {
initial_max_stream_data_bidi_local(0), original_connection_id(0),
initial_max_data(1), idle_timeout(1),
initial_max_bidi_streams(2), stateless_reset_token(2),
idle_timeout(3), max_packet_size(3),
preferred_address(4), initial_max_data(4),
max_packet_size(5), initial_max_stream_data_bidi_local(5),
stateless_reset_token(6), initial_max_stream_data_bidi_remote(6),
ack_delay_exponent(7), initial_max_stream_data_uni(7),
initial_max_uni_streams(8), initial_max_streams_bidi(8),
disable_migration(9), initial_max_streams_uni(9),
initial_max_stream_data_bidi_remote(10), ack_delay_exponent(10),
initial_max_stream_data_uni(11), max_ack_delay(11),
max_ack_delay(12), disable_migration(12),
original_connection_id(13), preferred_address(13),
(65535) (65535)
} TransportParameterId; } TransportParameterId;
struct { struct {
TransportParameterId parameter; TransportParameterId parameter;
opaque value<0..2^16-1>; opaque value<0..2^16-1>;
} TransportParameter; } TransportParameter;
struct { struct {
select (Handshake.msg_type) { select (Handshake.msg_type) {
case client_hello: case client_hello:
QuicVersion initial_version; QuicVersion initial_version;
case encrypted_extensions: case encrypted_extensions:
QuicVersion negotiated_version; QuicVersion negotiated_version;
QuicVersion supported_versions<4..2^8-4>; QuicVersion supported_versions<4..2^8-4>;
}; };
TransportParameter parameters<0..2^16-1>; TransportParameter parameters<0..2^16-1>;
} TransportParameters; } TransportParameters;
struct {
enum { IPv4(4), IPv6(6), (15) } ipVersion;
opaque ipAddress<4..2^8-1>;
uint16 port;
opaque connectionId<0..18>;
opaque statelessResetToken[16];
} PreferredAddress;
Figure 15: Definition of TransportParameters Figure 15: Definition of TransportParameters
The "extension_data" field of the quic_transport_parameters extension The "extension_data" field of the quic_transport_parameters extension
defined in [QUIC-TLS] contains a TransportParameters value. TLS defined in [QUIC-TLS] contains a TransportParameters value. TLS
encoding rules are therefore used to describe the encoding of encoding rules are therefore used to describe the encoding of
transport parameters. transport parameters.
QUIC encodes transport parameters into a sequence of octets, which QUIC encodes transport parameters into a sequence of bytes, which are
are then included in the cryptographic handshake. then included in the cryptographic handshake.
18.1. Transport Parameter Definitions 18.1. Transport Parameter Definitions
An endpoint MAY use the following transport parameters: This section details the transport parameters defined in this
document.
idle_timeout (0x0003): The idle timeout is a value in seconds that Many transport parameters listed here have integer values. Those
is encoded as an unsigned 16-bit integer. If this parameter is transport parameters that are identified as integers use a variable-
absent or zero then the idle timeout is disabled. length integer encoding (see Section 16) and have a default value of
0 if the transport parameter is absent, unless otherwise stated.
max_packet_size (0x0005): The maximum packet size parameter places a The following transport parameters are defined:
limit on the size of packets that the endpoint is willing to
receive, encoded as an unsigned 16-bit integer. This indicates
that packets larger than this limit will be dropped. The default
for this parameter is the maximum permitted UDP payload of 65527.
Values below 1200 are invalid. This limit only applies to
protected packets (Section 12.1).
ack_delay_exponent (0x0007): An 8-bit unsigned integer value original_connection_id (0x0000): The value of the Destination
indicating an exponent used to decode the ACK Delay field in the Connection ID field from the first Initial packet sent by the
ACK frame, see Section 19.15. If this value is absent, a default client. This transport parameter is only sent by a server. A
value of 3 is assumed (indicating a multiplier of 8). The default server MUST include the original_connection_id transport parameter
value is also used for ACK frames that are sent in Initial and if it sent a Retry packet.
Handshake packets. Values above 20 are invalid.
disable_migration (0x0009): The endpoint does not support connection idle_timeout (0x0001): The idle timeout is a value in seconds that
migration (Section 9). Peers MUST NOT send any packets, including is encoded as an integer. If this parameter is absent or zero
probing packets (Section 9.1), from a local address other than then the idle timeout is disabled.
that used to perform the handshake. This parameter is a zero-
length value.
max_ack_delay (0x000c): An 8 bit unsigned integer value indicating stateless_reset_token (0x0002): A stateless reset token is used in
the maximum amount of time in milliseconds by which the endpoint verifying a stateless reset, see Section 10.4. This parameter is
will delay sending acknowledgments. If this value is absent, a a sequence of 16 bytes. This transport parameter is only sent by
default of 25 milliseconds is assumed. a server.
Either peer MAY advertise an initial value for flow control of each max_packet_size (0x0003): The maximum packet size parameter is an
type of stream on which they might receive data. Each of the integer value that limits the size of packets that the endpoint is
following transport parameters is encoded as an unsigned 32-bit willing to receive. This indicates that packets larger than this
integer in units of octets: limit will be dropped. The default for this parameter is the
maximum permitted UDP payload of 65527. Values below 1200 are
invalid. This limit only applies to protected packets
(Section 12.1).
initial_max_stream_data_bidi_local (0x0000): The initial stream initial_max_data (0x0004): The initial maximum data parameter is an
maximum data for bidirectional, locally-initiated streams integer value that contains the initial value for the maximum
parameter contains the initial flow control limit for newly amount of data that can be sent on the connection. This is
created bidirectional streams opened by the endpoint that sets the equivalent to sending a MAX_DATA (Section 19.9) for the connection
transport parameter. In client transport parameters, this applies immediately after completing the handshake.
to streams with an identifier ending in 0x0; in server transport
parameters, this applies to streams ending in 0x1.
initial_max_stream_data_bidi_remote (0x000a): The initial stream initial_max_stream_data_bidi_local (0x0005): This parameter is an
maximum data for bidirectional, peer-initiated streams parameter integer value specifying the initial flow control limit for
contains the initial flow control limit for newly created locally-initiated bidirectional streams. This limit applies to
bidirectional streams opened by the endpoint that receives the newly created bidirectional streams opened by the endpoint that
transport parameter. In client transport parameters, this applies sends the transport parameter. In client transport parameters,
to streams with an identifier ending in 0x1; in server transport this applies to streams with an identifier with the least
parameters, this applies to streams ending in 0x0. significant two bits set to 0x0; in server transport parameters,
this applies to streams with the least significant two bits set to
0x1.
initial_max_stream_data_uni (0x000b): The initial stream maximum initial_max_stream_data_bidi_remote (0x0006): This parameter is an
data for unidirectional streams parameter contains the initial integer value specifying the initial flow control limit for peer-
flow control limit for newly created unidirectional streams opened initiated bidirectional streams. This limit applies to newly
by the endpoint that receives the transport parameter. In client created bidirectional streams opened by the endpoint that receives
transport parameters, this applies to streams with an identifier the transport parameter. In client transport parameters, this
ending in 0x3; in server transport parameters, this applies to applies to streams with an identifier with the least significant
streams ending in 0x2. two bits set to 0x1; in server transport parameters, this applies
to streams with the least significant two bits set to 0x0.
If present, transport parameters that set initial flow control limits initial_max_stream_data_uni (0x0007): This parameter is an integer
(initial_max_stream_data_bidi_local, value specifying the initial flow control limit for unidirectional
initial_max_stream_data_bidi_remote, and initial_max_stream_data_uni) streams. This limit applies to newly created bidirectional
are equivalent to sending a MAX_STREAM_DATA frame (Section 19.6) on streams opened by the endpoint that receives the transport
every stream of the corresponding type immediately after opening. If parameter. In client transport parameters, this applies to
the transport parameter is absent, streams of that type start with a streams with an identifier with the least significant two bits set
flow control limit of 0. to 0x3; in server transport parameters, this applies to streams
with the least significant two bits set to 0x2.
initial_max_data (0x0001): The initial maximum data parameter initial_max_streams_bidi (0x0008): The initial maximum bidirectional
contains the initial value for the maximum amount of data that can streams parameter is an integer value that contains the initial
be sent on the connection. This parameter is encoded as an maximum number of bidirectional streams the peer may initiate. If
unsigned 32-bit integer in units of octets. This is equivalent to this parameter is absent or zero, the peer cannot open
sending a MAX_DATA (Section 19.5) for the connection immediately bidirectional streams until a MAX_STREAMS frame is sent. Setting
after completing the handshake. If the transport parameter is this parameter is equivalent to sending a MAX_STREAMS
absent, the connection starts with a flow control limit of 0. (Section 19.11) of the corresponding type with the same value.
initial_max_bidi_streams (0x0002): The initial maximum bidirectional initial_max_streams_uni (0x0009): The initial maximum unidirectional
streams parameter contains the initial maximum number of streams parameter is an integer value that contains the initial
bidirectional streams the peer may initiate, encoded as an maximum number of unidirectional streams the peer may initiate.
unsigned 16-bit integer. If this parameter is absent or zero, If this parameter is absent or zero, the peer cannot open
bidirectional streams cannot be created until a MAX_STREAM_ID unidirectional streams until a MAX_STREAMS frame is sent. Setting
frame is sent. Setting this parameter is equivalent to sending a this parameter is equivalent to sending a MAX_STREAMS
MAX_STREAM_ID (Section 19.7) immediately after completing the (Section 19.11) of the corresponding type with the same value.
handshake containing the corresponding Stream ID. For example, a
value of 0x05 would be equivalent to receiving a MAX_STREAM_ID
containing 16 when received by a client or 17 when received by a
server.
initial_max_uni_streams (0x0008): The initial maximum unidirectional ack_delay_exponent (0x000a): The ACK delay exponent is an integer
streams parameter contains the initial maximum number of value indicating an exponent used to decode the ACK Delay field in
unidirectional streams the peer may initiate, encoded as an the ACK frame (Section 19.3). If this value is absent, a default
unsigned 16-bit integer. If this parameter is absent or zero, value of 3 is assumed (indicating a multiplier of 8). The default
unidirectional streams cannot be created until a MAX_STREAM_ID value is also used for ACK frames that are sent in Initial and
frame is sent. Setting this parameter is equivalent to sending a Handshake packets. Values above 20 are invalid.
MAX_STREAM_ID (Section 19.7) immediately after completing the
handshake containing the corresponding Stream ID. For example, a
value of 0x05 would be equivalent to receiving a MAX_STREAM_ID
containing 18 when received by a client or 19 when received by a
server.
A server MUST include the following transport parameter if it sent a max_ack_delay (0x000b): The maximum ACK delay is an integer value
Retry packet: indicating the maximum amount of time in milliseconds by which the
endpoint will delay sending acknowledgments. This value SHOULD
include the receiver's expected delays in alarms firing. For
example, if a receiver sets a timer for 5ms and alarms commonly
fire up to 1ms late, then it should send a max_ack_delay of 6ms.
If this value is absent, a default of 25 milliseconds is assumed.
original_connection_id (0x000d): The value of the Destination disable_migration (0x000c): The disable migration transport
Connection ID field from the first Initial packet sent by the parameter is included if the endpoint does not support connection
client. This transport parameter is only sent by the server. migration (Section 9). Peers of an endpoint that sets this
transport parameter MUST NOT send any packets, including probing
packets (Section 9.1), from a local address other than that used
to perform the handshake. This parameter is a zero-length value.
A server MAY include the following transport parameters: preferred_address (0x000d): The server's preferred address is used
to effect a change in server address at the end of the handshake,
as described in Section 9.6. The format of this transport
parameter is the PreferredAddress struct shown in Figure 16. This
transport parameter is only sent by a server.
stateless_reset_token (0x0006): The Stateless Reset Token is used in struct {
verifying a stateless reset, see Section 10.4. This parameter is enum { IPv4(4), IPv6(6), (15) } ipVersion;
a sequence of 16 octets. opaque ipAddress<4..2^8-1>;
uint16 port;
opaque connectionId<0..18>;
opaque statelessResetToken[16];
} PreferredAddress;
preferred_address (0x0004): The server's Preferred Address is used Figure 16: Preferred Address format
to effect a change in server address at the end of the handshake,
as described in Section 9.6. If present, transport parameters that set initial flow control limits
(initial_max_stream_data_bidi_local,
initial_max_stream_data_bidi_remote, and initial_max_stream_data_uni)
are equivalent to sending a MAX_STREAM_DATA frame (Section 19.10) on
every stream of the corresponding type immediately after opening. If
the transport parameter is absent, streams of that type start with a
flow control limit of 0.
A client MUST NOT include an original connection ID, a stateless A client MUST NOT include an original connection ID, a stateless
reset token, or a preferred address. A server MUST treat receipt of reset token, or a preferred address. A server MUST treat receipt of
any of these transport parameters as a connection error of type any of these transport parameters as a connection error of type
TRANSPORT_PARAMETER_ERROR. TRANSPORT_PARAMETER_ERROR.
19. Frame Types and Formats 19. Frame Types and Formats
As described in Section 12.4, packets contain one or more frames. As described in Section 12.4, packets contain one or more frames.
This section describes the format and semantics of the core QUIC This section describes the format and semantics of the core QUIC
frame types. frame types.
19.1. PADDING Frame 19.1. PADDING Frame
The PADDING frame (type=0x00) has no semantic value. PADDING frames The PADDING frame (type=0x00) has no semantic value. PADDING frames
can be used to increase the size of a packet. Padding can be used to can be used to increase the size of a packet. Padding can be used to
increase an initial client packet to the minimum required size, or to increase an initial client packet to the minimum required size, or to
provide protection against traffic analysis for protected packets. provide protection against traffic analysis for protected packets.
A PADDING frame has no content. That is, a PADDING frame consists of A PADDING frame has no content. That is, a PADDING frame consists of
the single octet that identifies the frame as a PADDING frame. the single byte that identifies the frame as a PADDING frame.
19.2. RST_STREAM Frame 19.2. PING Frame
An endpoint may use a RST_STREAM frame (type=0x01) to abruptly Endpoints can use PING frames (type=0x01) to verify that their peers
are still alive or to check reachability to the peer. The PING frame
contains no additional fields.
The receiver of a PING frame simply needs to acknowledge the packet
containing this frame.
The PING frame can be used to keep a connection alive when an
application or application protocol wishes to prevent the connection
from timing out. An application protocol SHOULD provide guidance
about the conditions under which generating a PING is recommended.
This guidance SHOULD indicate whether it is the client or the server
that is expected to send the PING. Having both endpoints send PING
frames without coordination can produce an excessive number of
packets and poor performance.
A connection will time out if no packets are sent or received for a
period longer than the time specified in the idle_timeout transport
parameter (see Section 10). However, state in middleboxes might time
out earlier than that. Though REQ-5 in [RFC4787] recommends a 2
minute timeout interval, experience shows that sending packets every
15 to 30 seconds is necessary to prevent the majority of middleboxes
from losing state for UDP flows.
19.3. ACK Frames
Receivers send ACK frames (types 0x02 and 0x03) to inform senders of
packets they have received and processed. The ACK frame contains one
or more ACK Blocks. ACK Blocks are ranges of acknowledged packets.
If the frame type is 0x03, ACK frames also contain the sum of QUIC
packets with associated ECN marks received on the connection up until
this point.
QUIC acknowledgements are irrevocable. Once acknowledged, a packet
remains acknowledged, even if it does not appear in a future ACK
frame. This is unlike TCP SACKs ([RFC2018]).
It is expected that a sender will reuse the same packet number across
different packet number spaces. ACK frames only acknowledge the
packet numbers that were transmitted by the sender in the same packet
number space of the packet that the ACK was received in.
Version Negotiation and Retry packets cannot be acknowledged because
they do not contain a packet number. Rather than relying on ACK
frames, these packets are implicitly acknowledged by the next Initial
packet sent by the client.
An ACK frame is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Largest Acknowledged (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACK Delay (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACK Block Count (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACK Blocks (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| [ECN Section] ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 17: ACK Frame Format
ACK frames contain the following fields:
Largest Acknowledged: A variable-length integer representing the
largest packet number the peer is acknowledging; this is usually
the largest packet number that the peer has received prior to
generating the ACK frame. Unlike the packet number in the QUIC
long or short header, the value in an ACK frame is not truncated.
ACK Delay: A variable-length integer including the time in
microseconds that the largest acknowledged packet, as indicated in
the Largest Acknowledged field, was received by this peer to when
this ACK was sent. The value of the ACK Delay field is scaled by
multiplying the encoded value by 2 to the power of the value of
the "ack_delay_exponent" transport parameter set by the sender of
the ACK frame. The "ack_delay_exponent" defaults to 3, or a
multiplier of 8 (see Section 18.1). Scaling in this fashion
allows for a larger range of values with a shorter encoding at the
cost of lower resolution.
ACK Block Count: A variable-length integer specifying the number of
Additional ACK Block (and Gap) fields after the First ACK Block.
ACK Blocks: Contains one or more blocks of packet numbers which have
been successfully received, see Section 19.3.1.
19.3.1. ACK Block Section
The ACK Block Section consists of alternating Gap and ACK Block
fields in descending packet number order. A First Ack Block field is
followed by a variable number of alternating Gap and Additional ACK
Blocks. The number of Gap and Additional ACK Block fields is
determined by the ACK Block Count field.
Gap and ACK Block fields use a relative integer encoding for
efficiency. Though each encoded value is positive, the values are
subtracted, so that each ACK Block describes progressively lower-
numbered packets. As long as contiguous ranges of packets are small,
the variable-length integer encoding ensures that each range can be
expressed in a small number of bytes.
The ACK frame uses the least significant bit (that is, type 0x03) to
indicate ECN feedback and report receipt of QUIC packets with
associated ECN codepoints of ECT(0), ECT(1), or CE in the packet's IP
header.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| First ACK Block (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Gap (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Additional ACK Block (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Gap (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Additional ACK Block (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Gap (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Additional ACK Block (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 18: ACK Block Section
Each ACK Block acknowledges a contiguous range of packets by
indicating the number of acknowledged packets that precede the
largest packet number in that block. A value of zero indicates that
only the largest packet number is acknowledged. Larger ACK Block
values indicate a larger range, with corresponding lower values for
the smallest packet number in the range. Thus, given a largest
packet number for the ACK, the smallest value is determined by the
formula:
smallest = largest - ack_block
The range of packets that are acknowledged by the ACK Block include
the range from the smallest packet number to the largest, inclusive.
The largest value for the First ACK Block is determined by the
Largest Acknowledged field; the largest for Additional ACK Blocks is
determined by cumulatively subtracting the size of all preceding ACK
Blocks and Gaps.
Each Gap indicates a range of packets that are not being
acknowledged. The number of packets in the gap is one higher than
the encoded value of the Gap Field.
The value of the Gap field establishes the largest packet number
value for the ACK Block that follows the gap using the following
formula:
largest = previous_smallest - gap - 2
If the calculated value for largest or smallest packet number for any
ACK Block is negative, an endpoint MUST generate a connection error
of type FRAME_ENCODING_ERROR indicating an error in an ACK frame.
The fields in the ACK Block Section are:
First ACK Block: A variable-length integer indicating the number of
contiguous packets preceding the Largest Acknowledged that are
being acknowledged.
Gap (repeated): A variable-length integer indicating the number of
contiguous unacknowledged packets preceding the packet number one
lower than the smallest in the preceding ACK Block.
Additional ACK Block (repeated): A variable-length integer
indicating the number of contiguous acknowledged packets preceding
the largest packet number, as determined by the preceding Gap.
19.3.2. ECN section
The ECN section should only be parsed when the ACK frame type is
0x03. The ECN section consists of 3 ECN counters as shown below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ECT(0) Count (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ECT(1) Count (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ECN-CE Count (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ECT(0) Count: A variable-length integer representing the total
number packets received with the ECT(0) codepoint.
ECT(1) Count: A variable-length integer representing the total
number packets received with the ECT(1) codepoint.
CE Count: A variable-length integer representing the total number
packets received with the CE codepoint.
ECN counters are maintained separately for each packet number space.
19.4. RESET_STREAM Frame
An endpoint uses a RESET_STREAM frame (type=0x04) to abruptly
terminate a stream. terminate a stream.
After sending a RST_STREAM, an endpoint ceases transmission and After sending a RESET_STREAM, an endpoint ceases transmission and
retransmission of STREAM frames on the identified stream. A receiver retransmission of STREAM frames on the identified stream. A receiver
of RST_STREAM can discard any data that it already received on that of RESET_STREAM can discard any data that it already received on that
stream. stream.
An endpoint that receives a RST_STREAM frame for a send-only stream An endpoint that receives a RESET_STREAM frame for a send-only stream
MUST terminate the connection with error PROTOCOL_VIOLATION. MUST terminate the connection with error PROTOCOL_VIOLATION.
The RST_STREAM frame is as follows: The RESET_STREAM frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream ID (i) ... | Stream ID (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Application Error Code (16) | | Application Error Code (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Final Offset (i) ... | Final Offset (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields are: RESET_STREAM frames contain the following fields:
Stream ID: A variable-length integer encoding of the Stream ID of Stream ID: A variable-length integer encoding of the Stream ID of
the stream being terminated. the stream being terminated.
Application Protocol Error Code: A 16-bit application protocol error Application Protocol Error Code: A 16-bit application protocol error
code (see Section 20.1) which indicates why the stream is being code (see Section 20.1) which indicates why the stream is being
closed. closed.
Final Offset: A variable-length integer indicating the absolute byte Final Offset: A variable-length integer indicating the absolute byte
offset of the end of data written on this stream by the RST_STREAM offset of the end of data written on this stream by the
sender. RESET_STREAM sender.
19.3. CONNECTION_CLOSE frame 19.5. STOP_SENDING Frame
An endpoint sends a CONNECTION_CLOSE frame (type=0x02) to notify its An endpoint uses a STOP_SENDING frame (type=0x05) to communicate that
peer that the connection is being closed. CONNECTION_CLOSE is used incoming data is being discarded on receipt at application request.
to signal errors at the QUIC layer, or the absence of errors (with This signals a peer to abruptly terminate transmission on a stream.
the NO_ERROR code).
If there are open streams that haven't been explicitly closed, they Receipt of a STOP_SENDING frame is invalid for a locally-initiated
are implicitly closed when the connection is closed. stream that has not yet been created or is in the "Ready" state (see
Section 3.1). Receiving a STOP_SENDING frame for a locally-initiated
send stream that is "Ready" or not yet created MUST be treated as a
connection error of type PROTOCOL_VIOLATION. An endpoint that
receives a STOP_SENDING frame for a receive-only stream MUST
terminate the connection with error PROTOCOL_VIOLATION.
The CONNECTION_CLOSE frame is as follows: The STOP_SENDING frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Code (16) | | Stream ID (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Frame Type (i) ... | Application Error Code (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
STOP_SENDING frames contain the following fields:
Stream ID: A variable-length integer carrying the Stream ID of the
stream being ignored.
Application Error Code: A 16-bit, application-specified reason the
sender is ignoring the stream (see Section 20.1).
19.6. CRYPTO Frame
The CRYPTO frame (type=0x06) is used to transmit cryptographic
handshake messages. It can be sent in all packet types. The CRYPTO
frame offers the cryptographic protocol an in-order stream of bytes.
CRYPTO frames are functionally identical to STREAM frames, except
that they do not bear a stream identifier; they are not flow
controlled; and they do not carry markers for optional offset,
optional length, and the end of the stream.
The CRYPTO frame is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reason Phrase Length (i) ... | Offset (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reason Phrase (*) ... | Length (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Crypto Data (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields of a CONNECTION_CLOSE frame are as follows: Figure 19: CRYPTO Frame Format
Error Code: A 16-bit error code which indicates the reason for CRYPTO frames contain the following fields:
closing this connection. CONNECTION_CLOSE uses codes from the
space defined in Section 20.
Frame Type: A variable-length integer encoding the type of frame Offset: A variable-length integer specifying the byte offset in the
that triggered the error. A value of 0 (equivalent to the mention stream for the data in this CRYPTO frame.
of the PADDING frame) is used when the frame type is unknown.
Reason Phrase Length: A variable-length integer specifying the Length: A variable-length integer specifying the length of the
length of the reason phrase in bytes. Note that a Crypto Data field in this CRYPTO frame.
CONNECTION_CLOSE frame cannot be split between packets, so in
practice any limits on packet size will also limit the space
available for a reason phrase.
Reason Phrase: A human-readable explanation for why the connection Crypto Data: The cryptographic message data.
was closed. This can be zero length if the sender chooses to not
give details beyond the Error Code. This SHOULD be a UTF-8
encoded string [RFC3629].
19.4. APPLICATION_CLOSE frame There is a separate flow of cryptographic handshake data in each
encryption level, each of which starts at an offset of 0. This
implies that each encryption level is treated as a separate CRYPTO
stream of data.
An APPLICATION_CLOSE frame (type=0x03) is used to signal an error Unlike STREAM frames, which include a Stream ID indicating to which
with the protocol that uses QUIC. stream the data belongs, the CRYPTO frame carries data for a single
stream per encryption level. The stream does not have an explicit
end, so CRYPTO frames do not have a FIN bit.
The APPLICATION_CLOSE frame is as follows: 19.7. NEW_TOKEN Frame
A server sends a NEW_TOKEN frame (type=0x07) to provide the client a
token to send in the header of an Initial packet for a future
connection.
The NEW_TOKEN frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Code (16) | | Token Length (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reason Phrase Length (i) ... | Token (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reason Phrase (*) ...
NEW_TOKEN frames contain the following fields:
Token Length: A variable-length integer specifying the length of the
token in bytes.
Token: An opaque blob that the client may use with a future Initial
packet.
19.8. STREAM Frames
STREAM frames implicitly create a stream and carry stream data. The
STREAM frame takes the form 0b00001XXX (or the set of values from
0x08 to 0x0f). The value of the three low-order bits of the frame
type determine the fields that are present in the frame.
o The OFF bit (0x04) in the frame type is set to indicate that there
is an Offset field present. When set to 1, the Offset field is
present. When set to 0, the Offset field is absent and the Stream
Data starts at an offset of 0 (that is, the frame contains the
first bytes of the stream, or the end of a stream that includes no
data).
o The LEN bit (0x02) in the frame type is set to indicate that there
is a Length field present. If this bit is set to 0, the Length
field is absent and the Stream Data field extends to the end of
the packet. If this bit is set to 1, the Length field is present.
o The FIN bit (0x01) of the frame type is set only on frames that
contain the final offset of the stream. Setting this bit
indicates that the frame marks the end of the stream.
An endpoint that receives a STREAM frame for a send-only stream MUST
terminate the connection with error PROTOCOL_VIOLATION.
The STREAM frames are as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream ID (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| [Offset (i)] ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| [Length (i)] ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Data (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields of an APPLICATION_CLOSE frame are as follows: Figure 20: STREAM Frame Format
Error Code: A 16-bit error code which indicates the reason for STREAM frames contain the following fields:
closing this connection. APPLICATION_CLOSE uses codes from the
application protocol error code space, see Section 20.1.
Reason Phrase Length: This field is identical in format and Stream ID: A variable-length integer indicating the stream ID of the
semantics to the Reason Phrase Length field from CONNECTION_CLOSE. stream (see Section 2.1).
Reason Phrase: This field is identical in format and semantics to Offset: A variable-length integer specifying the byte offset in the
the Reason Phrase field from CONNECTION_CLOSE. stream for the data in this STREAM frame. This field is present
when the OFF bit is set to 1. When the Offset field is absent,
the offset is 0.
APPLICATION_CLOSE has similar format and semantics to the Length: A variable-length integer specifying the length of the
CONNECTION_CLOSE frame (Section 19.3). Aside from the semantics of Stream Data field in this STREAM frame. This field is present
the Error Code field and the omission of the Frame Type field, both when the LEN bit is set to 1. When the LEN bit is set to 0, the
frames are used to close the connection. Stream Data field consumes all the remaining bytes in the packet.
19.5. MAX_DATA Frame Stream Data: The bytes from the designated stream to be delivered.
The MAX_DATA frame (type=0x04) is used in flow control to inform the When a Stream Data field has a length of 0, the offset in the STREAM
frame is the offset of the next byte that would be sent.
The first byte in the stream has an offset of 0. The largest offset
delivered on a stream - the sum of the re-constructed offset and data
length - MUST be less than 2^62.
19.9. MAX_DATA Frame
The MAX_DATA frame (type=0x10) is used in flow control to inform the
peer of the maximum amount of data that can be sent on the connection peer of the maximum amount of data that can be sent on the connection
as a whole. as a whole.
The frame is as follows: The MAX_DATA frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Data (i) ... | Maximum Data (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields in the MAX_DATA frame are as follows:
MAX_DATA frames contain the following fields:
Maximum Data: A variable-length integer indicating the maximum Maximum Data: A variable-length integer indicating the maximum
amount of data that can be sent on the entire connection, in units amount of data that can be sent on the entire connection, in units
of octets. of bytes.
All data sent in STREAM frames counts toward this limit. The sum of All data sent in STREAM frames counts toward this limit. The sum of
the largest received offsets on all streams - including streams in the largest received offsets on all streams - including streams in
terminal states - MUST NOT exceed the value advertised by a receiver. terminal states - MUST NOT exceed the value advertised by a receiver.
An endpoint MUST terminate a connection with a FLOW_CONTROL_ERROR An endpoint MUST terminate a connection with a FLOW_CONTROL_ERROR
error if it receives more data than the maximum data value that it error if it receives more data than the maximum data value that it
has sent, unless this is a result of a change in the initial limits has sent, unless this is a result of a change in the initial limits
(see Section 7.3.1). (see Section 7.3.1).
19.6. MAX_STREAM_DATA Frame 19.10. MAX_STREAM_DATA Frame
The MAX_STREAM_DATA frame (type=0x05) is used in flow control to The MAX_STREAM_DATA frame (type=0x11) is used in flow control to
inform a peer of the maximum amount of data that can be sent on a inform a peer of the maximum amount of data that can be sent on a
stream. stream.
An endpoint that receives a MAX_STREAM_DATA frame for a receive-only An endpoint that receives a MAX_STREAM_DATA frame for a receive-only
stream MUST terminate the connection with error PROTOCOL_VIOLATION. stream MUST terminate the connection with error PROTOCOL_VIOLATION.
An endpoint that receives a MAX_STREAM_DATA frame for a send-only An endpoint that receives a MAX_STREAM_DATA frame for a send-only
stream it has not opened MUST terminate the connection with error stream it has not opened MUST terminate the connection with error
PROTOCOL_VIOLATION. PROTOCOL_VIOLATION.
Note that an endpoint may legally receive a MAX_STREAM_DATA frame on Note that an endpoint may legally receive a MAX_STREAM_DATA frame on
a bidirectional stream it has not opened. a bidirectional stream it has not opened.
The frame is as follows: The MAX_STREAM_DATA frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream ID (i) ... | Stream ID (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Stream Data (i) ... | Maximum Stream Data (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields in the MAX_STREAM_DATA frame are as follows: MAX_STREAM_DATA frames contain the following fields:
Stream ID: The stream ID of the stream that is affected encoded as a Stream ID: The stream ID of the stream that is affected encoded as a
variable-length integer. variable-length integer.
Maximum Stream Data: A variable-length integer indicating the Maximum Stream Data: A variable-length integer indicating the
maximum amount of data that can be sent on the identified stream, maximum amount of data that can be sent on the identified stream,
in units of octets. in units of bytes.
When counting data toward this limit, an endpoint accounts for the When counting data toward this limit, an endpoint accounts for the
largest received offset of data that is sent or received on the largest received offset of data that is sent or received on the
stream. Loss or reordering can mean that the largest received offset stream. Loss or reordering can mean that the largest received offset
on a stream can be greater than the total size of data received on on a stream can be greater than the total size of data received on
that stream. Receiving STREAM frames might not increase the largest that stream. Receiving STREAM frames might not increase the largest
received offset. received offset.
The data sent on a stream MUST NOT exceed the largest maximum stream The data sent on a stream MUST NOT exceed the largest maximum stream
data value advertised by the receiver. An endpoint MUST terminate a data value advertised by the receiver. An endpoint MUST terminate a
connection with a FLOW_CONTROL_ERROR error if it receives more data connection with a FLOW_CONTROL_ERROR error if it receives more data
than the largest maximum stream data that it has sent for the than the largest maximum stream data that it has sent for the
affected stream, unless this is a result of a change in the initial affected stream, unless this is a result of a change in the initial
limits (see Section 7.3.1). limits (see Section 7.3.1).
19.7. MAX_STREAM_ID Frame 19.11. MAX_STREAMS Frames
The MAX_STREAM_ID frame (type=0x06) informs the peer of the maximum The MAX_STREAMS frames (type=0x12 and 0x13) inform the peer of the
stream ID that they are permitted to open. cumulative number of streams of a given type it is permitted to open.
A MAX_STREAMS frame with a type of 0x12 applies to bidirectional
streams, and a MAX_STREAMS frame with a type of 0x13 applies to
unidirectional streams.
The frame is as follows: The MAX_STREAMS frames are as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Maximum Stream ID (i) ... | Maximum Streams (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields in the MAX_STREAM_ID frame are as follows: MAX_STREAMS frames contain the following fields:
Maximum Stream ID: ID of the maximum unidirectional or bidirectional
peer-initiated stream ID for the connection encoded as a variable-
length integer. The limit applies to unidirectional steams if the
second least signification bit of the stream ID is 1, and applies
to bidirectional streams if it is 0.
Loss or reordering can mean that a MAX_STREAM_ID frame can be
received which states a lower stream limit than the client has
previously received. MAX_STREAM_ID frames which do not increase the
maximum stream ID MUST be ignored.
A peer MUST NOT initiate a stream with a higher stream ID than the
greatest maximum stream ID it has received. An endpoint MUST
terminate a connection with a STREAM_ID_ERROR error if a peer
initiates a stream with a higher stream ID than it has sent, unless
this is a result of a change in the initial limits (see
Section 7.3.1).
19.8. PING Frame
Endpoints can use PING frames (type=0x07) to verify that their peers Maximum Streams: A count of the cumulative number of streams of the
are still alive or to check reachability to the peer. The PING frame corresponding type that can be opened over the lifetime of the
contains no additional fields. connection.
The receiver of a PING frame simply needs to acknowledge the packet Loss or reordering can cause a MAX_STREAMS frame to be received which
containing this frame. states a lower stream limit than an endpoint has previously received.
MAX_STREAMS frames which do not increase the stream limit MUST be
ignored.
The PING frame can be used to keep a connection alive when an An endpoint MUST NOT open more streams than permitted by the current
application or application protocol wishes to prevent the connection stream limit set by its peer. For instance, a server that receives a
from timing out. An application protocol SHOULD provide guidance unidirectional stream limit of 3 is permitted to open stream 3, 7,
about the conditions under which generating a PING is recommended. and 11, but not stream 15. An endpoint MUST terminate a connection
This guidance SHOULD indicate whether it is the client or the server with a STREAM_LIMIT_ERROR error if a peer opens more streams than was
that is expected to send the PING. Having both endpoints send PING permitted.
frames without coordination can produce an excessive number of
packets and poor performance.
A connection will time out if no packets are sent or received for a Note that these frames (and the corresponding transport parameters)
period longer than the time specified in the idle_timeout transport do not describe the number of streams that can be opened
parameter (see Section 10). However, state in middleboxes might time concurrently. The limit includes streams that have been closed as
out earlier than that. Though REQ-5 in [RFC4787] recommends a 2 well as those that are open.
minute timeout interval, experience shows that sending packets every
15 to 30 seconds is necessary to prevent the majority of middleboxes
from losing state for UDP flows.
19.9. BLOCKED Frame 19.12. DATA_BLOCKED Frame
A sender SHOULD send a BLOCKED frame (type=0x08) when it wishes to A sender SHOULD send a DATA_BLOCKED frame (type=0x14) when it wishes
send data, but is unable to due to connection-level flow control (see to send data, but is unable to due to connection-level flow control
Section 4). BLOCKED frames can be used as input to tuning of flow (see Section 4). DATA_BLOCKED frames can be used as input to tuning
control algorithms (see Section 4.2). of flow control algorithms (see Section 4.2).
The BLOCKED frame is as follows: The DATA_BLOCKED frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offset (i) ... | Data Limit (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The BLOCKED frame contains a single field. DATA_BLOCKED frames contain the following fields:
Offset: A variable-length integer indicating the connection-level Data Limit: A variable-length integer indicating the connection-
offset at which the blocking occurred. level limit at which blocking occurred.
19.10. STREAM_BLOCKED Frame 19.13. STREAM_DATA_BLOCKED Frame
A sender SHOULD send a STREAM_BLOCKED frame (type=0x09) when it A sender SHOULD send a STREAM_DATA_BLOCKED frame (type=0x15) when it
wishes to send data, but is unable to due to stream-level flow wishes to send data, but is unable to due to stream-level flow
control. This frame is analogous to BLOCKED (Section 19.9). control. This frame is analogous to DATA_BLOCKED (Section 19.12).
An endpoint that receives a STREAM_BLOCKED frame for a send-only An endpoint that receives a STREAM_DATA_BLOCKED frame for a send-only
stream MUST terminate the connection with error PROTOCOL_VIOLATION. stream MUST terminate the connection with error PROTOCOL_VIOLATION.
The STREAM_BLOCKED frame is as follows: The STREAM_DATA_BLOCKED frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream ID (i) ... | Stream ID (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offset (i) ... | Stream Data Limit (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The STREAM_BLOCKED frame contains two fields: STREAM_DATA_BLOCKED frames contain the following fields:
Stream ID: A variable-length integer indicating the stream which is Stream ID: A variable-length integer indicating the stream which is
flow control blocked. flow control blocked.
Offset: A variable-length integer indicating the offset of the Stream Data Limit: A variable-length integer indicating the offset
stream at which the blocking occurred. of the stream at which the blocking occurred.
19.11. STREAM_ID_BLOCKED Frame 19.14. STREAMS_BLOCKED Frames
A sender SHOULD send a STREAM_ID_BLOCKED frame (type=0x0a) when it A sender SHOULD send a STREAMS_BLOCKED frame (type=0x16 or 0x17) when
wishes to open a stream, but is unable to due to the maximum stream it wishes to open a stream, but is unable to due to the maximum
ID limit set by its peer (see Section 19.7). This does not open the stream limit set by its peer (see Section 19.11). A STREAMS_BLOCKED
stream, but informs the peer that a new stream was needed, but the frame of type 0x16 is used to indicate reaching the bidirectional
stream limit prevented the creation of the stream. stream limit, and a STREAMS_BLOCKED frame of type 0x17 indicates
reaching the unidirectional stream limit.
The STREAM_ID_BLOCKED frame is as follows: A STREAMS_BLOCKED frame does not open the stream, but informs the
peer that a new stream was needed and the stream limit prevented the
creation of the stream.
The STREAMS_BLOCKED frames are as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream ID (i) ... | Stream Limit (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The STREAM_ID_BLOCKED frame contains a single field. STREAMS_BLOCKED frames contain the following fields:
Stream ID: A variable-length integer indicating the highest stream Stream Limit: A variable-length integer indicating the stream limit
ID that the sender was permitted to open. at the time the frame was sent.
19.12. NEW_CONNECTION_ID Frame 19.15. NEW_CONNECTION_ID Frame
An endpoint sends a NEW_CONNECTION_ID frame (type=0x0b) to provide An endpoint sends a NEW_CONNECTION_ID frame (type=0x18) to provide
its peer with alternative connection IDs that can be used to break its peer with alternative connection IDs that can be used to break
linkability when migrating connections (see Section 9.5). linkability when migrating connections (see Section 9.5).
The NEW_CONNECTION_ID frame is as follows: The NEW_CONNECTION_ID frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (8) | Sequence Number (i) ... | Sequence Number (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Connection ID (32..144) ... | Length (8) | |
+-+-+-+-+-+-+-+-+ Connection ID (32..144) +
| ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+ + + +
| | | |
+ Stateless Reset Token (128) + + Stateless Reset Token (128) +
| | | |
+ + + +
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields are: NEW_CONNECTION_ID frames contain the following fields:
Sequence Number: The sequence number assigned to the connection ID
by the sender. See Section 5.1.1.
Length: An 8-bit unsigned integer containing the length of the Length: An 8-bit unsigned integer containing the length of the
connection ID. Values less than 4 and greater than 18 are invalid connection ID. Values less than 4 and greater than 18 are invalid
and MUST be treated as a connection error of type and MUST be treated as a connection error of type
PROTOCOL_VIOLATION. PROTOCOL_VIOLATION.
Sequence Number: The sequence number assigned to the connection ID
by the sender. See Section 5.1.1.
Connection ID: A connection ID of the specified length. Connection ID: A connection ID of the specified length.
Stateless Reset Token: A 128-bit value that will be used for a Stateless Reset Token: A 128-bit value that will be used for a
stateless reset when the associated connection ID is used (see stateless reset when the associated connection ID is used (see
Section 10.4). Section 10.4).
An endpoint MUST NOT send this frame if it currently requires that An endpoint MUST NOT send this frame if it currently requires that
its peer send packets with a zero-length Destination Connection ID. its peer send packets with a zero-length Destination Connection ID.
Changing the length of a connection ID to or from zero-length makes Changing the length of a connection ID to or from zero-length makes
it difficult to identify when the value of the connection ID changed. it difficult to identify when the value of the connection ID changed.
skipping to change at page 101, line 13 skipping to change at page 109, line 15
connection error of type PROTOCOL_VIOLATION. connection error of type PROTOCOL_VIOLATION.
Transmission errors, timeouts and retransmissions might cause the Transmission errors, timeouts and retransmissions might cause the
same NEW_CONNECTION_ID frame to be received multiple times. Receipt same NEW_CONNECTION_ID frame to be received multiple times. Receipt
of the same frame multiple times MUST NOT be treated as a connection of the same frame multiple times MUST NOT be treated as a connection
error. A receiver can use the sequence number supplied in the error. A receiver can use the sequence number supplied in the
NEW_CONNECTION_ID frame to identify new connection IDs from old ones. NEW_CONNECTION_ID frame to identify new connection IDs from old ones.
If an endpoint receives a NEW_CONNECTION_ID frame that repeats a If an endpoint receives a NEW_CONNECTION_ID frame that repeats a
previously issued connection ID with a different Stateless Reset previously issued connection ID with a different Stateless Reset
Token or a different sequence number, the endpoint MAY treat that Token or a different sequence number, or if a sequence number is used
receipt as a connection error of type PROTOCOL_VIOLATION. for different connection IDs, the endpoint MAY treat that receipt as
a connection error of type PROTOCOL_VIOLATION.
19.13. RETIRE_CONNECTION_ID Frame 19.16. RETIRE_CONNECTION_ID Frame
An endpoint sends a RETIRE_CONNECTION_ID frame (type=0x1b) to An endpoint sends a RETIRE_CONNECTION_ID frame (type=0x19) to
indicate that it will no longer use a connection ID that was issued indicate that it will no longer use a connection ID that was issued
by its peer. This may include the connection ID provided during the by its peer. This may include the connection ID provided during the
handshake. Sending a RETIRE_CONNECTION_ID frame also serves as a handshake. Sending a RETIRE_CONNECTION_ID frame also serves as a
request to the peer to send additional connection IDs for future use request to the peer to send additional connection IDs for future use
(see Section 5.1). New connection IDs can be delivered to a peer (see Section 5.1). New connection IDs can be delivered to a peer
using the NEW_CONNECTION_ID frame (Section 19.12). using the NEW_CONNECTION_ID frame (Section 19.15).
Retiring a connection ID invalidates the stateless reset token Retiring a connection ID invalidates the stateless reset token
associated with that connection ID. associated with that connection ID.
The RETIRE_CONNECTION_ID frame is as follows: The RETIRE_CONNECTION_ID frame is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number (i) ... | Sequence Number (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields are: RETIRE_CONNECTION_ID frames contain the following fields:
Sequence Number: The sequence number of the connection ID being Sequence Number: The sequence number of the connection ID being
retired. See Section 5.1.2. retired. See Section 5.1.2.
Receipt of a RETIRE_CONNECTION_ID frame containing a sequence number Receipt of a RETIRE_CONNECTION_ID frame containing a sequence number
greater than any previously sent to the peer MAY be treated as a greater than any previously sent to the peer MAY be treated as a
connection error of type PROTOCOL_VIOLATION. connection error of type PROTOCOL_VIOLATION.
An endpoint cannot send this frame if it was provided with a zero- An endpoint cannot send this frame if it was provided with a zero-
length connection ID by its peer. An endpoint that provides a zero- length connection ID by its peer. An endpoint that provides a zero-
length connection ID MUST treat receipt of a RETIRE_CONNECTION_ID length connection ID MUST treat receipt of a RETIRE_CONNECTION_ID
frame as a connection error of type PROTOCOL_VIOLATION. frame as a connection error of type PROTOCOL_VIOLATION.
19.14. STOP_SENDING Frame 19.17. PATH_CHALLENGE Frame
An endpoint may use a STOP_SENDING frame (type=0x0c) to communicate
that incoming data is being discarded on receipt at application
request. This signals a peer to abruptly terminate transmission on a
stream.
Receipt of a STOP_SENDING frame is only valid for a send stream that
exists and is not in the "Ready" state (see Section 3.1). Receiving
a STOP_SENDING frame for a send stream that is "Ready" or non-
existent MUST be treated as a connection error of type
PROTOCOL_VIOLATION. An endpoint that receives a STOP_SENDING frame
for a receive-only stream MUST terminate the connection with error
PROTOCOL_VIOLATION.
The STOP_SENDING frame is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream ID (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Application Error Code (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields are:
Stream ID: A variable-length integer carrying the Stream ID of the
stream being ignored.
Application Error Code: A 16-bit, application-specified reason the
sender is ignoring the stream (see Section 20.1).
19.15. ACK Frame
Receivers send ACK frames (types 0x1a and 0x1b) to inform senders of
packets they have received and processed. The ACK frame contains one
or more ACK Blocks. ACK Blocks are ranges of acknowledged packets.
If the frame type is 0x1b, ACK frames also contain the sum of ECN
marks received on the connection up until this point.
QUIC acknowledgements are irrevocable. Once acknowledged, a packet
remains acknowledged, even if it does not appear in a future ACK
frame. This is unlike TCP SACKs ([RFC2018]).
It is expected that a sender will reuse the same packet number across
different packet number spaces. ACK frames only acknowledge the
packet numbers that were transmitted by the sender in the same packet
number space of the packet that the ACK was received in.
Version Negotiation and Retry packets cannot be acknowledged because
they do not contain a packet number. Rather than relying on ACK
frames, these packets are implicitly acknowledged by the next Initial
packet sent by the client.
An ACK frame is shown below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Largest Acknowledged (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACK Delay (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACK Block Count (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACK Blocks (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| [ECN Section] ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: ACK Frame Format
The fields in the ACK frame are as follows:
Largest Acknowledged: A variable-length integer representing the
largest packet number the peer is acknowledging; this is usually
the largest packet number that the peer has received prior to
generating the ACK frame. Unlike the packet number in the QUIC
long or short header, the value in an ACK frame is not truncated.
ACK Delay: A variable-length integer including the time in
microseconds that the largest acknowledged packet, as indicated in
the Largest Acknowledged field, was received by this peer to when
this ACK was sent. The value of the ACK Delay field is scaled by
multiplying the encoded value by 2 to the power of the value of
the "ack_delay_exponent" transport parameter set by the sender of
the ACK frame. The "ack_delay_exponent" defaults to 3, or a
multiplier of 8 (see Section 18.1). Scaling in this fashion
allows for a larger range of values with a shorter encoding at the
cost of lower resolution.
ACK Block Count: A variable-length integer specifying the number of
Additional ACK Block (and Gap) fields after the First ACK Block.
ACK Blocks: Contains one or more blocks of packet numbers which have
been successfully received, see Section 19.15.1.
19.15.1. ACK Block Section
The ACK Block Section consists of alternating Gap and ACK Block
fields in descending packet number order. A First Ack Block field is
followed by a variable number of alternating Gap and Additional ACK
Blocks. The number of Gap and Additional ACK Block fields is
determined by the ACK Block Count field.
Gap and ACK Block fields use a relative integer encoding for
efficiency. Though each encoded value is positive, the values are
subtracted, so that each ACK Block describes progressively lower-
numbered packets. As long as contiguous ranges of packets are small,
the variable-length integer encoding ensures that each range can be
expressed in a small number of octets.
The ACK frame uses the least significant bit(bit (that is, type 0x1b)
to indicate ECN feedback and report receipt of packets with ECN
codepoints of ECT(0), ECT(1), or CE in the packet's IP header.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| First ACK Block (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Gap (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Additional ACK Block (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Gap (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Additional ACK Block (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Gap (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Additional ACK Block (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 17: ACK Block Section
Each ACK Block acknowledges a contiguous range of packets by
indicating the number of acknowledged packets that precede the
largest packet number in that block. A value of zero indicates that
only the largest packet number is acknowledged. Larger ACK Block
values indicate a larger range, with corresponding lower values for
the smallest packet number in the range. Thus, given a largest
packet number for the ACK, the smallest value is determined by the
formula:
smallest = largest - ack_block
The range of packets that are acknowledged by the ACK Block include
the range from the smallest packet number to the largest, inclusive.
The largest value for the First ACK Block is determined by the
Largest Acknowledged field; the largest for Additional ACK Blocks is
determined by cumulatively subtracting the size of all preceding ACK
Blocks and Gaps.
Each Gap indicates a range of packets that are not being
acknowledged. The number of packets in the gap is one higher than
the encoded value of the Gap Field.
The value of the Gap field establishes the largest packet number
value for the ACK Block that follows the gap using the following
formula:
largest = previous_smallest - gap - 2
If the calculated value for largest or smallest packet number for any
ACK Block is negative, an endpoint MUST generate a connection error
of type FRAME_ENCODING_ERROR indicating an error in an ACK frame.
The fields in the ACK Block Section are:
First ACK Block: A variable-length integer indicating the number of
contiguous packets preceding the Largest Acknowledged that are
being acknowledged.
Gap (repeated): A variable-length integer indicating the number of
contiguous unacknowledged packets preceding the packet number one
lower than the smallest in the preceding ACK Block.
Additional ACK Block (repeated): A variable-length integer
indicating the number of contiguous acknowledged packets preceding
the largest packet number, as determined by the preceding Gap.