HTTPbis Working GroupM. Bishop
Intended status: Standards TrackOctober 5, 2022
Expires: April 8, 2023

The ORIGIN Extension in HTTP/3


The ORIGIN frame for HTTP/2 is equally applicable to HTTP/3, but needs to be separately registered. This document describes the ORIGIN frame for HTTP/3.

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1. Introduction

Existing RFCs define extensions to HTTP/2 [HTTP2] which remain useful in HTTP/3. Appendix A.2.3 of [HTTP3] describes the required updates for HTTP/2 frames to be used with HTTP/3.

[ORIGIN] defines the HTTP/2 ORIGIN frame, which indicates what origins are available on a given connection. It defines a single HTTP/2 frame type.

2. The ORIGIN HTTP/3 Frame

The ORIGIN HTTP/3 frame allows a server to indicate what origin(s) ([RFC6454]) the server would like the client to consider as members of the Origin Set (Section 2.3 of [ORIGIN]) for the connection within which it occurs.

The semantics of the frame payload are identical to those of the HTTP/2 frame defined in [ORIGIN]. Where HTTP/2 reserves Stream 0 for frames related to the state of the connection, HTTP/3 defines a pair of unidirectional streams called "control streams" for this purpose. Where [ORIGIN] indicates that the ORIGIN frame should be sent on Stream 0, this should be interpreted to mean the HTTP/3 control stream. The ORIGIN frame is sent from servers to clients on the server's control stream.

2.1. Frame Layout

The ORIGIN frame has a nearly identical layout to that used in HTTP/2, restated here for clarity. The ORIGIN frame type is 0xc (decimal 12) as in HTTP/2. The payload contains zero or more instances of the Origin-Entry field.

HTTP/3 Origin-Entry {
  Origin-Len (16),
  ASCII-Origin (..),

  Type (i) = 0x0c,
  Length (i),
  Origin-Entry (..) ...,

Figure 1: ORIGIN Frame Layout

An Origin-Entry is a length-delimited string. Specifically, it contains two fields:

An unsigned, 16-bit integer indicating the length, in octets, of the ASCII-Origin field.
An OPTIONAL sequence of characters containing the ASCII serialization of an origin ([RFC6454], Section 6.2) that the sender asserts this connection is or could be authoritative for.

3. Security Considerations

This document introduces no new security considerations beyond those discussed in [ORIGIN] and [HTTP3].

4. IANA Considerations

This document registers a frame type in the "HTTP/3 Frame Type" registry ([HTTP3]).

Table 1: Registered HTTP/3 Frame Types
Frame TypeValueSpecification
ORIGIN0xcSection 2

5. References

5.1. Normative References

Thomson, M., Ed. and C. Benfield, Ed., “HTTP/2”, RFC 9113, DOI 10.17487/RFC9113, June 2022, <>.
Bishop, M., Ed., “HTTP/3”, RFC 9114, DOI 10.17487/RFC9114, June 2022, <>.
Nottingham, M. and E. Nygren, “The ORIGIN HTTP/2 Frame”, RFC 8336, DOI 10.17487/RFC8336, March 2018, <>.

5.2. Informative References

Barth, A., “The Web Origin Concept”, RFC 6454, DOI 10.17487/RFC6454, December 2011, <>.

Author's Address

Mike Bishop