draft-ietf-httpbis-p5-range-26.txt		draft-ietf-httpbis-p5-range-latest.txt
	HTTPbis Working Group R. Fielding, Ed.		HTTPbis Working Group R. Fielding, Ed.
	Internet-Draft Adobe		Internet-Draft Adobe
	Obsoletes: 2616 (if approved) Y. Lafon, Ed.		Obsoletes: 2616 (if approved) Y. Lafon, Ed.
	Intended status: Standards Track W3C		Intended status: Standards Track W3C
	Expires: August 10, 2014 J. Reschke, Ed.		Expires: December 3, 2014 J. Reschke, Ed.
	greenbytes		greenbytes
	February 6, 2014		June 2014
	Hypertext Transfer Protocol (HTTP/1.1): Range Requests		Hypertext Transfer Protocol (HTTP/1.1): Range Requests
	draft-ietf-httpbis-p5-range-26		draft-ietf-httpbis-p5-range-latest
	Abstract		Abstract
	The Hypertext Transfer Protocol (HTTP) is a stateless application-		The Hypertext Transfer Protocol (HTTP) is a stateless application-
	level protocol for distributed, collaborative, hypertext information		level protocol for distributed, collaborative, hypertext information
	systems. This document defines range requests and the rules for		systems. This document defines range requests and the rules for
	constructing and combining responses to those requests.		constructing and combining responses to those requests.
	Editorial Note (To be removed by RFC Editor)		Editorial Note (To be removed by RFC Editor)
	Discussion of this draft takes place on the HTTPBIS working group		Discussion of this draft takes place on the HTTPBIS working group
	mailing list (ietf-http-wg@w3.org), which is archived at		mailing list (ietf-http-wg@w3.org), which is archived at
	<http://lists.w3.org/Archives/Public/ietf-http-wg/>.		<http://lists.w3.org/Archives/Public/ietf-http-wg/>.
	The current issues list is at		The current issues list is at
	<http://tools.ietf.org/wg/httpbis/trac/report/3> and related		<http://tools.ietf.org/wg/httpbis/trac/report/3> and related
	documents (including fancy diffs) can be found at		documents (including fancy diffs) can be found at
	<http://tools.ietf.org/wg/httpbis/>.		<http://tools.ietf.org/wg/httpbis/>.
	The changes in this draft are summarized in Appendix E.2.		_This is a temporary document for the purpose of tracking the
			editorial changes made during the AUTH48 (RFC publication) phase._
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
			This Internet-Draft will expire on December 3, 2014.
	This Internet-Draft will expire on August 10, 2014.
	Copyright Notice		Copyright Notice
	Copyright (c) 2014 IETF Trust and the persons identified as the		Copyright (c) 2014 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 3, line 31 ¶		skipping to change at page 3, line 31 ¶
	4.4. 416 Range Not Satisfiable . . . . . . . . . . . . . . . . 15		4.4. 416 Range Not Satisfiable . . . . . . . . . . . . . . . . 15
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
	5.1. Range Unit Registry . . . . . . . . . . . . . . . . . . . 15		5.1. Range Unit Registry . . . . . . . . . . . . . . . . . . . 15
	5.1.1. Procedure . . . . . . . . . . . . . . . . . . . . . . 15		5.1.1. Procedure . . . . . . . . . . . . . . . . . . . . . . 15
	5.1.2. Registrations . . . . . . . . . . . . . . . . . . . . 16		5.1.2. Registrations . . . . . . . . . . . . . . . . . . . . 16
	5.2. Status Code Registration . . . . . . . . . . . . . . . . . 16		5.2. Status Code Registration . . . . . . . . . . . . . . . . . 16
	5.3. Header Field Registration . . . . . . . . . . . . . . . . 16		5.3. Header Field Registration . . . . . . . . . . . . . . . . 16
	5.4. Internet Media Type Registration . . . . . . . . . . . . . 17		5.4. Internet Media Type Registration . . . . . . . . . . . . . 17
	5.4.1. Internet Media Type multipart/byteranges . . . . . . . 17		5.4.1. Internet Media Type multipart/byteranges . . . . . . . 17
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 18		6. Security Considerations . . . . . . . . . . . . . . . . . . . 18
	6.1. Denial of Service Attacks using Range . . . . . . . . . . 18		6.1. Denial-of-Service Attacks Using Range . . . . . . . . . . 18
	7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18		7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19		8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
	8.1. Normative References . . . . . . . . . . . . . . . . . . . 19		8.1. Normative References . . . . . . . . . . . . . . . . . . . 19
	8.2. Informative References . . . . . . . . . . . . . . . . . . 19		8.2. Informative References . . . . . . . . . . . . . . . . . . 19
	Appendix A. Internet Media Type multipart/byteranges . . . . . . 20		Appendix A. Internet Media Type multipart/byteranges . . . . . . 20
	Appendix B. Changes from RFC 2616 . . . . . . . . . . . . . . . . 21		Appendix B. Changes from RFC 2616 . . . . . . . . . . . . . . . . 21
	Appendix C. Imported ABNF . . . . . . . . . . . . . . . . . . . . 21		Appendix C. Imported ABNF . . . . . . . . . . . . . . . . . . . . 21
	Appendix D. Collected ABNF . . . . . . . . . . . . . . . . . . . 21		Appendix D. Collected ABNF . . . . . . . . . . . . . . . . . . . 21
	Appendix E. Change Log (to be removed by RFC Editor before
	publication) . . . . . . . . . . . . . . . . . . . . 23
	E.1. Since draft-ietf-httpbis-p5-range-24 . . . . . . . . . . . 23
	E.2. Since draft-ietf-httpbis-p5-range-25 . . . . . . . . . . . 23
	Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23		Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
	1. Introduction		1. Introduction
	Hypertext Transfer Protocol (HTTP) clients often encounter		Hypertext Transfer Protocol (HTTP) clients often encounter
	interrupted data transfers as a result of canceled requests or		interrupted data transfers as a result of canceled requests or
	dropped connections. When a client has stored a partial		dropped connections. When a client has stored a partial
	representation, it is desirable to request the remainder of that		representation, it is desirable to request the remainder of that
	representation in a subsequent request rather than transfer the		representation in a subsequent request rather than transfer the
	entire representation. Likewise, devices with limited local storage		entire representation. Likewise, devices with limited local storage
	skipping to change at page 4, line 37 ¶		skipping to change at page 4, line 37 ¶
	extensible range types, this specification only defines requests for		extensible range types, this specification only defines requests for
	byte ranges.		byte ranges.
	1.1. Conformance and Error Handling		1.1. Conformance and Error Handling
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	Conformance criteria and considerations regarding error handling are		Conformance criteria and considerations regarding error handling are
	defined in Section 2.5 of [Part1].		defined in Section 2.5 of [RFC7230].
	1.2. Syntax Notation		1.2. Syntax Notation
	This specification uses the Augmented Backus-Naur Form (ABNF)		This specification uses the Augmented Backus-Naur Form (ABNF)
	notation of [RFC5234] with a list extension, defined in Section 7 of		notation of [RFC5234] with a list extension, defined in Section 7 of
	[Part1], that allows for compact definition of comma-separated lists		[RFC7230], that allows for compact definition of comma-separated
	using a '#' operator (similar to how the '*' operator indicates		lists using a '#' operator (similar to how the '*' operator indicates
	repetition). Appendix C describes rules imported from other		repetition). Appendix C describes rules imported from other
	documents. Appendix D shows the collected grammar with all list		documents. Appendix D shows the collected grammar with all list
	operators expanded to standard ABNF notation.		operators expanded to standard ABNF notation.
	2. Range Units		2. Range Units
	A representation can be partitioned into subranges according to		A representation can be partitioned into subranges according to
	various structural units, depending on the structure inherent in the		various structural units, depending on the structure inherent in the
	representation's media type. This ""range unit"" is used in the		representation's media type. This ""range unit"" is used in the
	Accept-Ranges (Section 2.3) response header field to advertise		Accept-Ranges (Section 2.3) response header field to advertise
	skipping to change at page 5, line 17 ¶		skipping to change at page 5, line 17 ¶
	field to delineate the parts of a representation that are requested,		field to delineate the parts of a representation that are requested,
	and the Content-Range (Section 4.2) payload header field to describe		and the Content-Range (Section 4.2) payload header field to describe
	which part of a representation is being transferred.		which part of a representation is being transferred.
	range-unit = bytes-unit / other-range-unit		range-unit = bytes-unit / other-range-unit
	2.1. Byte Ranges		2.1. Byte Ranges
	Since representation data is transferred in payloads as a sequence of		Since representation data is transferred in payloads as a sequence of
	octets, a byte range is a meaningful substructure for any		octets, a byte range is a meaningful substructure for any
	representation transferable over HTTP (Section 3 of [Part2]). The		representation transferable over HTTP (Section 3 of [RFC7231]). The
	"bytes" range unit is defined for expressing subranges of the data's		"bytes" range unit is defined for expressing subranges of the data's
	octet sequence.		octet sequence.
	bytes-unit = "bytes"		bytes-unit = "bytes"
	A byte range request can specify a single range of bytes, or a set of		A byte-range request can specify a single range of bytes or a set of
	ranges within a single representation.		ranges within a single representation.
	byte-ranges-specifier = bytes-unit "=" byte-range-set		byte-ranges-specifier = bytes-unit "=" byte-range-set
	byte-range-set = 1#( byte-range-spec / suffix-byte-range-spec )		byte-range-set = 1#( byte-range-spec / suffix-byte-range-spec )
	byte-range-spec = first-byte-pos "-" [ last-byte-pos ]		byte-range-spec = first-byte-pos "-" [ last-byte-pos ]
	first-byte-pos = 1*DIGIT		first-byte-pos = 1*DIGIT
	last-byte-pos = 1*DIGIT		last-byte-pos = 1*DIGIT
	The first-byte-pos value in a byte-range-spec gives the byte-offset		The first-byte-pos value in a byte-range-spec gives the byte-offset
	of the first byte in a range. The last-byte-pos value gives the		of the first byte in a range. The last-byte-pos value gives the
	skipping to change at page 6, line 45 ¶		skipping to change at page 6, line 45 ¶
	bytes=500-600,601-999		bytes=500-600,601-999
	bytes=500-700,601-999		bytes=500-700,601-999
	If a valid byte-range-set includes at least one byte-range-spec with		If a valid byte-range-set includes at least one byte-range-spec with
	a first-byte-pos that is less than the current length of the		a first-byte-pos that is less than the current length of the
	representation, or at least one suffix-byte-range-spec with a non-		representation, or at least one suffix-byte-range-spec with a non-
	zero suffix-length, then the byte-range-set is satisfiable.		zero suffix-length, then the byte-range-set is satisfiable.
	Otherwise, the byte-range-set is unsatisfiable.		Otherwise, the byte-range-set is unsatisfiable.
	In the byte range syntax, first-byte-pos, last-byte-pos, and suffix-		In the byte-range syntax, first-byte-pos, last-byte-pos, and suffix-
	length are expressed as decimal number of octets. Since there is no		length are expressed as decimal number of octets. Since there is no
	predefined limit to the length of a payload, recipients MUST		predefined limit to the length of a payload, recipients MUST
	anticipate potentially large decimal numerals and prevent parsing		anticipate potentially large decimal numerals and prevent parsing
	errors due to integer conversion overflows.		errors due to integer conversion overflows.
	2.2. Other Range Units		2.2. Other Range Units
	Range units are intended to be extensible. New range units ought to		Range units are intended to be extensible. New range units ought to
	be registered with IANA, as defined in Section 5.1.		be registered with IANA, as defined in Section 5.1.
	skipping to change at page 8, line 15 ¶		skipping to change at page 8, line 15 ¶
	than GET.		than GET.
	An origin server MUST ignore a Range header field that contains a		An origin server MUST ignore a Range header field that contains a
	range unit it does not understand. A proxy MAY discard a Range		range unit it does not understand. A proxy MAY discard a Range
	header field that contains a range unit it does not understand.		header field that contains a range unit it does not understand.
	A server that supports range requests MAY ignore or reject a Range		A server that supports range requests MAY ignore or reject a Range
	header field that consists of more than two overlapping ranges, or a		header field that consists of more than two overlapping ranges, or a
	set of many small ranges that are not listed in ascending order,		set of many small ranges that are not listed in ascending order,
	since both are indications of either a broken client or a deliberate		since both are indications of either a broken client or a deliberate
	denial of service attack (Section 6.1). A client SHOULD NOT request		denial-of-service attack (Section 6.1). A client SHOULD NOT request
	multiple ranges that are inherently less efficient to process and		multiple ranges that are inherently less efficient to process and
	transfer than a single range that encompasses the same data.		transfer than a single range that encompasses the same data.
	A client that is requesting multiple ranges SHOULD list those ranges		A client that is requesting multiple ranges SHOULD list those ranges
	in ascending order (the order in which they would typically be		in ascending order (the order in which they would typically be
	received in a complete representation) unless there is a specific		received in a complete representation) unless there is a specific
	need to request a later part earlier. For example, a user agent		need to request a later part earlier. For example, a user agent
	processing a large representation with an internal catalog of parts		processing a large representation with an internal catalog of parts
	might need to request later parts first, particularly if the		might need to request later parts first, particularly if the
	representation consists of pages stored in reverse order and the user		representation consists of pages stored in reverse order and the user
	agent wishes to transfer one page at a time.		agent wishes to transfer one page at a time.
	The Range header field is evaluated after evaluating the precondition		The Range header field is evaluated after evaluating the precondition
	header fields defined in [Part4], and only if the result in absence		header fields defined in [RFC7232], and only if the result in absence
	of the Range header field would be a 200 (OK) response. In other		of the Range header field would be a 200 (OK) response. In other
	words, Range is ignored when a conditional GET would result in a 304		words, Range is ignored when a conditional GET would result in a 304
	(Not Modified) response.		(Not Modified) response.
	The If-Range header field (Section 3.2) can be used as a precondition		The If-Range header field (Section 3.2) can be used as a precondition
	to applying the Range header field.		to applying the Range header field.
	If all of the preconditions are true, the server supports the Range		If all of the preconditions are true, the server supports the Range
	header field for the target resource, and the specified range(s) are		header field for the target resource, and the specified range(s) are
	valid and satisfiable (as defined in Section 2.1), the server SHOULD		valid and satisfiable (as defined in Section 2.1), the server SHOULD
	skipping to change at page 9, line 16 ¶		skipping to change at page 9, line 16 ¶
	If a client has a partial copy of a representation and wishes to have		If a client has a partial copy of a representation and wishes to have
	an up-to-date copy of the entire representation, it could use the		an up-to-date copy of the entire representation, it could use the
	Range header field with a conditional GET (using either or both of		Range header field with a conditional GET (using either or both of
	If-Unmodified-Since and If-Match.) However, if the precondition		If-Unmodified-Since and If-Match.) However, if the precondition
	fails because the representation has been modified, the client would		fails because the representation has been modified, the client would
	then have to make a second request to obtain the entire current		then have to make a second request to obtain the entire current
	representation.		representation.
	The "If-Range" header field allows a client to "short-circuit" the		The "If-Range" header field allows a client to "short-circuit" the
	second request. Informally, its meaning is: if the representation is		second request. Informally, its meaning is as follows: if the
	unchanged, send me the part(s) that I am requesting in Range;		representation is unchanged, send me the part(s) that I am requesting
	otherwise, send me the entire representation.		in Range; otherwise, send me the entire representation.
	If-Range = entity-tag / HTTP-date		If-Range = entity-tag / HTTP-date
	A client MUST NOT generate an If-Range header field in a request that		A client MUST NOT generate an If-Range header field in a request that
	does not contain a Range header field. A server MUST ignore an If-		does not contain a Range header field. A server MUST ignore an If-
	Range header field received in a request that does not contain a		Range header field received in a request that does not contain a
	Range header field. An origin server MUST ignore an If-Range header		Range header field. An origin server MUST ignore an If-Range header
	field received in a request for a target resource that does not		field received in a request for a target resource that does not
	support Range requests.		support Range requests.
	A client MUST NOT generate an If-Range header field containing an		A client MUST NOT generate an If-Range header field containing an
	entity-tag that is marked as weak. A client MUST NOT generate an If-		entity-tag that is marked as weak. A client MUST NOT generate an If-
	Range header field containing an HTTP-date unless the client has no		Range header field containing an HTTP-date unless the client has no
	entity-tag for the corresponding representation and the date is a		entity-tag for the corresponding representation and the date is a
	strong validator in the sense defined by Section 2.2.2 of [Part4].		strong validator in the sense defined by Section 2.2.2 of [RFC7232].
	A server that evaluates an If-Range precondition MUST use the strong		A server that evaluates an If-Range precondition MUST use the strong
	comparison function when comparing entity-tags (Section 2.3.2 of		comparison function when comparing entity-tags (Section 2.3.2 of
	[Part4]) and MUST evaluate the condition as false if an HTTP-date		[RFC7232]) and MUST evaluate the condition as false if an HTTP-date
	validator is provided that is not a strong validator in the sense		validator is provided that is not a strong validator in the sense
	defined by Section 2.2.2 of [Part4]. A valid entity-tag can be		defined by Section 2.2.2 of [RFC7232]. A valid entity-tag can be
	distinguished from a valid HTTP-date by examining the first two		distinguished from a valid HTTP-date by examining the first two
	characters for a DQUOTE.		characters for a DQUOTE.
	If the validator given in the If-Range header field matches the		If the validator given in the If-Range header field matches the
	current validator for the selected representation of the target		current validator for the selected representation of the target
	resource, then the server SHOULD process the Range header field as		resource, then the server SHOULD process the Range header field as
	requested. If the validator does not match, the server MUST ignore		requested. If the validator does not match, the server MUST ignore
	the Range header field. Note that this comparison by exact match,		the Range header field. Note that this comparison by exact match,
	including when the validator is an HTTP-date, differs from the		including when the validator is an HTTP-date, differs from the
	"earlier than or equal to" comparison used when evaluating an If-		"earlier than or equal to" comparison used when evaluating an If-
	skipping to change at page 10, line 33 ¶		skipping to change at page 10, line 33 ¶
	Content-Range: bytes 21010-47021/47022		Content-Range: bytes 21010-47021/47022
	Content-Length: 26012		Content-Length: 26012
	Content-Type: image/gif		Content-Type: image/gif
	... 26012 bytes of partial image data ...		... 26012 bytes of partial image data ...
	If multiple parts are being transferred, the server generating the		If multiple parts are being transferred, the server generating the
	206 response MUST generate a "multipart/byteranges" payload, as		206 response MUST generate a "multipart/byteranges" payload, as
	defined in Appendix A, and a Content-Type header field containing the		defined in Appendix A, and a Content-Type header field containing the
	multipart/byteranges media type and its required boundary parameter.		multipart/byteranges media type and its required boundary parameter.
	To avoid confusion with single part responses, a server MUST NOT		To avoid confusion with single-part responses, a server MUST NOT
	generate a Content-Range header field in the HTTP header section of a		generate a Content-Range header field in the HTTP header section of a
	multiple part response (this field will be sent in each part		multiple part response (this field will be sent in each part
	instead).		instead).
	Within the header area of each body part in the multipart payload,		Within the header area of each body part in the multipart payload,
	the server MUST generate a Content-Range header field corresponding		the server MUST generate a Content-Range header field corresponding
	to the range being enclosed in that body part. If the selected		to the range being enclosed in that body part. If the selected
	representation would have had a Content-Type header field in a 200		representation would have had a Content-Type header field in a 200
	(OK) response, the server SHOULD generate that same Content-Type		(OK) response, the server SHOULD generate that same Content-Type
	field in the header area of each body part. For example:		field in the header area of each body part. For example:
	skipping to change at page 12, line 20 ¶		skipping to change at page 12, line 20 ¶
	If a 206 is generated in response to a request with an If-Range		If a 206 is generated in response to a request with an If-Range
	header field, the sender SHOULD NOT generate other representation		header field, the sender SHOULD NOT generate other representation
	header fields beyond those required above, because the client is		header fields beyond those required above, because the client is
	understood to already have a prior response containing those header		understood to already have a prior response containing those header
	fields. Otherwise, the sender MUST generate all of the		fields. Otherwise, the sender MUST generate all of the
	representation header fields that would have been sent in a 200 (OK)		representation header fields that would have been sent in a 200 (OK)
	response to the same request.		response to the same request.
	A 206 response is cacheable by default; i.e., unless otherwise		A 206 response is cacheable by default; i.e., unless otherwise
	indicated by explicit cache controls (see Section 4.2.2 of [Part6]).		indicated by explicit cache controls (see Section 4.2.2 of
			[RFC7234]).
	4.2. Content-Range		4.2. Content-Range
	The "Content-Range" header field is sent in a single part 206		The "Content-Range" header field is sent in a single part 206
	(Partial Content) response to indicate the partial range of the		(Partial Content) response to indicate the partial range of the
	selected representation enclosed as the message payload, sent in each		selected representation enclosed as the message payload, sent in each
	part of a multipart 206 response to indicate the range enclosed		part of a multipart 206 response to indicate the range enclosed
	within each body part, and sent in 416 (Range Not Satisfiable)		within each body part, and sent in 416 (Range Not Satisfiable)
	responses to provide information about the selected representation.		responses to provide information about the selected representation.
	skipping to change at page 13, line 27 ¶		skipping to change at page 13, line 29 ¶
	Content-Range: bytes 42-1233/*		Content-Range: bytes 42-1233/*
	A Content-Range field value is invalid if it contains a byte-range-		A Content-Range field value is invalid if it contains a byte-range-
	resp that has a last-byte-pos value less than its first-byte-pos		resp that has a last-byte-pos value less than its first-byte-pos
	value, or a complete-length value less than or equal to its last-		value, or a complete-length value less than or equal to its last-
	byte-pos value. The recipient of an invalid Content-Range MUST NOT		byte-pos value. The recipient of an invalid Content-Range MUST NOT
	attempt to recombine the received content with a stored		attempt to recombine the received content with a stored
	representation.		representation.
	A server generating a 416 (Range Not Satisfiable) response to a byte		A server generating a 416 (Range Not Satisfiable) response to a byte-
	range request SHOULD send a Content-Range header field with an		range request SHOULD send a Content-Range header field with an
	unsatisfied-range value, as in the following example:		unsatisfied-range value, as in the following example:
	Content-Range: bytes */1234		Content-Range: bytes */1234
	The complete-length in a 416 response indicates the current length of		The complete-length in a 416 response indicates the current length of
	the selected representation.		the selected representation.
	The "Content-Range" header field has no meaning for status codes that		The Content-Range header field has no meaning for status codes that
	do not explicitly describe its semantic. For this specification,		do not explicitly describe its semantic. For this specification,
	only the 206 (Partial Content) and 416 (Range Not Satisfiable) status		only the 206 (Partial Content) and 416 (Range Not Satisfiable) status
	codes describe a meaning for Content-Range.		codes describe a meaning for Content-Range.
	The following are examples of Content-Range values in which the		The following are examples of Content-Range values in which the
	selected representation contains a total of 1234 bytes:		selected representation contains a total of 1234 bytes:
	o The first 500 bytes:		o The first 500 bytes:
	Content-Range: bytes 0-499/1234		Content-Range: bytes 0-499/1234
	skipping to change at page 14, line 20 ¶		skipping to change at page 14, line 20 ¶
	Content-Range: bytes 734-1233/1234		Content-Range: bytes 734-1233/1234
	4.3. Combining Ranges		4.3. Combining Ranges
	A response might transfer only a subrange of a representation if the		A response might transfer only a subrange of a representation if the
	connection closed prematurely or if the request used one or more		connection closed prematurely or if the request used one or more
	Range specifications. After several such transfers, a client might		Range specifications. After several such transfers, a client might
	have received several ranges of the same representation. These		have received several ranges of the same representation. These
	ranges can only be safely combined if they all have in common the		ranges can only be safely combined if they all have in common the
	same strong validator (Section 2.1 of [Part4]).		same strong validator (Section 2.1 of [RFC7232]).
	A client that has received multiple partial responses to GET requests		A client that has received multiple partial responses to GET requests
	on a target resource MAY combine those responses into a larger		on a target resource MAY combine those responses into a larger
	continuous range if they share the same strong validator.		continuous range if they share the same strong validator.
	If the most recent response is an incomplete 200 (OK) response, then		If the most recent response is an incomplete 200 (OK) response, then
	the header fields of that response are used for any combined response		the header fields of that response are used for any combined response
	and replace those of the matching stored responses.		and replace those of the matching stored responses.
	If the most recent response is a 206 (Partial Content) response and		If the most recent response is a 206 (Partial Content) response and
	skipping to change at page 15, line 16 ¶		skipping to change at page 15, line 16 ¶
	The "416 (Range Not Satisfiable)" status code indicates that none of		The "416 (Range Not Satisfiable)" status code indicates that none of
	the ranges in the request's Range header field (Section 3.1) overlap		the ranges in the request's Range header field (Section 3.1) overlap
	the current extent of the selected resource or that the set of ranges		the current extent of the selected resource or that the set of ranges
	requested has been rejected due to invalid ranges or an excessive		requested has been rejected due to invalid ranges or an excessive
	request of small or overlapping ranges.		request of small or overlapping ranges.
	For byte ranges, failing to overlap the current extent means that the		For byte ranges, failing to overlap the current extent means that the
	first-byte-pos of all of the byte-range-spec values were greater than		first-byte-pos of all of the byte-range-spec values were greater than
	the current length of the selected representation. When this status		the current length of the selected representation. When this status
	code is generated in response to a byte range request, the sender		code is generated in response to a byte-range request, the sender
	SHOULD generate a Content-Range header field specifying the current		SHOULD generate a Content-Range header field specifying the current
	length of the selected representation (Section 4.2).		length of the selected representation (Section 4.2).
	For example:		For example:
	HTTP/1.1 416 Range Not Satisfiable		HTTP/1.1 416 Range Not Satisfiable
	Date: Fri, 20 Jan 2012 15:41:54 GMT		Date: Fri, 20 Jan 2012 15:41:54 GMT
	Content-Range: bytes */47022		Content-Range: bytes */47022
	Note: Because servers are free to ignore Range, many		Note: Because servers are free to ignore Range, many
	skipping to change at page 15, line 40 ¶		skipping to change at page 15, line 40 ¶
	task (albeit less efficiently) and partly because clients might		task (albeit less efficiently) and partly because clients might
	not stop making an invalid partial request until they have		not stop making an invalid partial request until they have
	received a complete representation. Thus, clients cannot depend		received a complete representation. Thus, clients cannot depend
	on receiving a 416 (Range Not Satisfiable) response even when it		on receiving a 416 (Range Not Satisfiable) response even when it
	is most appropriate.		is most appropriate.
	5. IANA Considerations		5. IANA Considerations
	5.1. Range Unit Registry		5.1. Range Unit Registry
	The HTTP Range Unit Registry defines the name space for the range		The "HTTP Range Unit Registry" defines the namespace for the range
	unit names and refers to their corresponding specifications. The		unit names and refers to their corresponding specifications. The
	registry will be created and maintained at (the suggested URI)		registry has been created and is now maintained at
	<http://www.iana.org/assignments/http-parameters>.		<http://www.iana.org/assignments/http-parameters>.
	5.1.1. Procedure		5.1.1. Procedure
	Registration of an HTTP Range Unit MUST include the following fields:		Registration of an HTTP Range Unit MUST include the following fields:
	o Name		o Name
	o Description		o Description
	o Pointer to specification text		o Pointer to specification text
	Values to be added to this name space require IETF Review (see		Values to be added to this namespace require IETF Review (see
	[RFC5226], Section 4.1).		[RFC5226], Section 4.1).
	5.1.2. Registrations		5.1.2. Registrations
	The initial HTTP Range Unit Registry shall contain the registrations		The initial range unit registry contains the registrations below:
	below:
	+-------------+---------------------------------------+-------------+		+-------------+---------------------------------------+-------------+
	| Range Unit | Description | Reference |		| Range Unit | Description | Reference |
	| Name | | |		| Name | | |
	+-------------+---------------------------------------+-------------+		+-------------+---------------------------------------+-------------+
	| bytes | a range of octets | Section 2.1 |		| bytes | a range of octets | Section 2.1 |
	| none | reserved as keyword, indicating no | Section 2.3 |		| none | reserved as keyword, indicating no | Section 2.3 |
	| | ranges are supported | |		| | ranges are supported | |
	+-------------+---------------------------------------+-------------+		+-------------+---------------------------------------+-------------+
	The change controller is: "IETF (iesg@ietf.org) - Internet		The change controller is: "IETF (iesg@ietf.org) - Internet
	Engineering Task Force".		Engineering Task Force".
	5.2. Status Code Registration		5.2. Status Code Registration
	The HTTP Status Code Registry located at		The "Hypertext Transfer Protocol (HTTP) Status Code Registry" located
	<http://www.iana.org/assignments/http-status-codes> shall be updated		at <http://www.iana.org/assignments/http-status-codes> has been
	with the registrations below:		updated to include the registrations below:
	+-------+-----------------------+-------------+		+-------+-----------------------+-------------+
	| Value | Description | Reference |		| Value | Description | Reference |
	+-------+-----------------------+-------------+		+-------+-----------------------+-------------+
	| 206 | Partial Content | Section 4.1 |		| 206 | Partial Content | Section 4.1 |
	| 416 | Range Not Satisfiable | Section 4.4 |		| 416 | Range Not Satisfiable | Section 4.4 |
	+-------+-----------------------+-------------+		+-------+-----------------------+-------------+
	5.3. Header Field Registration		5.3. Header Field Registration
	HTTP header fields are registered within the Message Header Field		HTTP header fields are registered within the "Message Headers"
	Registry maintained at <http://www.iana.org/assignments/		registry maintained at
	message-headers/message-header-index.html>.		<http://www.iana.org/assignments/message-headers/>.
	This document defines the following HTTP header fields, so their		This document defines the following HTTP header fields, so their
	associated registry entries shall be updated according to the		associated registry entries have been updated according to the
	permanent registrations below (see [BCP90]):		permanent registrations below (see [BCP90]):
	+-------------------+----------+----------+-------------+		+-------------------+----------+----------+-------------+
	| Header Field Name | Protocol | Status | Reference |		| Header Field Name | Protocol | Status | Reference |
	+-------------------+----------+----------+-------------+		+-------------------+----------+----------+-------------+
	| Accept-Ranges | http | standard | Section 2.3 |		| Accept-Ranges | http | standard | Section 2.3 |
	| Content-Range | http | standard | Section 4.2 |		| Content-Range | http | standard | Section 4.2 |
	| If-Range | http | standard | Section 3.2 |		| If-Range | http | standard | Section 3.2 |
	| Range | http | standard | Section 3.1 |		| Range | http | standard | Section 3.1 |
	+-------------------+----------+----------+-------------+		+-------------------+----------+----------+-------------+
	The change controller is: "IETF (iesg@ietf.org) - Internet		The change controller is: "IETF (iesg@ietf.org) - Internet
	Engineering Task Force".		Engineering Task Force".
	5.4. Internet Media Type Registration		5.4. Internet Media Type Registration
	IANA maintains the registry of Internet media types [BCP13] at		IANA maintains the registry of Internet media types [BCP13] at
	<http://www.iana.org/assignments/media-types>.		<http://www.iana.org/assignments/media-types>.
	This document serves as the specification for the Internet media type		This document serves as the specification for the Internet media type
	"multipart/byteranges". The following is to be registered with IANA.		"multipart/byteranges". The following has been registered with IANA.
	5.4.1. Internet Media Type multipart/byteranges		5.4.1. Internet Media Type multipart/byteranges
	Type name: multipart		Type name: multipart
	Subtype name: byteranges		Subtype name: byteranges
	Required parameters: boundary		Required parameters: boundary
	Optional parameters: N/A		Optional parameters: N/A
	skipping to change at page 18, line 14 ¶		skipping to change at page 18, line 14 ¶
	Deprecated alias names for this type: N/A		Deprecated alias names for this type: N/A
	Magic number(s): N/A		Magic number(s): N/A
	File extension(s): N/A		File extension(s): N/A
	Macintosh file type code(s): N/A		Macintosh file type code(s): N/A
	Person and email address to contact for further information: See		Person and email address to contact for further information: See
	Authors Section.		Authors' Addresses section.
	Intended usage: COMMON		Intended usage: COMMON
	Restrictions on usage: N/A		Restrictions on usage: N/A
	Author: See Authors Section.		Author: See Authors' Addresses section.
	Change controller: IESG		Change controller: IESG
	6. Security Considerations		6. Security Considerations
	This section is meant to inform developers, information providers,		This section is meant to inform developers, information providers,
	and users of known security concerns specific to the HTTP range		and users of known security concerns specific to the HTTP range
	request mechanisms. More general security considerations are		request mechanisms. More general security considerations are
	addressed in HTTP messaging [Part1] and semantics [Part2].		addressed in HTTP messaging [RFC7230] and semantics [RFC7231].
	6.1. Denial of Service Attacks using Range		6.1. Denial-of-Service Attacks Using Range
	Unconstrained multiple range requests are susceptible to denial of		Unconstrained multiple range requests are susceptible to denial-of-
	service attacks because the effort required to request many		service attacks because the effort required to request many
	overlapping ranges of the same data is tiny compared to the time,		overlapping ranges of the same data is tiny compared to the time,
	memory, and bandwidth consumed by attempting to serve the requested		memory, and bandwidth consumed by attempting to serve the requested
	data in many parts. Servers ought to ignore, coalesce, or reject		data in many parts. Servers ought to ignore, coalesce, or reject
	egregious range requests, such as requests for more than two		egregious range requests, such as requests for more than two
	overlapping ranges or for many small ranges in a single set,		overlapping ranges or for many small ranges in a single set,
	particularly when the ranges are requested out of order for no		particularly when the ranges are requested out of order for no
	apparent reason. Multipart range requests are not designed to		apparent reason. Multipart range requests are not designed to
	support random access.		support random access.
	7. Acknowledgments		7. Acknowledgments
	See Section 10 of [Part1].		See Section 10 of [RFC7230].
	8. References		8. References
	8.1. Normative References		8.1. Normative References
	[Part1] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
	Protocol (HTTP/1.1): Message Syntax and Routing",
	draft-ietf-httpbis-p1-messaging-26 (work in progress),
	February 2014.
	[Part2] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
	Protocol (HTTP/1.1): Semantics and Content",
	draft-ietf-httpbis-p2-semantics-26 (work in progress),
	February 2014.
	[Part4] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
	Protocol (HTTP/1.1): Conditional Requests",
	draft-ietf-httpbis-p4-conditional-26 (work in progress),
	February 2014.
	[Part6] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
	Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
	draft-ietf-httpbis-p6-cache-26 (work in progress),
	February 2014.
	[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail		[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
	Extensions (MIME) Part Two: Media Types", RFC 2046,		Extensions (MIME) Part Two: Media Types", RFC 2046,
	November 1996.		November 1996.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119, March 1997.		Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax		[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
	Specifications: ABNF", STD 68, RFC 5234, January 2008.		Specifications: ABNF", STD 68, RFC 5234, January 2008.
			[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
			Protocol (HTTP/1.1): Message Syntax and Routing",
			draft-ietf-httpbis-p1-messaging-latest (work in progress),
			June 2014.
			[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
			Protocol (HTTP/1.1): Semantics and Content",
			draft-ietf-httpbis-p2-semantics-latest (work in progress),
			June 2014.
			[RFC7232] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
			Protocol (HTTP/1.1): Conditional Requests",
			draft-ietf-httpbis-p4-conditional-latest (work in
			progress), June 2014.
			[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
			Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
			draft-ietf-httpbis-p6-cache-latest (work in progress),
			June 2014.
	8.2. Informative References		8.2. Informative References
	[BCP13] Freed, N., Klensin, J., and T. Hansen, "Media Type		[BCP13] Freed, N., Klensin, J., and T. Hansen, "Media Type
	Specifications and Registration Procedures", BCP 13,		Specifications and Registration Procedures", BCP 13,
	RFC 6838, January 2013.		RFC 6838, January 2013.
	[BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration		[BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration
	Procedures for Message Header Fields", BCP 90, RFC 3864,		Procedures for Message Header Fields", BCP 90, RFC 3864,
	September 2004.		September 2004.
	skipping to change at page 21, line 33 ¶		skipping to change at page 21, line 33 ¶
	The following core rules are included by reference, as defined in		The following core rules are included by reference, as defined in
	Appendix B.1 of [RFC5234]: ALPHA (letters), CR (carriage return),		Appendix B.1 of [RFC5234]: ALPHA (letters), CR (carriage return),
	CRLF (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double		CRLF (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double
	quote), HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed), OCTET (any		quote), HEXDIG (hexadecimal 0-9/A-F/a-f), LF (line feed), OCTET (any
	8-bit sequence of data), SP (space), and VCHAR (any visible US-ASCII		8-bit sequence of data), SP (space), and VCHAR (any visible US-ASCII
	character).		character).
	Note that all rules derived from token are to be compared case-		Note that all rules derived from token are to be compared case-
	insensitively, like range-unit and acceptable-ranges.		insensitively, like range-unit and acceptable-ranges.
	The rules below are defined in [Part1]:		The rules below are defined in [RFC7230]:
	OWS = <OWS, defined in [Part1], Section 3.2.3>		OWS = <OWS, see [RFC7230], Section 3.2.3>
	token = <token, defined in [Part1], Section 3.2.6>		token = <token, see [RFC7230], Section 3.2.6>
	The rules below are defined in other parts:		The rules below are defined in other parts:
	HTTP-date = <HTTP-date, defined in [Part2], Section 7.1.1.1>		HTTP-date = <HTTP-date, see [RFC7231], Section 7.1.1.1>
	entity-tag = <entity-tag, defined in [Part4], Section 2.3>		entity-tag = <entity-tag, see [RFC7232], Section 2.3>
	Appendix D. Collected ABNF		Appendix D. Collected ABNF
	In the collected ABNF below, list rules are expanded as per Section		In the collected ABNF below, list rules are expanded as per Section
	1.2 of [Part1].		1.2 of [RFC7230].
	Accept-Ranges = acceptable-ranges		Accept-Ranges = acceptable-ranges
	Content-Range = byte-content-range / other-content-range		Content-Range = byte-content-range / other-content-range
	HTTP-date = <HTTP-date, defined in [Part2], Section 7.1.1.1>		HTTP-date = <HTTP-date, see [RFC7231], Section 7.1.1.1>
	If-Range = entity-tag / HTTP-date		If-Range = entity-tag / HTTP-date
	OWS = <OWS, defined in [Part1], Section 3.2.3>		OWS = <OWS, see [RFC7230], Section 3.2.3>
	Range = byte-ranges-specifier / other-ranges-specifier		Range = byte-ranges-specifier / other-ranges-specifier
	acceptable-ranges = ( *( "," OWS ) range-unit *( OWS "," [ OWS		acceptable-ranges = ( *( "," OWS ) range-unit *( OWS "," [ OWS
	range-unit ] ) ) / "none"		range-unit ] ) ) / "none"
	byte-content-range = bytes-unit SP ( byte-range-resp /		byte-content-range = bytes-unit SP ( byte-range-resp /
	unsatisfied-range )		unsatisfied-range )
	byte-range = first-byte-pos "-" last-byte-pos		byte-range = first-byte-pos "-" last-byte-pos
	byte-range-resp = byte-range "/" ( complete-length / "*" )		byte-range-resp = byte-range "/" ( complete-length / "*" )
	byte-range-set = *( "," OWS ) ( byte-range-spec /		byte-range-set = *( "," OWS ) ( byte-range-spec /
	suffix-byte-range-spec ) *( OWS "," [ OWS ( byte-range-spec /		suffix-byte-range-spec ) *( OWS "," [ OWS ( byte-range-spec /
	suffix-byte-range-spec ) ] )		suffix-byte-range-spec ) ] )
	byte-range-spec = first-byte-pos "-" [ last-byte-pos ]		byte-range-spec = first-byte-pos "-" [ last-byte-pos ]
	byte-ranges-specifier = bytes-unit "=" byte-range-set		byte-ranges-specifier = bytes-unit "=" byte-range-set
	bytes-unit = "bytes"		bytes-unit = "bytes"
	complete-length = 1*DIGIT		complete-length = 1*DIGIT
	entity-tag = <entity-tag, defined in [Part4], Section 2.3>		entity-tag = <entity-tag, see [RFC7232], Section 2.3>
	first-byte-pos = 1*DIGIT		first-byte-pos = 1*DIGIT
	last-byte-pos = 1*DIGIT		last-byte-pos = 1*DIGIT
	other-content-range = other-range-unit SP other-range-resp		other-content-range = other-range-unit SP other-range-resp
	other-range-resp = *CHAR		other-range-resp = *CHAR
	other-range-set = 1*VCHAR		other-range-set = 1*VCHAR
	other-range-unit = token		other-range-unit = token
	other-ranges-specifier = other-range-unit "=" other-range-set		other-ranges-specifier = other-range-unit "=" other-range-set
	range-unit = bytes-unit / other-range-unit		range-unit = bytes-unit / other-range-unit
	suffix-byte-range-spec = "-" suffix-length		suffix-byte-range-spec = "-" suffix-length
	suffix-length = 1*DIGIT		suffix-length = 1*DIGIT
	token = <token, defined in [Part1], Section 3.2.6>		token = <token, see [RFC7230], Section 3.2.6>
	unsatisfied-range = "*/" complete-length		unsatisfied-range = "*/" complete-length
	Appendix E. Change Log (to be removed by RFC Editor before publication)
	Changes up to the IETF Last Call draft are summarized in <http://
	tools.ietf.org/html/draft-ietf-httpbis-p5-range-24#appendix-E>.
	E.1. Since draft-ietf-httpbis-p5-range-24
	Closed issues:
	o <http://tools.ietf.org/wg/httpbis/trac/ticket/506>: "APPSDIR
	review of draft-ietf-httpbis-p5-range-24"
	o <http://tools.ietf.org/wg/httpbis/trac/ticket/507>: "integer value
	parsing"
	o <http://tools.ietf.org/wg/httpbis/trac/ticket/508>: "broken
	sentence in description of 206"
	E.2. Since draft-ietf-httpbis-p5-range-25
	Closed issues:
	o <http://tools.ietf.org/wg/httpbis/trac/ticket/526>: "check media
	type registration templates"
	o <http://tools.ietf.org/wg/httpbis/trac/ticket/527>: "use of CHAR
	for other-range-set"
	o <http://tools.ietf.org/wg/httpbis/trac/ticket/538>: "add
	'stateless' to Abstract"
	o <http://tools.ietf.org/wg/httpbis/trac/ticket/542>: "improve
	introduction of list rule"
	o <http://tools.ietf.org/wg/httpbis/trac/ticket/549>: "augment
	security considerations with pointers to current research"
	Index		Index
	2		2
	206 Partial Content (status code) 10		206 Partial Content (status code) 10
	4		4
	416 Range Not Satisfiable (status code) 15		416 Range Not Satisfiable (status code) 15
	A		A
	Accept-Ranges header field 7		Accept-Ranges header field 7
End of changes. 49 change blocks.
	117 lines changed or deleted		76 lines changed or added
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