draft-ietf-httpbis-p5-range-01.txt		draft-ietf-httpbis-p5-range-02.txt
	Network Working Group R. Fielding, Ed.		Network Working Group R. Fielding, Ed.
	Internet-Draft Day Software		Internet-Draft Day Software
	Obsoletes: 2616 (if approved) J. Gettys		Obsoletes: 2616 (if approved) J. Gettys
	Intended status: Standards Track One Laptop per Child		Intended status: Standards Track One Laptop per Child
	Expires: July 15, 2008 J. Mogul		Expires: August 27, 2008 J. Mogul
	HP		HP
	H. Frystyk		H. Frystyk
	Microsoft		Microsoft
	L. Masinter		L. Masinter
	Adobe Systems		Adobe Systems
	P. Leach		P. Leach
	Microsoft		Microsoft
	T. Berners-Lee		T. Berners-Lee
	W3C/MIT		W3C/MIT
	Y. Lafon, Ed.		Y. Lafon, Ed.
	W3C		W3C
	J. Reschke, Ed.		J. Reschke, Ed.
	greenbytes		greenbytes
	January 12, 2008		February 24, 2008
	HTTP/1.1, part 5: Range Requests and Partial Responses		HTTP/1.1, part 5: Range Requests and Partial Responses
	draft-ietf-httpbis-p5-range-01		draft-ietf-httpbis-p5-range-02
	Status of this Memo		Status of this Memo
	By submitting this Internet-Draft, each author represents that any		By submitting this Internet-Draft, each author represents that any
	applicable patent or other IPR claims of which he or she is aware		applicable patent or other IPR claims of which he or she is aware
	have been or will be disclosed, and any of which he or she becomes		have been or will be disclosed, and any of which he or she becomes
	aware will be disclosed, in accordance with Section 6 of BCP 79.		aware will be disclosed, in accordance with Section 6 of BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that		Task Force (IETF), its areas, and its working groups. Note that
	skipping to change at page 1, line 49		skipping to change at page 1, line 49
	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."
	The list of current Internet-Drafts can be accessed at		The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt.		http://www.ietf.org/ietf/1id-abstracts.txt.
	The list of Internet-Draft Shadow Directories can be accessed at		The list of Internet-Draft Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html.		http://www.ietf.org/shadow.html.
	This Internet-Draft will expire on July 15, 2008.		This Internet-Draft will expire on August 27, 2008.
	Copyright Notice		Copyright Notice
	Copyright (C) The IETF Trust (2008).		Copyright (C) The IETF Trust (2008).
	Abstract		Abstract
	The Hypertext Transfer Protocol (HTTP) is an application-level		The Hypertext Transfer Protocol (HTTP) is an application-level
	protocol for distributed, collaborative, hypermedia information		protocol for distributed, collaborative, hypermedia information
	systems. HTTP has been in use by the World Wide Web global		systems. HTTP has been in use by the World Wide Web global
	skipping to change at page 3, line 9		skipping to change at page 3, line 9
	This draft incorporates those issue resolutions that were either		This draft incorporates those issue resolutions that were either
	collected in the original RFC2616 errata list		collected in the original RFC2616 errata list
	(<http://purl.org/NET/http-errata>), or which were agreed upon on the		(<http://purl.org/NET/http-errata>), or which were agreed upon on the
	mailing list between October 2006 and November 2007 (as published in		mailing list between October 2006 and November 2007 (as published in
	"draft-lafon-rfc2616bis-03").		"draft-lafon-rfc2616bis-03").
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
	1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 4		1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 4
	2. Range Units . . . . . . . . . . . . . . . . . . . . . . . . . 4		2. Notational Conventions and Generic Grammar . . . . . . . . . . 4
	3. Status Code Definitions . . . . . . . . . . . . . . . . . . . 5		3. Range Units . . . . . . . . . . . . . . . . . . . . . . . . . 5
	3.1. 206 Partial Content . . . . . . . . . . . . . . . . . . . 5		4. Status Code Definitions . . . . . . . . . . . . . . . . . . . 5
	3.2. 416 Requested Range Not Satisfiable . . . . . . . . . . . 6		4.1. 206 Partial Content . . . . . . . . . . . . . . . . . . . 5
	4. Combining Byte Ranges . . . . . . . . . . . . . . . . . . . . 6		4.2. 416 Requested Range Not Satisfiable . . . . . . . . . . . 6
	5. Header Field Definitions . . . . . . . . . . . . . . . . . . . 6		5. Combining Byte Ranges . . . . . . . . . . . . . . . . . . . . 6
	5.1. Accept-Ranges . . . . . . . . . . . . . . . . . . . . . . 7		6. Header Field Definitions . . . . . . . . . . . . . . . . . . . 7
	5.2. Content-Range . . . . . . . . . . . . . . . . . . . . . . 7		6.1. Accept-Ranges . . . . . . . . . . . . . . . . . . . . . . 7
	5.3. If-Range . . . . . . . . . . . . . . . . . . . . . . . . . 9		6.2. Content-Range . . . . . . . . . . . . . . . . . . . . . . 8
	5.4. Range . . . . . . . . . . . . . . . . . . . . . . . . . . 10		6.3. If-Range . . . . . . . . . . . . . . . . . . . . . . . . . 10
	5.4.1. Byte Ranges . . . . . . . . . . . . . . . . . . . . . 10		6.4. Range . . . . . . . . . . . . . . . . . . . . . . . . . . 10
	5.4.2. Range Retrieval Requests . . . . . . . . . . . . . . . 12		6.4.1. Byte Ranges . . . . . . . . . . . . . . . . . . . . . 10
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12		6.4.2. Range Retrieval Requests . . . . . . . . . . . . . . . 12
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 13		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
	8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13		8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13		9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
	9.1. Normative References . . . . . . . . . . . . . . . . . . . 13		10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
	9.2. Informative References . . . . . . . . . . . . . . . . . . 14		10.1. Normative References . . . . . . . . . . . . . . . . . . . 13
			10.2. Informative References . . . . . . . . . . . . . . . . . . 14
	Appendix A. Internet Media Type multipart/byteranges . . . . . . 14		Appendix A. Internet Media Type multipart/byteranges . . . . . . 14
	Appendix B. Compatibility with Previous Versions . . . . . . . . 15		Appendix B. Compatibility with Previous Versions . . . . . . . . 16
	B.1. Changes from RFC 2068 . . . . . . . . . . . . . . . . . . 15		B.1. Changes from RFC 2068 . . . . . . . . . . . . . . . . . . 16
	B.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 16		B.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 17
	Appendix C. Change Log (to be removed by RFC Editor before		Appendix C. Change Log (to be removed by RFC Editor before
	publication) . . . . . . . . . . . . . . . . . . . . 16		publication) . . . . . . . . . . . . . . . . . . . . 17
	C.1. Since RFC2616 . . . . . . . . . . . . . . . . . . . . . . 16		C.1. Since RFC2616 . . . . . . . . . . . . . . . . . . . . . . 17
	C.2. Since draft-ietf-httpbis-p5-range-00 . . . . . . . . . . . 16		C.2. Since draft-ietf-httpbis-p5-range-00 . . . . . . . . . . . 17
	Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16		C.3. Since draft-ietf-httpbis-p5-range-01 . . . . . . . . . . . 17
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18		Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
	Intellectual Property and Copyright Statements . . . . . . . . . . 21		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
			Intellectual Property and Copyright Statements . . . . . . . . . . 22
	1. Introduction		1. Introduction
	HTTP clients often encounter interrupted data transfers as a result		HTTP clients often encounter interrupted data transfers as a result
	of cancelled requests or dropped connections. When a cache has		of cancelled requests or dropped connections. When a cache has
	stored a partial representation, it is desirable to request the		stored a partial representation, it is desirable to request the
	remainder of that representation in a subsequent request rather than		remainder of that representation in a subsequent request rather than
	transfer the entire representation. There are also a number of Web		transfer the entire representation. There are also a number of Web
	applications that benefit from being able to request only a subset of		applications that benefit from being able to request only a subset of
	a larger representation, such as a single page of a very large		a larger representation, such as a single page of a very large
	skipping to change at page 4, line 45		skipping to change at page 4, line 45
	An implementation is not compliant if it fails to satisfy one or more		An implementation is not compliant if it fails to satisfy one or more
	of the MUST or REQUIRED level requirements for the protocols it		of the MUST or REQUIRED level requirements for the protocols it
	implements. An implementation that satisfies all the MUST or		implements. An implementation that satisfies all the MUST or
	REQUIRED level and all the SHOULD level requirements for its		REQUIRED level and all the SHOULD level requirements for its
	protocols is said to be "unconditionally compliant"; one that		protocols is said to be "unconditionally compliant"; one that
	satisfies all the MUST level requirements but not all the SHOULD		satisfies all the MUST level requirements but not all the SHOULD
	level requirements for its protocols is said to be "conditionally		level requirements for its protocols is said to be "conditionally
	compliant."		compliant."
	2. Range Units		2. Notational Conventions and Generic Grammar
			This specification uses the ABNF syntax defined in Section 2.1 of
			[Part1] and the core rules defined in Section 2.2 of [Part1]:
			[[abnf.dep: ABNF syntax and basic rules will be adopted from RFC
			5234, see <http://tools.ietf.org/wg/httpbis/trac/ticket/36>.]]
			DIGIT = <DIGIT, defined in [Part1], Section 2.2>
			SP = <SP, defined in [Part1], Section 2.2>
			token = <token, defined in [Part1], Section 2.2>
			The ABNF rules below are defined in other parts:
			HTTP-date = <HTTP-date, defined in [Part1], Section 3.3.1>
			entity-tag = <entity-tag, defined in [Part4], Section 3>
			3. Range Units
	HTTP/1.1 allows a client to request that only part (a range of) the		HTTP/1.1 allows a client to request that only part (a range of) the
	response entity be included within the response. HTTP/1.1 uses range		response entity be included within the response. HTTP/1.1 uses range
	units in the Range (Section 5.4) and Content-Range (Section 5.2)		units in the Range (Section 6.4) and Content-Range (Section 6.2)
	header fields. An entity can be broken down into subranges according		header fields. An entity can be broken down into subranges according
	to various structural units.		to various structural units.
	range-unit = bytes-unit | other-range-unit		range-unit = bytes-unit | other-range-unit
	bytes-unit = "bytes"		bytes-unit = "bytes"
	other-range-unit = token		other-range-unit = token
	The only range unit defined by HTTP/1.1 is "bytes". HTTP/1.1		The only range unit defined by HTTP/1.1 is "bytes". HTTP/1.1
	implementations MAY ignore ranges specified using other units.		implementations MAY ignore ranges specified using other units.
	HTTP/1.1 has been designed to allow implementations of applications		HTTP/1.1 has been designed to allow implementations of applications
	that do not depend on knowledge of ranges.		that do not depend on knowledge of ranges.
	3. Status Code Definitions		4. Status Code Definitions
	3.1. 206 Partial Content		4.1. 206 Partial Content
	The server has fulfilled the partial GET request for the resource.		The server has fulfilled the partial GET request for the resource.
	The request MUST have included a Range header field (Section 5.4)		The request MUST have included a Range header field (Section 6.4)
	indicating the desired range, and MAY have included an If-Range		indicating the desired range, and MAY have included an If-Range
	header field (Section 5.3) to make the request conditional.		header field (Section 6.3) to make the request conditional.
	The response MUST include the following header fields:		The response MUST include the following header fields:
	o Either a Content-Range header field (Section 5.2) indicating the		o Either a Content-Range header field (Section 6.2) indicating the
	range included with this response, or a multipart/byteranges		range included with this response, or a multipart/byteranges
	Content-Type including Content-Range fields for each part. If a		Content-Type including Content-Range fields for each part. If a
	Content-Length header field is present in the response, its value		Content-Length header field is present in the response, its value
	MUST match the actual number of OCTETs transmitted in the message-		MUST match the actual number of OCTETs transmitted in the message-
	body.		body.
	o Date		o Date
	o ETag and/or Content-Location, if the header would have been sent		o ETag and/or Content-Location, if the header would have been sent
	in a 200 response to the same request		in a 200 response to the same request
	skipping to change at page 5, line 49		skipping to change at page 6, line 23
	differ from that sent in any previous response for the same		differ from that sent in any previous response for the same
	variant		variant
	If the 206 response is the result of an If-Range request, the		If the 206 response is the result of an If-Range request, the
	response SHOULD NOT include other entity-headers. Otherwise, the		response SHOULD NOT include other entity-headers. Otherwise, the
	response MUST include all of the entity-headers that would have been		response MUST include all of the entity-headers that would have been
	returned with a 200 (OK) response to the same request.		returned with a 200 (OK) response to the same request.
	A cache MUST NOT combine a 206 response with other previously cached		A cache MUST NOT combine a 206 response with other previously cached
	content if the ETag or Last-Modified headers do not match exactly,		content if the ETag or Last-Modified headers do not match exactly,
	see Section 4.		see Section 5.
	A cache that does not support the Range and Content-Range headers		A cache that does not support the Range and Content-Range headers
	MUST NOT cache 206 (Partial Content) responses.		MUST NOT cache 206 (Partial Content) responses.
	3.2. 416 Requested Range Not Satisfiable		4.2. 416 Requested Range Not Satisfiable
	A server SHOULD return a response with this status code if a request		A server SHOULD return a response with this status code if a request
	included a Range request-header field (Section 5.4), and none of the		included a Range request-header field (Section 6.4), and none of the
	range-specifier values in this field overlap the current extent of		range-specifier values in this field overlap the current extent of
	the selected resource, and the request did not include an If-Range		the selected resource, and the request did not include an If-Range
	request-header field. (For byte-ranges, this means that the first-		request-header field. (For byte-ranges, this means that the first-
	byte-pos of all of the byte-range-spec values were greater than the		byte-pos of all of the byte-range-spec values were greater than the
	current length of the selected resource.)		current length of the selected resource.)
	When this status code is returned for a byte-range request, the		When this status code is returned for a byte-range request, the
	response SHOULD include a Content-Range entity-header field		response SHOULD include a Content-Range entity-header field
	specifying the current length of the selected resource (see		specifying the current length of the selected resource (see
	Section 5.2). This response MUST NOT use the multipart/byteranges		Section 6.2). This response MUST NOT use the multipart/byteranges
	content-type.		content-type.
	4. Combining Byte Ranges		5. Combining Byte Ranges
	A response might transfer only a subrange of the bytes of an entity-		A response might transfer only a subrange of the bytes of an entity-
	body, either because the request included one or more Range		body, either because the request included one or more Range
	specifications, or because a connection was broken prematurely.		specifications, or because a connection was broken prematurely.
	After several such transfers, a cache might have received several		After several such transfers, a cache might have received several
	ranges of the same entity-body.		ranges of the same entity-body.
	If a cache has a stored non-empty set of subranges for an entity, and		If a cache has a stored non-empty set of subranges for an entity, and
	an incoming response transfers another subrange, the cache MAY		an incoming response transfers another subrange, the cache MAY
	combine the new subrange with the existing set if both the following		combine the new subrange with the existing set if both the following
	conditions are met:		conditions are met:
	o Both the incoming response and the cache entry have a cache		o Both the incoming response and the cache entry have a cache
	validator.		validator.
	o The two cache validators match using the strong comparison		o The two cache validators match using the strong comparison
	function (see Section 4 of [Part4]).		function (see Section 5 of [Part4]).
	If either requirement is not met, the cache MUST use only the most		If either requirement is not met, the cache MUST use only the most
	recent partial response (based on the Date values transmitted with		recent partial response (based on the Date values transmitted with
	every response, and using the incoming response if these values are		every response, and using the incoming response if these values are
	equal or missing), and MUST discard the other partial information.		equal or missing), and MUST discard the other partial information.
	5. Header Field Definitions		6. Header Field Definitions
	This section defines the syntax and semantics of HTTP/1.1 header		This section defines the syntax and semantics of HTTP/1.1 header
	fields related to range requests and partial responses.		fields related to range requests and partial responses.
	For entity-header fields, both sender and recipient refer to either		For entity-header fields, both sender and recipient refer to either
	the client or the server, depending on who sends and who receives the		the client or the server, depending on who sends and who receives the
	entity.		entity.
	5.1. Accept-Ranges		6.1. Accept-Ranges
	The Accept-Ranges response-header field allows the server to indicate		The Accept-Ranges response-header field allows the server to indicate
	its acceptance of range requests for a resource:		its acceptance of range requests for a resource:
	Accept-Ranges = "Accept-Ranges" ":" acceptable-ranges		Accept-Ranges = "Accept-Ranges" ":" acceptable-ranges
	acceptable-ranges = 1#range-unit | "none"		acceptable-ranges = 1#range-unit | "none"
	Origin servers that accept byte-range requests MAY send		Origin servers that accept byte-range requests MAY send
	Accept-Ranges: bytes		Accept-Ranges: bytes
	but are not required to do so. Clients MAY generate byte-range		but are not required to do so. Clients MAY generate byte-range
	requests without having received this header for the resource		requests without having received this header for the resource
	involved. Range units are defined in Section 2.		involved. Range units are defined in Section 3.
	Servers that do not accept any kind of range request for a resource		Servers that do not accept any kind of range request for a resource
	MAY send		MAY send
	Accept-Ranges: none		Accept-Ranges: none
	to advise the client not to attempt a range request.		to advise the client not to attempt a range request.
	5.2. Content-Range		6.2. Content-Range
	The Content-Range entity-header is sent with a partial entity-body to		The Content-Range entity-header is sent with a partial entity-body to
	specify where in the full entity-body the partial body should be		specify where in the full entity-body the partial body should be
	applied. Range units are defined in Section 2.		applied. Range units are defined in Section 3.
	Content-Range = "Content-Range" ":" content-range-spec		Content-Range = "Content-Range" ":" content-range-spec
	content-range-spec = byte-content-range-spec		content-range-spec = byte-content-range-spec
	byte-content-range-spec = bytes-unit SP		byte-content-range-spec = bytes-unit SP
	byte-range-resp-spec "/"		byte-range-resp-spec "/"
	( instance-length | "*" )		( instance-length | "*" )
	byte-range-resp-spec = (first-byte-pos "-" last-byte-pos)		byte-range-resp-spec = (first-byte-pos "-" last-byte-pos)
	| "*"		| "*"
	instance-length = 1*DIGIT		instance-length = 1*DIGIT
	The header SHOULD indicate the total length of the full entity-body,		The header SHOULD indicate the total length of the full entity-body,
	unless this length is unknown or difficult to determine. The		unless this length is unknown or difficult to determine. The
	asterisk "*" character means that the instance-length is unknown at		asterisk "*" character means that the instance-length is unknown at
	the time when the response was generated.		the time when the response was generated.
	Unlike byte-ranges-specifier values (see Section 5.4.1), a byte-		Unlike byte-ranges-specifier values (see Section 6.4.1), a byte-
	range-resp-spec MUST only specify one range, and MUST contain		range-resp-spec MUST only specify one range, and MUST contain
	absolute byte positions for both the first and last byte of the		absolute byte positions for both the first and last byte of the
	range.		range.
	A byte-content-range-spec with a byte-range-resp-spec whose last-		A byte-content-range-spec with a byte-range-resp-spec whose last-
	byte-pos value is less than its first-byte-pos value, or whose		byte-pos value is less than its first-byte-pos value, or whose
	instance-length value is less than or equal to its last-byte-pos		instance-length value is less than or equal to its last-byte-pos
	value, is invalid. The recipient of an invalid byte-content-range-		value, is invalid. The recipient of an invalid byte-content-range-
	spec MUST ignore it and any content transferred along with it.		spec MUST ignore it and any content transferred along with it.
	skipping to change at page 9, line 33		skipping to change at page 10, line 8
	If the server ignores a byte-range-spec because it is syntactically		If the server ignores a byte-range-spec because it is syntactically
	invalid, the server SHOULD treat the request as if the invalid Range		invalid, the server SHOULD treat the request as if the invalid Range
	header field did not exist. (Normally, this means return a 200		header field did not exist. (Normally, this means return a 200
	response containing the full entity).		response containing the full entity).
	If the server receives a request (other than one including an If-		If the server receives a request (other than one including an If-
	Range request-header field) with an unsatisfiable Range request-		Range request-header field) with an unsatisfiable Range request-
	header field (that is, all of whose byte-range-spec values have a		header field (that is, all of whose byte-range-spec values have a
	first-byte-pos value greater than the current length of the selected		first-byte-pos value greater than the current length of the selected
	resource), it SHOULD return a response code of 416 (Requested range		resource), it SHOULD return a response code of 416 (Requested range
	not satisfiable) (Section 3.2).		not satisfiable) (Section 4.2).
	Note: clients cannot depend on servers to send a 416 (Requested		Note: clients cannot depend on servers to send a 416 (Requested
	range not satisfiable) response instead of a 200 (OK) response for		range not satisfiable) response instead of a 200 (OK) response for
	an unsatisfiable Range request-header, since not all servers		an unsatisfiable Range request-header, since not all servers
	implement this request-header.		implement this request-header.
	5.3. If-Range		6.3. If-Range
	If a client has a partial copy of an entity in its cache, and wishes		If a client has a partial copy of an entity in its cache, and wishes
	to have an up-to-date copy of the entire entity in its cache, it		to have an up-to-date copy of the entire entity in its cache, it
	could use the Range request-header with a conditional GET (using		could use the Range request-header with a conditional GET (using
	either or both of If-Unmodified-Since and If-Match.) However, if the		either or both of If-Unmodified-Since and If-Match.) However, if the
	condition fails because the entity has been modified, the client		condition fails because the entity has been modified, the client
	would then have to make a second request to obtain the entire current		would then have to make a second request to obtain the entire current
	entity-body.		entity-body.
	The If-Range header allows a client to "short-circuit" the second		The If-Range header allows a client to "short-circuit" the second
	skipping to change at page 10, line 23		skipping to change at page 10, line 46
	header SHOULD only be used together with a Range header, and MUST be		header SHOULD only be used together with a Range header, and MUST be
	ignored if the request does not include a Range header, or if the		ignored if the request does not include a Range header, or if the
	server does not support the sub-range operation.		server does not support the sub-range operation.
	If the entity tag given in the If-Range header matches the current		If the entity tag given in the If-Range header matches the current
	entity tag for the entity, then the server SHOULD provide the		entity tag for the entity, then the server SHOULD provide the
	specified sub-range of the entity using a 206 (Partial Content)		specified sub-range of the entity using a 206 (Partial Content)
	response. If the entity tag does not match, then the server SHOULD		response. If the entity tag does not match, then the server SHOULD
	return the entire entity using a 200 (OK) response.		return the entire entity using a 200 (OK) response.
	5.4. Range		6.4. Range
	5.4.1. Byte Ranges		6.4.1. Byte Ranges
	Since all HTTP entities are represented in HTTP messages as sequences		Since all HTTP entities are represented in HTTP messages as sequences
	of bytes, the concept of a byte range is meaningful for any HTTP		of bytes, the concept of a byte range is meaningful for any HTTP
	entity. (However, not all clients and servers need to support byte-		entity. (However, not all clients and servers need to support byte-
	range operations.)		range operations.)
	Byte range specifications in HTTP apply to the sequence of bytes in		Byte range specifications in HTTP apply to the sequence of bytes in
	the entity-body (not necessarily the same as the message-body).		the entity-body (not necessarily the same as the message-body).
	A byte range operation MAY specify a single range of bytes, or a set		A byte range operation MAY specify a single range of bytes, or a set
	skipping to change at page 12, line 4		skipping to change at page 12, line 25
	o The second 500 bytes (byte offsets 500-999, inclusive): bytes=500-		o The second 500 bytes (byte offsets 500-999, inclusive): bytes=500-
	999		999
	o The final 500 bytes (byte offsets 9500-9999, inclusive): bytes=-		o The final 500 bytes (byte offsets 9500-9999, inclusive): bytes=-
	500		500
	o Or bytes=9500-		o Or bytes=9500-
	o The first and last bytes only (bytes 0 and 9999): bytes=0-0,-1		o The first and last bytes only (bytes 0 and 9999): bytes=0-0,-1
	o Several legal but not canonical specifications of the second 500		o Several legal but not canonical specifications of the second 500
	bytes (byte offsets 500-999, inclusive):		bytes (byte offsets 500-999, inclusive):
	bytes=500-600,601-999		bytes=500-600,601-999
	bytes=500-700,601-999		bytes=500-700,601-999
	5.4.2. Range Retrieval Requests		6.4.2. Range Retrieval Requests
	HTTP retrieval requests using conditional or unconditional GET		HTTP retrieval requests using conditional or unconditional GET
	methods MAY request one or more sub-ranges of the entity, instead of		methods MAY request one or more sub-ranges of the entity, instead of
	the entire entity, using the Range request header, which applies to		the entire entity, using the Range request header, which applies to
	the entity returned as the result of the request:		the entity returned as the result of the request:
	Range = "Range" ":" ranges-specifier		Range = "Range" ":" ranges-specifier
	A server MAY ignore the Range header. However, HTTP/1.1 origin		A server MAY ignore the Range header. However, HTTP/1.1 origin
	servers and intermediate caches ought to support byte ranges when		servers and intermediate caches ought to support byte ranges when
	skipping to change at page 12, line 40		skipping to change at page 13, line 14
	instead of 200 (OK).		instead of 200 (OK).
	o The presence of a Range header in a conditional GET (a request		o The presence of a Range header in a conditional GET (a request
	using one or both of If-Modified-Since and If-None-Match, or one		using one or both of If-Modified-Since and If-None-Match, or one
	or both of If-Unmodified-Since and If-Match) modifies what is		or both of If-Unmodified-Since and If-Match) modifies what is
	returned if the GET is otherwise successful and the condition is		returned if the GET is otherwise successful and the condition is
	true. It does not affect the 304 (Not Modified) response returned		true. It does not affect the 304 (Not Modified) response returned
	if the conditional is false.		if the conditional is false.
	In some cases, it might be more appropriate to use the If-Range		In some cases, it might be more appropriate to use the If-Range
	header (see Section 5.3) in addition to the Range header.		header (see Section 6.3) in addition to the Range header.
	If a proxy that supports ranges receives a Range request, forwards		If a proxy that supports ranges receives a Range request, forwards
	the request to an inbound server, and receives an entire entity in		the request to an inbound server, and receives an entire entity in
	reply, it SHOULD only return the requested range to its client. It		reply, it SHOULD only return the requested range to its client. It
	SHOULD store the entire received response in its cache if that is		SHOULD store the entire received response in its cache if that is
	consistent with its cache allocation policies.		consistent with its cache allocation policies.
	6. IANA Considerations		7. IANA Considerations
	TBD.		[[anchor2: TBD.]]
	7. Security Considerations		8. Security Considerations
	No additional security considerations have been identified beyond		No additional security considerations have been identified beyond
	those applicable to HTTP in general [Part1].		those applicable to HTTP in general [Part1].
	8. Acknowledgments		9. Acknowledgments
	Most of the specification of ranges is based on work originally done		Most of the specification of ranges is based on work originally done
	by Ari Luotonen and John Franks, with additional input from Steve		by Ari Luotonen and John Franks, with additional input from Steve
	Zilles, Daniel W. Connolly, Roy T. Fielding, Jim Gettys, Martin		Zilles, Daniel W. Connolly, Roy T. Fielding, Jim Gettys, Martin
	Hamilton, Koen Holtman, Shel Kaplan, Paul Leach, Alex Lopez-Ortiz,		Hamilton, Koen Holtman, Shel Kaplan, Paul Leach, Alex Lopez-Ortiz,
	Larry Masinter, Jeff Mogul, Lou Montulli, David W. Morris, Luigi		Larry Masinter, Jeff Mogul, Lou Montulli, David W. Morris, Luigi
	Rizzo, and Bill Weihl.		Rizzo, and Bill Weihl.
	9. References		10. References
	9.1. Normative References		10.1. Normative References
	[Part1] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,		[Part1] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
	Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,		Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
	and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections,		and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections,
	and Message Parsing", draft-ietf-httpbis-p1-messaging-01		and Message Parsing", draft-ietf-httpbis-p1-messaging-02
	(work in progress), January 2008.		(work in progress), February 2008.
	[Part3] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,		[Part3] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
	Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,		Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
	and J. Reschke, Ed., "HTTP/1.1, part 3: Message Payload		and J. Reschke, Ed., "HTTP/1.1, part 3: Message Payload
	and Content Negotiation", draft-ietf-httpbis-p3-payload-01		and Content Negotiation", draft-ietf-httpbis-p3-payload-02
	(work in progress), January 2008.		(work in progress), February 2008.
	[Part4] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,		[Part4] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
	Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,		Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
	and J. Reschke, Ed., "HTTP/1.1, part 4: Conditional		and J. Reschke, Ed., "HTTP/1.1, part 4: Conditional
	Requests", draft-ietf-httpbis-p4-conditional-01 (work in		Requests", draft-ietf-httpbis-p4-conditional-02 (work in
	progress), January 2008.		progress), February 2008.
	[Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,		[Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
	Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,		Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
	and J. Reschke, Ed., "HTTP/1.1, part 6: Caching",		and J. Reschke, Ed., "HTTP/1.1, part 6: Caching",
	draft-ietf-httpbis-p6-cache-01 (work in progress),		draft-ietf-httpbis-p6-cache-02 (work in progress),
	January 2008.		February 2008.
	[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.
	9.2. Informative References		10.2. Informative References
	[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,		[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
	Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext		Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
	Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.		Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
			[RFC4288] Freed, N. and J. Klensin, "Media Type Specifications and
			Registration Procedures", BCP 13, RFC 4288, December 2005.
	Appendix A. Internet Media Type multipart/byteranges		Appendix A. Internet Media Type multipart/byteranges
	When an HTTP 206 (Partial Content) response message includes the		When an HTTP 206 (Partial Content) response message includes the
	content of multiple ranges (a response to a request for multiple non-		content of multiple ranges (a response to a request for multiple non-
	overlapping ranges), these are transmitted as a multipart message-		overlapping ranges), these are transmitted as a multipart message-
	body. The media type for this purpose is called "multipart/		body [RFC2046]. The media type for this purpose is called
	byteranges".		"multipart/byteranges". The following is to be registered with IANA
			[RFC4288].
	The multipart/byteranges media type includes two or more parts, each		The multipart/byteranges media type includes two or more parts, each
	with its own Content-Type and Content-Range fields. The required		with its own Content-Type and Content-Range fields. The required
	boundary parameter specifies the boundary string used to separate		boundary parameter specifies the boundary string used to separate
	each body-part.		each body-part.
	Media Type name: multipart		Type name: multipart
	Media subtype name: byteranges		Subtype name: byteranges
	Required parameters: boundary		Required parameters: boundary
	Optional parameters: none		Optional parameters: none
	Encoding considerations: only "7bit", "8bit", or "binary" are		Encoding considerations: only "7bit", "8bit", or "binary" are
	permitted		permitted
	Security considerations: none		Security considerations: none
			Interoperability considerations: none
			Published specification: This specification (see Appendix A).
			Applications that use this media type:
			Additional information:
			Magic number(s): none
			File extension(s): none
			Macintosh file type code(s): none
			Person and email address to contact for further information: See
			Authors Section.
			Intended usage: COMMON
			Restrictions on usage: none
			Author/Change controller: IESG
	For example:		For example:
	HTTP/1.1 206 Partial Content		HTTP/1.1 206 Partial Content
	Date: Wed, 15 Nov 1995 06:25:24 GMT		Date: Wed, 15 Nov 1995 06:25:24 GMT
	Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT		Last-Modified: Wed, 15 Nov 1995 04:58:08 GMT
	Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES		Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES
	--THIS_STRING_SEPARATES		--THIS_STRING_SEPARATES
	Content-type: application/pdf		Content-type: application/pdf
	Content-range: bytes 500-999/8000		Content-range: bytes 500-999/8000
	skipping to change at page 15, line 45		skipping to change at page 16, line 45
	version documented in HTTP/1.1.		version documented in HTTP/1.1.
	Appendix B. Compatibility with Previous Versions		Appendix B. Compatibility with Previous Versions
	B.1. Changes from RFC 2068		B.1. Changes from RFC 2068
	Transfer-coding and message lengths all interact in ways that		Transfer-coding and message lengths all interact in ways that
	required fixing exactly when chunked encoding is used (to allow for		required fixing exactly when chunked encoding is used (to allow for
	transfer encoding that may not be self delimiting); it was important		transfer encoding that may not be self delimiting); it was important
	to straighten out exactly how message lengths are computed.		to straighten out exactly how message lengths are computed.
	(Section 5.2, see also [Part1], [Part3] and [Part6])		(Section 6.2, see also [Part1], [Part3] and [Part6])
	There are situations where a server (especially a proxy) does not		There are situations where a server (especially a proxy) does not
	know the full length of a response but is capable of serving a		know the full length of a response but is capable of serving a
	byterange request. We therefore need a mechanism to allow byteranges		byterange request. We therefore need a mechanism to allow byteranges
	with a content-range not indicating the full length of the message.		with a content-range not indicating the full length of the message.
	(Section 5.2)		(Section 6.2)
	Range request responses would become very verbose if all meta-data		Range request responses would become very verbose if all meta-data
	were always returned; by allowing the server to only send needed		were always returned; by allowing the server to only send needed
	headers in a 206 response, this problem can be avoided. (Section 3.1		headers in a 206 response, this problem can be avoided. (Section 4.1
	and 5.3)		and 6.3)
	Fix problem with unsatisfiable range requests; there are two cases:		Fix problem with unsatisfiable range requests; there are two cases:
	syntactic problems, and range doesn't exist in the document. The 416		syntactic problems, and range doesn't exist in the document. The 416
	status code was needed to resolve this ambiguity needed to indicate		status code was needed to resolve this ambiguity needed to indicate
	an error for a byte range request that falls outside of the actual		an error for a byte range request that falls outside of the actual
	contents of a document. (Section 3.2, 5.2)		contents of a document. (Section 4.2, 6.2)
	B.2. Changes from RFC 2616		B.2. Changes from RFC 2616
	Clarify that it is not ok to use a weak cache validator in a 206		Clarify that it is not ok to use a weak cache validator in a 206
	response. (Section 3.1)		response. (Section 4.1)
	Appendix C. Change Log (to be removed by RFC Editor before publication)		Appendix C. Change Log (to be removed by RFC Editor before publication)
	C.1. Since RFC2616		C.1. Since RFC2616
	Extracted relevant partitions from [RFC2616].		Extracted relevant partitions from [RFC2616].
	C.2. Since draft-ietf-httpbis-p5-range-00		C.2. Since draft-ietf-httpbis-p5-range-00
	Closed issues:		Closed issues:
	skipping to change at page 16, line 43		skipping to change at page 17, line 43
	o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/18>: "Cache		o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/18>: "Cache
	validators in 206 responses"		validators in 206 responses"
	(<http://purl.org/NET/http-errata#ifrange206>)		(<http://purl.org/NET/http-errata#ifrange206>)
	o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35>: "Normative		o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/35>: "Normative
	and Informative references"		and Informative references"
	o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/86>: "Normative		o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/86>: "Normative
	up-to-date references"		up-to-date references"
			C.3. Since draft-ietf-httpbis-p5-range-01
			Closed issues:
			o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/55>: "Updating
			to RFC4288"
			Ongoing work on ABNF conversion
			(<http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36>):
			o Add explicit references to BNF syntax and rules imported from
			other parts of the specification.
	Index		Index
	2		2
	206 Partial Content (status code) 5		206 Partial Content (status code) 5
	4		4
	416 Requested Range Not Satisfiable (status code) 6		416 Requested Range Not Satisfiable (status code) 6
	A		A
	Accept-Ranges header 7		Accept-Ranges header 7
	C		C
	Content-Range header 7		Content-Range header 8
	G		G
	Grammar		Grammar
	Accept-Ranges 7		Accept-Ranges 7
	acceptable-ranges 7		acceptable-ranges 7
	byte-content-range-spec 7		byte-content-range-spec 8
	byte-range-resp-spec 7		byte-range-resp-spec 8
	byte-range-set 10		byte-range-set 11
	byte-range-spec 10		byte-range-spec 11
	byte-ranges-specifier 10		byte-ranges-specifier 11
	bytes-unit 5		bytes-unit 5
	Content-Range 7		Content-Range 8
	content-range-spec 7		content-range-spec 8
	first-byte-pos 10		first-byte-pos 11
	If-Range 10		If-Range 10
	instance-length 7		instance-length 8
	last-byte-pos 10		last-byte-pos 11
	other-range-unit 5		other-range-unit 5
	Range 12		Range 12
	range-unit 5		range-unit 5
	ranges-specifier 10		ranges-specifier 11
	suffix-byte-range-spec 11		suffix-byte-range-spec 11
	suffix-length 11		suffix-length 11
	H		H
	Headers		Headers
	Accept-Ranges 7		Accept-Ranges 7
	Content-Range 7		Content-Range 8
	If-Range 9		If-Range 10
	Range 10		Range 10
	I		I
	If-Range header 9		If-Range header 10
	M		M
	Media Type		Media Type
	multipart/byteranges 14		multipart/byteranges 14
	multipart/x-byteranges 15		multipart/x-byteranges 16
	multipart/byteranges Media Type 14		multipart/byteranges Media Type 14
	multipart/x-byteranges Media Type 15		multipart/x-byteranges Media Type 16
	R		R
	Range header 10		Range header 10
	S		S
	Status Codes		Status Codes
	206 Partial Content 5		206 Partial Content 5
	416 Requested Range Not Satisfiable 6		416 Requested Range Not Satisfiable 6
	Authors' Addresses		Authors' Addresses
	Roy T. Fielding (editor)		Roy T. Fielding (editor)
	Day Software		Day Software
	23 Corporate Plaza DR, Suite 280		23 Corporate Plaza DR, Suite 280
End of changes. 67 change blocks.
	99 lines changed or deleted		160 lines changed or added
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