draft-ietf-httpbis-p6-cache-02.txt		draft-ietf-httpbis-p6-cache-03.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: August 27, 2008 J. Mogul		Expires: December 19, 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
	February 24, 2008		June 17, 2008
	HTTP/1.1, part 6: Caching		HTTP/1.1, part 6: Caching
	draft-ietf-httpbis-p6-cache-02		draft-ietf-httpbis-p6-cache-03
	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 August 27, 2008.		This Internet-Draft will expire on December 19, 2008.
	Copyright Notice
	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
	information initiative since 1990. This document is Part 6 of the		information initiative since 1990. This document is Part 6 of the
	seven-part specification that defines the protocol referred to as		seven-part specification that defines the protocol referred to as
	"HTTP/1.1" and, taken together, obsoletes RFC 2616. Part 6 defines		"HTTP/1.1" and, taken together, obsoletes RFC 2616. Part 6 defines
	requirements on HTTP caches and the associated header fields that		requirements on HTTP caches and the associated header fields that
	control cache behavior or indicate cacheable response messages.		control cache behavior or indicate cacheable response messages.
	Editorial Note (To be removed by RFC Editor)		Editorial Note (To be removed by RFC Editor)
	Discussion of this draft should take place on the HTTPBIS working		Discussion of this draft should take place on the HTTPBIS working
	group mailing list (ietf-http-wg@w3.org). The current issues list is		group mailing list (ietf-http-wg@w3.org). The current issues list is
	at <http://www.tools.ietf.org/wg/httpbis/trac/report/11> and related		at <http://www.tools.ietf.org/wg/httpbis/trac/report/11> and related
	documents (including fancy diffs) can be found at		documents (including fancy diffs) can be found at
	<http://www.tools.ietf.org/wg/httpbis/>.		<http://www.tools.ietf.org/wg/httpbis/>.
	This draft incorporates those issue resolutions that were either		The changes in this draft are summarized in Appendix B.4.
	collected in the original RFC2616 errata list
	(<http://purl.org/NET/http-errata>), or which were agreed upon on the
	mailing list between October 2006 and November 2007 (as published in
	"draft-lafon-rfc2616bis-03").
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
	1.1. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . 5		1.1. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . 5
	1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6		1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
	1.3. Requirements . . . . . . . . . . . . . . . . . . . . . . . 7		1.3. Requirements . . . . . . . . . . . . . . . . . . . . . . . 7
	2. Notational Conventions and Generic Grammar . . . . . . . . . . 8		2. Notational Conventions and Generic Grammar . . . . . . . . . . 8
	3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 8		3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	3.1. Cache Correctness . . . . . . . . . . . . . . . . . . . . 8		3.1. Cache Correctness . . . . . . . . . . . . . . . . . . . . 8
	skipping to change at page 4, line 5		skipping to change at page 4, line 5
	16.2.2. What May be Stored by Caches . . . . . . . . . . . . 30		16.2.2. What May be Stored by Caches . . . . . . . . . . . . 30
	16.2.3. Modifications of the Basic Expiration Mechanism . . . 31		16.2.3. Modifications of the Basic Expiration Mechanism . . . 31
	16.2.4. Cache Revalidation and Reload Controls . . . . . . . 33		16.2.4. Cache Revalidation and Reload Controls . . . . . . . 33
	16.2.5. No-Transform Directive . . . . . . . . . . . . . . . 35		16.2.5. No-Transform Directive . . . . . . . . . . . . . . . 35
	16.2.6. Cache Control Extensions . . . . . . . . . . . . . . 36		16.2.6. Cache Control Extensions . . . . . . . . . . . . . . 36
	16.3. Expires . . . . . . . . . . . . . . . . . . . . . . . . . 37		16.3. Expires . . . . . . . . . . . . . . . . . . . . . . . . . 37
	16.4. Pragma . . . . . . . . . . . . . . . . . . . . . . . . . . 38		16.4. Pragma . . . . . . . . . . . . . . . . . . . . . . . . . . 38
	16.5. Vary . . . . . . . . . . . . . . . . . . . . . . . . . . . 38		16.5. Vary . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
	16.6. Warning . . . . . . . . . . . . . . . . . . . . . . . . . 39		16.6. Warning . . . . . . . . . . . . . . . . . . . . . . . . . 39
	17. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42		17. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42
			17.1. Message Header Registration . . . . . . . . . . . . . . . 42
	18. Security Considerations . . . . . . . . . . . . . . . . . . . 42		18. Security Considerations . . . . . . . . . . . . . . . . . . . 42
	19. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 42		19. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 43
	20. References . . . . . . . . . . . . . . . . . . . . . . . . . . 42		20. References . . . . . . . . . . . . . . . . . . . . . . . . . . 43
	20.1. Normative References . . . . . . . . . . . . . . . . . . . 42		20.1. Normative References . . . . . . . . . . . . . . . . . . . 43
	20.2. Informative References . . . . . . . . . . . . . . . . . . 44		20.2. Informative References . . . . . . . . . . . . . . . . . . 44
	Appendix A. Compatibility with Previous Versions . . . . . . . . 44		Appendix A. Compatibility with Previous Versions . . . . . . . . 44
	A.1. Changes from RFC 2068 . . . . . . . . . . . . . . . . . . 44		A.1. Changes from RFC 2068 . . . . . . . . . . . . . . . . . . 44
	A.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 44		A.2. Changes from RFC 2616 . . . . . . . . . . . . . . . . . . 45
	Appendix B. Change Log (to be removed by RFC Editor before		Appendix B. Change Log (to be removed by RFC Editor before
	publication) . . . . . . . . . . . . . . . . . . . . 44		publication) . . . . . . . . . . . . . . . . . . . . 45
	B.1. Since RFC2616 . . . . . . . . . . . . . . . . . . . . . . 45		B.1. Since RFC2616 . . . . . . . . . . . . . . . . . . . . . . 45
	B.2. Since draft-ietf-httpbis-p6-cache-00 . . . . . . . . . . . 45		B.2. Since draft-ietf-httpbis-p6-cache-00 . . . . . . . . . . . 45
	B.3. Since draft-ietf-httpbis-p6-cache-01 . . . . . . . . . . . 45		B.3. Since draft-ietf-httpbis-p6-cache-01 . . . . . . . . . . . 46
			B.4. Since draft-ietf-httpbis-p6-cache-02 . . . . . . . . . . . 46
	Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46		Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 48		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 49
	Intellectual Property and Copyright Statements . . . . . . . . . . 51		Intellectual Property and Copyright Statements . . . . . . . . . . 52
	1. Introduction		1. Introduction
	HTTP is typically used for distributed information systems, where		HTTP is typically used for distributed information systems, where
	performance can be improved by the use of response caches, and		performance can be improved by the use of response caches, and
	includes a number of elements intended to make caching work as well		includes a number of elements intended to make caching work as well
	as possible. Because these elements interact with each other, it is		as possible. Because these elements interact with each other, it is
	useful to describe the caching design of HTTP separately. This		useful to describe the caching design of HTTP separately. This
	document defines aspects of HTTP/1.1 related to caching and reusing		document defines aspects of HTTP/1.1 related to caching and reusing
	response messages.		response messages.
	skipping to change at page 42, line 25		skipping to change at page 42, line 25
	If an implementation receives a message with a warning-value that		If an implementation receives a message with a warning-value that
	includes a warn-date, and that warn-date is different from the Date		includes a warn-date, and that warn-date is different from the Date
	value in the response, then that warning-value MUST be deleted from		value in the response, then that warning-value MUST be deleted from
	the message before storing, forwarding, or using it. (This prevents		the message before storing, forwarding, or using it. (This prevents
	bad consequences of naive caching of Warning header fields.) If all		bad consequences of naive caching of Warning header fields.) If all
	of the warning-values are deleted for this reason, the Warning header		of the warning-values are deleted for this reason, the Warning header
	MUST be deleted as well.		MUST be deleted as well.
	17. IANA Considerations		17. IANA Considerations
	[[anchor1: TBD.]]		17.1. Message Header Registration
			The Message Header Registry located at <http://www.iana.org/
			assignments/message-headers/message-header-index.html> should be
			updated with the permanent registrations below (see [RFC3864]):
			+-------------------+----------+----------+--------------+
			| Header Field Name | Protocol | Status | Reference |
			+-------------------+----------+----------+--------------+
			| Age | http | standard | Section 16.1 |
			| Cache-Control | http | standard | Section 16.2 |
			| Expires | http | standard | Section 16.3 |
			| Pragma | http | standard | Section 16.4 |
			| Vary | http | standard | Section 16.5 |
			| Warning | http | standard | Section 16.6 |
			+-------------------+----------+----------+--------------+
			The change controller is: "IETF (iesg@ietf.org) - Internet
			Engineering Task Force".
	18. Security Considerations		18. Security Considerations
	Caching proxies provide additional potential vulnerabilities, since		Caching proxies provide additional potential vulnerabilities, since
	the contents of the cache represent an attractive target for		the contents of the cache represent an attractive target for
	malicious exploitation. Because cache contents persist after an HTTP		malicious exploitation. Because cache contents persist after an HTTP
	request is complete, an attack on the cache can reveal information		request is complete, an attack on the cache can reveal information
	long after a user believes that the information has been removed from		long after a user believes that the information has been removed from
	the network. Therefore, cache contents should be protected as		the network. Therefore, cache contents should be protected as
	sensitive information.		sensitive information.
	skipping to change at page 43, line 11		skipping to change at page 43, line 27
	[ISO-8859-1]		[ISO-8859-1]
	International Organization for Standardization,		International Organization for Standardization,
	"Information technology -- 8-bit single-byte coded graphic		"Information technology -- 8-bit single-byte coded graphic
	character sets -- Part 1: Latin alphabet No. 1", ISO/		character sets -- Part 1: Latin alphabet No. 1", ISO/
	IEC 8859-1:1998, 1998.		IEC 8859-1:1998, 1998.
	[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-02		and Message Parsing", draft-ietf-httpbis-p1-messaging-03
	(work in progress), February 2008.		(work in progress), June 2008.
	[Part2] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,		[Part2] 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 2: Message		and J. Reschke, Ed., "HTTP/1.1, part 2: Message
	Semantics", draft-ietf-httpbis-p2-semantics-02 (work in		Semantics", draft-ietf-httpbis-p2-semantics-03 (work in
	progress), February 2008.		progress), June 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-02		and Content Negotiation", draft-ietf-httpbis-p3-payload-03
	(work in progress), February 2008.		(work in progress), June 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-02 (work in		Requests", draft-ietf-httpbis-p4-conditional-03 (work in
	progress), February 2008.		progress), June 2008.
	[Part5] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,		[Part5] 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 5: Range Requests and		and J. Reschke, Ed., "HTTP/1.1, part 5: Range Requests and
	Partial Responses", draft-ietf-httpbis-p5-range-02 (work		Partial Responses", draft-ietf-httpbis-p5-range-03 (work
	in progress), February 2008.		in progress), June 2008.
	[Part7] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,		[Part7] 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 7: Authentication",		and J. Reschke, Ed., "HTTP/1.1, part 7: Authentication",
	draft-ietf-httpbis-p7-auth-02 (work in progress),		draft-ietf-httpbis-p7-auth-03 (work in progress),
	February 2008.		June 2008.
	[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions)		[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
	Part Three: Message Header Extensions for Non-ASCII Text",		Part Three: Message Header Extensions for Non-ASCII Text",
	RFC 2047, November 1996.		RFC 2047, 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.
	20.2. Informative References		20.2. Informative References
	[RFC1305] Mills, D., "Network Time Protocol (Version 3)		[RFC1305] Mills, D., "Network Time Protocol (Version 3)
	Specification, Implementation", RFC 1305, March 1992.		Specification, Implementation", RFC 1305, March 1992.
	[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.
			[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
			Procedures for Message Header Fields", BCP 90, RFC 3864,
			September 2004.
	Appendix A. Compatibility with Previous Versions		Appendix A. Compatibility with Previous Versions
	A.1. Changes from RFC 2068		A.1. Changes from RFC 2068
	A case was missed in the Cache-Control model of HTTP/1.1; s-maxage		A case was missed in the Cache-Control model of HTTP/1.1; s-maxage
	was introduced to add this missing case. (Sections 6, 16.2, 16.2.3)		was introduced to add this missing case. (Sections 6, 16.2, 16.2.3)
	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
	skipping to change at page 46, line 4		skipping to change at page 46, line 21
	o Use names of RFC4234 core rules DQUOTE and HTAB (work in progress		o Use names of RFC4234 core rules DQUOTE and HTAB (work in progress
	on <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36>)		on <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36>)
	B.3. Since draft-ietf-httpbis-p6-cache-01		B.3. Since draft-ietf-httpbis-p6-cache-01
	Closed issues:		Closed issues:
	o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/82>: "rel_path		o <http://www3.tools.ietf.org/wg/httpbis/trac/ticket/82>: "rel_path
	not used"		not used"
	Other changes:		Other changes:
	o Get rid of duplicate BNF rule names ("host" -> "uri-host") (work		o Get rid of duplicate BNF rule names ("host" -> "uri-host") (work
	in progress on		in progress on
	<http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36>)		<http://www3.tools.ietf.org/wg/httpbis/trac/ticket/36>)
	o Add explicit references to BNF syntax and rules imported from		o Add explicit references to BNF syntax and rules imported from
	other parts of the specification.		other parts of the specification.
			B.4. Since draft-ietf-httpbis-p6-cache-02
			Ongoing work on IANA Message Header Registration
			(<http://www3.tools.ietf.org/wg/httpbis/trac/ticket/40>):
			o Reference RFC 3984, and update header registrations for headers
			defined in this document.
	Index		Index
	A		A
	age 7		age 7
	Age header 27		Age header 27
	C		C
	cache 5		cache 5
	Cache Directives		Cache Directives
	max-age 32		max-age 32-33
	max-age 33
	max-stale 32		max-stale 32
	min-fresh 32		min-fresh 32
	must-revalidate 34		must-revalidate 34
	no-cache 29		no-cache 29
	no-store 30		no-store 30
	no-transform 35		no-transform 35
	only-if-cached 34		only-if-cached 34
	private 29		private 29
	proxy-revalidate 35		proxy-revalidate 35
	public 29		public 29
	skipping to change at page 47, line 34		skipping to change at page 48, line 11
	Age 27		Age 27
	Cache-Control 27		Cache-Control 27
	Expires 37		Expires 37
	Pragma 38		Pragma 38
	Vary 38		Vary 38
	Warning 39		Warning 39
	heuristic expiration time 7		heuristic expiration time 7
	M		M
	max-age		max-age
	Cache Directive 32		Cache Directive 32-33
	Cache Directive 33
	max-stale		max-stale
	Cache Directive 32		Cache Directive 32
	min-fresh		min-fresh
	Cache Directive 32		Cache Directive 32
	must-revalidate		must-revalidate
	Cache Directive 34		Cache Directive 34
	N		N
	no-cache		no-cache
	Cache Directive 29		Cache Directive 29
	skipping to change at page 51, line 44		skipping to change at line 2337
	attempt made to obtain a general license or permission for the use of		attempt made to obtain a general license or permission for the use of
	such proprietary rights by implementers or users of this		such proprietary rights by implementers or users of this
	specification can be obtained from the IETF on-line IPR repository at		specification can be obtained from the IETF on-line IPR repository at
	http://www.ietf.org/ipr.		http://www.ietf.org/ipr.
	The IETF invites any interested party to bring to its attention any		The IETF invites any interested party to bring to its attention any
	copyrights, patents or patent applications, or other proprietary		copyrights, patents or patent applications, or other proprietary
	rights that may cover technology that may be required to implement		rights that may cover technology that may be required to implement
	this standard. Please address the information to the IETF at		this standard. Please address the information to the IETF at
	ietf-ipr@ietf.org.		ietf-ipr@ietf.org.
	Acknowledgment
	Funding for the RFC Editor function is provided by the IETF
	Administrative Support Activity (IASA).
End of changes. 24 change blocks.
	38 lines changed or deleted		61 lines changed or added
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