p6-cache-orig.txt		draft-fielding-http-p6-cache-00.txt
	Network Working Group R. Fielding		Network Working Group R. Fielding, Ed.
	Internet-Draft UC Irvine		Internet-Draft Day Software
	Obsoletes: 2068, 2616, 2617 J. Gettys		Obsoletes: 2068, 2616, 2617 J. Gettys
	(if approved) Compaq/W3C		(if approved) J. Mogul
	Intended status: Standards Track J. Mogul		Intended status: Standards Track HP
	Expires: March 4, 2008 Compaq		Expires: May 14, 2008 H. Frystyk
	H. Frystyk		Microsoft
	W3C/MIT
	L. Masinter		L. Masinter
	Xerox		Adobe Systems
	P. Leach		P. Leach
	Microsoft		Microsoft
	T. Berners-Lee		T. Berners-Lee
	W3C/MIT		W3C/MIT
	September 2007		November 11, 2007
	HTTP/1.1, part 6: Caching		HTTP/1.1, part 6: Caching
	draft-fielding-http-p6-cache-00		draft-fielding-http-p6-cache-00
	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.
	skipping to change at page 1, line 45		skipping to change at page 1, line 44
	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 March 4, 2008.		This Internet-Draft will expire on May 14, 2008.
	Copyright Notice		Copyright Notice
	Copyright (C) The IETF Trust (2007).		Copyright (C) The IETF Trust (2007).
	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
	eight-part specification that defines the protocol referred to as		eight-part specification that defines the protocol referred to as
	"HTTP/1.1" and, taken together, updates RFC 2616 and RFC 2617. Part		"HTTP/1.1" and, taken together, updates RFC 2616 and RFC 2617. Part
	4 defines requirements on HTTP caches and the associated header		6 defines requirements on HTTP caches and the associated header
	fields that control cache behavior or indicate cacheable response		fields that control cache behavior or indicate cacheable response
	messages.		messages.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
	1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4		1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
	1.2. Delta Seconds . . . . . . . . . . . . . . . . . . . . . . 5		1.2. Delta Seconds . . . . . . . . . . . . . . . . . . . . . . 5
	2. Caching in HTTP . . . . . . . . . . . . . . . . . . . . . . . 5		2. Caching in HTTP . . . . . . . . . . . . . . . . . . . . . . . 5
	2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 5		2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 5
	skipping to change at page 3, line 19		skipping to change at page 3, line 19
	3.2.1. What is Cacheable . . . . . . . . . . . . . . . . . . 28		3.2.1. What is Cacheable . . . . . . . . . . . . . . . . . . 28
	3.2.2. What May be Stored by Caches . . . . . . . . . . . . . 29		3.2.2. What May be Stored by Caches . . . . . . . . . . . . . 29
	3.2.3. Modifications of the Basic Expiration Mechanism . . . 30		3.2.3. Modifications of the Basic Expiration Mechanism . . . 30
	3.2.4. Cache Revalidation and Reload Controls . . . . . . . . 32		3.2.4. Cache Revalidation and Reload Controls . . . . . . . . 32
	3.2.5. No-Transform Directive . . . . . . . . . . . . . . . . 34		3.2.5. No-Transform Directive . . . . . . . . . . . . . . . . 34
	3.2.6. Cache Control Extensions . . . . . . . . . . . . . . . 35		3.2.6. Cache Control Extensions . . . . . . . . . . . . . . . 35
	3.3. Expires . . . . . . . . . . . . . . . . . . . . . . . . . 36		3.3. Expires . . . . . . . . . . . . . . . . . . . . . . . . . 36
	3.4. Pragma . . . . . . . . . . . . . . . . . . . . . . . . . . 37		3.4. Pragma . . . . . . . . . . . . . . . . . . . . . . . . . . 37
	3.5. Vary . . . . . . . . . . . . . . . . . . . . . . . . . . . 37		3.5. Vary . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
	3.6. Warning . . . . . . . . . . . . . . . . . . . . . . . . . 38		3.6. Warning . . . . . . . . . . . . . . . . . . . . . . . . . 38
	4. Security Considerations . . . . . . . . . . . . . . . . . . . 41		4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41
	5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 41		5. Security Considerations . . . . . . . . . . . . . . . . . . . 41
	6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 41		6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 41
			7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 41
	Appendix A. Changes from RFC 2068 . . . . . . . . . . . . . . . . 42		Appendix A. Changes from RFC 2068 . . . . . . . . . . . . . . . . 42
	Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42		Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 44		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 44
	Intellectual Property and Copyright Statements . . . . . . . . . . 47		Intellectual Property and Copyright Statements . . . . . . . . . . 47
	1. Introduction		1. Introduction
	This document will define aspects of HTTP related to caching response		This document will define aspects of HTTP related to caching response
	messages. Right now it only includes the extracted relevant sections		messages. Right now it only includes the extracted relevant sections
	of RFC 2616 [RFC2616] without edit.		of RFC 2616 [RFC2616] without edit.
	skipping to change at page 19, line 21		skipping to change at page 19, line 21
	o Connection		o Connection
	o Keep-Alive		o Keep-Alive
	o Proxy-Authenticate		o Proxy-Authenticate
	o Proxy-Authorization		o Proxy-Authorization
	o TE		o TE
	o Trailers		o Trailer
	o Transfer-Encoding		o Transfer-Encoding
	o Upgrade		o Upgrade
	All other headers defined by HTTP/1.1 are end-to-end headers.		All other headers defined by HTTP/1.1 are end-to-end headers.
	Other hop-by-hop headers MUST be listed in a Connection header,		Other hop-by-hop headers MUST be listed in a Connection header ([Part
	([Part 1]) to be introduced into HTTP/1.1 (or later).		1]).
	2.5.2. Non-modifiable Headers		2.5.2. Non-modifiable Headers
	Some features of the HTTP/1.1 protocol, such as Digest		Some features of the HTTP/1.1 protocol, such as Digest
	Authentication, depend on the value of certain end-to-end headers. A		Authentication, depend on the value of certain end-to-end headers. A
	transparent proxy SHOULD NOT modify an end-to-end header unless the		transparent proxy SHOULD NOT modify an end-to-end header unless the
	definition of that header requires or specifically allows that.		definition of that header requires or specifically allows that.
	A transparent proxy MUST NOT modify any of the following fields in a		A transparent proxy MUST NOT modify any of the following fields in a
	request or response, and it MUST NOT add any of these fields if not		request or response, and it MUST NOT add any of these fields if not
	skipping to change at page 24, line 36		skipping to change at page 24, line 36
	is either the entity referred to by the Request-URI, or by the		is either the entity referred to by the Request-URI, or by the
	Location or Content-Location headers (if present). These methods		Location or Content-Location headers (if present). These methods
	are:		are:
	o PUT		o PUT
	o DELETE		o DELETE
	o POST		o POST
	In order to prevent denial of service attacks, an invalidation based		An invalidation based on the URI in a Location or Content-Location
	on the URI in a Location or Content-Location header MUST only be		header MUST NOT be performed if the host part of that URI differs
	performed if the host part is the same as in the Request-URI.		from the host part in the Request-URI. This helps prevent denial of
			service attacks.
	A cache that passes through requests for methods it does not		A cache that passes through requests for methods it does not
	understand SHOULD invalidate any entities referred to by the Request-		understand SHOULD invalidate any entities referred to by the Request-
	URI.		URI.
	2.11. Write-Through Mandatory		2.11. Write-Through Mandatory
	All methods that might be expected to cause modifications to the		All methods that might be expected to cause modifications to the
	origin server's resources MUST be written through to the origin		origin server's resources MUST be written through to the origin
	server. This currently includes all methods except for GET and HEAD.		server. This currently includes all methods except for GET and HEAD.
	skipping to change at page 41, line 23		skipping to change at page 41, line 23
	each warning-value a warn-date that matches the date in the response.		each warning-value a warn-date that matches the date in the response.
	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.
	4. Security Considerations		4. IANA Considerations
			TBD.
			5. 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.
	5. Acknowledgments		6. Acknowledgments
	Much of the content and presentation of the caching design is due to		Much of the content and presentation of the caching design is due to
	suggestions and comments from individuals including: Shel Kaphan,		suggestions and comments from individuals including: Shel Kaphan,
	Paul Leach, Koen Holtman, David Morris, and Larry Masinter.		Paul Leach, Koen Holtman, David Morris, and Larry Masinter.
	Based on an XML translation of RFC 2616 by Julian Reschke.		Based on an XML translation of RFC 2616 by Julian Reschke.
	6. References		7. 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.
	[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.
	[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
	skipping to change at page 42, line 32		skipping to change at page 42, line 36
	Index		Index
	A		A
	age 4		age 4
	Age header 26		Age header 26
	C		C
	cache 4		cache 4
	Cache Directives		Cache Directives
	max-age 31		max-age 31
	max-age 32		max-age 33
	max-stale 31		max-stale 31
	min-fresh 31		min-fresh 31
	must-revalidate 33		must-revalidate 33
	no-cache 28		no-cache 28
	no-store 29		no-store 29
	no-transform 34		no-transform 34
	only-if-cached 33		only-if-cached 33
	private 28		private 28
	proxy-revalidate 34		proxy-revalidate 34
	public 28		public 28
	skipping to change at page 43, line 23		skipping to change at page 43, line 27
	Cache-Control 27		Cache-Control 27
	cache-directive 27		cache-directive 27
	cache-extension 27		cache-extension 27
	cache-request-directive 27		cache-request-directive 27
	cache-response-directive 27		cache-response-directive 27
	delta-seconds 5		delta-seconds 5
	Expires 36		Expires 36
	extension-pragma 37		extension-pragma 37
	Pragma 37		Pragma 37
	pragma-directive 37		pragma-directive 37
	Vary 37		Vary 38
	warn-agent 39		warn-agent 39
	warn-code 39		warn-code 39
	warn-date 39		warn-date 39
	warn-text 39		warn-text 39
	Warning 39		Warning 39
	warning-value 39		warning-value 39
	H		H
	Headers		Headers
	Age 26		Age 26
	Cache-Control 26		Cache-Control 26
	Expires 36		Expires 36
	Pragma 37		Pragma 37
	Vary 37		Vary 37
	Warning 38		Warning 38
	heuristic expiration time 4		heuristic expiration time 4
	M		M
	max-age		max-age
	Cache Directive 31		Cache Directive 31
	Cache Directive 32		Cache Directive 33
	max-stale		max-stale
	Cache Directive 31		Cache Directive 31
	min-fresh		min-fresh
	Cache Directive 31		Cache Directive 31
	must-revalidate		must-revalidate
	Cache Directive 33		Cache Directive 33
	N		N
	no-cache		no-cache
	Cache Directive 28		Cache Directive 28
	no-store		no-store
	Cache Directive 29		Cache Directive 29
	no-transform		no-transform
	Cache Directive 34		Cache Directive 34
	O		O
	only-if-cached		only-if-cached
	skipping to change at page 44, line 40		skipping to change at page 45, line 7
	V		V
	validator 5		validator 5
	Vary header 37		Vary header 37
	W		W
	Warning header 38		Warning header 38
	Authors' Addresses		Authors' Addresses
	Roy T. Fielding		Roy T. Fielding (editor)
	Department of Information and Computer Science		Day Software
	University of California, Irvine		23 Corporate Plaza DR, Suite 280
	Irvine, CA 92697-3425		Newport Beach, CA 92660
			USA
			Phone: +1-949-706-5300
			Fax: +1-949-706-5305
			Email: fielding@gbiv.com
			URI: http://roy.gbiv.com/
	Fax: +1(949)824-1715
	Email: fielding@ics.uci.edu
	James Gettys		James Gettys
	World Wide Web Consortium		Hewlett-Packard Company
	MIT Laboratory for Computer Science, NE43-356		HP Labs, Cambridge Research Laboratory
	545 Technology Square		One Cambridge Center
	Cambridge, MA 02139		Cambridge, MA 02138
			USA
	Fax: +1(617)258-8682		Email: Jim.Gettys@hp.com
	Email: jg@w3.org
	Jeffrey C. Mogul		Jeffrey C. Mogul
	Compaq Computer Corporation		Hewlett-Packard Company
	Western Research Laboratory		HP Labs, Large Scale Systems Group
	250 University Avenue		1501 Page Mill Road, MS 1177
	Palo Alto, CA 94305		Palo Alto, CA 94304
			USA
	Email: mogul@wrl.dec.com		Email: JeffMogul@acm.org
	Henrik Frystyk Nielsen		Henrik Frystyk Nielsen
	World Wide Web Consortium		Microsoft Corporation
	MIT Laboratory for Computer Science, NE43-356		1 Microsoft Way
	545 Technology Square		Redmond, WA 98052
	Cambridge, MA 02139		USA
	Fax: +1(617)258-8682
	Email: frystyk@w3.org
			Email: henrikn@microsoft.com
	Larry Masinter		Larry Masinter
	Xerox Corporation		Adobe Systems, Incorporated
	MIT Laboratory for Computer Science, NE43-356		345 Park Ave
	3333 Coyote Hill Road		San Jose, CA 95110
	Palo Alto, CA 94034		USA
	Email: masinter@parc.xerox.com		Email: LMM@acm.org
			URI: http://larry.masinter.net/
	Paul J. Leach		Paul J. Leach
	Microsoft Corporation		Microsoft Corporation
	1 Microsoft Way		1 Microsoft Way
	Redmond, WA 98052		Redmond, WA 98052
	Email: paulle@microsoft.com		Email: paulle@microsoft.com
	Tim Berners-Lee		Tim Berners-Lee
	World Wide Web Consortium		World Wide Web Consortium
	MIT Laboratory for Computer Science, NE43-356		MIT Laboratory for Computer Science
	545 Technology Square		545 Technology Square
	Cambridge, MA 02139		Cambridge, MA 02139
			USA
	Fax: +1(617)258-8682		Fax: +1 (617) 258 8682
	Email: timbl@w3.org		Email: timbl@w3.org
	Full Copyright Statement		Full Copyright Statement
	Copyright (C) The IETF Trust (2007).		Copyright (C) The IETF Trust (2007).
	This document is subject to the rights, licenses and restrictions		This document is subject to the rights, licenses and restrictions
	contained in BCP 78, and except as set forth therein, the authors		contained in BCP 78, and except as set forth therein, the authors
	retain all their rights.		retain all their rights.
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