draft-ietf-httpbis-no-vary-search-09.txt		draft-ietf-httpbis-no-vary-search-latest.txt
	HyperText Transfer Protocol		HyperText Transfer Protocol
	Internet-Draft		Internet-Draft
	Intended status: Standards Track , Ed.		Intended status: Standards Track , Ed.
	Expires: February 18, 2027 Google LLC		Expires: March 11, 2027 Google LLC
	August 17, 2026		September 07, 2026
	The No-Vary-Search HTTP Caching Extension		The No-Vary-Search HTTP Caching Extension
	draft-ietf-httpbis-no-vary-search-09		draft-ietf-httpbis-no-vary-search-latest
	Abstract		Abstract
	This specification defines an extension to HTTP Caching, changing how		This specification defines an extension to HTTP Caching, changing how
	the URI query component impacts caching. It introduces the ""No-		the URI query component impacts caching. It introduces the ""No-
	Vary-Search"" response header field, which allows origin servers to		Vary-Search"" response header field, which allows origin servers to
	signal to caches that certain parts of the query component do not		signal to caches that certain parts of the query component do not
	semantically affect the served response and can be ignored for cache		semantically affect the served response and can be ignored for cache
	matching purposes.		matching purposes.
	skipping to change at page 2, line 10 ¶		skipping to change at page 2, line 10 ¶
	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 https://datatracker.ietf.org/drafts/current/.		Drafts is at https://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 February 18, 2027.		This Internet-Draft will expire on March 11, 2027.
	Copyright Notice		Copyright Notice
	Copyright (c) 2026 IETF Trust and the persons identified as the		Copyright (c) 2026 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
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://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 10, line 16 ¶		skipping to change at page 10, line 16 ¶
	The following illustrates how various inputs are parsed, in terms of		The following illustrates how various inputs are parsed, in terms of
	their impact on the resulting no-vary params and vary params:		their impact on the resulting no-vary params and vary params:
	+--------------------+----------------------------------------------+		+--------------------+----------------------------------------------+
	| Input | Result |		| Input | Result |
	+--------------------+----------------------------------------------+		+--------------------+----------------------------------------------+
	| "No-Vary-Search: | no-vary params: (empty list) vary params: |		| "No-Vary-Search: | no-vary params: (empty list) vary params: |
	| key-order" | *wildcard* vary on key order: false |		| key-order" | *wildcard* vary on key order: false |
	| | |		| | |
			| "No-Vary-Search: | no-vary params: (empty list) vary params: |
			| key-order=?1" | *wildcard* vary on key order: false |
			| | |
	| "No-Vary-Search: | no-vary params: << ""a"" >> vary params: |		| "No-Vary-Search: | no-vary params: << ""a"" >> vary params: |
	| params=("a")" | *wildcard* |		| params=("a")" | *wildcard* |
	| | |		| | |
	| "No-Vary-Search: | no-vary params: *wildcard* vary params: << |		| "No-Vary-Search: | no-vary params: *wildcard* vary params: << |
	| except=("x")" | ""x"" >> |		| except=("x")" | ""x"" >> |
	| | |		| | |
	| "No-Vary-Search: | no-vary params: (empty list) vary params: |		| "No-Vary-Search: | no-vary params: (empty list) vary params: |
	| params=()" | *wildcard* |		| params=()" | *wildcard* |
	| | |		| | |
	| "No-Vary-Search: | no-vary params: *wildcard* vary params: |		| "No-Vary-Search: | no-vary params: *wildcard* vary params: |
	skipping to change at page 17, line 18 ¶		skipping to change at page 17, line 18 ¶
	+------------+----------------+-------------------------------------+		+------------+----------------+-------------------------------------+
	| null | "?" | A null query is parsed the same as |		| null | "?" | A null query is parsed the same as |
	| | | an empty string |		| | | an empty string |
	| | | |		| | | |
	| "?a=x" | "?%61=%78" | Parsing performs percent-decoding |		| "?a=x" | "?%61=%78" | Parsing performs percent-decoding |
	| | | |		| | | |
	| "?a=e" | "?a=%C3%A9" | Parsing performs percent-decoding |		| "?a=e" | "?a=%C3%A9" | Parsing performs percent-decoding |
	| | | |		| | | |
	| "?a=%f6" | "?a=%ef%bf%bd" | An invalid UTF-8 sequence and the |		| "?a=%f6" | "?a=%ef%bf%bd" | An invalid UTF-8 sequence and the |
	| | | literal U+FFFD character are both |		| | | literal U+FFFD character are both |
	| | | parsed as U+FFFD ( ) |		| | | parsed as U+FFFD (&#65533;) |
	| | | |		| | | |
	| "?a=x&&&&" | "?a=x" | Parsing splits on "&" and discards |		| "?a=x&&&&" | "?a=x" | Parsing splits on "&" and discards |
	| | | empty strings |		| | | empty strings |
	| | | |		| | | |
	| "?a=" | "?a" | Both parse as having an empty |		| "?a=" | "?a" | Both parse as having an empty |
	| | | string value for "a" |		| | | string value for "a" |
	| | | |		| | | |
	| "?a=%20" | "?a= &" | "%20" is parsed as U+0020 SPACE |		| "?a=%20" | "?a= &" | "%20" is parsed as U+0020 SPACE |
	| | | |		| | | |
	| "?a=+" | "?a= &" | "+" is parsed as U+0020 SPACE |		| "?a=+" | "?a= &" | "+" is parsed as U+0020 SPACE |
	skipping to change at page 17, line 45 ¶		skipping to change at page 17, line 45 ¶
	7. Caching		7. Caching
	To reuse a stored response, Section 4 of [HTTP-CACHING] requires that		To reuse a stored response, Section 4 of [HTTP-CACHING] requires that
	the presented target URI and that of the stored response match. If a		the presented target URI and that of the stored response match. If a
	cache implements the "No-Vary-Search" extension, this matching		cache implements the "No-Vary-Search" extension, this matching
	requirement is also satisfied if the URIs are equivalent modulo URL		requirement is also satisfied if the URIs are equivalent modulo URL
	variation config (Section 6) given the stored response's "No-Vary-		variation config (Section 6) given the stored response's "No-Vary-
	Search" header.		Search" header.
			Note that while Section 5.2.3 of [HTTP-CACHING] defines cache
			extensions as "Cache-Control" directives, the ""No-Vary-Search""
			response header field is defined as a standalone header. This design
			choice leverages Structured Fields ([STRUCTURED-FIELDS]) to provide a
			robust parsing model without overloading the existing, complex
			"Cache-Control" parsing logic.
			The ""No-Vary-Search"" response header field operates in addition to
			content negotiation and the "Vary" header field (see Section 4.1 of
			[HTTP-CACHING]).
	This document does not alter the requirements for cache invalidation		This document does not alter the requirements for cache invalidation
	(see Section 4.4 of [HTTP-CACHING]). A cache MAY invalidate stored		(see Section 4.4 of [HTTP-CACHING]). A cache MAY invalidate stored
	responses for URIs that are equivalent modulo URL variation config,		responses for URIs that are equivalent modulo URL variation config,
	but is not required to do so. Therefore, state-changing requests		but is not required to do so. Therefore, state-changing requests
	might not invalidate all conceptually equivalent responses.		might not invalidate all conceptually equivalent responses.
	Note that the ""No-Vary-Search"" response header field operates in
	addition to content negotiation and the "Vary" header field (see
	Section 4.1 of [HTTP-CACHING]).
	Cache implementations MAY fail to reuse a stored response whose		Cache implementations MAY fail to reuse a stored response whose
	target URI matches _only_ modulo URL variation config, if the cache		target URI matches _only_ modulo URL variation config, if the cache
	has a stored response with a more recent "Date" header field which:		has a stored response with a more recent "Date" header field which:
	o has a target URI which is equal to the presented target URI,		o has a target URI which is equal to the presented target URI,
	excluding the query, and		excluding the query, and
	o has a non-empty value for the ""No-Vary-Search"" response header		o has a non-empty value for the ""No-Vary-Search"" response header
	field, and		field, and
End of changes. 7 change blocks.
	9 lines changed or deleted		19 lines changed or added
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