< draft-ietf-httpbis-cache-header-01.txt		draft-ietf-httpbis-cache-header-02.txt >
	HTTP M. Nottingham		HTTP M. Nottingham
	Internet-Draft Fastly		Internet-Draft Fastly
	Intended status: Standards Track November 2, 2019		Intended status: Standards Track November 4, 2019
	Expires: May 5, 2020		Expires: May 7, 2020
	The Cache-Status HTTP Response Header		The Cache-Status HTTP Response Header
	draft-ietf-httpbis-cache-header-01		draft-ietf-httpbis-cache-header-02
	Abstract		Abstract
	To aid debugging, HTTP caches often append headers to a response		To aid debugging, HTTP caches often append headers to a response
	detailing how they handled the request. This specification codifies		detailing how they handled the request. This specification codifies
	that practice and updates it for HTTP's current caching model.		that practice and updates it for HTTP's current caching model.
	Note to Readers		Note to Readers
	_RFC EDITOR: please remove this section before publication_		_RFC EDITOR: please remove this section before publication_
	skipping to change at page 1, line 44 ¶		skipping to change at page 1, line 44 ¶
	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 May 5, 2020.		This Internet-Draft will expire on May 7, 2020.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 IETF Trust and the persons identified as the		Copyright (c) 2019 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 2, line 27 ¶		skipping to change at page 2, line 27 ¶
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3		1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
	2. The Cache-Status HTTP Response Header . . . . . . . . . . . . 3		2. The Cache-Status HTTP Response Header . . . . . . . . . . . . 3
	2.1. The fwd parameter . . . . . . . . . . . . . . . . . . . . 4		2.1. The fwd parameter . . . . . . . . . . . . . . . . . . . . 4
	2.2. The fwd-res parameter . . . . . . . . . . . . . . . . . . 4		2.2. The fwd-res parameter . . . . . . . . . . . . . . . . . . 4
	2.3. The fwd-stored parameter . . . . . . . . . . . . . . . . 4		2.3. The fwd-stored parameter . . . . . . . . . . . . . . . . 5
	2.4. The res-fresh parameter . . . . . . . . . . . . . . . . . 5		2.4. The res-fresh parameter . . . . . . . . . . . . . . . . . 5
	2.5. The cache-fresh parameter . . . . . . . . . . . . . . . . 5		2.5. The cache-fresh parameter . . . . . . . . . . . . . . . . 5
	2.6. The collapse-hit parameter . . . . . . . . . . . . . . . 5		2.6. The collapse-hit parameter . . . . . . . . . . . . . . . 5
	2.7. The collapse-wait parameter . . . . . . . . . . . . . . . 5		2.7. The collapse-wait parameter . . . . . . . . . . . . . . . 5
	2.8. The key parameter . . . . . . . . . . . . . . . . . . . . 5		2.8. The key parameter . . . . . . . . . . . . . . . . . . . . 6
	3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 5		3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 6
	4. Security Considerations . . . . . . . . . . . . . . . . . . . 6		4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7		5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	5.1. Normative References . . . . . . . . . . . . . . . . . . 7		5.1. Normative References . . . . . . . . . . . . . . . . . . 7
	5.2. Informative References . . . . . . . . . . . . . . . . . 7		5.2. Informative References . . . . . . . . . . . . . . . . . 8
	5.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 8		5.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
	1. Introduction		1. Introduction
	To aid debugging, HTTP caches often append headers to a response		To aid debugging, HTTP caches often append headers to a response
	detailing how they handled the request.		detailing how they handled the request.
	Unfortunately, the semantics of these headers are often unclear, and		Unfortunately, the semantics of these headers are often unclear, and
	both the semantics and syntax used vary greatly between		both the semantics and syntax used vary greatly between
	skipping to change at page 4, line 19 ¶		skipping to change at page 4, line 19 ¶
	cache-fresh = sh-integer		cache-fresh = sh-integer
	collapse-hit = sh-boolean		collapse-hit = sh-boolean
	collapse-wait = sh-integer		collapse-wait = sh-integer
	key = sh-string		key = sh-string
	2.1. The fwd parameter		2.1. The fwd parameter
	"fwd" indicates why the request went forward. If it is not present,		"fwd" indicates why the request went forward. If it is not present,
	the value defaults to "none".		the value defaults to "none".
	It can have one of the following values: * none - The request did not		It can have one of the following values:
	go forward; i.e., it was a hit, and was served from the cache. *
	bypass - The cache was configured to not handle this request * uri-		o none - The request did not go forward; i.e., it was a hit, and was
	miss - The cache did not contain any responses that matched the		served from the cache.
	request URI * vary-miss - The cache contained a response that matched
	the request URI, but could not select a response based upon this		o bypass - The cache was configured to not handle this request
	request's headers. * miss - The cache did not contain any responses
	that could be used to satisfy this request (to be used when an		o uri-miss - The cache did not contain any responses that matched
	implementation cannot distinguish between uri-miss and vary-miss) *		the request URI
	res-stale - The cache was able to select a response for the request,
	but it was stale * req-stale - The cache was able to select a fresh		o vary-miss - The cache contained a response that matched the
	response for the request, but client request headers (e.g., Cache-		request URI, but could not select a response based upon this
	Control request directives) did not allow its use		request's headers.
			o miss - The cache did not contain any responses that could be used
			to satisfy this request (to be used when an implementation cannot
			distinguish between uri-miss and vary-miss)
			o res-stale - The cache was able to select a response for the
			request, but it was stale
			o req-stale - The cache was able to select a fresh response for the
			request, but client request headers (e.g., Cache-Control request
			directives) did not allow its use
	2.2. The fwd-res parameter		2.2. The fwd-res parameter
	"fwd-res" indicates what the result of the forward request was. It		"fwd-res" indicates what the result of the forward request was. It
	is only valid when fwd is "res-stale" or "req-stale", and defaults to		is only valid when fwd is "res-stale" or "req-stale", and defaults to
	"full" if not present when fwd is one of those values.		"full" if not present when fwd is one of those values.
	It can have one of the following values: * full - indicates that the		It can have one of the following values:
	response was a complete response (any status code except 304 Not
	Modified and 206 Partial Response) * partial - indicates that the		o full - indicates that the response was a complete response (any
	response was a 206 Partial Response * notmod - indicates that the		status code except 304 Not Modified and 206 Partial Response)
	response was a 304 Not Modified
			o partial - indicates that the response was a 206 Partial Response
			o notmod - indicates that the response was a 304 Not Modified
	2.3. The fwd-stored parameter		2.3. The fwd-stored parameter
	"fwd-stored" indicates whether the cache stored the response; a true		"fwd-stored" indicates whether the cache stored the response; a true
	value indicates that it did. Only valid when fwd is not "none".		value indicates that it did. Only valid when fwd is not "none".
	2.4. The res-fresh parameter		2.4. The res-fresh parameter
	"res-fresh" indicates the response's remaining freshness lifetime (as		"res-fresh" indicates the response's remaining freshness lifetime (as
	per [I-D.ietf-httpbis-cache], Section 4.2.1), as an integer number of		per [I-D.ietf-httpbis-cache], Section 4.2.1), as an integer number of
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