draft-ietf-httpbis-compression-dictionary-05.txt		draft-ietf-httpbis-compression-dictionary-06.txt
	HTTP P. Meenan, Ed.		HTTP P. Meenan, Ed.
	Internet-Draft Google LLC		Internet-Draft Google LLC
	Intended status: Standards Track Y. Weiss, Ed.		Intended status: Standards Track Y. Weiss, Ed.
	Expires: 14 December 2024 Shopify Inc		Expires: 6 January 2025 Shopify Inc
	12 June 2024		5 July 2024
	Compression Dictionary Transport		Compression Dictionary Transport
	draft-ietf-httpbis-compression-dictionary-05		draft-ietf-httpbis-compression-dictionary-06
	Abstract		Abstract
	This specification defines a mechanism for using designated HTTP		This specification defines a mechanism for using designated HTTP
	responses as an external dictionary for future HTTP responses for		responses as an external dictionary for future HTTP responses for
	compression schemes that support using external dictionaries (e.g.,		compression schemes that support using external dictionaries (e.g.,
	Brotli (RFC 7932) and Zstandard (RFC 8878)).		Brotli (RFC 7932) and Zstandard (RFC 8878)).
	About This Document		About This Document
	skipping to change at page 2, line 4 ¶		skipping to change at page 2, line 4 ¶
	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 14 December 2024.		This Internet-Draft will expire on 6 January 2025.
	Copyright Notice		Copyright Notice
	Copyright (c) 2024 IETF Trust and the persons identified as the		Copyright (c) 2024 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 (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	skipping to change at page 2, line 41 ¶		skipping to change at page 2, line 41 ¶
	2.2. Available-Dictionary . . . . . . . . . . . . . . . . . . 6		2.2. Available-Dictionary . . . . . . . . . . . . . . . . . . 6
	2.2.1. Dictionary freshness requirement . . . . . . . . . . 6		2.2.1. Dictionary freshness requirement . . . . . . . . . . 6
	2.2.2. Dictionary URL matching . . . . . . . . . . . . . . . 6		2.2.2. Dictionary URL matching . . . . . . . . . . . . . . . 6
	2.2.3. Multiple matching dictionaries . . . . . . . . . . . 7		2.2.3. Multiple matching dictionaries . . . . . . . . . . . 7
	2.3. Dictionary-ID . . . . . . . . . . . . . . . . . . . . . . 7		2.3. Dictionary-ID . . . . . . . . . . . . . . . . . . . . . . 7
	3. The 'compression-dictionary' Link Relation Type . . . . . . . 8		3. The 'compression-dictionary' Link Relation Type . . . . . . . 8
	4. Dictionary-Compressed Brotli . . . . . . . . . . . . . . . . 8		4. Dictionary-Compressed Brotli . . . . . . . . . . . . . . . . 8
	5. Dictionary-Compressed Zstandard . . . . . . . . . . . . . . . 9		5. Dictionary-Compressed Zstandard . . . . . . . . . . . . . . . 9
	6. Negotiating the content encoding . . . . . . . . . . . . . . 10		6. Negotiating the content encoding . . . . . . . . . . . . . . 10
	6.1. Accept-Encoding . . . . . . . . . . . . . . . . . . . . . 10		6.1. Accept-Encoding . . . . . . . . . . . . . . . . . . . . . 10
	6.2. Content-Encoding . . . . . . . . . . . . . . . . . . . . 10		6.2. Content-Encoding . . . . . . . . . . . . . . . . . . . . 11
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
	7.1. Content Encoding . . . . . . . . . . . . . . . . . . . . 11		7.1. Content Encoding . . . . . . . . . . . . . . . . . . . . 11
	7.2. Header Field Registration . . . . . . . . . . . . . . . . 11		7.2. Header Field Registration . . . . . . . . . . . . . . . . 11
	7.3. Link Relation Registration . . . . . . . . . . . . . . . 12		7.3. Link Relation Registration . . . . . . . . . . . . . . . 12
	8. Compatibility Considerations . . . . . . . . . . . . . . . . 12		8. Compatibility Considerations . . . . . . . . . . . . . . . . 12
	9. Security Considerations . . . . . . . . . . . . . . . . . . . 12		9. Security Considerations . . . . . . . . . . . . . . . . . . . 12
	9.1. Changing content . . . . . . . . . . . . . . . . . . . . 12		9.1. Changing content . . . . . . . . . . . . . . . . . . . . 12
	9.2. Reading content . . . . . . . . . . . . . . . . . . . . . 13		9.2. Reading content . . . . . . . . . . . . . . . . . . . . . 13
	9.3. Security Mitigations . . . . . . . . . . . . . . . . . . 13		9.3. Security Mitigations . . . . . . . . . . . . . . . . . . 13
	9.3.1. Cross-origin protection . . . . . . . . . . . . . . . 13		9.3.1. Cross-origin protection . . . . . . . . . . . . . . . 13
	skipping to change at page 9, line 5 ¶		skipping to change at page 9, line 5 ¶
	The "dcb" content encoding identifies a resource that is a		The "dcb" content encoding identifies a resource that is a
	"Dictionary-Compressed Brotli" stream.		"Dictionary-Compressed Brotli" stream.
	A "Dictionary-Compressed Brotli" stream has a fixed header that is		A "Dictionary-Compressed Brotli" stream has a fixed header that is
	followed by a Shared Brotli [SHARED-BROTLI] stream. The header		followed by a Shared Brotli [SHARED-BROTLI] stream. The header
	consists of a fixed 4 byte sequence and a 32 byte hash of the		consists of a fixed 4 byte sequence and a 32 byte hash of the
	external dictionary that was used. The Shared Brotli stream is		external dictionary that was used. The Shared Brotli stream is
	created using the referenced external dictionary and a compression		created using the referenced external dictionary and a compression
	window that is at most 16 MB in size.		window that is at most 16 MB in size.
			The dictionary used for the "dcb" content encoding is a "raw"
			dictionary type as defined in Section 2.1.4 and is treated as a
			prefix dictionary as defined in section 9.2 of the Shared Brotli
			Compressed Data Format draft. [SHARED-BROTLI]
	The 36-byte fixed header is as follows:		The 36-byte fixed header is as follows:
	Magic_Number: 4 fixed bytes: 0xff, 0x44, 0x43, 0x42.		Magic_Number: 4 fixed bytes: 0xff, 0x44, 0x43, 0x42.
	SHA_256_Hash: 32 Bytes. SHA-256 hash digest of the dictionary		SHA_256_Hash: 32 Bytes. SHA-256 hash digest of the dictionary
	[SHA-256].		[SHA-256].
	Clients that announce support for dcb content encoding MUST be able		Clients that announce support for dcb content encoding MUST be able
	to decompress resources that were compressed with a window size of up		to decompress resources that were compressed with a window size of up
	to 16 MB.		to 16 MB.
	skipping to change at page 9, line 31 ¶		skipping to change at page 9, line 36 ¶
	5. Dictionary-Compressed Zstandard		5. Dictionary-Compressed Zstandard
	The "dcz" content encoding identifies a resource that is a		The "dcz" content encoding identifies a resource that is a
	"Dictionary-Compressed Zstandard" stream.		"Dictionary-Compressed Zstandard" stream.
	A "Dictionary-Compressed Zstandard" stream is a binary stream that		A "Dictionary-Compressed Zstandard" stream is a binary stream that
	starts with a 40-byte fixed header and is followed by a Zstandard		starts with a 40-byte fixed header and is followed by a Zstandard
	[RFC8878] stream of the response that has been compressed with an		[RFC8878] stream of the response that has been compressed with an
	external dictionary.		external dictionary.
			The dictionary used for the "dcz" content encoding is a "raw"
			dictionary type as defined in Section 2.1.4 and is treated as a raw
			dictionary as per section 5 of RFC 8878.
	The 40-byte header consists of a fixed 8-byte sequence followed by		The 40-byte header consists of a fixed 8-byte sequence followed by
	the 32-byte SHA-256 hash of the external dictionary that was used to		the 32-byte SHA-256 hash of the external dictionary that was used to
	compress the resource:		compress the resource:
	Magic_Number: 8 fixed bytes: 0x5e, 0x2a, 0x4d, 0x18, 0x20, 0x00,		Magic_Number: 8 fixed bytes: 0x5e, 0x2a, 0x4d, 0x18, 0x20, 0x00,
	0x00, 0x00.		0x00, 0x00.
	SHA_256_Hash: 32 Bytes. SHA-256 hash digest of the dictionary		SHA_256_Hash: 32 Bytes. SHA-256 hash digest of the dictionary
	[SHA-256].		[SHA-256].
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