draft-ietf-quic-qpack-01.txt		draft-ietf-quic-qpack-02.txt
	QUIC C. Krasic		QUIC C. Krasic
	Internet-Draft Netflix		Internet-Draft Netflix
	Intended status: Standards Track M. Bishop		Intended status: Standards Track M. Bishop
	Expires: December 30, 2018 Akamai Technologies		Expires: February 16, 2019 Akamai Technologies
	A. Frindell, Ed.		A. Frindell, Ed.
	Facebook		Facebook
	June 28, 2018		August 15, 2018
	QPACK: Header Compression for HTTP over QUIC		QPACK: Header Compression for HTTP over QUIC
	draft-ietf-quic-qpack-01		draft-ietf-quic-qpack-02
	Abstract		Abstract
	This specification defines QPACK, a compression format for		This specification defines QPACK, a compression format for
	efficiently representing HTTP header fields, to be used in HTTP over		efficiently representing HTTP header fields, to be used in HTTP over
	QUIC. This is a variation of HPACK header compression that seeks to		QUIC. This is a variation of HPACK header compression that seeks to
	reduce head-of-line blocking.		reduce head-of-line blocking.
	Note to Readers		Note to Readers
	skipping to change at page 1, line 46 ¶		skipping to change at page 1, line 46 ¶
	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 December 30, 2018.		This Internet-Draft will expire on February 16, 2019.
	Copyright Notice		Copyright Notice
	Copyright (c) 2018 IETF Trust and the persons identified as the		Copyright (c) 2018 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
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	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 . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Header Tables . . . . . . . . . . . . . . . . . . . . . . . . 3		2. Header Tables . . . . . . . . . . . . . . . . . . . . . . . . 4
	2.1. Static Table . . . . . . . . . . . . . . . . . . . . . . 4		2.1. Static Table . . . . . . . . . . . . . . . . . . . . . . 4
	2.2. Dynamic Table . . . . . . . . . . . . . . . . . . . . . . 4		2.2. Dynamic Table . . . . . . . . . . . . . . . . . . . . . . 4
	2.2.1. Absolute and Relative Indexing . . . . . . . . . . . 5		2.2.1. Absolute and Relative Indexing . . . . . . . . . . . 5
	2.2.2. Post-Base Indexing . . . . . . . . . . . . . . . . . 6		2.2.2. Post-Base Indexing . . . . . . . . . . . . . . . . . 6
	2.3. Avoiding Head-of-Line Blocking in HTTP/QUIC . . . . . . . 7		2.3. Avoiding Head-of-Line Blocking in HTTP/QUIC . . . . . . . 7
	2.3.1. State Synchronization . . . . . . . . . . . . . . . . 8		2.3.1. State Synchronization . . . . . . . . . . . . . . . . 8
	3. Conventions and Definitions . . . . . . . . . . . . . . . . . 8		3. Conventions and Definitions . . . . . . . . . . . . . . . . . 9
	3.1. Notational Conventions . . . . . . . . . . . . . . . . . 9		3.1. Notational Conventions . . . . . . . . . . . . . . . . . 9
	4. Configuration . . . . . . . . . . . . . . . . . . . . . . . . 9		4. Configuration . . . . . . . . . . . . . . . . . . . . . . . . 9
	5. Wire Format . . . . . . . . . . . . . . . . . . . . . . . . . 9		5. Wire Format . . . . . . . . . . . . . . . . . . . . . . . . . 10
	5.1. Primitives . . . . . . . . . . . . . . . . . . . . . . . 10		5.1. Primitives . . . . . . . . . . . . . . . . . . . . . . . 10
	5.1.1. Prefixed Integers . . . . . . . . . . . . . . . . . . 10		5.1.1. Prefixed Integers . . . . . . . . . . . . . . . . . . 10
	5.1.2. String Literals . . . . . . . . . . . . . . . . . . . 10		5.1.2. String Literals . . . . . . . . . . . . . . . . . . . 10
	5.2. QPACK Encoder Stream . . . . . . . . . . . . . . . . . . 11		5.2. QPACK Encoder Stream . . . . . . . . . . . . . . . . . . 11
	5.2.1. Insert With Name Reference . . . . . . . . . . . . . 11		5.2.1. Insert With Name Reference . . . . . . . . . . . . . 11
	5.2.2. Insert Without Name Reference . . . . . . . . . . . . 11		5.2.2. Insert Without Name Reference . . . . . . . . . . . . 12
	5.2.3. Duplicate . . . . . . . . . . . . . . . . . . . . . . 12		5.2.3. Duplicate . . . . . . . . . . . . . . . . . . . . . . 12
	5.2.4. Dynamic Table Size Update . . . . . . . . . . . . . . 12		5.2.4. Dynamic Table Size Update . . . . . . . . . . . . . . 13
	5.3. QPACK Decoder Stream . . . . . . . . . . . . . . . . . . 13		5.3. QPACK Decoder Stream . . . . . . . . . . . . . . . . . . 13
	5.3.1. Table State Synchronize . . . . . . . . . . . . . . . 13		5.3.1. Table State Synchronize . . . . . . . . . . . . . . . 13
	5.3.2. Header Acknowledgement . . . . . . . . . . . . . . . 14		5.3.2. Header Acknowledgement . . . . . . . . . . . . . . . 14
	5.3.3. Stream Cancellation . . . . . . . . . . . . . . . . . 14		5.3.3. Stream Cancellation . . . . . . . . . . . . . . . . . 15
	5.4. Request and Push Streams . . . . . . . . . . . . . . . . 15		5.4. Request and Push Streams . . . . . . . . . . . . . . . . 15
	5.4.1. Header Data Prefix . . . . . . . . . . . . . . . . . 15		5.4.1. Header Data Prefix . . . . . . . . . . . . . . . . . 15
	5.4.2. Instructions . . . . . . . . . . . . . . . . . . . . 16		5.4.2. Instructions . . . . . . . . . . . . . . . . . . . . 17
	6. Encoding Strategies . . . . . . . . . . . . . . . . . . . . . 19		6. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 19
	6.1. Single Pass Encoding . . . . . . . . . . . . . . . . . . 19		7. Encoding Strategies . . . . . . . . . . . . . . . . . . . . . 20
	6.2. Preventing Eviction Races . . . . . . . . . . . . . . . . 19		7.1. Single Pass Encoding . . . . . . . . . . . . . . . . . . 20
	6.3. Reference Tracking . . . . . . . . . . . . . . . . . . . 19		7.2. Preventing Eviction Races . . . . . . . . . . . . . . . . 20
	6.3.1. Blocked Eviction . . . . . . . . . . . . . . . . . . 20		7.3. Reference Tracking . . . . . . . . . . . . . . . . . . . 20
	6.3.2. Blocked Decoding . . . . . . . . . . . . . . . . . . 20		7.3.1. Blocked Eviction . . . . . . . . . . . . . . . . . . 20
	6.4. Speculative table updates . . . . . . . . . . . . . . . . 20		7.3.2. Blocked Decoding . . . . . . . . . . . . . . . . . . 21
	6.5. Sample One Pass Encoding Algorithm . . . . . . . . . . . 20		7.4. Speculative table updates . . . . . . . . . . . . . . . . 21
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 22		7.5. Sample One Pass Encoding Algorithm . . . . . . . . . . . 21
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22		8. Security Considerations . . . . . . . . . . . . . . . . . . . 23
	8.1. Settings Registration . . . . . . . . . . . . . . . . . . 22		9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
	8.2. Stream Type Registration . . . . . . . . . . . . . . . . 22		9.1. Settings Registration . . . . . . . . . . . . . . . . . . 23
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 22		9.2. Stream Type Registration . . . . . . . . . . . . . . . . 23
	9.1. Normative References . . . . . . . . . . . . . . . . . . 22		9.3. Error Code Registration . . . . . . . . . . . . . . . . . 23
	9.2. Informative References . . . . . . . . . . . . . . . . . 23		10. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
	9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 23		10.1. Normative References . . . . . . . . . . . . . . . . . . 24
	Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 23		10.2. Informative References . . . . . . . . . . . . . . . . . 24
	A.1. Since draft-ietf-quic-qpack-00 . . . . . . . . . . . . . 23		10.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 24
	A.2. Since draft-ietf-quic-qcram-00 . . . . . . . . . . . . . 24		Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 25
	Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 24		A.1. Since draft-ietf-quic-qpack-01 . . . . . . . . . . . . . 25
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25		A.2. Since draft-ietf-quic-qpack-00 . . . . . . . . . . . . . 25
			A.3. Since draft-ietf-quic-qcram-00 . . . . . . . . . . . . . 25
			Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 25
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
	1. Introduction		1. Introduction
	The QUIC transport protocol was designed from the outset to support		The QUIC transport protocol was designed from the outset to support
	HTTP semantics, and its design subsumes many of the features of		HTTP semantics, and its design subsumes many of the features of
	HTTP/2. HTTP/2 used HPACK ([RFC7541]) for header compression, but		HTTP/2. HTTP/2 uses HPACK ([RFC7541]) for header compression, but
	QUIC's stream multiplexing comes into some conflict with HPACK. A		QUIC's stream multiplexing comes into some conflict with HPACK. A
	key goal of the design of QUIC is to improve stream multiplexing		key goal of the design of QUIC is to improve stream multiplexing
	relative to HTTP/2 by reducing head-of-line blocking. If HPACK were		relative to HTTP/2 by reducing head-of-line blocking. If HPACK were
	used for HTTP/QUIC, it would induce head-of-line blocking due to		used for HTTP/QUIC, it would induce head-of-line blocking due to
	built-in assumptions of a total ordering across frames on all		built-in assumptions of a total ordering across frames on all
	streams.		streams.
	QUIC is described in [QUIC-TRANSPORT]. The HTTP/QUIC mapping is		QUIC is described in [QUIC-TRANSPORT]. The HTTP/QUIC mapping is
	described in [QUIC-HTTP]. For a full description of HTTP/2, see		described in [QUIC-HTTP]. For a full description of HTTP/2, see
	[RFC7540]. The description of HPACK is [RFC7541], with important		[RFC7540]. The description of HPACK is [RFC7541].
	terminology in Section 1.3.
	QPACK reuses core concepts from HPACK, but is redesigned to allow		QPACK reuses core concepts from HPACK, but is redesigned to allow
	correctness in the presence of out-of-order delivery, with		correctness in the presence of out-of-order delivery, with
	flexibility for implementations to balance between resilience against		flexibility for implementations to balance between resilience against
	head-of-line blocking and optimal compression ratio. The design		head-of-line blocking and optimal compression ratio. The design
	goals are to closely approach the compression ratio of HPACK with		goals are to closely approach the compression ratio of HPACK with
	substantially less head-of-line blocking under the same loss		substantially less head-of-line blocking under the same loss
	conditions.		conditions.
	2. Header Tables		2. Header Tables
	skipping to change at page 4, line 4 ¶		skipping to change at page 4, line 10 ¶
	head-of-line blocking and optimal compression ratio. The design		head-of-line blocking and optimal compression ratio. The design
	goals are to closely approach the compression ratio of HPACK with		goals are to closely approach the compression ratio of HPACK with
	substantially less head-of-line blocking under the same loss		substantially less head-of-line blocking under the same loss
	conditions.		conditions.
	2. Header Tables		2. Header Tables
	Like HPACK, QPACK uses two tables for associating header fields to		Like HPACK, QPACK uses two tables for associating header fields to
	indexes. The static table (see Section 2.1) is predefined and		indexes. The static table (see Section 2.1) is predefined and
	contains common header fields (some of them with an empty value).		contains common header fields (some of them with an empty value).
	The dynamic table (see Section 2.2) built up over the course of the		The dynamic table (see Section 2.2) built up over the course of the
	connection and can be used by the encoder to index header fields		connection and can be used by the encoder to index header fields
	repeated in the encoded header lists.		repeated in the encoded header lists.
	Unlike in HPACK, entries in the QPACK static and dynamic tables are		Unlike in HPACK, entries in the QPACK static and dynamic tables are
	addressed separately. The following sections describe how entries in		addressed separately. The following sections describe how entries in
	each table is addressed.		each table is addressed.
	2.1. Static Table		2.1. Static Table
	The static table consists of a predefined static list of header		The static table consists of a predefined static list of header
	fields, each of which has a fixed index over time. Its entries are		fields, each of which has a fixed index over time. Its entries are
	defined in Appendix A of [RFC7541]. Note that because HPACK did not		defined in Appendix A of [RFC7541]. Note that because HPACK did not
	use zero-based references, there is no value at index zero of the		use zero-based references, there is no value at index zero of the
	static table.		static table.
	2.2. Dynamic Table		2.2. Dynamic Table
	The dynamic table consists of a list of header fields maintained in		The dynamic table consists of a list of header fields maintained in
	first-in, first-out order. The dynamic table is initially empty.		first-in, first-out order. The dynamic table is initially empty.
	Entries are added by instructions on the Encoder Stream (see		Entries are added by instructions on the encoder stream (see
	Section 5.2).		Section 5.2).
	Before a new entry is added to the dynamic table, entries are evicted		Before a new entry is added to the dynamic table, entries are evicted
	from the end of the dynamic table until the size of the dynamic table		from the end of the dynamic table until the size of the dynamic table
	is less than or equal to (maximum size - new entry size) or until the		is less than or equal to (maximum size - new entry size) or until the
	table is empty.		table is empty.
	If the size of the new entry is less than or equal to the maximum		If the size of the new entry is less than or equal to the maximum
	size, that entry is added to the table. It is an error to attempt to		size, that entry is added to the table. It is an error to attempt to
	add an entry that is larger than the maximum size; this MUST be		add an entry that is larger than the maximum size; this MUST be
	skipping to change at page 5, line 7 ¶		skipping to change at page 5, line 12 ¶
	the same name and same value). Therefore, duplicate entries MUST NOT		the same name and same value). Therefore, duplicate entries MUST NOT
	be treated as an error by a decoder.		be treated as an error by a decoder.
	The encoder decides how to update the dynamic table and as such can		The encoder decides how to update the dynamic table and as such can
	control how much memory is used by the dynamic table. To limit the		control how much memory is used by the dynamic table. To limit the
	memory requirements of the decoder, the dynamic table size is		memory requirements of the decoder, the dynamic table size is
	strictly bounded.		strictly bounded.
	The decoder determines the maximum size that the encoder is permitted		The decoder determines the maximum size that the encoder is permitted
	to use for the dynamic table. In HTTP/QUIC, this value is determined		to use for the dynamic table. In HTTP/QUIC, this value is determined
	by the SETTINGS_HEADER_TABLE_SIZE setting (see Section 4.2.5.2 of		by the SETTINGS_HEADER_TABLE_SIZE setting (see Section 4).
	[QUIC-HTTP]).
	An encoder can choose to use less capacity than this maximum size		An encoder can choose to use less capacity than this maximum size
	(see Section 5.2.4), but the chosen size MUST stay lower than or		(see Section 5.2.4), but the chosen size MUST stay lower than or
	equal to the maximum set by the decoder. Whenever the maximum size		equal to the maximum set by the decoder. Whenever the maximum size
	for the dynamic table is reduced, entries are evicted from the end of		for the dynamic table is reduced, entries are evicted from the end of
	the dynamic table until the size of the dynamic table is less than or		the dynamic table until the size of the dynamic table is less than or
	equal to the maximum size.		equal to the maximum size.
	This mechanism can be used to completely clear entries from the		This mechanism can be used to completely clear entries from the
	dynamic table by setting a maximum size of 0, which can subsequently		dynamic table by setting a maximum size of 0, which can subsequently
	skipping to change at page 5, line 33 ¶		skipping to change at page 5, line 37 ¶
	Each entry possesses both an absolute index which is fixed for the		Each entry possesses both an absolute index which is fixed for the
	lifetime of that entry and a relative index which changes over time		lifetime of that entry and a relative index which changes over time
	based on the context of the reference. The first entry inserted has		based on the context of the reference. The first entry inserted has
	an absolute index of "1"; indices increase sequentially with each		an absolute index of "1"; indices increase sequentially with each
	insertion.		insertion.
	The relative index begins at zero and increases in the opposite		The relative index begins at zero and increases in the opposite
	direction from the absolute index. Determining which entry has a		direction from the absolute index. Determining which entry has a
	relative index of "0" depends on the context of the reference.		relative index of "0" depends on the context of the reference.
	On the control stream, a relative index of "0" always refers to the		On the encoder stream, a relative index of "0" always refers to the
	most recently inserted value in the dynamic table. Note that this		most recently inserted value in the dynamic table. Note that this
	means the entry referenced by a given relative index will change		means the entry referenced by a given relative index will change
	while interpreting instructions on the encoder stream.		while interpreting instructions on the encoder stream.
	+---+---------------+-----------+		+---+---------------+-----------+
	| n | ... | d + 1 | Absolute Index		| n | ... | d + 1 | Absolute Index
	+ - +---------------+ - - - - - +		+ - +---------------+ - - - - - +
	| 0 | ... | n - d - 1 | Relative Index		| 0 | ... | n - d - 1 | Relative Index
	+---+---------------+-----------+		+---+---------------+-----------+
	^ |		^ |
	| V		| V
	Insertion Point Dropping Point		Insertion Point Dropping Point
	n = count of entries inserted		n = count of entries inserted
	d = count of entries dropped		d = count of entries dropped
	Example Dynamic Table Indexing - Control Stream		Example Dynamic Table Indexing - Control Stream
	Because frames from request streams can be delivered out of order		Because frames from request streams can be delivered out of order
	with instructions on the control stream, relative indices are		with instructions on the encoder stream, relative indices are
	relative to the Base Index at the beginning of the header block (see		relative to the Base Index at the beginning of the header block (see
	Section 5.4.1). The Base Index is an absolute index. When		Section 5.4.1). The Base Index is an absolute index. When
	interpreting the rest of the frame, the entry identified by Base		interpreting the rest of the frame, the entry identified by Base
	Index has a relative index of zero. The relative indices of entries		Index has a relative index of zero. The relative indices of entries
	do not change while interpreting headers on a request or push stream.		do not change while interpreting headers on a request or push stream.
	Base Index		Base Index
	|		|
	V		V
	+---+-----+-----+-----+-------+		+---+-----+-----+-----+-------+
	skipping to change at page 7, line 6 ¶		skipping to change at page 7, line 23 ¶
	n = count of entries inserted		n = count of entries inserted
	d = count of entries dropped		d = count of entries dropped
	Dynamic Table Indexing - Post-Base References		Dynamic Table Indexing - Post-Base References
	If the decoder encounters a reference to an entry which has already		If the decoder encounters a reference to an entry which has already
	been dropped from the table or which is greater than the declared		been dropped from the table or which is greater than the declared
	Largest Reference (see Section 5.4.1), this MUST be treated as a		Largest Reference (see Section 5.4.1), this MUST be treated as a
	stream error of type "HTTP_QPACK_DECOMPRESSION_FAILED" error code.		stream error of type "HTTP_QPACK_DECOMPRESSION_FAILED" error code.
	If this reference occurs on the control stream, this MUST be treated		If this reference occurs on the encoder stream, this MUST be treated
	as a session error.		as a session error.
	2.3. Avoiding Head-of-Line Blocking in HTTP/QUIC		2.3. Avoiding Head-of-Line Blocking in HTTP/QUIC
	Because QUIC does not guarantee order between data on different		Because QUIC does not guarantee order between data on different
	streams, a header block might reference an entry in the dynamic table		streams, a header block might reference an entry in the dynamic table
	that has not yet been received.		that has not yet been received.
	Each header block contains a Largest Reference which identifies the		Each header block contains a Largest Reference which identifies the
	table state necessary for decoding. If the greatest absolute index		table state necessary for decoding. If the greatest absolute index
	skipping to change at page 8, line 10 ¶		skipping to change at page 8, line 24 ¶
	Note that the decoder might not actually become blocked on every		Note that the decoder might not actually become blocked on every
	stream which risks becoming blocked. If the decoder encounters more		stream which risks becoming blocked. If the decoder encounters more
	blocked streams than it promised to support, it SHOULD treat this as		blocked streams than it promised to support, it SHOULD treat this as
	a stream error of type HTTP_QPACK_DECOMPRESSION_FAILED.		a stream error of type HTTP_QPACK_DECOMPRESSION_FAILED.
	2.3.1. State Synchronization		2.3.1. State Synchronization
	The decoder stream signals key events at the decoder that permit the		The decoder stream signals key events at the decoder that permit the
	encoder to track the decoder's state. These events are:		encoder to track the decoder's state. These events are:
	o Successful processing of a header block		o Complete processing of a header block
	o Abandonment of a stream which might have remaining header blocks		o Abandonment of a stream which might have remaining header blocks
	o Receipt of new dynamic table entries		o Receipt of new dynamic table entries
	Regardless of whether a header block contained blocking references,		Regardless of whether a header block contained blocking references,
	the knowledge that it was processed successfully permits the encoder		the knowledge that it has been processed permits the encoder to evict
	to avoid evicting entries while references remain outstanding; see		entries to which no unacknowledged references remain; see
	Section 6.3.1. When a stream is reset or abandoned, the indication		Section 7.3.1. When a stream is reset or abandoned, the indication
	that these header blocks will never be processed serves a similar		that these header blocks will never be processed serves a similar
	function; see Section 5.3.3.		function; see Section 5.3.3.
	For the encoder to identify which dynamic table entries can be safely		For the encoder to identify which dynamic table entries can be safely
	used without a stream becoming blocked, the encoder tracks the		used without a stream becoming blocked, the encoder tracks the
	absolute index of the decoder's Largest Known Received entry.		absolute index of the decoder's Largest Known Received entry.
	When blocking references are permitted, the encoder uses		When blocking references are permitted, the encoder uses
	acknowledgement of header blocks to identify the Largest Known		acknowledgement of header blocks to identify the Largest Known
	Received index, as described in Section 5.3.2.		Received index, as described in Section 5.3.2.
	skipping to change at page 9, line 32 ¶		skipping to change at page 9, line 49 ¶
	x ... Indicates that x is variable-length and extends to the end of		x ... Indicates that x is variable-length and extends to the end of
	the region.		the region.
	4. Configuration		4. Configuration
	QPACK defines two settings which are included in the HTTP/QUIC		QPACK defines two settings which are included in the HTTP/QUIC
	SETTINGS frame.		SETTINGS frame.
	SETTINGS_HEADER_TABLE_SIZE (0x1): An integer with a maximum value of		SETTINGS_HEADER_TABLE_SIZE (0x1): An integer with a maximum value of
	2^30 - 1. The default value is 4,096 bytes. See (TODO: reference		2^30 - 1. The default value is 4,096 bytes. See Section 2.2 for
	PR#1357) for usage.		usage.
	SETTINGS_QPACK_BLOCKED_STREAMS (0x7): An integer with a maximum		SETTINGS_QPACK_BLOCKED_STREAMS (0x7): An integer with a maximum
	value of 2^16 - 1. The default value is 100. See Section 2.3.		value of 2^16 - 1. The default value is 100. See Section 2.3.
	5. Wire Format		5. Wire Format
	QPACK instructions occur in three locations, each of which uses a		QPACK instructions occur in three locations, each of which uses a
	separate instruction space:		separate instruction space:
	o The encoder stream is a unidirectional stream of type "0x48"		o The encoder stream is a unidirectional stream of type "0x48"
	skipping to change at page 11, line 23 ¶		skipping to change at page 11, line 37 ¶
	The contents of the encoder stream are an unframed sequence of the		The contents of the encoder stream are an unframed sequence of the
	following instructions.		following instructions.
	5.2.1. Insert With Name Reference		5.2.1. Insert With Name Reference
	An addition to the header table where the header field name matches		An addition to the header table where the header field name matches
	the header field name of an entry stored in the static table or the		the header field name of an entry stored in the static table or the
	dynamic table starts with the '1' one-bit pattern. The "S" bit		dynamic table starts with the '1' one-bit pattern. The "S" bit
	indicates whether the reference is to the static (S=1) or dynamic		indicates whether the reference is to the static (S=1) or dynamic
	(S=0) table. The header field name is represented using the relative		(S=0) table. The 6-bit prefix integer (see Section 5.1 of [RFC7541])
	index of that entry, which is represented as an integer with a 6-bit		that follows is used to locate the table entry for the header name.
	prefix (see Section 5.1 of [RFC7541]).		When S=1, the number represents the static table index; when S=0, the
			number is the relative index of the entry in the dynamic table.
	The header name reference is followed by the header field value		The header name reference is followed by the header field value
	represented as a string literal (see Section 5.2 of [RFC7541]).		represented as a string literal (see Section 5.2 of [RFC7541]).
	0 1 2 3 4 5 6 7		0 1 2 3 4 5 6 7
	+---+---+---+---+---+---+---+---+		+---+---+---+---+---+---+---+---+
	| 1 | S | Name Index (6+) |		| 1 | S | Name Index (6+) |
	+---+---+-----------------------+		+---+---+-----------------------+
	| H | Value Length (7+) |		| H | Value Length (7+) |
	+---+---------------------------+		+---+---------------------------+
	skipping to change at page 13, line 10 ¶		skipping to change at page 13, line 30 ¶
	Figure 2: Maximum Dynamic Table Size Change		Figure 2: Maximum Dynamic Table Size Change
	The new maximum size MUST be lower than or equal to the limit		The new maximum size MUST be lower than or equal to the limit
	determined by the protocol using QPACK. A value that exceeds this		determined by the protocol using QPACK. A value that exceeds this
	limit MUST be treated as a decoding error. In HTTP/QUIC, this limit		limit MUST be treated as a decoding error. In HTTP/QUIC, this limit
	is the value of the SETTINGS_HEADER_TABLE_SIZE parameter (see		is the value of the SETTINGS_HEADER_TABLE_SIZE parameter (see
	Section 4) received from the decoder.		Section 4) received from the decoder.
	Reducing the maximum size of the dynamic table can cause entries to		Reducing the maximum size of the dynamic table can cause entries to
	be evicted (see Section 4.3 of [RFC7541]). This MUST NOT cause the		be evicted (see Section 4.3 of [RFC7541]). This MUST NOT cause the
	eviction of entries with outstanding references (see Section 6.3).		eviction of entries with outstanding references (see Section 7.3).
	Changing the size of the dynamic table is not acknowledged as this		Changing the size of the dynamic table is not acknowledged as this
	instruction does not insert an entry.		instruction does not insert an entry.
	5.3. QPACK Decoder Stream		5.3. QPACK Decoder Stream
	The decoder stream carries information used to ensure consistency of		The decoder stream carries information used to ensure consistency of
	the dynamic table. Information is sent from the QPACK decoder to the		the dynamic table. Information is sent from the QPACK decoder to the
	QPACK encoder; that is, the server informs the client about the		QPACK encoder; that is, the server informs the client about the
	processing of the client's header blocks and table updates, and the		processing of the client's header blocks and table updates, and the
	client informs the server about the processing of the server's header		client informs the server about the processing of the server's header
	skipping to change at page 14, line 7 ¶		skipping to change at page 14, line 27 ¶
	table entry will provide the most timely feedback to the encoder, but		table entry will provide the most timely feedback to the encoder, but
	could be redundant with other decoder feedback. By delaying a		could be redundant with other decoder feedback. By delaying a
	Table State Synchronize, a decoder might be able to coalesce multiple		Table State Synchronize, a decoder might be able to coalesce multiple
	Table State Synchronize instructions, or replace them entirely with		Table State Synchronize instructions, or replace them entirely with
	Header Acknowledgements. However, delaying too long may lead to		Header Acknowledgements. However, delaying too long may lead to
	compression inefficiencies if the encoder waits for an entry to be		compression inefficiencies if the encoder waits for an entry to be
	acknowledged before using it.		acknowledged before using it.
	5.3.2. Header Acknowledgement		5.3.2. Header Acknowledgement
	After processing a header block on a request or push stream, the		After processing a header block whose declared Largest Reference is
	decoder emits a Header Acknowledgement instruction on the decoder		not zero, the decoder emits a Header Acknowledgement instruction on
	stream. The instruction begins with the '1' one-bit pattern and		the decoder stream. The instruction begins with the '1' one-bit
	includes the request stream's stream ID, encoded as a 7-bit prefix		pattern and includes the request stream's stream ID, encoded as a
	integer. It is used by the peer's QPACK encoder to know when it is		7-bit prefix integer. It is used by the peer's QPACK encoder to know
	safe to evict an entry.		when it is safe to evict an entry.
	The same Stream ID can be identified multiple times, as multiple		The same Stream ID can be identified multiple times, as multiple
	header blocks can be sent on a single stream in the case of		header blocks can be sent on a single stream in the case of
	intermediate responses, trailers, and pushed requests. Since header		intermediate responses, trailers, and pushed requests. Since header
	frames on each stream are received and processed in order, this gives		frames on each stream are received and processed in order, this gives
	the encoder precise feedback on which header blocks within a stream		the encoder precise feedback on which header blocks within a stream
	have been fully processed.		have been fully processed.
	0 1 2 3 4 5 6 7		0 1 2 3 4 5 6 7
	+---+---+---+---+---+---+---+---+		+---+---+---+---+---+---+---+---+
	skipping to change at page 17, line 9 ¶		skipping to change at page 17, line 37 ¶
	starts with the '1' 1-bit pattern, followed by the "S" bit indicating		starts with the '1' 1-bit pattern, followed by the "S" bit indicating
	whether the reference is into the static (S=1) or dynamic (S=0)		whether the reference is into the static (S=1) or dynamic (S=0)
	table. Finally, the relative index of the matching header field is		table. Finally, the relative index of the matching header field is
	represented as an integer with a 6-bit prefix (see Section 5.1 of		represented as an integer with a 6-bit prefix (see Section 5.1 of
	[RFC7541]).		[RFC7541]).
	5.4.2.2. Indexed Header Field With Post-Base Index		5.4.2.2. Indexed Header Field With Post-Base Index
	If the entry is in the dynamic table with an absolute index greater		If the entry is in the dynamic table with an absolute index greater
	than Base Index, the representation starts with the '0001' 4-bit		than Base Index, the representation starts with the '0001' 4-bit
	pattern, followed by the post-base index (see Section 2.2.1) of the		pattern, followed by the post-base index (see Section 2.2.2) of the
	matching header field, represented as an integer with a 4-bit prefix		matching header field, represented as an integer with a 4-bit prefix
	(see Section 5.1 of [RFC7541]).		(see Section 5.1 of [RFC7541]).
	0 1 2 3 4 5 6 7		0 1 2 3 4 5 6 7
	+---+---+---+---+---+---+---+---+		+---+---+---+---+---+---+---+---+
	| 0 | 0 | 0 | 1 | Index (4+) |		| 0 | 0 | 0 | 1 | Index (4+) |
	+---+---+---+---+---------------+		+---+---+---+---+---------------+
	Indexed Header Field with Post-Base Index		Indexed Header Field with Post-Base Index
	skipping to change at page 18, line 16 ¶		skipping to change at page 18, line 43 ¶
	absolute index less than or equal to Base Index, the header field		absolute index less than or equal to Base Index, the header field
	name is represented using the relative index of that entry, which is		name is represented using the relative index of that entry, which is
	represented as an integer with a 4-bit prefix (see Section 5.1 of		represented as an integer with a 4-bit prefix (see Section 5.1 of
	[RFC7541]). The "S" bit indicates whether the reference is to the		[RFC7541]). The "S" bit indicates whether the reference is to the
	static (S=1) or dynamic (S=0) table.		static (S=1) or dynamic (S=0) table.
	5.4.2.4. Literal Header Field With Post-Base Name Reference		5.4.2.4. Literal Header Field With Post-Base Name Reference
	For entries in the dynamic table with an absolute index greater than		For entries in the dynamic table with an absolute index greater than
	Base Index, the header field name is represented using the post-base		Base Index, the header field name is represented using the post-base
	index of that entry (see Section 2.2.1) encoded as an integer with a		index of that entry (see Section 2.2.2) encoded as an integer with a
	3-bit prefix.		3-bit prefix.
	0 1 2 3 4 5 6 7		0 1 2 3 4 5 6 7
	+---+---+---+---+---+---+---+---+		+---+---+---+---+---+---+---+---+
	| 0 | 0 | 0 | 0 | N |NameIdx(3+)|		| 0 | 0 | 0 | 0 | N |NameIdx(3+)|
	+---+---+---+---+---+-----------+		+---+---+---+---+---+-----------+
	| H | Value Length (7+) |		| H | Value Length (7+) |
	+---+---------------------------+		+---+---------------------------+
	| Value String (Length octets) |		| Value String (Length octets) |
	+-------------------------------+		+-------------------------------+
	skipping to change at page 19, line 18 ¶		skipping to change at page 19, line 48 ¶
	+---+---+---+---+---+-----------+		+---+---+---+---+---+-----------+
	| Name String (Length octets) |		| Name String (Length octets) |
	+---+---------------------------+		+---+---------------------------+
	| H | Value Length (7+) |		| H | Value Length (7+) |
	+---+---------------------------+		+---+---------------------------+
	| Value String (Length octets) |		| Value String (Length octets) |
	+-------------------------------+		+-------------------------------+
	Literal Header Field Without Name Reference		Literal Header Field Without Name Reference
	6. Encoding Strategies		6. Error Handling
	6.1. Single Pass Encoding		The following error code is defined for HTTP/QUIC to indicate all
			failures of QPACK which prevent the stream or connection from
			continuing:
			HTTP_QPACK_DECOMPRESSION_FAILED (0x06): QPACK failed to decompress a
			frame and cannot continue.
			7. Encoding Strategies
			7.1. Single Pass Encoding
	An encoder making a single pass over a list of headers must choose		An encoder making a single pass over a list of headers must choose
	Base Index before knowing Largest Reference. When trying to		Base Index before knowing Largest Reference. When trying to
	reference a header inserted to the table after encoding has begun,		reference a header inserted to the table after encoding has begun,
	the entry is encoded with different instructions that tell the		the entry is encoded with different instructions that tell the
	decoder to use an absolute index greater than the Base Index.		decoder to use an absolute index greater than the Base Index.
	6.2. Preventing Eviction Races		7.2. Preventing Eviction Races
	Due to out-of-order arrival, QPACK's eviction algorithm requires		Due to out-of-order arrival, QPACK's eviction algorithm requires
	changes (relative to HPACK) to avoid the possibility that an indexed		changes (relative to HPACK) to avoid the possibility that an indexed
	representation is decoded after the referenced entry has already been		representation is decoded after the referenced entry has already been
	evicted. QPACK employs a two-phase eviction algorithm, in which the		evicted. QPACK employs a two-phase eviction algorithm, in which the
	encoder will not evict entries that have outstanding (unacknowledged)		encoder will not evict entries that have outstanding (unacknowledged)
	references.		references.
	6.3. Reference Tracking		7.3. Reference Tracking
	An encoder MUST ensure that a header block which references a dynamic		An encoder MUST ensure that a header block which references a dynamic
	table entry is not received by the decoder after the referenced entry		table entry is not received by the decoder after the referenced entry
	has already been evicted. An encoder also respects the limit set by		has already been evicted. An encoder also respects the limit set by
	the decoder on the number of streams that are allowed to become		the decoder on the number of streams that are allowed to become
	blocked. Even if the decoder is willing to tolerate blocked streams,		blocked. Even if the decoder is willing to tolerate blocked streams,
	the encoder might choose to avoid them in certain cases.		the encoder might choose to avoid them in certain cases.
	In order to enable this, the encoder will need to track outstanding		In order to enable this, the encoder will need to track outstanding
	(unacknowledged) header blocks and table updates using feedback		(unacknowledged) header blocks and table updates using feedback
	received from the decoder.		received from the decoder.
	6.3.1. Blocked Eviction		7.3.1. Blocked Eviction
	The encoder MUST NOT permit an entry to be evicted while a reference		The encoder MUST NOT permit an entry to be evicted while a reference
	to that entry remains unacknowledged. If a new header to be inserted		to that entry remains unacknowledged. If a new header to be inserted
	into the dynamic table would cause the eviction of such an entry, the		into the dynamic table would cause the eviction of such an entry, the
	encoder MUST NOT emit the insert instruction until the reference has		encoder MUST NOT emit the insert instruction until the reference has
	been processed by the decoder and acknowledged.		been processed by the decoder and acknowledged.
	The encoder can emit a literal representation for the new header in		The encoder can emit a literal representation for the new header in
	order to avoid encoding delays, and MAY insert the header into the		order to avoid encoding delays, and MAY insert the header into the
	table later if desired.		table later if desired.
	To ensure that the blocked eviction case is rare, references to the		To ensure that the blocked eviction case is rare, references to the
	oldest entries in the dynamic table SHOULD be avoided. When one of		oldest entries in the dynamic table SHOULD be avoided. When one of
	the oldest entries in the table is still actively used for		the oldest entries in the table is still actively used for
	references, the encoder SHOULD emit an Duplicate representation		references, the encoder SHOULD emit an Duplicate representation
	instead (see Section 5.2.3).		instead (see Section 5.2.3).
	6.3.2. Blocked Decoding		7.3.2. Blocked Decoding
	For header blocks encoded in non-blocking mode, the encoder needs to		For header blocks encoded in non-blocking mode, the encoder needs to
	forego indexed representations that refer to table updates which have		forego indexed representations that refer to table updates which have
	not yet been acknowledged with Section 5.3. Since all table updates		not yet been acknowledged with Section 5.3. Since all table updates
	are processed in sequence on the control stream, an index into the		are processed in sequence on the encoder stream, an index into the
	dynamic table is sufficient to track which entries have been		dynamic table is sufficient to track which entries have been
	acknowledged.		acknowledged.
	To track blocked streams, the necessary Base Index value for each		To track blocked streams, the necessary Base Index value for each
	stream can be used. Whenever the decoder processes a table update,		stream can be used. Whenever the decoder processes a table update,
	it can begin decoding any blocked streams that now have their		it can begin decoding any blocked streams that now have their
	dependencies satisfied.		dependencies satisfied.
	6.4. Speculative table updates		7.4. Speculative table updates
	Implementations can _speculatively_ send header frames on the HTTP		Implementations can _speculatively_ send header frames on the HTTP
	Control Streams which are not needed for any current HTTP request or		Control Streams which are not needed for any current HTTP request or
	response. Such headers could be used strategically to improve		response. Such headers could be used strategically to improve
	performance. For instance, the encoder might decide to _refresh_ by		performance. For instance, the encoder might decide to _refresh_ by
	sending Duplicate representations for popular header fields		sending Duplicate representations for popular header fields
	(Section 5.2.3), ensuring they have small indices and hence minimal		(Section 5.2.3), ensuring they have small indices and hence minimal
	size on the wire.		size on the wire.
	6.5. Sample One Pass Encoding Algorithm		7.5. Sample One Pass Encoding Algorithm
	Pseudo-code for single pass encoding, excluding handling of		Pseudo-code for single pass encoding, excluding handling of
	duplicates, non-blocking mode, and reference tracking.		duplicates, non-blocking mode, and reference tracking.
	baseIndex = dynamicTable.baseIndex		baseIndex = dynamicTable.baseIndex
	largestReference = 0		largestReference = 0
	for header in headers:		for header in headers:
	staticIdx = staticTable.getIndex(header)		staticIdx = staticTable.getIndex(header)
	if staticIdx:		if staticIdx:
	encodeIndexReference(streamBuffer, staticIdx)		encodeIndexReference(streamBuffer, staticIdx)
	skipping to change at page 22, line 5 ¶		skipping to change at page 23, line 5 ¶
	# encode the prefix		# encode the prefix
	encodeInteger(prefixBuffer, 0x00, largestReference, 8)		encodeInteger(prefixBuffer, 0x00, largestReference, 8)
	if baseIndex >= largestReference:		if baseIndex >= largestReference:
	encodeInteger(prefixBuffer, 0, baseIndex - largestReference, 7)		encodeInteger(prefixBuffer, 0, baseIndex - largestReference, 7)
	else:		else:
	encodeInteger(prefixBuffer, 0x80,		encodeInteger(prefixBuffer, 0x80,
	largestReference - baseIndex, 7)		largestReference - baseIndex, 7)
	return controlBuffer, prefixBuffer + streamBuffer		return controlBuffer, prefixBuffer + streamBuffer
	7. Security Considerations		8. Security Considerations
	TBD.		TBD.
	8. IANA Considerations		9. IANA Considerations
	8.1. Settings Registration		9.1. Settings Registration
	This document creates two new settings in the "HTTP/QUIC Settings"		This document creates two new settings in the "HTTP/QUIC Settings"
	registry established in [QUIC-HTTP].		registry established in [QUIC-HTTP].
	The entries in the following table are registered by this document.		The entries in the following table are registered by this document.
	+-----------------------+------+---------------+		+-----------------------+------+---------------+
	| Setting Name | Code | Specification |		| Setting Name | Code | Specification |
	+-----------------------+------+---------------+		+-----------------------+------+---------------+
	| HEADER_TABLE_SIZE | 0x1 | Section 4 |		| HEADER_TABLE_SIZE | 0x1 | Section 4 |
	| | | |		| | | |
	| QPACK_BLOCKED_STREAMS | 0x7 | Section 4 |		| QPACK_BLOCKED_STREAMS | 0x7 | Section 4 |
	+-----------------------+------+---------------+		+-----------------------+------+---------------+
	8.2. Stream Type Registration		9.2. Stream Type Registration
	This document creates two new settings in the "HTTP/QUIC Stream Type"		This document creates two new settings in the "HTTP/QUIC Stream Type"
	registry established in [QUIC-HTTP].		registry established in [QUIC-HTTP].
	The entries in the following table are registered by this document.		The entries in the following table are registered by this document.
	+----------------------+------+---------------+--------+		+----------------------+------+---------------+--------+
	| Stream Type | Code | Specification | Sender |		| Stream Type | Code | Specification | Sender |
	+----------------------+------+---------------+--------+		+----------------------+------+---------------+--------+
	| QPACK Encoder Stream | 0x48 | Section 5 | Both |		| QPACK Encoder Stream | 0x48 | Section 5 | Both |
	| | | | |		| | | | |
	| QPACK Decoder Stream | 0x68 | Section 5 | Both |		| QPACK Decoder Stream | 0x68 | Section 5 | Both |
	+----------------------+------+---------------+--------+		+----------------------+------+---------------+--------+
	9. References		9.3. Error Code Registration
	9.1. Normative References		This document establishes one new error code in the "HTTP/QUIC Error
			Code" registry established in [QUIC-HTTP].
			Name: HTTP_QPACK_DECOMPRESSION_FAILED
			Code: 0x06
			Description: QPACK failed to interpret an instruction and cannot
			continue.
			10. References
			10.1. Normative References
	[QUIC-HTTP]		[QUIC-HTTP]
	Bishop, M., Ed., "Hypertext Transfer Protocol (HTTP) over		Bishop, M., Ed., "Hypertext Transfer Protocol (HTTP) over
	QUIC", draft-ietf-quic-http-13 (work in progress), June		QUIC", draft-ietf-quic-http-14 (work in progress), August
	2018.		2018.
			[QUIC-TRANSPORT]
			Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
			Multiplexed and Secure Transport", draft-ietf-quic-
			transport-13 (work in progress), August 2018.
	[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,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	[RFC7541] Peon, R. and H. Ruellan, "HPACK: Header Compression for		[RFC7541] Peon, R. and H. Ruellan, "HPACK: Header Compression for
	HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015,		HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015,
	<https://www.rfc-editor.org/info/rfc7541>.		<https://www.rfc-editor.org/info/rfc7541>.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC		[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	9.2. Informative References		10.2. Informative References
	[QUIC-TRANSPORT]
	Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
	and Secure Transport", draft-ietf-quic-transport-12 (work
	in progress), May 2018.
	[RFC2360] Scott, G., "Guide for Internet Standards Writers", BCP 22,		[RFC2360] Scott, G., "Guide for Internet Standards Writers", BCP 22,
	RFC 2360, DOI 10.17487/RFC2360, June 1998,		RFC 2360, DOI 10.17487/RFC2360, June 1998,
	<https://www.rfc-editor.org/info/rfc2360>.		<https://www.rfc-editor.org/info/rfc2360>.
	[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext		[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
	Transfer Protocol Version 2 (HTTP/2)", RFC 7540,		Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
	DOI 10.17487/RFC7540, May 2015,		DOI 10.17487/RFC7540, May 2015,
	<https://www.rfc-editor.org/info/rfc7540>.		<https://www.rfc-editor.org/info/rfc7540>.
	9.3. URIs		10.3. URIs
	[1] https://mailarchive.ietf.org/arch/search/?email_list=quic		[1] https://mailarchive.ietf.org/arch/search/?email_list=quic
	[2] https://github.com/quicwg		[2] https://github.com/quicwg
	[3] https://github.com/quicwg/base-drafts/labels/-qpack		[3] https://github.com/quicwg/base-drafts/labels/-qpack
	Appendix A. Change Log		Appendix A. Change Log
	*RFC Editor's Note:* Please remove this section prior to		*RFC Editor's Note:* Please remove this section prior to
	publication of a final version of this document.		publication of a final version of this document.
	A.1. Since draft-ietf-quic-qpack-00		A.1. Since draft-ietf-quic-qpack-01
			o Only header blocks that reference the dynamic table are
			acknowledged (#1603, #1605)
			A.2. Since draft-ietf-quic-qpack-00
	o Renumbered instructions for consistency (#1471, #1472)		o Renumbered instructions for consistency (#1471, #1472)
	o Decoder is allowed to validate largest reference (#1404, #1469)		o Decoder is allowed to validate largest reference (#1404, #1469)
	o Header block acknowledgments also acknowledge the associated		o Header block acknowledgments also acknowledge the associated
	largest reference (#1370, #1400)		largest reference (#1370, #1400)
	o Added an acknowledgment for unread streams (#1371, #1400)		o Added an acknowledgment for unread streams (#1371, #1400)
	o Removed framing from encoder stream (#1361,#1467)		o Removed framing from encoder stream (#1361,#1467)
	o Control streams use typed unidirectional streams rather than fixed		o Control streams use typed unidirectional streams rather than fixed
	stream IDs (#910,#1359)		stream IDs (#910,#1359)
	A.2. Since draft-ietf-quic-qcram-00		A.3. Since draft-ietf-quic-qcram-00
	o Separate instruction sets for table updates and header blocks		o Separate instruction sets for table updates and header blocks
	(#1235, #1142, #1141)		(#1235, #1142, #1141)
	o Reworked indexing scheme (#1176, #1145, #1136, #1130, #1125,		o Reworked indexing scheme (#1176, #1145, #1136, #1130, #1125,
	#1314)		#1314)
	o Added mechanisms that support one-pass encoding (#1138, #1320)		o Added mechanisms that support one-pass encoding (#1138, #1320)
	o Added a setting to control the number of blocked decoders (#238,		o Added a setting to control the number of blocked decoders (#238,
End of changes. 49 change blocks.
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