draft-ietf-httpbis-http2-03.txt		draft-ietf-httpbis-http2-04.txt
	HTTPbis Working Group M. Belshe		HTTPbis Working Group M. Belshe
	Internet-Draft Twist		Internet-Draft Twist
	Intended status: Standards Track R. Peon		Intended status: Standards Track R. Peon
	Expires: November 30, 2013 Google, Inc		Expires: January 9, 2014 Google, Inc
	M. Thomson, Ed.		M. Thomson, Ed.
	Microsoft		Microsoft
	A. Melnikov, Ed.		A. Melnikov, Ed.
	Isode Ltd		Isode Ltd
	May 29, 2013		July 8, 2013
	Hypertext Transfer Protocol version 2.0		Hypertext Transfer Protocol version 2.0
	draft-ietf-httpbis-http2-03		draft-ietf-httpbis-http2-04
	Abstract		Abstract
	This specification describes an optimized expression of the syntax of		This specification describes an optimized expression of the syntax of
	the Hypertext Transfer Protocol (HTTP). The HTTP/2.0 encapsulation		the Hypertext Transfer Protocol (HTTP). The HTTP/2.0 encapsulation
	enables more efficient use of network resources and reduced		enables more efficient use of network resources and reduced
	perception of latency by allowing header field compression and		perception of latency by allowing header field compression and
	multiple concurrent messages on the same connection. It also		multiple concurrent messages on the same connection. It also
	introduces unsolicited push of representations from servers to		introduces unsolicited push of representations from servers to
	clients.		clients.
	This document is an alternative to, but does not obsolete the		This document is an alternative to, but does not obsolete the
	HTTP/1.1 message format or protocol. HTTP's existing semantics		HTTP/1.1 message format or protocol. HTTP's existing semantics
	remain unchanged.		remain unchanged.
			This version of the draft has been marked for implementation.
			Interoperability testing will occur in the HTTP/2.0 interim in
			Hamburg, DE, starting 2013-08-05.
	Editorial Note (To be removed by RFC Editor)		Editorial Note (To be removed by RFC Editor)
	Discussion of this draft takes place on the HTTPBIS working group		Discussion of this draft takes place on the HTTPBIS working group
	mailing list (ietf-http-wg@w3.org), which is archived at		mailing list (ietf-http-wg@w3.org), which is archived at
	<http://lists.w3.org/Archives/Public/ietf-http-wg/>.		<http://lists.w3.org/Archives/Public/ietf-http-wg/>.
	Working Group information and related documents can be found at		Working Group information and related documents can be found at
	<http://tools.ietf.org/wg/httpbis/> (Wiki) and		<http://tools.ietf.org/wg/httpbis/> (Wiki) and
	<https://github.com/http2/http2-spec> (source code and issues		<https://github.com/http2/http2-spec> (source code and issues
	tracker).		tracker).
	skipping to change at page 2, line 12 ¶		skipping to change at page 2, line 16 ¶
	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 http://datatracker.ietf.org/drafts/current/.		Drafts is at http://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 November 30, 2013.		This Internet-Draft will expire on January 9, 2014.
	Copyright Notice		Copyright Notice
	Copyright (c) 2013 IETF Trust and the persons identified as the		Copyright (c) 2013 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
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://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 34 ¶		skipping to change at page 2, line 38 ¶
	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 . . . . . . . . . . . . . . . . . . . . . . . . . 5		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
	1.1. Document Organization . . . . . . . . . . . . . . . . . . 5		1.1. Document Organization . . . . . . . . . . . . . . . . . . 5
	1.2. Conventions and Terminology . . . . . . . . . . . . . . . 6		1.2. Conventions and Terminology . . . . . . . . . . . . . . . 6
	2. Starting HTTP/2.0 . . . . . . . . . . . . . . . . . . . . . . 6		2. HTTP/2.0 Protocol Overview . . . . . . . . . . . . . . . . . . 6
	2.1. HTTP/2.0 Version Identification . . . . . . . . . . . . . 7		2.1. HTTP Frames . . . . . . . . . . . . . . . . . . . . . . . 7
	2.2. Starting HTTP/2.0 for "http:" URIs . . . . . . . . . . . . 8		2.2. HTTP Multiplexing . . . . . . . . . . . . . . . . . . . . 7
	2.3. Starting HTTP/2.0 for "https:" URIs . . . . . . . . . . . 8		2.3. HTTP Semantics . . . . . . . . . . . . . . . . . . . . . . 7
	2.4. Starting HTTP/2.0 with Prior Knowledge . . . . . . . . . . 9		3. Starting HTTP/2.0 . . . . . . . . . . . . . . . . . . . . . . 7
	3. HTTP/2.0 Framing Layer . . . . . . . . . . . . . . . . . . . . 9		3.1. HTTP/2.0 Version Identification . . . . . . . . . . . . . 8
	3.1. Connection . . . . . . . . . . . . . . . . . . . . . . . . 9		3.2. Starting HTTP/2.0 for "http" URIs . . . . . . . . . . . . 8
	3.2. Connection Header . . . . . . . . . . . . . . . . . . . . 9		3.2.1. HTTP2-Settings Header Field . . . . . . . . . . . . . 10
	3.3. Framing . . . . . . . . . . . . . . . . . . . . . . . . . 10		3.3. Starting HTTP/2.0 for "https" URIs . . . . . . . . . . . . 10
	3.3.1. Frame Header . . . . . . . . . . . . . . . . . . . . . 10		3.4. Starting HTTP/2.0 with Prior Knowledge . . . . . . . . . . 10
	3.3.2. Frame Size . . . . . . . . . . . . . . . . . . . . . . 12		3.5. Connection Header . . . . . . . . . . . . . . . . . . . . 11
	3.4. Streams . . . . . . . . . . . . . . . . . . . . . . . . . 12		4. HTTP Frames . . . . . . . . . . . . . . . . . . . . . . . . . 12
	3.4.1. Stream Creation . . . . . . . . . . . . . . . . . . . 13		4.1. Frame Header . . . . . . . . . . . . . . . . . . . . . . . 12
	3.4.2. Stream priority . . . . . . . . . . . . . . . . . . . 13		4.2. Frame Size . . . . . . . . . . . . . . . . . . . . . . . . 13
	3.4.3. Stream half-close . . . . . . . . . . . . . . . . . . 14		4.3. Header Compression and Decompression . . . . . . . . . . . 13
	3.4.4. Stream close . . . . . . . . . . . . . . . . . . . . . 14		5. Streams and Multiplexing . . . . . . . . . . . . . . . . . . . 14
	3.5. Error Handling . . . . . . . . . . . . . . . . . . . . . . 15		5.1. Stream States . . . . . . . . . . . . . . . . . . . . . . 14
	3.5.1. Connection Error Handling . . . . . . . . . . . . . . 15		5.1.1. Stream Identifiers . . . . . . . . . . . . . . . . . . 18
	3.5.2. Stream Error Handling . . . . . . . . . . . . . . . . 16		5.1.2. Stream Concurrency . . . . . . . . . . . . . . . . . . 18
	3.5.3. Error Codes . . . . . . . . . . . . . . . . . . . . . 16		5.2. Flow Control . . . . . . . . . . . . . . . . . . . . . . . 18
	3.6. Stream Flow Control . . . . . . . . . . . . . . . . . . . 17		5.2.1. Flow Control Principles . . . . . . . . . . . . . . . 19
	3.6.1. Flow Control Principles . . . . . . . . . . . . . . . 17		5.2.2. Appropriate Use of Flow Control . . . . . . . . . . . 20
	3.6.2. Appropriate Use of Flow Control . . . . . . . . . . . 18		5.3. Stream priority . . . . . . . . . . . . . . . . . . . . . 20
	3.7. Header Blocks . . . . . . . . . . . . . . . . . . . . . . 19		5.4. Error Handling . . . . . . . . . . . . . . . . . . . . . . 21
	3.8. Frame Types . . . . . . . . . . . . . . . . . . . . . . . 19		5.4.1. Connection Error Handling . . . . . . . . . . . . . . 21
	3.8.1. DATA Frames . . . . . . . . . . . . . . . . . . . . . 20		5.4.2. Stream Error Handling . . . . . . . . . . . . . . . . 22
	3.8.2. HEADERS+PRIORITY . . . . . . . . . . . . . . . . . . . 20		5.4.3. Connection Termination . . . . . . . . . . . . . . . . 22
	3.8.3. RST_STREAM . . . . . . . . . . . . . . . . . . . . . . 21		6. Frame Definitions . . . . . . . . . . . . . . . . . . . . . . 22
	3.8.4. SETTINGS . . . . . . . . . . . . . . . . . . . . . . . 21		6.1. DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
	3.8.5. PUSH_PROMISE . . . . . . . . . . . . . . . . . . . . . 25		6.2. HEADERS . . . . . . . . . . . . . . . . . . . . . . . . . 23
	3.8.6. PING . . . . . . . . . . . . . . . . . . . . . . . . . 26		6.3. PRIORITY . . . . . . . . . . . . . . . . . . . . . . . . . 24
	3.8.7. GOAWAY . . . . . . . . . . . . . . . . . . . . . . . . 26		6.4. RST_STREAM . . . . . . . . . . . . . . . . . . . . . . . . 25
	3.8.8. HEADERS . . . . . . . . . . . . . . . . . . . . . . . 28		6.5. SETTINGS . . . . . . . . . . . . . . . . . . . . . . . . . 26
	3.8.9. WINDOW_UPDATE . . . . . . . . . . . . . . . . . . . . 29		6.5.1. Setting Format . . . . . . . . . . . . . . . . . . . . 26
	4. HTTP Message Exchanges . . . . . . . . . . . . . . . . . . . . 32		6.5.2. Defined Settings . . . . . . . . . . . . . . . . . . . 27
	4.1. Connection Management . . . . . . . . . . . . . . . . . . 32		6.6. PUSH_PROMISE . . . . . . . . . . . . . . . . . . . . . . . 27
	4.2. HTTP Request/Response . . . . . . . . . . . . . . . . . . 33		6.7. PING . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
	4.2.1. HTTP Header Fields and HTTP/2.0 Headers . . . . . . . 33		6.8. GOAWAY . . . . . . . . . . . . . . . . . . . . . . . . . . 29
	4.2.2. Request . . . . . . . . . . . . . . . . . . . . . . . 33		6.9. WINDOW_UPDATE . . . . . . . . . . . . . . . . . . . . . . 31
	4.2.3. Response . . . . . . . . . . . . . . . . . . . . . . . 34		6.9.1. The Flow Control Window . . . . . . . . . . . . . . . 32
	4.3. Server Push Transactions . . . . . . . . . . . . . . . . . 35		6.9.2. Initial Flow Control Window Size . . . . . . . . . . . 33
	4.3.1. Server implementation . . . . . . . . . . . . . . . . 36		6.9.3. Reducing the Stream Window Size . . . . . . . . . . . 34
	4.3.2. Client implementation . . . . . . . . . . . . . . . . 37		6.9.4. Ending Flow Control . . . . . . . . . . . . . . . . . 34
	5. Design Rationale and Notes . . . . . . . . . . . . . . . . . . 38		7. Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . 35
	5.1. Separation of Framing Layer and Application Layer . . . . 38		8. HTTP Message Exchanges . . . . . . . . . . . . . . . . . . . . 36
	5.2. Error handling - Framing Layer . . . . . . . . . . . . . . 39		8.1. HTTP Request/Response Exchange . . . . . . . . . . . . . . 36
	5.3. One Connection per Domain . . . . . . . . . . . . . . . . 39		8.1.1. Examples . . . . . . . . . . . . . . . . . . . . . . . 37
	5.4. Fixed vs Variable Length Fields . . . . . . . . . . . . . 39		8.1.2. Request Header Fields . . . . . . . . . . . . . . . . 38
	5.5. Server Push . . . . . . . . . . . . . . . . . . . . . . . 40		8.1.3. Response Header Fields . . . . . . . . . . . . . . . . 39
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 40		8.1.4. GZip Content-Encoding . . . . . . . . . . . . . . . . 40
	6.1. Server Authority and Same-Origin . . . . . . . . . . . . . 40		8.1.5. Request Reliability Mechanisms in HTTP/2.0 . . . . . . 40
	6.2. Cross-Protocol Attacks . . . . . . . . . . . . . . . . . . 40		8.2. Server Push . . . . . . . . . . . . . . . . . . . . . . . 41
	6.3. Cacheability of Pushed Resources . . . . . . . . . . . . . 41		9. Additional HTTP Requirements/Considerations . . . . . . . . . 43
	7. Privacy Considerations . . . . . . . . . . . . . . . . . . . . 41		9.1. Frame Size Limits for HTTP . . . . . . . . . . . . . . . . 43
	7.1. Long Lived Connections . . . . . . . . . . . . . . . . . . 41		9.2. Connection Management . . . . . . . . . . . . . . . . . . 43
	7.2. SETTINGS frame . . . . . . . . . . . . . . . . . . . . . . 41		10. Security Considerations . . . . . . . . . . . . . . . . . . . 43
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42		10.1. Server Authority and Same-Origin . . . . . . . . . . . . . 43
	8.1. Frame Type Registry . . . . . . . . . . . . . . . . . . . 42		10.2. Cross-Protocol Attacks . . . . . . . . . . . . . . . . . . 44
	8.2. Error Code Registry . . . . . . . . . . . . . . . . . . . 43		10.3. Cacheability of Pushed Resources . . . . . . . . . . . . . 44
	8.3. Settings Registry . . . . . . . . . . . . . . . . . . . . 43		11. Privacy Considerations . . . . . . . . . . . . . . . . . . . . 45
	9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 44		12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 45
	10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 44		12.1. Frame Type Registry . . . . . . . . . . . . . . . . . . . 45
	10.1. Normative References . . . . . . . . . . . . . . . . . . . 44		12.2. Error Code Registry . . . . . . . . . . . . . . . . . . . 46
	10.2. Informative References . . . . . . . . . . . . . . . . . . 45		12.3. Settings Registry . . . . . . . . . . . . . . . . . . . . 47
			12.4. HTTP2-Settings Header Field Registration . . . . . . . . . 47
			13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 48
			14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 48
			14.1. Normative References . . . . . . . . . . . . . . . . . . . 48
			14.2. Informative References . . . . . . . . . . . . . . . . . . 50
	Appendix A. Change Log (to be removed by RFC Editor before		Appendix A. Change Log (to be removed by RFC Editor before
	publication) . . . . . . . . . . . . . . . . . . . . 46		publication) . . . . . . . . . . . . . . . . . . . . 50
			A.1. Since draft-ietf-httpbis-http2-03 . . . . . . . . . . . . 50
	A.1. Since draft-ietf-httpbis-http2-02 . . . . . . . . . . . . 46		A.2. Since draft-ietf-httpbis-http2-02 . . . . . . . . . . . . 50
	A.2. Since draft-ietf-httpbis-http2-01 . . . . . . . . . . . . 46		A.3. Since draft-ietf-httpbis-http2-01 . . . . . . . . . . . . 50
	A.3. Since draft-ietf-httpbis-http2-00 . . . . . . . . . . . . 47		A.4. Since draft-ietf-httpbis-http2-00 . . . . . . . . . . . . 51
	A.4. Since draft-mbelshe-httpbis-spdy-00 . . . . . . . . . . . 47		A.5. Since draft-mbelshe-httpbis-spdy-00 . . . . . . . . . . . 51
	1. Introduction		1. Introduction
	The Hypertext Transfer Protocol (HTTP) is a wildly successful		The Hypertext Transfer Protocol (HTTP) is a wildly successful
	protocol. However, the HTTP/1.1 message encapsulation ([HTTP-p1],		protocol. However, the HTTP/1.1 message format ([HTTP-p1], Section
	Section 3) is optimized for implementation simplicity and		3) is optimized for implementation simplicity and accessibility, not
	accessibility, not application performance. As such it has several		application performance. As such it has several characteristics that
	characteristics that have a negative overall effect on application		have a negative overall effect on application performance.
	performance.
	In particular, HTTP/1.0 only allows one request to be delivered at a		In particular, HTTP/1.0 only allows one request to be delivered at a
	time on a given connection. HTTP/1.1 pipelining only partially		time on a given connection. HTTP/1.1 pipelining only partially
	addressed request concurrency, and is not widely deployed.		addressed request concurrency, and is not widely deployed.
	Therefore, clients that need to make many requests (as is common on		Therefore, clients that need to make many requests (as is common on
	the Web) typically use multiple connections to a server in order to		the Web) typically use multiple connections to a server in order to
	reduce perceived latency.		reduce perceived latency.
	Furthermore, HTTP/1.1 header fields are often repetitive and verbose,		Furthermore, HTTP/1.1 header fields are often repetitive and verbose,
	which, in addition to generating more or larger network packets, can		which, in addition to generating more or larger network packets, can
	skipping to change at page 5, line 47 ¶		skipping to change at page 5, line 46 ¶
	HTTP/1.x. This means less competition with other flows, and longer-		HTTP/1.x. This means less competition with other flows, and longer-
	lived connections, which in turn leads to better utilization of		lived connections, which in turn leads to better utilization of
	available network capacity.		available network capacity.
	Finally, this encapsulation also enables more scalable processing of		Finally, this encapsulation also enables more scalable processing of
	messages through use of binary message framing.		messages through use of binary message framing.
	1.1. Document Organization		1.1. Document Organization
	The HTTP/2.0 Specification is split into three parts: starting		The HTTP/2.0 Specification is split into three parts: starting
	HTTP/2.0 (Section 2), which covers how a HTTP/2.0 connection is		HTTP/2.0 (Section 3), which covers how a HTTP/2.0 connection is
	initiated; a framing layer (Section 3), which multiplexes a single		initiated; a framing layer (Section 4), which multiplexes a single
	TCP connection into independent frames of various types; and an HTTP		TCP connection into independent frames of various types; and an HTTP
	layer (Section 4), which specifies the mechanism for expressing HTTP		layer (Section 8), which specifies the mechanism for expressing HTTP
	interactions using the framing layer. While some of the framing		interactions using the framing layer. While some of the framing
	layer concepts are isolated from HTTP, building a generic framing		layer concepts are isolated from HTTP, building a generic framing
	layer has not been a goal. The framing layer is tailored to the		layer has not been a goal. The framing layer is tailored to the
	needs of the HTTP protocol and server push.		needs of the HTTP protocol and server push.
	1.2. Conventions and Terminology		1.2. Conventions and Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in RFC 2119 [RFC2119].		document are to be interpreted as described in RFC 2119 [RFC2119].
	skipping to change at page 6, line 47 ¶		skipping to change at page 6, line 46 ¶
	server: The endpoint which did not initiate the HTTP connection.		server: The endpoint which did not initiate the HTTP connection.
	connection error: An error on the HTTP/2.0 connection.		connection error: An error on the HTTP/2.0 connection.
	stream: A bi-directional flow of frames across a virtual channel		stream: A bi-directional flow of frames across a virtual channel
	within the HTTP/2.0 connection.		within the HTTP/2.0 connection.
	stream error: An error on the individual HTTP/2.0 stream.		stream error: An error on the individual HTTP/2.0 stream.
	2. Starting HTTP/2.0		2. HTTP/2.0 Protocol Overview
	HTTP/2.0 uses the same "http:" and "https:" URI schemes used by		HTTP/2.0 provides an optimized transport for HTTP semantics.
	HTTP/1.1. As a result, implementations processing requests for
	target resource URIs like "http://example.org/foo" or		An HTTP/2.0 connection is an application level protocol running on
	"https://example.com/bar" are required to first discover whether the		top of a TCP connection ([RFC0793]). The client is the TCP
	upstream server (the immediate peer to which the client wishes to		connection initiator.
	establish a connection) supports HTTP/2.0.
			This document describes the HTTP/2.0 protocol using a logical
			structure that is formed of three parts: framing, streams, and
			application mapping. This structure is provided primarily as an aid
			to specification, implementations are free to diverge from this
			structure as necessary.
			2.1. HTTP Frames
			HTTP/2.0 provides an efficient serialization of HTTP semantics. HTTP
			requests and responses are encoded into length-prefixed frames (see
			Section 4.1).
			HTTP headers are compressed into a series of frames that contain
			header block fragments (see Section 4.3).
			2.2. HTTP Multiplexing
			HTTP/2.0 provides the ability to multiplex multiple HTTP requests and
			responses onto a single connection. Multiple requests or responses
			can be sent concurrently on a connection using streams (Section 5).
			In order to maintain independent streams, flow control and
			prioritization are necessary.
			2.3. HTTP Semantics
			HTTP/2.0 defines how HTTP requests and responses are mapped to
			streams (see Section 8) and introduces a new interaction model,
			server push (Section 8.2).
			3. Starting HTTP/2.0
			HTTP/2.0 uses the same "http" and "https" URI schemes used by
			HTTP/1.1. HTTP/2.0 shares the same default port numbers: 80 for
			"http" URIs and 443 for "https" URIs. As a result, implementations
			processing requests for target resource URIs like
			"http://example.org/foo" or "https://example.com/bar" are required to
			first discover whether the upstream server (the immediate peer to
			which the client wishes to establish a connection) supports HTTP/2.0.
	The means by which support for HTTP/2.0 is determined is different		The means by which support for HTTP/2.0 is determined is different
	for "http" and "https" URIs. Discovery for "https:" URIs is		for "http" and "https" URIs. Discovery for "http" URIs is described
	described in Section 2.3. Discovery for "http" URIs is described		in Section 3.2. Discovery for "https" URIs is described in
	here.		Section 3.3.
	2.1. HTTP/2.0 Version Identification		3.1. HTTP/2.0 Version Identification
	The protocol defined in this document is identified using the string		The protocol defined in this document is identified using the string
	"HTTP/2.0". This identification is used in the HTTP/1.1 Upgrade		"HTTP/2.0". This identification is used in the HTTP/1.1 Upgrade
	header field, in the TLS application layer protocol negotiation		header field, in the TLS application layer protocol negotiation
	extension [TLSALPN] field and other places where protocol		extension [TLSALPN] field, and other places where protocol
	identification is required.		identification is required.
	Negotiating "HTTP/2.0" implies the use of the transport, security,		Negotiating "HTTP/2.0" implies the use of the transport, security,
	framing and message semantics described in this document.		framing and message semantics described in this document.
	[[anchor3: Editor's Note: please remove the following text prior to		[[anchor6: Editor's Note: please remove the following text prior to
	the publication of a final version of this document.]]		the publication of a final version of this document.]]
	Only implementations of the final, published RFC can identify		Only implementations of the final, published RFC can identify
	themselves as "HTTP/2.0". Until such an RFC exists, implementations		themselves as "HTTP/2.0". Until such an RFC exists, implementations
	MUST NOT identify themselves using "HTTP/2.0".		MUST NOT identify themselves using "HTTP/2.0".
	Examples and text throughout the rest of this document use "HTTP/2.0"		Examples and text throughout the rest of this document use "HTTP/2.0"
	as a matter of editorial convenience only. Implementations of draft		as a matter of editorial convenience only. Implementations of draft
	versions MUST NOT identify using this string.		versions MUST NOT identify using this string.
	skipping to change at page 8, line 5 ¶		skipping to change at page 8, line 41 ¶
	Non-compatible experiments that are based on these draft versions		Non-compatible experiments that are based on these draft versions
	MUST instead replace the string "draft" with a different identifier.		MUST instead replace the string "draft" with a different identifier.
	For example, an experimental implementation of packet mood-based		For example, an experimental implementation of packet mood-based
	encoding based on draft-ietf-httpbis-http2-07 might identify itself		encoding based on draft-ietf-httpbis-http2-07 might identify itself
	as "HTTP-emo-07/2.0". Note that any label MUST conform to the		as "HTTP-emo-07/2.0". Note that any label MUST conform to the
	"token" syntax defined in Section 3.2.6 of [HTTP-p1]. Experimenters		"token" syntax defined in Section 3.2.6 of [HTTP-p1]. Experimenters
	are encouraged to coordinate their experiments on the		are encouraged to coordinate their experiments on the
	ietf-http-wg@w3.org mailing list.		ietf-http-wg@w3.org mailing list.
	2.2. Starting HTTP/2.0 for "http:" URIs		3.2. Starting HTTP/2.0 for "http" URIs
	A client that makes a request to an "http:" URI without prior		A client that makes a request to an "http" URI without prior
	knowledge about support for HTTP/2.0 uses the HTTP Upgrade mechanism		knowledge about support for HTTP/2.0 uses the HTTP Upgrade mechanism
	(Section 6.7 of [HTTP-p1]). The client makes an HTTP/1.1 request		(Section 6.7 of [HTTP-p1]). The client makes an HTTP/1.1 request
	that includes an Upgrade header field identifying HTTP/2.0.		that includes an Upgrade header field identifying HTTP/2.0. The
			HTTP/1.1 request MUST include an HTTP2-Settings (Section 3.2.1)
			header field.
	For example:		For example:
	GET /default.htm HTTP/1.1		GET /default.htm HTTP/1.1
	Host: server.example.com		Host: server.example.com
	Connection: Upgrade		Connection: Upgrade, HTTP2-Settings
	Upgrade: HTTP/2.0		Upgrade: HTTP/2.0
			HTTP2-Settings: <base64url encoding of HTTP/2.0 SETTINGS payload>
			Requests that contain a request entity body MUST be sent in their
			entirety before the client can send HTTP/2.0 frames. This means that
			a large request entity can block the use of the connection until it
			is completely sent.
			If concurrency of an initial request with subsequent requests is
			important, a small request can be used to perform the upgrade to
			HTTP/2.0, at the cost of an additional round trip.
	A server that does not support HTTP/2.0 can respond to the request as		A server that does not support HTTP/2.0 can respond to the request as
	though the Upgrade header field were absent:		though the Upgrade header field were absent:
	HTTP/1.1 200 OK		HTTP/1.1 200 OK
	Content-length: 243		Content-length: 243
	Content-type: text/html		Content-type: text/html
	...
	A server that supports HTTP/2.0 can accept the upgrade with a 101		...
			A server that supports HTTP/2.0 accepts the upgrade with a 101
	(Switching Protocols) status code. After the empty line that		(Switching Protocols) status code. After the empty line that
	terminates the 101 response, the server can begin sending HTTP/2.0		terminates the 101 response, the server can begin sending HTTP/2.0
	frames. These frames MUST include a response to the request that		frames. These frames MUST include a response to the request that
	initiated the Upgrade.		initiated the Upgrade.
	HTTP/1.1 101 Switching Protocols		HTTP/1.1 101 Switching Protocols
	Connection: Upgrade		Connection: Upgrade
	Upgrade: HTTP/2.0		Upgrade: HTTP/2.0
	[ HTTP/2.0 connection ...		[ HTTP/2.0 connection ...
	The first HTTP/2.0 frame sent by the server is a SETTINGS frame		The first HTTP/2.0 frame sent by the server is a SETTINGS frame
	(Section 3.8.4). Upon receiving the 101 response, the client sends a		(Section 6.5). Upon receiving the 101 response, the client sends a
	connection header (Section 3.2), which includes a SETTINGS frame.		connection header (Section 3.5), which includes a SETTINGS frame.
	2.3. Starting HTTP/2.0 for "https:" URIs		The HTTP/1.1 request that is sent prior to upgrade is associated with
			stream 1 and is assigned the highest possible priority. Stream 1 is
			implicitly half closed from the client toward the server, since the
			request is completed as an HTTP/1.1 request. After commencing the
			HTTP/2.0 connection, stream 1 is used for the response.
	A client that makes a request to an "https:" URI without prior		3.2.1. HTTP2-Settings Header Field
			A client that upgrades from HTTP/1.1 to HTTP/2.0 MUST include an
			"HTTP2-Settings" header field. The "HTTP2-Settings" header field is
			a hop-by-hop header field that includes settings that govern the
			HTTP/2.0 connection, provided in anticipation of the server accepting
			the request to upgrade. A server MUST reject an attempt to upgrade
			if this header is not present.
			HTTP2-Settings = token68
			The content of the "HTTP2-Settings" header field is the payload of a
			SETTINGS frame (Section 6.5), encoded as a base64url string (that is,
			the URL- and filename-safe Base64 encoding described in Section 5 of
			[RFC4648], with any trailing '=' characters omitted). The ABNF
			[RFC5234] production for "token68" is defined in Section 2.1 of
			[HTTP-p7].
			The client MUST include values for the following settings
			(Section 6.5.1):
			o SETTINGS_MAX_CONCURRENT_STREAMS
			o SETTINGS_INITIAL_WINDOW_SIZE
			As a hop-by-hop header field, the "Connection" header field MUST
			include a value of "HTTP2-Settings" in addition to "Upgrade" when
			upgrading to HTTP/2.0.
			A server decodes and interprets these values as it would any other
			SETTINGS frame. Providing these values in the Upgrade request
			ensures that the protocol does not require default values for the
			above settings, and gives a client an opportunity to provide other
			settings prior to receiving any frames from the server.
			3.3. Starting HTTP/2.0 for "https" URIs
			A client that makes a request to an "https" URI without prior
	knowledge about support for HTTP/2.0 uses TLS [RFC5246] with the		knowledge about support for HTTP/2.0 uses TLS [RFC5246] with the
	application layer protocol negotiation extension [TLSALPN].		application layer protocol negotiation extension [TLSALPN].
	Once TLS negotiation is complete, both the client and the server send		Once TLS negotiation is complete, both the client and the server send
	a connection header (Section 3.2).		a connection header (Section 3.5).
	2.4. Starting HTTP/2.0 with Prior Knowledge		3.4. Starting HTTP/2.0 with Prior Knowledge
	A client can learn that a particular server supports HTTP/2.0 by		A client can learn that a particular server supports HTTP/2.0 by
	other means. A client MAY immediately send HTTP/2.0 frames to a		other means. A client MAY immediately send HTTP/2.0 frames to a
	server that is known to support HTTP/2.0. This only affects the		server that is known to support HTTP/2.0, after the connection header
	resolution of "http:" URIs, servers supporting HTTP/2.0 are required		(Section 3.5). This only affects the resolution of "http" URIs;
	to support protocol negotiation in TLS [TLSALPN] for "https:" URIs.		servers supporting HTTP/2.0 are required to support protocol
			negotiation in TLS [TLSALPN] for "https" URIs.
	Prior support for HTTP/2.0 is not a strong signal that a given server		Prior support for HTTP/2.0 is not a strong signal that a given server
	will support HTTP/2.0 for future connections. It is possible for		will support HTTP/2.0 for future connections. It is possible for
	server configurations to change or for configurations to differ		server configurations to change or for configurations to differ
	between instances in clustered server. Interception proxies (a.k.a.		between instances in clustered server. Interception proxies (a.k.a.
	"transparent" proxies) are another source of variability.		"transparent" proxies) are another source of variability.
	3. HTTP/2.0 Framing Layer		3.5. Connection Header
	3.1. Connection
	The HTTP/2.0 connection is an Application Level protocol running on
	top of a TCP connection ([RFC0793]). The client is the TCP
	connection initiator.
	HTTP/2.0 connections are persistent. That is, for best performance,
	it is expected a clients will not close connections until it is
	determined that no further communication with a server is necessary
	(for example, when a user navigates away from a particular web page),
	or until the server closes the connection.
	Servers are encouraged to maintain open connections for as long as
	possible, but are permitted to terminate idle connections if
	necessary. When either endpoint chooses to close the transport-level
	TCP connection, the terminating endpoint MUST first send a GOAWAY
	(Section 3.8.7) frame so that both endpoints can reliably determine
	whether previously sent frames have been processed and gracefully
	complete or terminate any necessary remaining tasks.
	3.2. Connection Header
	Upon establishment of a TCP connection and determination that		Upon establishment of a TCP connection and determination that
	HTTP/2.0 will be used by both peers to communicate, each endpoint		HTTP/2.0 will be used by both peers, each endpoint MUST send a
	MUST send a connection header as a final confirmation and to		connection header as a final confirmation and to establish the
	establish the default parameters for the HTTP/2.0 connection.		initial settings for the HTTP/2.0 connection.
	The client connection header is a sequence of 24 octets (in hex		The client connection header is a sequence of 24 octets, which in hex
	notation)		notation are:
	464f4f202a20485454502f322e300d0a0d0a42410d0a0d0a		505249202a20485454502f322e300d0a0d0a534d0d0a0d0a
	(the string "FOO * HTTP/2.0\r\n\r\nBA\r\n\r\n") followed by a
	SETTINGS frame (Section 3.8.4). The client sends the client		(the string "PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n") followed by a
	connection header immediately upon receipt of a 101 Switching		SETTINGS frame (Section 6.5). The client sends the client connection
	Protocols response (indicating a successful upgrade), or after		header immediately upon receipt of a 101 Switching Protocols response
	receiving a TLS Finished message from the server. If starting an		(indicating a successful upgrade), or after receiving a TLS Finished
	HTTP/2.0 connection with prior knowledge of server support for the		message from the server. If starting an HTTP/2.0 connection with
	protocol, the client connection header is sent upon connection		prior knowledge of server support for the protocol, the client
	establishment.		connection header is sent upon connection establishment.
	The client connection header is selected so that a large		The client connection header is selected so that a large
	proportion of HTTP/1.1 or HTTP/1.0 servers and intermediaries do		proportion of HTTP/1.1 or HTTP/1.0 servers and intermediaries do
	not attempt to process further frames. Note that this does not		not attempt to process further frames. Note that this does not
	address the concerns raised in [TALKING].		address the concerns raised in [TALKING].
	The server connection header consists of just a SETTINGS frame		The server connection header consists of just a SETTINGS frame
	(Section 3.8.4) that MUST be the first frame the server sends in the		(Section 6.5) that MUST be the first frame the server sends in the
	HTTP/2.0 connection.		HTTP/2.0 connection.
	To avoid unnecessary latency, clients are permitted to send		To avoid unnecessary latency, clients are permitted to send
	additional frames to the server immediately after sending the client		additional frames to the server immediately after sending the client
	connection header, without waiting to receive the server connection		connection header, without waiting to receive the server connection
	header. It is important to note, however, that the server connection		header. It is important to note, however, that the server connection
	header SETTINGS frame might include parameters that necessarily alter		header SETTINGS frame might include parameters that necessarily alter
	how a client is expected to communicate with the server. Upon		how a client is expected to communicate with the server. Upon
	receiving the SETTINGS frame, the client is expected to honor any		receiving the SETTINGS frame, the client is expected to honor any
	parameters established.		parameters established.
	Clients and servers MUST terminate the TCP connection if either peer		Clients and servers MUST terminate the TCP connection if either peer
	does not begin with a valid connection header. A GOAWAY frame		does not begin with a valid connection header. A GOAWAY frame
	(Section 3.8.7) MAY be omitted if it is clear that the peer is not		(Section 6.8) MAY be omitted if it is clear that the peer is not
	using HTTP/2.0.		using HTTP/2.0.
	3.3. Framing		4. HTTP Frames
	Once the HTTP/2.0 connection is established, clients and servers can		Once the HTTP/2.0 connection is established, endpoints can begin
	begin exchanging frames.		exchanging frames.
	3.3.1. Frame Header		4.1. Frame Header
	HTTP/2.0 frames share a common base format consisting of an 8-byte		All frames begin with an 8-octet header followed by a payload of
	header followed by 0 to 65535 bytes of data.		between 0 and 65,535 octets.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Length (16) | Type (8) | Flags (8) |		| Length (16) | Type (8) | Flags (8) |
	+-+-------------+---------------+-------------------------------+		+-+-------------+---------------+-------------------------------+
	|R| Stream Identifier (31) |		|R| Stream Identifier (31) |
	+-+-------------------------------------------------------------+		+-+-------------------------------------------------------------+
	| Frame Data (0...) ...		| Frame Payload (0...) ...
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	Frame Header		Frame Header
	The fields of the frame header are defined as:		The fields of the frame header are defined as:
	Length: The length of the frame data expressed as an unsigned 16-bit		Length: The length of the frame payload expressed as an unsigned 16-
	integer. The 8 bytes of the frame header are not included in this		bit integer. The 8 octets of the frame header are not included in
	value.		this value.
	Type: The 8-bit type of the frame. The frame type determines how		Type: The 8-bit type of the frame. The frame type determines how
	the remainder of the frame header and data are interpreted.		the remainder of the frame header and payload are interpreted.
	Implementations MUST ignore unsupported and unrecognized frame		Implementations MUST ignore unsupported and unrecognized frame
	types.		types.
	Flags: An 8-bit field reserved for frame-type specific boolean		Flags: An 8-bit field reserved for frame-type specific boolean
	flags.		flags.
	The least significant bit (0x1) - the FINAL bit - is defined for		Flags are assigned semantics specific to the indicated frame type.
	all frame types as an indication that this frame is the last the		Flags that have no defined semantics for a particular frame type
	endpoint will send for the identified stream. Setting this flag		MUST be ignored, and MUST be left unset (0) when sending.
	causes the stream to enter the half-closed state (Section 3.4.3).
	Implementations MUST process the FINAL bit for all frames whose
	stream identifier field is not 0x0. The FINAL bit MUST NOT be set
	on frames that use a stream identifier of 0.
	The remaining flags can be assigned semantics specific to the
	indicated frame type. Flags that have no defined semantics for a
	particular frame type MUST be ignored, and MUST be left unset (0)
	when sending.
	R: A reserved 1-bit field. The semantics of this bit are undefined		R: A reserved 1-bit field. The semantics of this bit are undefined
	and the bit MUST remain unset (0) when sending and MUST be ignored		and the bit MUST remain unset (0) when sending and MUST be ignored
	when receiving.		when receiving.
	Stream Identifier: A 31-bit stream identifier (see Section 3.4.1).		Stream Identifier: A 31-bit stream identifier (see Section 5.1.1).
	A value 0 is reserved for frames that are associated with the		A value 0 is reserved for frames that are associated with the
	connection as a whole as opposed to an individual stream.		connection as a whole as opposed to an individual stream.
	The structure and content of the remaining frame data is dependent		The structure and content of the frame payload is dependent entirely
	entirely on the frame type.		on the frame type.
	3.3.2. Frame Size		4.2. Frame Size
	Implementations with limited resources might not be capable of		The maximum size of a frame payload varies by frame type and use.
	processing large frame sizes. Such implementations MAY choose to		The absolute maximum size is 65,535 octets. All implementations
	place additional limits on the maximum frame size. However, all		SHOULD be capable of receiving and minimally processing frames up to
	implementations MUST be capable of receiving and processing frames		this size.
	containing at least 8192 octets of data. [[anchor6: Ed. Question:
	Does this minimum include the 8-byte header or just the frame data?]]
	An implementation MUST terminate a stream immediately if it is unable		Certain frame types, such as PING (see Section 6.7), impose
	to process a frame due it's size. This is done by sending an		additional limits on the amount of payload data allowed. Likewise,
	RST_STREAM frame (Section 3.8.3) containing the FRAME_TOO_LARGE error		additional size limits can be set by specific application uses (see
	code.		Section 9).
	[[anchor7: <https://github.com/http2/http2-spec/issues/28>: Need a		If a frame size exceeds any defined limit, or is too small to contain
	way to signal the maximum frame size; no way to RST_STREAM on non-		mandatory frame data, the endpoint MUST send a FRAME_TOO_LARGE error.
	stream-related frames.]]		Frame size errors in frames that affect connection-level state MUST
			be treated as a connection error (Section 5.4.1).
	3.4. Streams		4.3. Header Compression and Decompression
	A "stream" is an independent, bi-directional sequence of frames		A header in HTTP/2.0 is a name-value pair with one or more associated
	exchanged between the client and server within an HTTP/2.0		values. They are used within HTTP request and response messages as
	connection. Streams have several important characteristics:		well as server push operations (see Section 8.2).
	o Streams can be established and used unilaterally or shared by		Header sets are logical collections of zero or more header fields
	either the client or server.		arranged at the application layer. When transmitted over a
			connection, the header set is serialized into a header block using
			HTTP Header Compression [COMPRESSION]. The serialized header block
			is then divided into one or more octet sequences, called header block
			fragments, and transmitted within the payload of HEADERS
			(Section 6.2) or PUSH_PROMISE (Section 6.6) frames. The receiving
			endpoint reassembles the header block by concatenating the individual
			fragments, then decompresses the block to reconstruct the header set.
	o Streams can be rejected or cancelled by either endpoint.		Header block fragments can only be sent as the payload of HEADERS or
			PUSH_PROMISE frames.
	o Multiple types of frames can be sent by either endpoint within a		A compressed and encoded header block is transmitted in one or more
	single stream.		HEADERS or PUSH_PROMISE frames. If the number of octets in the block
			is greater than the space remaining in the frame, the block is
			divided into multiple fragments, which are then transmitted in
			multiple frames.
	o The order in which frames are sent within a stream is significant.		Header blocks MUST be transmitted as a contiguous sequence of frames,
	Recipients are required to process frames in the order they are		with no interleaved frames of any other type, or from any other
	received.		stream. The last frame in a sequence of HEADERS frames MUST have the
			END_HEADERS flag set. The last frame in a sequence of PUSH_PROMISE
			frames MUST have the END_PUSH_PROMISE flag set.
	o Streams optionally carry a set of name-value header pairs that are		HEADERS and PUSH_PROMISE frames carry data that can modify the
	expressed within the headers block of HEADERS+PRIORITY, HEADERS,		compression context maintained by a receiver. An endpoint receiving
	or PUSH_PROMISE frames.		HEADERS or PUSH_PROMISE frames MUST reassemble header blocks and
			perform decompression even if the frames are to be discarded, which
			is likely to occur after a stream is reset. A receiver MUST
			terminate the connection with a connection error (Section 5.4.1) of
			type COMPRESSION_ERROR, if it does not decompress a header block.
			5. Streams and Multiplexing
			A "stream" is an independent, bi-directional sequence of HEADER and
			DATA frames exchanged between the client and server within an
			HTTP/2.0 connection. Streams have several important characteristics:
	o A single HTTP/2.0 connection can contain multiple concurrently		o A single HTTP/2.0 connection can contain multiple concurrently
	active streams, with either endpoint interleaving frames from		active streams, with either endpoint interleaving frames from
	multiple streams.		multiple streams.
	3.4.1. Stream Creation		o Streams can be established and used unilaterally or shared by
			either the client or server.
	There is no coordination or shared action between the client and
	server required to create a stream. Rather, new streams are
	established by sending a frame whose stream identifier field
	references a previously unused stream identifier.
	All streams are identified by an unsigned 31-bit integer. Streams
	initiated by a client use odd numbered stream identifiers; those
	initiated by the server use even numbered stream identifiers. A
	stream identifier of zero MUST NOT be used to establish a new stream.
	The identifier of a newly established stream MUST be numerically
	greater than all previously established streams from that endpoint
	within the HTTP/2.0 connection, unless the identifier has been
	reserved using a PUSH_PROMISE (Section 3.8.5) frame. An endpoint
	that receives an unexpected stream identifier MUST respond with a
	connection error (Section 3.5.1) of type PROTOCOL_ERROR.
	A peer can limit the total number of concurrently active streams
	using the SETTINGS_MAX_CONCURRENT_STREAMS parameters within a
	SETTINGS frame. The maximum concurrent streams setting is specific
	to each endpoint and applies only to the peer. That is, clients
	specify the maximum number of concurrent streams the server can
	initiate, and servers specify the maximum number of concurrent
	streams the client can initiate. Peer endpoints MUST NOT exceed this
	limit. All concurrently active streams initiated by an endpoint,
	including streams that are half-open (Section 3.4.3) in any
	direction, count toward that endpoint's limit.
	Stream identifiers cannot be reused within a connection. Long-lived
	connections can cause an endpoint to exhaust the available range of
	stream identifiers. A client that is unable to establish a new
	stream identifier can establish a new connection for new streams.
	Either endpoint can request the early termination of an unwanted
	stream by sending an RST_STREAM frame (Section 3.5.2) with an error
	code of either REFUSED_STREAM (if no frames have been processed) or
	CANCEL (if at least one frame has been processed). Such termination
	might not take effect immediately as the peer might have sent
	additional frames on the stream prior to receiving the termination
	request.
	3.4.2. Stream priority
	The endpoint establishing a new stream can assign a priority for the		o Streams can be closed by either endpoint.
	stream. Priority is represented as an unsigned 31-bit integer. 0
	represents the highest priority and 2^31-1 represents the lowest
	priority.
	The purpose of this value is to allow the initiating endpoint to		o The order in which frames are sent within a stream is significant.
	request that frames for the stream be processed with higher priority		Recipients process frames in the order they are received.
	relative to any other concurrently active streams. That is, if an
	endpoint receives interleaved frames for multiple streams, the
	endpoint ought to make a best-effort attempt at processing frames for
	higher priority streams before processing those for lower priority
	streams.
	Explicitly setting the priority for a stream does not guarantee any		o Streams are identified by an integer. Stream identifiers are
	particular processing order for the stream relative to any other		assigned to streams by the endpoint that initiates a stream.
	stream. Nor is there is any mechanism provided by which the
	initiator of a stream can force or require a receiving endpoint to
	process frames from one stream before processing frames from another.
	3.4.3. Stream half-close		5.1. Stream States
	When an endpoint sends a frame for a stream with the FINAL flag set,		The lifecycle of a stream is shown in Figure 1.
	the stream is considered to be half-closed for that endpoint.
	Subsequent frames MUST NOT be sent by that endpoint for the half
	closed stream for the remaining duration of the HTTP/2.0 connection.
	When both endpoints have sent frames with the FINAL flag set, the
	stream is considered to be fully closed.
	If an endpoint receives additional frames for a stream that was		+--------+
	previously half-closed by the sending peer, the recipient MUST		PP | | PP
	respond with a stream error (Section 3.5.2) of type STREAM_CLOSED.		,--------| idle |--------.
			/ | | \
			v +--------+ v
			+----------+ | +----------+
			| | | H | |
			,---| reserved | | | reserved |---.
			| | (local) | v | (remote) | |
			| +----------+ +--------+ +----------+ |
			| | ES | | ES | |
			| | H ,-------| open |-------. | H |
			| | / | | \ | |
			| v v +--------+ v v |
			| +----------+ | +----------+ |
			| | half | | | half | |
			| | closed | | R | closed | |
			| | (remote) | | | (local) | |
			| +----------+ | +----------+ |
			| | v | |
			| | ES / R +--------+ ES / R | |
			| `----------->| |<-----------' |
			| R | closed | R |
			`-------------------->| |<--------------------'
			+--------+
	An endpoint that has not yet half-closed a stream by sending the		Figure 1: Stream States
	FINAL flag can continue sending frames on the stream.
	It is not necessary for an endpoint to half-close a stream for which		Both endpoints have a subjective view of the state of a stream that
	it has not sent any frames. This allows endpoints to use fully		could be different when frames are in transit. Endpoints do not
	unidirectional streams that do not require explicit action or		coordinate the creation of streams, they are created unilaterally by
	acknowledgement from the receiver.		either endpoint. The negative consequences of a mismatch in states
			are limited to the "closed" state after sending RST_STREAM, where
			frames might be received for some time after closing.
	3.4.4. Stream close		Streams have the following states:
	Streams can be terminated in the following ways:		idle:
			All streams start in the "idle" state. In this state, no frames
			have been exchanged.
	Normal termination: Normal stream termination occurs when both		The following transitions are valid from this state:
	client and server have half-closed the stream by sending a frame
	containing a FINAL flag (Section 3.3.1).
	Half-close on unidirectional stream: A stream that only has frames		* Sending or receiving a HEADERS frame causes the stream to
	sent in one direction can be tentatively considered to be closed		become "open". The stream identifier is selected as described
	once a frame containing a FINAL flag is sent. The active sender		in Section 5.1.1.
	on the stream MUST be prepared to receive frames after closing the
	stream.
	Abrupt termination: Either peer can send a RST_STREAM control frame		* Sending a PUSH_PROMISE frame marks the associated stream for
	at any time to terminate an active stream. RST_STREAM contains an		later use. The stream state for the reserved stream
	error code to indicate the reason for termination. A RST_STREAM		transitions to "reserved (local)".
	indicates that the sender will transmit no further data on the
	stream and that the receiver is advised to cease transmission on
	it.
	The sender of a RST_STREAM frame MUST allow for frames that have		* Receiving a PUSH_PROMISE frame marks the associated stream as
	already been sent by the peer prior to the RST_STREAM being		reserved by the remote peer. The state of the stream becomes
	processed. If in-transit frames alter connection state, these		"reserved (remote)".
	frames cannot be safely discarded. See Stream Error Handling
	(Section 3.5.2) for more details.
	TCP connection teardown: If the TCP connection is torn down while		reserved (local):
	un-closed streams exist, then the endpoint MUST assume that the		A stream in the "reserved (local)" state is one that has been
	stream was abnormally interrupted and may be incomplete.		promised by sending a PUSH_PROMISE frame. A PUSH_PROMISE frame
			reserves an idle stream by associating the stream with an open
			stream that was initiated by the remote peer (see Section 8.2).
	3.5. Error Handling		In this state, only the following transitions are possible:
	HTTP/2.0 framing permits two classes of error:		* The endpoint can send a HEADERS frame. This causes the stream
			to open in a "half closed (remote)" state.
	o An error condition that renders the entire connection unusable is		* Either endpoint can send a RST_STREAM frame to cause the stream
	a connection error.		to become "closed". This releases the stream reservation.
	o An error in an individual stream is a stream error.		An endpoint MUST NOT send any other type of frame in this state.
	3.5.1. Connection Error Handling		reserved (remote):
			A stream in the "reserved (remote)" state has been reserved by a
			remote peer.
	A connection error is any error which prevents further processing of		In this state, only the following transitions are possible:
	the framing layer or which corrupts any connection state.
	An endpoint that encounters a connection error MUST first send a		* Receiving a HEADERS frame causes the stream to transition to
	GOAWAY (Section 3.8.7) frame with the stream identifier of the last		"half closed (local)".
	stream that it successfully received from its peer. The GOAWAY frame
	includes an error code that indicates why the connection is
	terminating. After sending the GOAWAY frame, the endpoint MUST close
	the TCP connection.
	It is possible that the GOAWAY will not be reliably received by the		* Either endpoint can send a RST_STREAM frame to cause the stream
	receiving endpoint. In the event of a connection error, GOAWAY only		to become "closed". This releases the stream reservation.
	provides a best-effort attempt to communicate with the peer about why
	the connection is being terminated.
	An endpoint can end a connection at any time. In particular, an		Receiving any other type of frame MUST be treated as a stream
	endpoint MAY choose to treat a stream error as a connection error if		error (Section 5.4.2) of type PROTOCOL_ERROR.
	the error is recurrent. Endpoints SHOULD send a GOAWAY frame when
	ending a connection, as long as circumstances permit it.
	3.5.2. Stream Error Handling		open:
			The "open" state is where both peers can send frames. In this
			state, sending peers observe advertised stream level flow control
			limits (Section 5.2).
	A stream error is an error related to a specific stream identifier		From this state either endpoint can send a frame with a END_STREAM
	that does not affect processing of other streams at the framing		flag set, which causes the stream to transition into one of the
	layer.		"half closed" states: an endpoint sending a END_STREAM flag causes
			the stream state to become "half closed (local)"; an endpoint
			receiving a END_STREAM flag causes the stream state to become
			"half closed (remote)".
	An endpoint that detects a stream error sends a RST_STREAM		Either endpoint can send a RST_STREAM frame from this state,
	(Section 3.8.3) frame that contains the stream identifier of the		causing it to transition immediately to "closed".
	stream where the error occurred. The RST_STREAM frame includes an
	error code that indicates the type of error.
	A RST_STREAM is the last frame that an endpoint can send on a stream.		half closed (local):
	The peer that sends the RST_STREAM frame MUST be prepared to receive		A stream that is "half closed (local)" cannot be used for sending
	any frames that were sent or enqueued for sending by the remote peer.		frames.
	These frames can be ignored, except where they modify connection
	state (such as the state maintained for header compression
	(Section 3.7)).
	Normally, an endpoint SHOULD NOT send more than one RST_STREAM frame		A stream transitions from this state to "closed" when a frame that
	for any stream. However, an endpoint MAY send additional RST_STREAM		contains a END_STREAM flag is received, or when either peer sends
	frames if it receives frames on a closed stream after more than a		a RST_STREAM frame.
	round trip time. This behavior is permitted to deal with misbehaving
	implementations.
	An endpoint MUST NOT send a RST_STREAM in response to an RST_STREAM		half closed (remote):
	frame, to avoid looping.		A stream that is "half closed (remote)" is no longer being used by
			the peer to send frames. In this state, an endpoint is no longer
			obligated to maintain a receiver flow control window if it
			performs flow control.
	3.5.3. Error Codes		If an endpoint receives additional frames for a stream that is in
			this state it MUST respond with a stream error (Section 5.4.2) of
			type STREAM_CLOSED.
	Error codes are 32-bit fields that are used in RST_STREAM and GOAWAY		A stream can transition from this state to "closed" by sending a
	frames to convey the reasons for the stream or connection error.		frame that contains a END_STREAM flag, or when either peer sends a
			RST_STREAM frame.
	Error codes share a common code space. Some error codes only apply		closed:
	to specific conditions and have no defined semantics in certain frame		The "closed" state is the terminal state.
	types.
	The following error codes are defined:		An endpoint MUST NOT send frames on a closed stream. An endpoint
			that receives a frame after receiving a RST_STREAM or a frame
			containing a END_STREAM flag on that stream MUST treat that as a
			stream error (Section 5.4.2) of type STREAM_CLOSED.
	NO_ERROR (0): The associated condition is not as a result of an		If this state is reached as a result of sending a RST_STREAM
	error. For example, a GOAWAY might include this code to indicate		frame, the peer that receives the RST_STREAM might have already
	graceful shutdown of a connection.		sent - or enqueued for sending - frames on the stream that cannot
			be withdrawn. An endpoint that sends a RST_STREAM frame MUST
			ignore frames that it receives on closed streams after it has sent
			a RST_STREAM frame. An endpoint MAY choose to limit the period
			over which it ignores frames and treat frames that arrive after
			this time as being in error.
	PROTOCOL_ERROR (1): The endpoint detected an unspecific protocol		An endpoint might receive a PUSH_PROMISE frame after it sends
	error. This error is for use when a more specific error code is		RST_STREAM. PUSH_PROMISE causes a stream to become "reserved".
	not available.		If promised streams are not desired, a RST_STREAM can be used to
			close any of those streams.
	INTERNAL_ERROR (2): The endpoint encountered an unexpected internal		5.1.1. Stream Identifiers
	error.
	FLOW_CONTROL_ERROR (3): The endpoint detected that its peer violated		Streams are identified with an unsigned 31-bit integer. Streams
	the flow control protocol.		initiated by a client MUST use odd-numbered stream identifiers; those
			initiated by the server MUST use even-numbered stream identifiers. A
			stream identifier of zero (0x0) is used for connection control
			message; the stream identifier zero MUST NOT be used to establish a
			new stream.
	INVALID_STREAM (4): The endpoint received a frame for an inactive		The identifier of a newly established stream MUST be numerically
	stream.		greater than all streams that the initiating endpoint has opened or
			reserved. This governs streams that are opened using a HEADERS frame
			and streams that are reserved using PUSH_PROMISE. An endpoint that
			receives an unexpected stream identifier MUST respond with a
			connection error (Section 5.4.1) of type PROTOCOL_ERROR.
	STREAM_CLOSED (5): The endpoint received a frame after a stream was		Stream identifiers cannot be reused. Long-lived connections can
	half-closed.		result in endpoint exhausting the available range of stream
			identifiers. A client that is unable to establish a new stream
			identifier can establish a new connection for new streams.
	FRAME_TOO_LARGE (6): The endpoint received a frame that was larger		5.1.2. Stream Concurrency
	than the maximum size that it supports.
	REFUSED_STREAM (7): The endpoint is refusing the stream before		A peer can limit the number of concurrently active streams using the
	processing its payload.		SETTINGS_MAX_CONCURRENT_STREAMS parameters within a SETTINGS frame.
			The maximum concurrent streams setting is specific to each endpoint
			and applies only to the peer that receives the setting. That is,
			clients specify the maximum number of concurrent streams the server
			can initiate, and servers specify the maximum number of concurrent
			streams the client can initiate. Endpoints MUST NOT exceed the limit
			set by their peer.
	CANCEL (8): Used by the creator of a stream to indicate that the		Streams that are in the "open" state, or either of the "half closed"
	stream is no longer needed.		states count toward the maximum number of streams that an endpoint is
			permitted to open. Streams in any of these three states count toward
			the limit advertised in the SETTINGS_MAX_CONCURRENT_STREAMS setting
			(see Section 6.5.2).
	COMPRESSION_ERROR (9): The endpoint is unable to maintain the		Streams in either of the "reserved" states do not count as open, even
	compression context for the connection.		if a small amount of application state is retained to ensure that the
			promised stream can be successfully used.
	3.6. Stream Flow Control		5.2. Flow Control
	Using streams for multiplexing introduces contention over use of the		Using streams for multiplexing introduces contention over use of the
	TCP connection, resulting in blocked streams. A flow control scheme		TCP connection, resulting in blocked streams. A flow control scheme
	ensures that streams on the same connection do not destructively		ensures that streams on the same connection do not destructively
	interfere with each other.		interfere with each other. Flow control is used for both individual
			streams and for the connection as a whole.
	HTTP/2.0 provides for flow control through use of the WINDOW_UPDATE		HTTP/2.0 provides for flow control through use of the WINDOW_UPDATE
	(Section 3.8.9) frame type.		(Section 6.9) frame type.
	3.6.1. Flow Control Principles		5.2.1. Flow Control Principles
	Experience with TCP congestion control has shown that algorithms can		Experience with TCP congestion control has shown that algorithms can
	evolve over time to become more sophisticated without requiring		evolve over time to become more sophisticated without requiring
	protocol changes. TCP congestion control and its evolution is		protocol changes. TCP congestion control and its evolution is
	clearly different from HTTP/2.0 flow control, though the evolution of		clearly different from HTTP/2.0 flow control, though the evolution of
	TCP congestion control algorithms shows that a similar approach could		TCP congestion control algorithms shows that a similar approach could
	be feasible for HTTP/2.0 flow control.		be feasible for HTTP/2.0 flow control.
	HTTP/2.0 stream flow control aims to allow for future improvements to		HTTP/2.0 stream flow control aims to allow for future improvements to
	flow control algorithms without requiring protocol changes. Flow		flow control algorithms without requiring protocol changes. Flow
	control in HTTP/2.0 has the following characteristics:		control in HTTP/2.0 has the following characteristics:
	1. Flow control is hop-by-hop, not end-to-end.		1. Flow control is hop-by-hop, not end-to-end.
	2. Flow control is based on window update frames. Receivers		2. Flow control is based on window update frames. Receivers
	advertise how many octets they are prepared to receive on a		advertise how many bytes they are prepared to receive on a stream
	stream. This is a credit-based scheme.		and for the entire connection. This is a credit-based scheme.
	3. Flow control is directional with overall control provided by the		3. Flow control is directional with overall control provided by the
	receiver. A receiver MAY choose to set any window size that it		receiver. A receiver MAY choose to set any window size that it
	desires for each stream and for the entire connection. A sender		desires for each stream and for the entire connection. A sender
	MUST respect flow control limits imposed by a receiver. Clients,		MUST respect flow control limits imposed by a receiver. Clients,
	servers and intermediaries all independently advertise their flow		servers and intermediaries all independently advertise their flow
	control preferences as a receiver and abide by the flow control		control preferences as a receiver and abide by the flow control
	limits set by their peer when sending.		limits set by their peer when sending.
	4. The initial value for the flow control window is 65536 bytes for		4. The initial value for the flow control window is 65536 bytes for
	both new streams and the overall connection.		both new streams and the overall connection.
	5. The frame type determines whether flow control applies to a		5. The frame type determines whether flow control applies to a
	frame. Of the frames specified in this document, only data		frame. Of the frames specified in this document, only DATA
	frames are subject to flow control; all other frame types do not		frames are subject to flow control; all other frame types do not
	consume space in the advertised flow control window. This		consume space in the advertised flow control window. This
	ensures that important control frames are not blocked by flow		ensures that important control frames are not blocked by flow
	control.		control.
	6. Flow control can be disabled by a receiver. A receiver can		6. Flow control can be disabled by a receiver. A receiver can
	choose to either disable flow control for a stream or connection		choose to either disable flow control for a stream or connection
	by declaring an infinite flow control limit.		by sending a window update frame with a specific flag. See
			Ending Flow Control (Section 6.9.4) for more details.
	7. HTTP/2.0 standardizes only the format of the window update frame		7. HTTP/2.0 standardizes only the format of the WINDOW_UPDATE frame
	(Section 3.8.9). This does not stipulate how a receiver decides		(Section 6.9). This does not stipulate how a receiver decides
	when to send this frame or the value that it sends. Nor does it		when to send this frame or the value that it sends. Nor does it
	specify how a sender chooses to send packets. Implementations		specify how a sender chooses to send packets. Implementations
	are able to select any algorithm that suits their needs.		are able to select any algorithm that suits their needs.
	Implementations are also responsible for managing how requests and		Implementations are also responsible for managing how requests and
	responses are sent based on priority; choosing how to avoid head of		responses are sent based on priority; choosing how to avoid head of
	line blocking for requests; and managing the creation of new streams.		line blocking for requests; and managing the creation of new streams.
	Algorithm choices for these could interact with any flow control		Algorithm choices for these could interact with any flow control
	algorithm.		algorithm.
	3.6.2. Appropriate Use of Flow Control		5.2.2. Appropriate Use of Flow Control
	Flow control is defined to protect endpoints (client, server or		Flow control is defined to protect endpoints that are operating under
	intermediary) that are operating under resource constraints. For		resource constraints. For example, a proxy needs to share memory
	example, a proxy needs to share memory between many connections, and		between many connections, and also might have a slow upstream
	also might have a slow upstream connection and a fast downstream one.		connection and a fast downstream one. Flow control addresses cases
	Flow control addresses cases where the receiver is unable process		where the receiver is unable process data on one stream, yet wants to
	data on one stream, yet wants to continue to process other streams in		continue to process other streams in the same connection.
	the same connection.
	Deployments that do not require this capability SHOULD disable flow		Deployments that do not require this capability SHOULD disable flow
	control for data that is being received. Note that flow control		control for data that is being received. Note that flow control
	cannot be disabled for sending. Sending data is always subject to		cannot be disabled for sending. Sending data is always subject to
	the flow control window advertised by the receiver.		the flow control window advertised by the receiver.
	Deployments with constrained resources (for example, memory) MAY		Deployments with constrained resources (for example, memory) MAY
	employ flow control to limit the amount of memory a peer can consume.		employ flow control to limit the amount of memory a peer can consume.
	Note, however, that this can lead to suboptimal use of available		Note, however, that this can lead to suboptimal use of available
	network resources if flow control is enabled without knowledge of the		network resources if flow control is enabled without knowledge of the
	bandwidth-delay product (see [RFC1323]).		bandwidth-delay product (see [RFC1323]).
	Even with full awareness of the current bandwidth-delay product,		Even with full awareness of the current bandwidth-delay product,
	implementation of flow control is difficult. However, it can ensure		implementation of flow control is difficult. However, it can ensure
	that constrained resources are protected without any reduction in		that constrained resources are protected without any reduction in
	connection utilization.		connection utilization.
	3.7. Header Blocks		5.3. Stream priority
	The header block is found in the HEADERS, HEADERS+PRIORITY and		The endpoint establishing a new stream can assign a priority for the
	PUSH_PROMISE frames. The header block consists of a set of header		stream. Priority is represented as an unsigned 31-bit integer. 0
	fields, which are name-value pairs. Headers are compressed using		represents the highest priority and 2^31-1 represents the lowest
	black magic.		priority.
	Compression of header fields is a work in progress, as is the format		The purpose of this value is to allow the initiating endpoint to
	of this block.		request that frames for the stream be processed with a specified
			priority relative to other concurrently active streams. That is, if
			an endpoint receives interleaved frames for multiple streams, the
			endpoint ought to make a best-effort attempt at processing frames for
			higher priority streams before processing those for lower priority
			streams.
	The contents of header blocks MUST be processed by the compression		Explicitly setting the priority for a stream does not guarantee any
	context, even if stream has been reset or the frame is discarded. If		particular processing order for the stream relative to any other
	header blocks cannot be processed, the receiver MUST treat the		stream. Nor is there any mechanism provided by which the initiator
	connection with a connection error (Section 3.5.1) of type		of a stream can force or require a receiving endpoint to process
	COMPRESSION_ERROR.		frames from one stream before processing frames from another.
	3.8. Frame Types		Unless explicitly specified in the HEADERS frame (Section 6.2) during
			stream creation, the default stream priority is 2^30. Pushed streams
			(Section 8.2) are assumed to inherit the priority of the associated
			stream plus one (or 2^31-1 if the the associated stream priority is
			2^31-1), i.e. they have priority one lower than the associated
			stream.
			5.4. Error Handling
			HTTP/2.0 framing permits two classes of error:
			o An error condition that renders the entire connection unusable is
			a connection error.
			o An error in an individual stream is a stream error.
			A list of error codes is included in Section 7.
			5.4.1. Connection Error Handling
			A connection error is any error which prevents further processing of
			the framing layer or which corrupts any connection state.
			An endpoint that encounters a connection error SHOULD first send a
			GOAWAY (Section 6.8) frame with the stream identifier of the last
			stream that it successfully received from its peer. The GOAWAY frame
			includes an error code that indicates why the connection is
			terminating. After sending the GOAWAY frame, the endpoint MUST close
			the TCP connection.
			It is possible that the GOAWAY will not be reliably received by the
			receiving endpoint. In the event of a connection error, GOAWAY only
			provides a best-effort attempt to communicate with the peer about why
			the connection is being terminated.
			An endpoint can end a connection at any time. In particular, an
			endpoint MAY choose to treat a stream error as a connection error if
			the error is recurrent. Endpoints SHOULD send a GOAWAY frame when
			ending a connection, as long as circumstances permit it.
			5.4.2. Stream Error Handling
			A stream error is an error related to a specific stream identifier
			that does not affect processing of other streams.
			An endpoint that detects a stream error sends a RST_STREAM
			(Section 6.4) frame that contains the stream identifier of the stream
			where the error occurred. The RST_STREAM frame includes an error
			code that indicates the type of error.
			A RST_STREAM is the last frame that an endpoint can send on a stream.
			The peer that sends the RST_STREAM frame MUST be prepared to receive
			any frames that were sent or enqueued for sending by the remote peer.
			These frames can be ignored, except where they modify connection
			state (such as the state maintained for header compression
			(Section 4.3)).
			Normally, an endpoint SHOULD NOT send more than one RST_STREAM frame
			for any stream. However, an endpoint MAY send additional RST_STREAM
			frames if it receives frames on a closed stream after more than a
			round trip time. This behavior is permitted to deal with misbehaving
			implementations.
			An endpoint MUST NOT send a RST_STREAM in response to an RST_STREAM
			frame, to avoid looping.
			5.4.3. Connection Termination
			If the TCP connection is torn down while streams remain in open or
			half closed states, then the endpoint MUST assume that the stream was
			abnormally interrupted and could be incomplete.
			6. Frame Definitions
	This specification defines a number of frame types, each identified		This specification defines a number of frame types, each identified
	by a unique 8-bit type code. Each frame type serves a distinct		by a unique 8-bit type code. Each frame type serves a distinct
	purpose either in the establishment and management of the connection		purpose either in the establishment and management of the connection
	as a whole, or of individual streams.		as a whole, or of individual streams.
	The transmission of specific frame types can alter the state of a		The transmission of specific frame types can alter the state of a
	connection. If endpoints fail to maintain a synchronized view of the		connection. If endpoints fail to maintain a synchronized view of the
	connection state, successful communication within the connection will		connection state, successful communication within the connection will
	no longer be possible. Therefore, it is important that endpoints		no longer be possible. Therefore, it is important that endpoints
	have a shared comprehension of how the state is affected by the use		have a shared comprehension of how the state is affected by the use
	any given frame. Accordingly, while it is expected that new frame		any given frame. Accordingly, while it is expected that new frame
	types will be introduced by extensions to this protocol, only frames		types will be introduced by extensions to this protocol, only frames
	defined by this document are permitted to alter the connection state.		defined by this document are permitted to alter the connection state.
	3.8.1. DATA Frames		6.1. DATA
	DATA frames (type=0x0) convey arbitrary, variable-length sequences of		DATA frames (type=0x0) convey arbitrary, variable-length sequences of
	octets associated with a stream. One or more DATA frames are used,		octets associated with a stream. One or more DATA frames are used,
	for instance, to carry HTTP request or response payloads.		for instance, to carry HTTP request or response payloads.
	The DATA frame does not define any type-specific flags.		The DATA frame defines the following flags:
			END_STREAM (0x1): Bit 1 being set indicates that this frame is the
			last that the endpoint will send for the identified stream.
			Setting this flag causes the stream to enter a "half closed" state
			(Section 5.1).
			RESERVED (0x2): Bit 2 is reserved for future use.
	DATA frames MUST be associated with a stream. If a DATA frame is		DATA frames MUST be associated with a stream. If a DATA frame is
	received whose stream identifier field is 0x0, the recipient MUST		received whose stream identifier field is 0x0, the recipient MUST
	respond with a connection error (Section 3.5.1) of type		respond with a connection error (Section 5.4.1) of type
	PROTOCOL_ERROR.		PROTOCOL_ERROR.
	3.8.2. HEADERS+PRIORITY		6.2. HEADERS
	The HEADERS+PRIORITY frame (type=0x1) allows the sender to set header		The HEADERS frame (type=0x1) carries name-value pairs. The HEADERS
	fields and stream priority at the same time.		is used to open a stream (Section 5.1). Any number of HEADERS frames
			can be sent on an existing stream at any time.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|X| Priority (31) |		|X| Priority (31) |
	+-+-------------------------------------------------------------+		+-+-------------------------------------------------------------+
	| Header Block (*) ...		| Header Block Fragment (*) ...
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	HEADERS+PRIORITY Frame Payload		HEADERS Frame Payload
	The HEADERS+PRIORITY frame is identical to the HEADERS frame		The HEADERS frame defines the following flags:
	(Section 3.8.8), preceded by a single reserved bit and a 31-bit
	priority; see Section 3.4.2.
	HEADERS+PRIORITY uses the same flags as the HEADERS frame, except		END_STREAM (0x1): Bit 1 being set indicates that this frame is the
	that a HEADERS+PRIORITY frame with a CONTINUES bit MUST be followed		last that the endpoint will send for the identified stream.
	by another HEADERS+PRIORITY frame. See HEADERS frame (Section 3.8.8)		Setting this flag causes the stream to enter a "half closed" state
	for any flags.		(Section 5.1).
	HEADERS+PRIORITY frames MUST be associated with a stream. If a		RESERVED (0x2): Bit 2 is reserved for future use.
	HEADERS+PRIORITY frame is received whose stream identifier field is
	0x0, the recipient MUST respond with a connection error
	(Section 3.5.1) of type PROTOCOL_ERROR.
	The HEADERS+PRIORITY frame modifies the connection state as defined		END_HEADERS (0x4): The END_HEADERS bit indicates that this frame
	in Section 3.7.		ends the sequence of header block fragments necessary to provide a
			complete set of headers.
	3.8.3. RST_STREAM		The payload for a complete header block is provided by a sequence
			of HEADERS frames, terminated by a HEADERS frame with the
			END_HEADERS flag set. Once the sequence terminates, the payload
			of all HEADERS frames are concatenated and interpreted as a single
			block.
			A HEADERS frame without the END_HEADERS flag set MUST be followed
			by a HEADERS frame for the same stream. A receiver MUST treat the
			receipt of any other type of frame or a frame on a different
			stream as a connection error (Section 5.4.1) of type
			PROTOCOL_ERROR.
			PRIORITY (0x8): Bit 4 being set indicates that the first four octets
			of this frame contain a single reserved bit and a 31-bit priority;
			see Section 5.3. If this bit is not set, the four bytes do not
			appear and the frame only contains a header block fragment.
			The payload of a HEADERS frame contains a header block fragment
			(Section 4.3).
			HEADERS frames MUST be associated with a stream. If a HEADERS frame
			is received whose stream identifier field is 0x0, the recipient MUST
			respond with a connection error (Section 5.4.1) of type
			PROTOCOL_ERROR.
			The HEADERS frame changes the connection state as defined in
			Section 4.3.
			6.3. PRIORITY
			The PRIORITY frame (type=0x2) specifies the sender-advised priority
			of a stream. It can be sent at any time for an existing stream.
			This enables reprioritisation of existing streams.
			0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			|X| Priority (31) |
			+-+-------------------------------------------------------------+
			PRIORITY Frame Payload
			The payload of a PRIORITY frame contains a single reserved bit and a
			31-bit priority.
			The PRIORITY frame does not define any flags.
			The PRIORITY frame is associated with an existing stream. If a
			PRIORITY frame is received with a stream identifier of 0x0, the
			recipient MUST respond with a connection error (Section 5.4.1) of
			type PROTOCOL_ERROR.
			6.4. RST_STREAM
	The RST_STREAM frame (type=0x3) allows for abnormal termination of a		The RST_STREAM frame (type=0x3) allows for abnormal termination of a
	stream. When sent by the initiator of a stream, it indicates that		stream. When sent by the initiator of a stream, it indicates that
	they wish to cancel the stream. When sent by the receiver of a		they wish to cancel the stream or that an error condition has
	stream, it indicates that either the receiver is rejecting the		occurred. When sent by the receiver of a stream, it indicates that
	stream, requesting that the stream be cancelled or that an error		either the receiver is rejecting the stream, requesting that the
	condition has occurred.		stream be cancelled or that an error condition has occurred.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Error Code (32) |		| Error Code (32) |
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	RST_STREAM Frame Payload		RST_STREAM Frame Payload
	The RST_STREAM frame contains a single unsigned, 32-bit integer		The RST_STREAM frame contains a single unsigned, 32-bit integer
	identifying the error code (Section 3.5.3). The error code indicates		identifying the error code (Section 7). The error code indicates why
	why the stream is being terminated.		the stream is being terminated.
	No type-flags are defined.		The RST_STREAM frame does not define any flags.
	The RST_STREAM frame fully terminates the referenced stream and		The RST_STREAM frame fully terminates the referenced stream and
	causes it to enter the closed state. After receiving a RST_STREAM on		causes it to enter the closed state. After receiving a RST_STREAM on
	a stream, the receiver MUST NOT send additional frames for that		a stream, the receiver MUST NOT send additional frames for that
	stream. However, after sending the RST_STREAM, the sending endpoint		stream. However, after sending the RST_STREAM, the sending endpoint
	MUST be prepared to receive and process additional frames sent on the		MUST be prepared to receive and process additional frames sent on the
	stream that might have been sent by the peer prior to the arrival of		stream that might have been sent by the peer prior to the arrival of
	the RST_STREAM.		the RST_STREAM.
	RST_STREAM frames MUST be associated with a stream. If a RST_STREAM		RST_STREAM frames MUST be associated with a stream. If a RST_STREAM
	frame is received whose stream identifier field is 0x0 the recipient		frame is received whose stream identifier field is 0x0 the recipient
	MUST respond with a connection error (Section 3.5.1) of type		MUST respond with a connection error (Section 5.4.1) of type
	PROTOCOL_ERROR.		PROTOCOL_ERROR.
	3.8.4. SETTINGS		6.5. SETTINGS
	The SETTINGS frame (type=0x4) conveys configuration parameters that		The SETTINGS frame (type=0x4) conveys configuration parameters that
	affect how endpoints communicate. The parameters are either		affect how endpoints communicate. The parameters are either
	constraints on peer behavior or preferences.		constraints on peer behavior or preferences.
	SETTINGS frames MUST be sent at the start of a connection, and MAY be		SETTINGS frames MUST be sent at the start of a connection, and MAY be
	sent at any other time by either endpoint over the lifetime of the		sent at any other time by either endpoint over the lifetime of the
	connection.		connection.
	Implementations MUST support all of the settings defined by this		Implementations MUST support all of the settings defined by this
	specification and MAY support additional settings defined by		specification and MAY support additional settings defined by
	extensions. Unsupported or unrecognized settings MUST be ignored.		extensions. Unsupported or unrecognized settings MUST be ignored.
	New settings MUST NOT be defined or implemented in a way that		New settings MUST NOT be defined or implemented in a way that
	requires endpoints to understand then in order to communicate		requires endpoints to understand them in order to communicate
	successfully.		successfully.
	A SETTINGS frame is not required to include every defined setting;		A SETTINGS frame is not required to include every defined setting;
	senders can include only those parameters for which it has accurate		senders can include only those parameters for which it has accurate
	values and a need to convey. When multiple parameters are sent, they		values and a need to convey. When multiple parameters are sent, they
	SHOULD be sent in order of numerically lowest ID to highest ID. A		SHOULD be sent in order of numerically lowest ID to highest ID. A
	single SETTINGS frame MUST NOT contain multiple values for the same		single SETTINGS frame MUST NOT contain multiple values for the same
	ID. If the receiver of a SETTINGS frame discovers multiple values		ID. If the receiver of a SETTINGS frame discovers multiple values
	for the same ID, it MUST ignore all values for that ID except the		for the same ID, it MUST ignore all values for that ID except the
	first one.		first one.
	Over the lifetime of a connection, an endpoint MAY send multiple		Over the lifetime of a connection, an endpoint MAY send multiple
	SETTINGS frames containing previously unspecified parameters or new		SETTINGS frames containing previously unspecified parameters or new
	values for parameters whose values have already been established.		values for parameters whose values have already been established.
	Only the most recent value provided setting value applies.		Only the most recent provided setting value applies.
	The SETTINGS frame defines the following flag:
	CLEAR_PERSISTED (0x2): Bit 2 being set indicates a request to clear		The SETTINGS frame does not define any flags.
	any previously persisted settings before processing the settings.
	Clients MUST NOT set this flag.
	SETTINGS frames always apply to a connection, never a single stream.		SETTINGS frames always apply to a connection, never a single stream.
	The stream identifier for a settings frame MUST be zero. If an		The stream identifier for a settings frame MUST be zero. If an
	endpoint receives a SETTINGS frame whose stream identifier field is		endpoint receives a SETTINGS frame whose stream identifier field is
	anything other than 0x0, the endpoint MUST respond with a connection		anything other than 0x0, the endpoint MUST respond with a connection
	error (Section 3.5.1) of type PROTOCOL_ERROR.		error (Section 5.4.1) of type PROTOCOL_ERROR.
	3.8.4.1. Setting Format		The SETTINGS frame affects connection state. A badly formed or
			incomplete SETTINGS frame MUST be treated as a connection error
			(Section 5.4.1).
			6.5.1. Setting Format
	The payload of a SETTINGS frame consists of zero or more settings.		The payload of a SETTINGS frame consists of zero or more settings.
	Each setting consists of an 8-bit flags field specifying per-item		Each setting consists of an 8-bit reserved field, an unsigned 24-bit
	instructions, an unsigned 24-bit setting identifier, and an unsigned		setting identifier, and an unsigned 32-bit value.
	32-bit value.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|SettingFlags(8)| Setting Identifier (24) |		| Reserved (8) | Setting Identifier (24) |
	+---------------+-----------------------------------------------+		+---------------+-----------------------------------------------+
	| Value (32) |		| Value (32) |
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	Setting Format
	Two flags are defined for the 8-bit flags field:
	PERSIST_VALUE (0x1): Bit 1 (the least significant bit) being set
	indicates a request from the server to the client to persist this
	setting. A client MUST NOT set this flag.
	PERSISTED (0x2): Bit 2 being set indicates that this setting is a
	persisted setting being returned by the client to the server.
	This also indicates that this setting is not a client setting, but
	a value previously set by the server. A server MUST NOT set this
	flag.
	3.8.4.2. Setting Persistence
	[[anchor12: Note that persistence of settings is under discussion in
	the WG and might be removed in a future version of this document.]]
	A server endpoint can request that configuration parameters sent to a
	client in a SETTINGS frame are to be persisted by the client across
	HTTP/2.0 connections and returned to the server in any new SETTINGS
	frame the client sends to the server in the current connection or any
	future connections.
	Persistence is requested on a per-setting basis by setting the
	PERSIST_VALUE flag (0x1).
	Client endpoints are not permitted to make such requests. Servers
	MUST ignore any attempt by clients to request that a server persist
	configuration parameters.
	Persistence of configuration parameters is done on a per-origin basis
	(see [RFC6454]). That is, when a client establishes a connection
	with a server, and the server requests that the client maintain
	persistent settings, the client SHOULD return the persisted settings
	on all future connections to the same origin, IP address and TCP
	port.
	Whenever the client sends a SETTINGS frame in the current connection,
	or establishes a new connection with the same origin, persisted
	configuration parameters are sent with the PERSISTED flag (0x2) set
	for each persisted parameter.
	Persisted settings accumulate until the server requests that all
	previously persisted settings are to be cleared by setting the
	CLEAR_PERSISTED (0x2) flag on the SETTINGS frame.
	For example, if the server sends IDs 1, 2, and 3 with the		Setting Format
	FLAG_SETTINGS_PERSIST_VALUE in a first SETTINGS frame, and then sends
	IDs 4 and 5 with the FLAG_SETTINGS_PERSIST_VALUE in a subsequent
	SETTINGS frame, the client will return values for all 5 settings (1,
	2, 3, 4, and 5 in this example) to the server.
	3.8.4.3. Defined Settings		6.5.2. Defined Settings
	The following settings are defined:		The following settings are defined:
	SETTINGS_UPLOAD_BANDWIDTH (1): indicates the sender's estimated
	upload bandwidth for this connection. The value is an the
	integral number of kilobytes per second that the sender predicts
	as an expected maximum upload channel capacity.
	SETTINGS_DOWNLOAD_BANDWIDTH (2): indicates the sender's estimated
	download bandwidth for this connection. The value is an integral
	number of kilobytes per second that the sender predicts as an
	expected maximum download channel capacity.
	SETTINGS_ROUND_TRIP_TIME (3): indicates the sender's estimated
	round-trip-time for this connection. The round trip time is
	defined as the minimum amount of time to send a control frame from
	this client to the remote and receive a response. The value is
	represented in milliseconds.
	SETTINGS_MAX_CONCURRENT_STREAMS (4): indicates the maximum number of		SETTINGS_MAX_CONCURRENT_STREAMS (4): indicates the maximum number of
	concurrent streams that the sender will allow. This limit is		concurrent streams that the sender will allow. This limit is
	directional: it applies to the number of streams that the sender		directional: it applies to the number of streams that the sender
	permits the receiver to create. By default there is no limit. It		permits the receiver to create. By default there is no limit. It
	is recommended that this value be no smaller than 100, so as to		is recommended that this value be no smaller than 100, so as to
	not unnecessarily limit parallelism.		not unnecessarily limit parallelism.
	SETTINGS_CURRENT_CWND (5): indicates the sender's current TCP CWND
	value.
	SETTINGS_DOWNLOAD_RETRANS_RATE (6): indicates the sender's
	retransmission rate (bytes retransmitted / total bytes
	transmitted).
	SETTINGS_INITIAL_WINDOW_SIZE (7): indicates the sender's initial		SETTINGS_INITIAL_WINDOW_SIZE (7): indicates the sender's initial
	stream window size (in bytes) for new streams.		window size (in bytes) for stream level flow control.
			This settings affects the window size of all streams, including
			existing streams, see Section 6.9.2.
	SETTINGS_FLOW_CONTROL_OPTIONS (10): indicates that streams directed		SETTINGS_FLOW_CONTROL_OPTIONS (10): indicates that streams directed
	to the sender will not be subject to flow control. The least		to the sender will not be subject to flow control. The least
	significant bit (0x1) is set to indicate that new streams are not		significant bit (0x1) of the value is set to indicate that new
	flow controlled. All other bits are reserved.		streams are not flow controlled. All other bits are reserved.
	This setting applies to all streams, including existing streams.		This setting applies to all streams, including existing streams.
	These bits cannot be cleared once set, see Section 3.8.9.4.		These bits cannot be cleared once set, see Section 6.9.4.
	3.8.5. PUSH_PROMISE		6.6. PUSH_PROMISE
	The PUSH_PROMISE frame (type=0x5) is used to notify the peer endpoint		The PUSH_PROMISE frame (type=0x5) is used to notify the peer endpoint
	in advance of streams the sender intends to initiate. The		in advance of streams the sender intends to initiate. The
	PUSH_PROMISE frame includes the unsigned 31-bit identifier of the		PUSH_PROMISE frame includes the unsigned 31-bit identifier of the
	stream the endpoint plans to create along with a minimal set of		stream the endpoint plans to create along with a minimal set of
	headers that provide additional context for the stream. Section 4.3		headers that provide additional context for the stream. Section 8.2
	contains a thorough description of the use of PUSH_PROMISE frames.		contains a thorough description of the use of PUSH_PROMISE frames.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|X| Promised-Stream-ID (31) |		|X| Promised-Stream-ID (31) |
	+-+-------------------------------------------------------------+		+-+-------------------------------------------------------------+
	| Header Block (*) ...		| Header Block Fragment (*) ...
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	PUSH_PROMISE Payload Format		PUSH_PROMISE Payload Format
	The payload of a PUSH_PROMISE includes a "Promised-Stream-ID". This		The payload of a PUSH_PROMISE includes a "Promised-Stream-ID". This
	unsigned 31-bit integer identifies the stream the endpoint intends to		unsigned 31-bit integer identifies the stream the endpoint intends to
	start sending frames for. The promised stream identifier MUST be a		start sending frames for. The promised stream identifier MUST be a
	valid choice for the next stream sent by the sender (see new stream		valid choice for the next stream sent by the sender (see new stream
	identifier (Section 3.4.1)).		identifier (Section 5.1.1)).
	PUSH_PROMISE frames MUST be associated with an existing stream. If		Following the "Promised-Stream-ID" is a header block fragment
	the stream identifier field specifies the value 0x0, a recipient MUST		(Section 4.3).
	respond with a connection error (Section 3.5.1) of type
	PROTOCOL_ERROR.
	The state of promised streams is bound to the state of the original		PUSH_PROMISE frames MUST be associated with an existing, peer-
	associated stream on which the PUSH_PROMISE frame were sent. If the		initiated stream. If the stream identifier field specifies the value
	originating stream state changes to fully closed, all associated		0x0, a recipient MUST respond with a connection error (Section 5.4.1)
	promised streams fully close as well. [[anchor13: Ed. Note: We need		of type PROTOCOL_ERROR.
	clarification on this point. How synchronized are the lifecycles of
	streams and associated promised streams?]]
	PUSH_PROMISE uses the same flags as the HEADERS frame, except that a		The PUSH_PROMISE frame defines the following flags:
	PUSH_PROMISE frame with a CONTINUES bit MUST be followed by another
	PUSH_PROMISE frame. See HEADERS frame (Section 3.8.8) for any flags.		END_PUSH_PROMISE (0x1): The END_PUSH_PROMISE bit indicates that this
			frame ends the sequence of header block fragments necessary to
			provide a complete set of headers.
			The payload for a complete header block is provided by a sequence
			of PUSH_PROMISE frames, terminated by a PUSH_PROMISE frame with
			the END_PUSH_PROMISE flag set. Once the sequence terminates, the
			payload of all PUSH_PROMISE frames are concatenated and
			interpreted as a single block.
			A PUSH_PROMISE frame without the END_PUSH_PROMISE flag set MUST be
			followed by a PUSH_PROMISE frame for the same stream. A receiver
			MUST treat the receipt of any other type of frame or a frame on a
			different stream as a connection error (Section 5.4.1) of type
			PROTOCOL_ERROR.
	Promised streams are not required to be used in order promised. The		Promised streams are not required to be used in order promised. The
	PUSH_PROMISE only reserves stream identifiers for later use.		PUSH_PROMISE only reserves stream identifiers for later use.
	Recipients of PUSH_PROMISE frames can choose to reject promised		Recipients of PUSH_PROMISE frames can choose to reject promised
	streams by returning a RST_STREAM referencing the promised stream		streams by returning a RST_STREAM referencing the promised stream
	identifier back to the sender of the PUSH_PROMISE.		identifier back to the sender of the PUSH_PROMISE.
	The PUSH_PROMISE frame modifies the connection state as defined in		The PUSH_PROMISE frame modifies the connection state as defined in
	Section 3.7.		Section 4.3.
	3.8.6. PING		6.7. PING
	The PING frame (type=0x6) is a mechanism for measuring a minimal		The PING frame (type=0x6) is a mechanism for measuring a minimal
	round-trip time from the sender, as well as determining whether an		round-trip time from the sender, as well as determining whether an
	idle connection is still functional. PING frames can be sent from		idle connection is still functional. PING frames can be sent from
	any endpoint.		any endpoint.
	PING frames consist of an arbitrary, variable-length sequence of		0 1 2 3
	octets. Receivers of a PING send a response PING frame with the PONG		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	flag set and precisely the same sequence of octets back to the sender		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	as soon as possible.		| |
			| Opaque Data (64) |
			| |
			+---------------------------------------------------------------+
	Processing of PING frames SHOULD be performed with the highest		PING Payload Format
	priority if there are additional frames waiting to be processed.
	The PING frame defines one type-specific flag:		In addition to the frame header, PING frames MUST contain 8 octets of
			data in the payload. A sender can include any value it chooses and
			use those bytes in any fashion.
	PONG (0x2): Bit 2 being set indicates that this PING frame is a PING		Receivers of a PING frame that does not include a PONG flag MUST send
			a PING frame with the PONG flag set in response, with an identical
			payload. PING responses SHOULD given higher priority than any other
			frame.
			The PING frame defines the following flags:
			PONG (0x1): Bit 1 being set indicates that this PING frame is a PING
	response. An endpoint MUST set this flag in PING responses. An		response. An endpoint MUST set this flag in PING responses. An
	endpoint MUST NOT respond to PING frames containing this flag.		endpoint MUST NOT respond to PING frames containing this flag.
	PING frames are not associated with any individual stream. If a PING		PING frames are not associated with any individual stream. If a PING
	frame is received with a stream identifier field value other than		frame is received with a stream identifier field value other than
	0x0, the recipient MUST respond with a connection error		0x0, the recipient MUST respond with a connection error
	(Section 3.5.1) of type PROTOCOL_ERROR.		(Section 5.4.1) of type PROTOCOL_ERROR.
	3.8.7. GOAWAY		Receipt of a PING frame with a length field value other than 8 MUST
			be treated as a connection error (Section 5.4.1) of type
			PROTOCOL_ERROR.
			6.8. GOAWAY
	The GOAWAY frame (type=0x7) informs the remote peer to stop creating		The GOAWAY frame (type=0x7) informs the remote peer to stop creating
	streams on this connection. It can be sent from the client or the		streams on this connection. It can be sent from the client or the
	server. Once sent, the sender will ignore frames sent on new streams		server. Once sent, the sender will ignore frames sent on new streams
	for the remainder of the connection. Receivers of a GOAWAY frame		for the remainder of the connection. Receivers of a GOAWAY frame
	MUST NOT open additional streams on the connection, although a new		MUST NOT open additional streams on the connection, although a new
	connection can be established for new streams. The purpose of this		connection can be established for new streams. The purpose of this
	frame is to allow an endpoint to gracefully stop accepting new		frame is to allow an endpoint to gracefully stop accepting new
	streams (perhaps for a reboot or maintenance), while still finishing		streams (perhaps for a reboot or maintenance), while still finishing
	processing of previously established streams.		processing of previously established streams.
	skipping to change at page 27, line 11 ¶		skipping to change at page 30, line 22 ¶
	There is an inherent race condition between an endpoint starting new		There is an inherent race condition between an endpoint starting new
	streams and the remote sending a GOAWAY frame. To deal with this		streams and the remote sending a GOAWAY frame. To deal with this
	case, the GOAWAY contains the stream identifier of the last stream		case, the GOAWAY contains the stream identifier of the last stream
	which was processed on the sending endpoint in this connection. If		which was processed on the sending endpoint in this connection. If
	the receiver of the GOAWAY used streams that are newer than the		the receiver of the GOAWAY used streams that are newer than the
	indicated stream identifier, they were not processed by the sender		indicated stream identifier, they were not processed by the sender
	and the receiver may treat the streams as though they had never been		and the receiver may treat the streams as though they had never been
	created at all (hence the receiver may want to re-create the streams		created at all (hence the receiver may want to re-create the streams
	later on a new connection).		later on a new connection).
	Endpoints should always send a GOAWAY frame before closing a		Endpoints SHOULD always send a GOAWAY frame before closing a
	connection so that the remote can know whether a stream has been		connection so that the remote can know whether a stream has been
	partially processed or not. (For example, if an HTTP client sends a		partially processed or not. For example, if an HTTP client sends a
	POST at the same time that a server closes a connection, the client		POST at the same time that a server closes a connection, the client
	cannot know if the server started to process that POST request if the		cannot know if the server started to process that POST request if the
	server does not send a GOAWAY frame to indicate where it stopped		server does not send a GOAWAY frame to indicate where it stopped
	working).		working. An endpoint might choose to close a connection without
			sending GOAWAY for misbehaving peers.
	After sending a GOAWAY frame, the sender can ignore frames for new
	streams.
	[[anchor14: Issue: connection state that is established by those		After sending a GOAWAY frame, the sender can discard frames for new
	"ignored" frames cannot be ignored without the state in the two peers		streams. However, any frames that alter connection state cannot be
	becoming unsynchronized.]]		completely ignored. For instance, HEADERS and PUSH_PROMISE frames
			MUST be minimally processed to ensure a consistent compression state
			(see Section 4.3).
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|X| Last-Stream-ID (31) |		|X| Last-Stream-ID (31) |
	+-+-------------------------------------------------------------+		+-+-------------------------------------------------------------+
	| Error Code (32) |		| Error Code (32) |
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
			| Additional Debug Data (*) |
			+---------------------------------------------------------------+
	GOAWAY Payload Format		GOAWAY Payload Format
	The GOAWAY frame does not define any type-specific flags.		The GOAWAY frame does not define any flags.
	The GOAWAY frame applies to the connection, not a specific stream.		The GOAWAY frame applies to the connection, not a specific stream.
	The stream identifier MUST be zero.		The stream identifier MUST be zero.
	The last stream identifier in the GOAWAY frame contains the highest		The last stream identifier in the GOAWAY frame contains the highest
	numbered stream identifier for which the sender of the GOAWAY frame		numbered stream identifier for which the sender of the GOAWAY frame
	has received frames on and might have taken some action on. All		has received frames on and might have taken some action on. All
	streams up to and including the identified stream might have been		streams up to and including the identified stream might have been
	processed in some way. The last stream identifier is set to 0 if no		processed in some way. The last stream identifier is set to 0 if no
	streams were processed.		streams were processed.
	Note: In this case, "processed" means that some data from the		Note: In this case, "processed" means that some data from the
	stream was passed to some higher layer of software that might have		stream was passed to some higher layer of software that might have
	taken some action as a result.		taken some action as a result.
	On streams with lower or equal numbered identifiers that do not close		On streams with lower or equal numbered identifiers that were not
	completely prior to the connection being closed, re-attempting		closed completely prior to the connection being closed, re-attempting
	requests, transactions, or any protocol activity is not possible		requests, transactions, or any protocol activity is not possible
	(with the exception of idempotent actions like HTTP GET, PUT, or		(with the exception of idempotent actions like HTTP GET, PUT, or
	DELETE). Any protocol activity that uses higher numbered streams can		DELETE). Any protocol activity that uses higher numbered streams can
	be safely retried using a new connection.		be safely retried using a new connection.
	Activity on streams numbered lower or equal to the last stream		Activity on streams numbered lower or equal to the last stream
	identifier might still complete successfully. The sender of a GOAWAY		identifier might still complete successfully. The sender of a GOAWAY
	frame gracefully shut down a connection by sending a GOAWAY frame,		frame might gracefully shut down a connection by sending a GOAWAY
	maintaining the connection in an open state until all in-progress		frame, maintaining the connection in an open state until all in-
	streams complete.		progress streams complete.
	The last stream ID MUST be 0 if no streams were acted upon.		The last stream ID MUST be 0 if no streams were acted upon.
	The GOAWAY frame also contains a 32-bit error code (Section 3.5.3)		The GOAWAY frame also contains a 32-bit error code (Section 7) that
	that contains the reason for closing the connection.		contains the reason for closing the connection.
	3.8.8. HEADERS
	The HEADERS frame (type=0x8) provides header fields for a stream.
	Any number of HEADERS frames can may be sent on an existing stream at
	any time.
	Additional type-specific flags for the HEADERS frame are:
	CONTINUES (0x2): The CONTINUES bit indicates that this frame does
	not contain the entire payload necessary to provide a complete set
	of headers.
	The payload for a complete set of headers is provided by a
	sequence of HEADERS frames, terminated by a HEADERS frame without
	the CONTINUES bit. Once the sequence terminates, the payload of
	all HEADERS frames are concatenated and interpreted as a single
	block.
	A HEADERS frame that includes a CONTINUES bit MUST be followed by
	a HEADERS frame for the same stream. A receiver MUST treat the
	receipt of any other type of frame or a frame on a different
	stream as a connection error (Section 3.5.1) of type
	PROTOCOL_ERROR.
	The payload of a HEADERS frame contains a Headers Block
	(Section 3.7).
	The HEADERS frame is associated with an existing stream. If a
	HEADERS frame is received with a stream identifier of 0x0, the
	recipient MUST respond with a stream error (Section 3.5.2) of type
	PROTOCOL_ERROR.
	The HEADERS frame changes the connection state as defined in		Endpoints MAY append opaque data to the payload of any GOAWAY frame.
	Section 3.7.		Additional debug data is intended for diagnostic purposes only and
			carries no semantic value. Debug data MUST NOT be persistently
			stored, since it could contain sensitive information.
	3.8.9. WINDOW_UPDATE		6.9. WINDOW_UPDATE
	The WINDOW_UPDATE frame (type=0x9) is used to implement flow control.		The WINDOW_UPDATE frame (type=0x9) is used to implement flow control.
	Flow control operates at two levels: on each individual stream and on		Flow control operates at two levels: on each individual stream and on
	the entire connection.		the entire connection.
	Both types of flow control are hop by hop; that is, only between the		Both types of flow control are hop by hop; that is, only between the
	two endpoints. Intermediaries do not forward WINDOW_UPDATE frames		two endpoints. Intermediaries do not forward WINDOW_UPDATE frames
	between dependent connections. However, throttling of data transfer		between dependent connections. However, throttling of data transfer
	by any receiver can indirectly cause the propagation of flow control		by any receiver can indirectly cause the propagation of flow control
	information toward the original sender.		information toward the original sender.
	Flow control only applies to frames that are identified as being		Flow control only applies to frames that are identified as being
	subject to flow control. Of the frame types defined in this		subject to flow control. Of the frame types defined in this
	document, this includes only DATA frame. Frames that are exempt from		document, this includes only DATA frame. Frames that are exempt from
	flow control MUST be accepted and processed, unless the receiver is		flow control MUST be accepted and processed, unless the receiver is
	unable to assign resources to handling the frame. A receiver MAY		unable to assign resources to handling the frame. A receiver MAY
	respond with a stream error (Section 3.5.2) or connection error		respond with a stream error (Section 5.4.2) or connection error
	(Section 3.5.1) of type FLOW_CONTROL_ERROR if it is unable accept a		(Section 5.4.1) of type FLOW_CONTROL_ERROR if it is unable accept a
	frame.		frame.
	The following additional flags are defined for the WINDOW_UPDATE		0 1 2 3
	frame:		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			|X| Window Size Increment (31) |
			+-+-------------------------------------------------------------+
	END_FLOW_CONTROL (0x2): Bit 2 being set indicates that flow control		WINDOW_UPDATE Payload Format
			The payload of a WINDOW_UPDATE frame is one reserved bit, plus an
			unsigned 31-bit integer indicating the number of bytes that the
			sender can transmit in addition to the existing flow control window.
			The legal range for the increment to the flow control window is 1 to
			2^31 - 1 (0x7fffffff) bytes.
			The WINDOW_UPDATE frame defines the following flags:
			END_FLOW_CONTROL (0x1): Bit 1 being set indicates that flow control
	for the identified stream or connection has been ended; subsequent		for the identified stream or connection has been ended; subsequent
	frames do not need to be flow controlled.		frames do not need to be flow controlled.
	The WINDOW_UPDATE frame can be specific to a stream or to the entire		The WINDOW_UPDATE frame can be specific to a stream or to the entire
	connection. In the former case, the frame's stream identifier		connection. In the former case, the frame's stream identifier
	indicates the affected stream; in the latter, the value "0" indicates		indicates the affected stream; in the latter, the value "0" indicates
	that the entire connection is the subject of the frame.		that the entire connection is the subject of the frame.
	The payload of a WINDOW_UPDATE frame is a 32-bit value indicating the		6.9.1. The Flow Control Window
	additional number of bytes that the sender can transmit in addition
	to the existing flow control window. The legal range for this field
	is 1 to 2^31 - 1 (0x7fffffff) bytes; the most significant bit of this
	value is reserved.
	3.8.9.1. The Flow Control Window
	Flow control in HTTP/2.0 is implemented using a window kept by each		Flow control in HTTP/2.0 is implemented using a window kept by each
	sender on every stream. The flow control window is a simple integer		sender on every stream. The flow control window is a simple integer
	value that indicates how many bytes of data the sender is permitted		value that indicates how many bytes of data the sender is permitted
	to transmit; as such, its size is a measure of the buffering		to transmit; as such, its size is a measure of the buffering
	capability of the receiver.		capability of the receiver.
	Two flow control windows are applicable; the stream flow control		Two flow control windows are applicable; the stream flow control
	window and the connection flow control window. The sender MUST NOT		window and the connection flow control window. The sender MUST NOT
	send a flow controlled frame with a length that exceeds the space		send a flow controlled frame with a length that exceeds the space
	available in either of the flow control windows advertised by the		available in either of the flow control windows advertised by the
	receiver. Frames with zero length with the FINAL flag set (for		receiver. Frames with zero length with the END_STREAM flag set (for
	example, an empty data frame) MAY be sent if there is no available		example, an empty data frame) MAY be sent if there is no available
	space in either flow control window.		space in either flow control window.
	For flow control calculations, the 8 byte frame header is not		For flow control calculations, the 8 byte frame header is not
	counted.		counted.
	After sending a flow controlled frame, the sender reduces the space		After sending a flow controlled frame, the sender reduces the space
	available in both windows by the length of the transmitted frame.		available in both windows by the length of the transmitted frame.
	The receiver of a frame sends a WINDOW_UPDATE frame as it consumes		The receiver of a frame sends a WINDOW_UPDATE frame as it consumes
	skipping to change at page 30, line 47 ¶		skipping to change at page 33, line 32 ¶
	control window to exceed this maximum it MUST terminate either the		control window to exceed this maximum it MUST terminate either the
	stream or the connection, as appropriate. For streams, the sender		stream or the connection, as appropriate. For streams, the sender
	sends a RST_STREAM with the error code of FLOW_CONTROL_ERROR code;		sends a RST_STREAM with the error code of FLOW_CONTROL_ERROR code;
	for the connection, a GOAWAY frame with a FLOW_CONTROL_ERROR code.		for the connection, a GOAWAY frame with a FLOW_CONTROL_ERROR code.
	Flow controlled frames from the sender and WINDOW_UPDATE frames from		Flow controlled frames from the sender and WINDOW_UPDATE frames from
	the receiver are completely asynchronous with respect to each other.		the receiver are completely asynchronous with respect to each other.
	This property allows a receiver to aggressively update the window		This property allows a receiver to aggressively update the window
	size kept by the sender to prevent streams from stalling.		size kept by the sender to prevent streams from stalling.
	3.8.9.2. Initial Flow Control Window Size		6.9.2. Initial Flow Control Window Size
	When a HTTP/2.0 connection is first established, new streams are		When a HTTP/2.0 connection is first established, new streams are
	created with an initial flow control window size of 65535 bytes. The		created with an initial flow control window size of 65535 bytes. The
	connection flow control window is 65536 bytes. Both endpoints can		connection flow control window is 65535 bytes. Both endpoints can
	adjust the initial window size for new streams by including a value		adjust the initial window size for new streams by including a value
	for SETTINGS_INITIAL_WINDOW_SIZE in the SETTINGS frame that forms		for SETTINGS_INITIAL_WINDOW_SIZE in the SETTINGS frame that forms
	part of the connection header.		part of the connection header.
	Prior to receiving a SETTINGS frame that sets a value for		Prior to receiving a SETTINGS frame that sets a value for
	SETTINGS_INITIAL_WINDOW_SIZE, a client can only use the default		SETTINGS_INITIAL_WINDOW_SIZE, an endpoint can only use the default
	initial window size when sending flow controlled frames. Similarly,		initial window size when sending flow controlled frames. Similarly,
	the connection flow control window is set to the default initial		the connection flow control window is set to the default initial
	window size until a WINDOW_UPDATE frame is received.		window size until a WINDOW_UPDATE frame is received.
	A SETTINGS frame can alter the initial flow control window size for		A SETTINGS frame can alter the initial flow control window size for
	all current streams. When the value of SETTINGS_INITIAL_WINDOW_SIZE		all current streams. When the value of SETTINGS_INITIAL_WINDOW_SIZE
	changes, a receiver MUST adjust the size of all flow control windows		changes, a receiver MUST adjust the size of all stream flow control
	that it maintains by the difference between the new value and the old		windows that it maintains by the difference between the new value and
	value.		the old value. A SETTINGS frame cannot alter the connection flow
			control window.
	A change to SETTINGS_INITIAL_WINDOW_SIZE could cause the available		A change to SETTINGS_INITIAL_WINDOW_SIZE could cause the available
	space in a flow control window to become negative. A sender MUST		space in a flow control window to become negative. A sender MUST
	track the negative flow control window, and MUST NOT send new flow		track the negative flow control window, and MUST NOT send new flow
	controlled frames until it receives WINDOW_UPDATE frames that cause		controlled frames until it receives WINDOW_UPDATE frames that cause
	the flow control window to become positive.		the flow control window to become positive.
	For example, if the server sets the initial window size to be 16KB,		For example, if the client sends 64KB immediately on connection
	and the client sends 64KB immediately on connection establishment,		establishment, and the server sets the initial window size to be
	the client will recalculate the available flow control window to be		16KB, the client will recalculate the available flow control window
	-48KB on receipt of the SETTINGS frame. The client retains a		to be -48KB on receipt of the SETTINGS frame. The client retains a
	negative flow control window until WINDOW_UPDATE frames restore the		negative flow control window until WINDOW_UPDATE frames restore the
	window to being positive, after which the client can resume sending.		window to being positive, after which the client can resume sending.
	3.8.9.3. Reducing the Stream Window Size		6.9.3. Reducing the Stream Window Size
	A receiver that wishes to use a smaller flow control window than the		A receiver that wishes to use a smaller flow control window than the
	current size can send a new SETTINGS frame. However, the receiver		current size can send a new SETTINGS frame. However, the receiver
	MUST be prepared to receive data that exceeds this window size, since		MUST be prepared to receive data that exceeds this window size, since
	the sender might send data that exceeds the lower limit prior to		the sender might send data that exceeds the lower limit prior to
	processing the SETTINGS frame.		processing the SETTINGS frame.
	A receiver has two options for handling streams that exceed flow		A receiver has two options for handling streams that exceed flow
	control limits:		control limits:
	skipping to change at page 32, line 6 ¶		skipping to change at page 34, line 41 ¶
	FLOW_CONTROL_ERROR error code for the affected streams.		FLOW_CONTROL_ERROR error code for the affected streams.
	2. The receiver can accept the streams and tolerate the resulting		2. The receiver can accept the streams and tolerate the resulting
	head of line blocking, sending WINDOW_UPDATE frames as it		head of line blocking, sending WINDOW_UPDATE frames as it
	consumes data.		consumes data.
	If a receiver decides to accept streams, both sides MUST recompute		If a receiver decides to accept streams, both sides MUST recompute
	the available flow control window based on the initial window size		the available flow control window based on the initial window size
	sent in the SETTINGS.		sent in the SETTINGS.
	3.8.9.4. Ending Flow Control		6.9.4. Ending Flow Control
	After a receiver reads in a frame that marks the end of a stream (for		After a receiver reads in a frame that marks the end of a stream (for
	example, a data stream with a FINAL flag set), it MUST cease		example, a data stream with a END_STREAM flag set), it MUST cease
	transmission of WINDOW_UPDATE frames for that stream. A sender is		transmission of WINDOW_UPDATE frames for that stream. A sender is
	not obligated to maintain the available flow control window for		not obligated to maintain the available flow control window for
	streams that it is no longer sending on.		streams that it is no longer sending on.
	Flow control can be disabled for all streams or the connection using		Flow control can be disabled for all streams on the connection using
	the SETTINGS_FLOW_CONTROL_OPTIONS setting. An implementation that		the SETTINGS_FLOW_CONTROL_OPTIONS setting. An implementation that
	does not wish to perform flow control can use this in the initial		does not wish to perform stream flow control can use this in the
	SETTINGS exchange.		initial SETTINGS exchange.
	Flow control can be disabled for an individual stream or the overall		Flow control can be disabled for an individual stream or the overall
	connection by sending a WINDOW_UPDATE with the END_FLOW_CONTROL flag		connection by sending a WINDOW_UPDATE with the END_FLOW_CONTROL flag
	set. The payload of a WINDOW_UPDATE frame that has the		set. The payload of a WINDOW_UPDATE frame that has the
	END_FLOW_CONTROL flag set is ignored.		END_FLOW_CONTROL flag set is ignored.
	Flow control cannot be enabled again once disabled. Any attempt to		Flow control cannot be enabled again once disabled. Any attempt to
	re-enable flow control - by sending a WINDOW_UPDATE or by clearing		re-enable flow control - by sending a WINDOW_UPDATE or by clearing
	the bits on the SETTINGS_FLOW_CONTROL_OPTIONS setting - MUST be		the bits on the SETTINGS_FLOW_CONTROL_OPTIONS setting - MUST be
	rejected with a FLOW_CONTROL_ERROR error code.		rejected with a FLOW_CONTROL_ERROR error code.
	4. HTTP Message Exchanges		7. Error Codes
			Error codes are 32-bit fields that are used in RST_STREAM and GOAWAY
			frames to convey the reasons for the stream or connection error.
			Error codes share a common code space. Some error codes only apply
			to specific conditions and have no defined semantics in certain frame
			types.
			The following error codes are defined:
			NO_ERROR (0): The associated condition is not as a result of an
			error. For example, a GOAWAY might include this code to indicate
			graceful shutdown of a connection.
			PROTOCOL_ERROR (1): The endpoint detected an unspecific protocol
			error. This error is for use when a more specific error code is
			not available.
			INTERNAL_ERROR (2): The endpoint encountered an unexpected internal
			error.
			FLOW_CONTROL_ERROR (3): The endpoint detected that its peer violated
			the flow control protocol.
			STREAM_CLOSED (5): The endpoint received a frame after a stream was
			half closed.
			FRAME_TOO_LARGE (6): The endpoint received a frame that was larger
			than the maximum size that it supports.
			REFUSED_STREAM (7): The endpoint refuses the stream prior to
			performing any application processing, see Section 8.1.5 for
			details.
			CANCEL (8): Used by the endpoint to indicate that the stream is no
			longer needed.
			COMPRESSION_ERROR (9): The endpoint is unable to maintain the
			compression context for the connection.
			8. HTTP Message Exchanges
	HTTP/2.0 is intended to be as compatible as possible with current		HTTP/2.0 is intended to be as compatible as possible with current
	web-based applications. This means that, from the perspective of the		web-based applications. This means that, from the perspective of the
	server business logic or application API, the features of HTTP are		server business logic or application API, the features of HTTP are
	unchanged. To achieve this, all of the application request and		unchanged. To achieve this, all of the application request and
	response header semantics are preserved, although the syntax of		response header semantics are preserved, although the syntax of
	conveying those semantics has changed. Thus, the rules from HTTP/1.1		conveying those semantics has changed. Thus, the rules from HTTP/1.1
	([HTTP-p1], [HTTP-p2], [HTTP-p4], [HTTP-p5], [HTTP-p6], and		([HTTP-p1], [HTTP-p2], [HTTP-p4], [HTTP-p5], [HTTP-p6], and
	[HTTP-p7]) apply with the changes in the sections below.		[HTTP-p7]) apply with the changes in the sections below.
	4.1. Connection Management		8.1. HTTP Request/Response Exchange
	Clients SHOULD NOT open more than one HTTP/2.0 connection to a given
	origin ([RFC6454]) concurrently.
	Note that it is possible for one HTTP/2.0 connection to be finishing
	(e.g. a GOAWAY frame has been sent, but not all streams have
	finished), while another HTTP/2.0 connection is starting.
	4.2. HTTP Request/Response
	4.2.1. HTTP Header Fields and HTTP/2.0 Headers
	At the application level, HTTP uses name-value pairs in its header
	fields. Because HTTP/2.0 merges the existing HTTP header fields with
	HTTP/2.0 headers, there is a possibility that some HTTP applications
	already use a particular header field name. To avoid any conflicts,
	all header fields introduced for layering HTTP over HTTP/2.0 are
	prefixed with ":". ":" is not a valid sequence in HTTP/1.* header
	field naming, preventing any possible conflict.
	4.2.2. Request		A client sends an HTTP request on a new stream, using a previously
			unused stream identifier (Section 5.1.1). A server sends an HTTP
			response on the same stream as the request.
	The client initiates a request by sending a HEADERS+PRIORITY frame.		An HTTP request or response each consist of:
	Requests that do not contain a body MUST set the FINAL flag,
	indicating that the client intends to send no further data on this
	stream, unless the server intends to push resources (see
	Section 4.3). HEADERS+PRIORITY frame does not contain the FINAL flag
	for requests that contain a body. The body of a request follows as a
	series of DATA frames. The last DATA frame sets the FINAL flag to
	indicate the end of the body.
	The header fields included in the HEADERS+PRIORITY frame contain all		o one contiguous sequence of HEADERS frames;
	of the HTTP header fields associated with an HTTP request. The
	definitions of these headers are largely unchanged relative to
	HTTP/1.1, with a few notable exceptions:
	o The HTTP/1.1 request-line has been split into two separate header		o zero or more DATA frames; and
	fields named :method and :path, whose values specify the HTTP
	method for the request and the request-target, respectively. The
	HTTP-version component of the request-line is removed entirely
	from the headers.
	o The host and optional port portions of the request URI (see		o optionally, a contiguous sequence of HEADERS frames
	[RFC3986], Section 3.2), is specified using the new :host header
	field. [[anchor21: Ed. Note: it needs to be clarified whether or
	not this replaces the existing HTTP/1.1 Host header.]]
	o A new :scheme header field has been added to specify the scheme		The last frame in the sequence bears an END_STREAM flag.
	portion of the request-target (e.g. "https")
	o All header field names MUST be lowercased, and the definitions of		Other frames, including HEADERS, MAY be interspersed with these
	all header field names defined by HTTP/1.1 are updated to be all		frames, but those frames do not carry HTTP semantics.
	lowercase.
	o The Connection, Host, Keep-Alive, Proxy-Connection, and Transfer-		Trailing header fields are carried in a header block that also
	Encoding header fields are no longer valid and MUST not be sent.		terminates the stream. That is, a sequence of HEADERS frames that
			carries an END_STREAM flag on the last frame. Header blocks after
			the first that do not terminate the stream are not part of an HTTP
			request or response.
	All HTTP Requests MUST include the ":method", ":path", ":host", and		An HTTP request/response exchange fully consumes a single stream. A
	":scheme" header fields.		request starts with the HEADERS frame that puts the stream into an
			"open" state and ends with a frame bearing END_STREAM, which causes
			the stream to become "half closed" for the client. A response starts
			with a HEADERS frame and ends with a frame bearing END_STREAM, which
			places the stream in the "closed" state.
	Header fields whose names begin with ":" (whether defined in this		8.1.1. Examples
	document or future extensions to this document) MUST appear before
	any other header fields.
	If a client sends a HEADERS+PRIORITY frame that omits a mandatory		For example, an HTTP GET request that includes request header fields
	header, the server MUST reply with a HTTP 400 Bad Request reply.		and no body, is transmitted as a single contiguous sequence of
	[[anchor22: Ed: why PROTOCOL_ERROR on missing ":status" in the		HEADERS frames containing the serialized block of request header
	response, but HTTP 400 here?]]		fields. The last HEADERS frame in the sequence has both the
			END_HEADERS and END_STREAM flag set:
	If a server receives a request where the sum of the data frame		GET /resource HTTP/1.1 HEADERS
	payload lengths does not equal the size of the Content-Length header		Host: example.org ==> + END_STREAM
	field, the server MUST return a 400 (Bad Request) error.		Accept: image/jpeg + END_HEADERS
			:method = get
			:scheme = https
			:host = example.org
			:path = /resource
			accept = image/jpeg
	Although POSTs are inherently chunked, POST requests SHOULD also be		Similarly, a response that includes only response header fields is
	accompanied by a Content-Length header field. First, it informs the		transmitted as a sequence of HEADERS frames containing the serialized
	server of how much data to expect, which the server can use to track		block of response header fields. The last HEADERS frame in the
	overall progress and provide appropriate user feedback. More		sequence has both the END_HEADERS and END_STREAM flag set:
	importantly, some HTTP server implementations fail to correctly
	process requests that omit the Content-Length header field. Many
	existing clients send a Content-Length header field, and some server
	implementations have come to depend upon its presence.
	A client provides priority in requests as a hint to the server. A		HTTP/1.1 204 No Content HEADERS
	server SHOULD attempt to provide responses to higher priority		Content-Length: 0 ===> + END_STREAM
	requests before lower priority requests. A server could send lower		+ END_HEADERS
	priority responses during periods that higher priority responses are		:status = 204
	unavailable to ensure better utilization of a connection.		content-length: 0
	If the server receives a data frame prior to a HEADERS+PRIORITY frame		An HTTP POST request that includes request header fields and payload
	the server MUST treat this as a stream error (Section 3.5.2) of type		data is transmitted as one or more HEADERS frames containing the
	PROTOCOL_ERROR.		request headers followed by one or more DATA frames, with the last
			HEADERS frame having the END_HEADERS flag set and the final DATA
			frame having the END_STREAM flag set:
	4.2.3. Response		POST /resource HTTP/1.1 HEADERS
			Host: example.org ==> - END_STREAM
			Content-Type: image/jpeg + END_HEADERS
			Content-Length: 123 :method = post
			:scheme = https
			{binary data} :host = example.org
			:path = /resource
			content-type = image/jpeg
			content-length = 123
	The server responds to a client request using the same stream		DATA
	identifier that was used by the request. An HTTP response begins		+ END_STREAM
	with a HEADERS frame. An HTTP response body consists of a series of		{binary data}
	DATA frames. The last data frame contains a FINAL flag to indicate
	the end of the response. A response that contains no body (such as a
	204 or 304 response) consists only of a HEADERS frame that contains
	the FINAL flag to indicate no further data will be sent on the
	stream.
	The response status line is unfolded into name-value pairs like		A response that includes header fields and payload data is
	other HTTP header fields and must be present:		transmitted as one or more HEADERS frames followed by one or more
			DATA frames, with the last DATA frame in the sequence having the
			END_STREAM flag set:
	":status": The HTTP response status code (e.g. "200" or "200 OK")		HTTP/1.1 200 OK HEADERS
			Content-Type: image/jpeg ==> - END_STREAM
			Content-Length: 123 + END_HEADERS
			:status = 200
			{binary data} content-type = image/jpeg
			content-length = 123
	All header field names starting with ":" (whether defined in this		DATA
	document or future extensions to this document) MUST appear before		+ END_STREAM
	any other header fields.		{binary data}
	All header field names MUST be all lowercase.		Trailing header fields are sent as a header block after both the
			request or response header block and all the DATA frames have been
			sent. The sequence of HEADERS frames that bears the trailers
			includes a terminal frame that has both END_HEADERS and END_STREAM
			flags set.
	The Connection, Keep-Alive, Proxy-Connection, and Transfer-		HTTP/1.1 200 OK HEADERS
	Encoding header fields are not valid and MUST not be sent.		Content-Type: image/jpeg ===> - END_STREAM
			Content-Length: 123 + END_HEADERS
			TE: trailers :status = 200
			123 content-type = image/jpeg
			{binary data} content-length = 123
			0
			Foo: bar DATA
			- END_STREAM
			{binary data}
	Responses MAY be accompanied by a Content-Length header field for		HEADERS
	advisory purposes. This allows clients to learn the full size of		+ END_STREAM
	an entity prior to receiving all the data frames. This can help		+ END_HEADERS
	in, for example, reporting progress.		foo: bar
	If a client receives a response where the sum of the data frame		8.1.2. Request Header Fields
	payload length does not equal the size of the Content-Length
	header field, the client MUST ignore the content length header
	field. [[anchor23: Ed: See
	<https://github.com/http2/http2-spec/issues/46>.]]
	If a client receives a response with an absent or duplicated status		The definitions of the request header fields are largely unchanged
	header, the client MUST treat this as a stream error (Section 3.5.2)		relative to HTTP/1.1, with a few notable exceptions:
	of type PROTOCOL_ERROR.
	If the client receives a data frame prior to a HEADERS frame the		o The HTTP/1.1 request-line has been split into two separate header
	client MUST treat this as a stream error (Section 3.5.2) of type		fields named :method and :path, whose values specify the HTTP
	PROTOCOL_ERROR.		method for the request and the request-target, respectively. The
			HTTP-version component of the request-line is removed entirely
			from the headers.
	Clients MUST support gzip compression. Regardless of the value of		o The host and optional port portions of the request URI (see
	the Accept-Encoding header field, a server MAY send responses with		[RFC3986], Section 3.2), are specified using the new :host header
	gzip or deflate encoding. A compressed response MUST still bear an		field. [[anchor13: Ed. Note: it needs to be clarified whether or
	appropriate Content-Encoding header field.		not this replaces the existing HTTP/1.1 Host header.]]
	4.3. Server Push Transactions		o A new :scheme header field has been added to specify the scheme
			portion of the request-target (e.g. "https")
	HTTP/2.0 enables a server to send multiple replies to a client for a		o All header field names MUST be lowercased, and the definitions of
	single request. The rationale for this feature is that sometimes a		all header field names defined by HTTP/1.1 are updated to be all
	server knows that it will need to send multiple resources in response		lowercase.
	to a single request. Without server push features, the client must
	first download the primary resource, then discover the secondary
	resource(s), and request them.
	Server push is an optional feature. The		o The Connection, Host, Keep-Alive, Proxy-Connection, and Transfer-
	SETTINGS_MAX_CONCURRENT_STREAMS setting from the client limits the		Encoding header fields are no longer valid and MUST NOT be sent.
	number of resources that can be concurrently pushed by a server.		[[anchor14: Ed. Note: And "TE" I presume?]]
	Server push can be disabled by clients that do not wish to receive
	pushed resources by advertising a SETTINGS_MAX_CONCURRENT_STREAMS
	SETTING (Section 3.8.4) of zero. This prevents servers from creating
	the streams necessary to push resources.
	Clients receiving a pushed response MUST validate that the server is		All HTTP Requests MUST include the ":method", ":path", ":host", and
	authorized to push the resource using the same-origin policy		":scheme" header fields.
	([RFC6454], Section 3). For example, a HTTP/2.0 connection to
	"example.com" is generally [[anchor24: Ed: weaselly use of
	"generally", needs better definition]] not permitted to push a
	response for "www.example.org".
	A client that accepts pushed resources caches those resources as		Header fields whose names begin with ":" (whether defined in this
	though they were responses to GET requests.		document or future extensions to this document) MUST appear before
			any other header fields. [[anchor15: Ed. Note: This requirement is
			currently pending review. Consider it "on hold" for the moment.]]
	Pushing of resources avoids the round-trip delay, but also creates a		All HTTP Requests that include a body SHOULD include the "content-
	potential race where a server can be pushing content which a client		length" header field. If a server receives a request where the sum
	is in the process of requesting. The PUSH_PROMISE frame reduces the		of the DATA frame payload lengths does not equal the value of the
	chances of this condition occurring, while retaining the performance		"content-length" header field, the server MUST return a 400 (Bad
	benefit.		Request) error.
	Pushed responses are associated with a request at the HTTP/2.0		If a client omits a mandatory header field from the request, the
	framing layer. The PUSH_PROMISE is sent on the stream for the		server MUST reply with a HTTP 400 Bad Request reply.
	associated request, which allows a receiver to correlate the pushed
	resource with a request. The pushed stream inherits all of the
	request header fields from the associated stream with the exception
	of resource identification header fields (":host", ":scheme", and
	":path"), which are provided as part of the PUSH_PROMISE frame.
	Pushed resources always have an associated ":method" of "GET". A		8.1.3. Response Header Fields
	cache MUST store these inherited and implied request header fields
	with the cached resource.
	4.3.1. Server implementation		The definitions of the response header fields are largely unchanged
			relative to HTTP/1.1, with a few notable exceptions:
	A server pushes resources in association with a request from the		o The response status line has been reduced to a single ":status"
	client. Prior to closing the response stream, the server sends a		header field whose value specifies only the numeric response
	PUSH_PROMISE for each resource that it intends to push. The		status code. The status text component of the HTTP/1.1 response
	PUSH_PROMISE includes header fields that allow the client to identify		has been dropped entirely.
	the resource (":scheme", ":host", and ":path").
	A server can push multiple resources in response to a request, but		o The response MUST contain exactly one :status header field with
	all pushed resources MUST be promised on the response stream for the		exactly one response status value. If the client receives an HTTP
	associated request. A server cannot send a PUSH_PROMISE on a new		response that does not include the :status field, or provides
	stream or a half-closed stream.		multiple response status code values, it MUST respond with a
			stream error (Section 5.4.2) of type PROTOCOL_ERROR.
	The server SHOULD include any header fields in a PUSH_PROMISE that		o All header field names MUST be lowercased, and the definitions of
	would allow a cache to determine if the resource is already cached		all header field names defined by HTTP/1.1 are updated to be all
	(see [HTTP-p6], Section 4).		lowercase.
	After sending a PUSH_PROMISE, the server commences transmission of a		o The Connection, Keep-Alive, Proxy-Connection, and Transfer-
	pushed resource. A pushed resource uses a server-initiated stream.		Encoding header fields are not valid and MUST NOT be sent.
	The server sends frames on this stream in the same order as an HTTP
	response (Section 4.2.3): a HEADERS frame followed by DATA frames.
	Many uses of server push are to send content that a client is likely		Header fields whose names begin with ":" (whether defined in this
	to discover a need for based on the content of a response		document or future extensions to this document) MUST appear before
	representation. To minimize the chances that a client will make a		any other header fields. [[anchor16: Ed. Note: This requirement is
	request for resources that are being pushed - causing duplicate		currently pending review. Consider it "on hold" for the moment.]]
	copies of a resource to be sent by the server - a PUSH_PROMISE frame
	SHOULD be sent prior to any content in the response representation
	that might allow a client to discover the pushed resource and request
	it.
	The server MUST only push resources that could have been returned		8.1.4. GZip Content-Encoding
	from a GET request.
	Note: A server does not need to have all response header fields		Clients MUST support gzip compression for HTTP response bodies.
	available at the time it issues a PUSH_PROMISE frame. All remaining		Regardless of the value of the accept-encoding header field, a server
	header fields are included in the HEADERS frame. The HEADERS frame		MAY send responses with gzip or deflate encoding. A compressed
	MUST NOT duplicate header fields from the PUSH_PROMISE frames.		response MUST still bear an appropriate content-encoding header
			field.
	4.3.2. Client implementation		8.1.5. Request Reliability Mechanisms in HTTP/2.0
	When fetching a resource the client has 3 possibilities:		In HTTP/1.1, an HTTP client is unable to retry a non-idempotent
			request when an error occurs, because there is no means to determine
			the nature of the error. It is possible that some server processing
			occurred prior to the error, which could result in undesirable
			effects if the request were reattempted.
	1. the resource is not being pushed		HTTP/2.0 provides two mechanisms for providing a guarantee to a
			client that a request has not been processed:
	2. the resource is being pushed, but the data has not yet arrived		o The GOAWAY frame indicates the highest stream number that might
			have been processed. Requests on streams with higher numbers are
			therefore guaranteed to be safe to retry.
	3. the resource is being pushed, and the data has started to arrive		o The REFUSED_STREAM error code can be included in a RST_STREAM
			frame to indicate that the stream is being closed prior to any
			processing having occurred. Any request that was sent on the
			reset stream can be safely retried.
	A client SHOULD NOT issue GET requests for a resource that has been		In both cases, clients MAY automatically retry all requests,
	promised. A client is instead advised to wait for the pushed		including those with non-idempotent methods.
	resource to arrive.
	When a client receives a PUSH_PROMISE frame from the server without a		A server MUST NOT indicate that a stream has not been processed
	the ":host", ":scheme", and ":path" header fields, it MUST treat this		unless it can guarantee that fact. If frames that are on a stream
	as a stream error (Section 3.5.2) of type PROTOCOL_ERROR.		are passed to the application layer for any stream, then
			REFUSED_STREAM MUST NOT be used for that stream, and a GOAWAY frame
			MUST include a stream identifier that is greater than or equal to the
			given stream identifier.
	To cancel individual server push streams, the client can issue a		In addition to these mechanisms, the PING frame provides a way for a
	stream error (Section 3.5.2) of type CANCEL. After receiving a		client to easily test a connection. Connections that remain idle can
	PUSH_PROMISE frame, the client is able to cancel the pushed resource		become broken as some middleboxes (for instance, network address
	before receiving any frames on the promised stream. The server		translators, or load balancers) silently discard connection bindings.
	ceases transmission of the pushed resource; if the server has not		The PING frame allows a client to safely test whether a connection is
	commenced transmission, it does not start.		still active without sending a request.
	To cancel all server push streams related to a request, the client		8.2. Server Push
	may issue a stream error (Section 3.5.2) of type CANCEL on the
	associated-stream-id. By cancelling that stream, the server MUST
	immediately stop sending frames for any streams with
	in-association-to for the original stream. [[anchor27: Ed: Triggering
	side-effects on stream reset is going to be problematic for the
	framing layer. Purely from a design perspective, it's a layering
	violation. More practically speaking, the base request stream might
	already be removed. Special handling logic would be required.]]
	A client can choose to time out pushed streams if the server does not		HTTP/2.0 enables a server to pre-emptively send (or "push") multiple
	provide the resource in a timely fashion. A stream error		associated resources to a client in response to a single request.
	(Section 3.5.2) of type CANCEL can be used to stop a timed out push.		This feature becomes particularly helpful when the server knows the
			client will need to have those resources available in order to fully
			process the originally requested resource.
	If the server sends a HEADERS frame containing header fields that		Pushing additional resources is optional, and is negotiated only
	duplicate values on a previous HEADERS or PUSH_PROMISE frames on the		between individual endpoints. For instance, an intermediary could
	same stream, the client MUST treat this as a stream error		receive pushed resources from the server but is not required to
	(Section 3.5.2) of type PROTOCOL_ERROR.		forward those on to the client. How to make use of the pushed
			resources is up to that intermediary. Equally, the intermediary
			might choose to push additional resources to the client, without any
			action taken by the server.
	If the server sends a HEADERS frame after sending a data frame for		Server push is semantically equivalent to a server responding to a
	the same stream, the client MAY ignore the HEADERS frame. Ignoring		GET request for that resource. The PUSH_PROMISE frame, or frames,
	the HEADERS frame after a data frame prevents handling of HTTP's		sent by the server includes a header block that contains the request
	trailing header fields (Section 4.1.1 of [HTTP-p1]).		headers that the server has assumed.
	5. Design Rationale and Notes		Pushed resources are always associated with an explicit request from
			a client. The PUSH_PROMISE frames sent by the server are sent on the
			stream created for the original request. The PUSH_PROMSE frame
			includes a promised stream identifier, chosen from the stream
			identifiers available to the server (see Section 5.1.1). Any header
			fields that are not specified in the PUSH_PROMISE frames sent by the
			server are inherited from the original request sent by the client.
	Authors' notes: The notes in this section have no bearing on the		The header fields in PUSH_PROMISE MUST include the ":scheme", ":host"
	HTTP/2.0 protocol as specified within this document, and none of		and ":path" header fields that identify the resource that is being
	these notes should be considered authoritative about how the protocol		pushed. A PUSH_PROMISE always implies an HTTP method of GET. If a
	works. However, these notes may prove useful in future debates about		client receives a PUSH_PROMISE that does not include these header
	how to resolve protocol ambiguities or how to evolve the protocol		fields, or a value for the ":method" header field, it MUST respond
	going forward. They may be removed before the final draft.		with a stream error (Section 5.4.2) of type PROTOCOL_ERROR.
	5.1. Separation of Framing Layer and Application Layer		After sending the PUSH_PROMISE frame, the server can begin delivering
			the pushed resource on a new, server-initiated stream that uses the
			promised stream identifier. This stream is already implicitly "half
			closed" to the client (Section 5.1). The server uses this stream to
			transmit an HTTP response, using the same sequence of frames as
			defined in Section 8.1.
	Readers may note that this specification sometimes blends the framing		Once a client receives a PUSH_PROMISE frame and chooses to accept the
	layer (Section 3) with requirements of a specific application - HTTP		pushed resource, the client SHOULD NOT issue any subsequent GET
	(Section 4). This is reflected in the request/response nature of the		requests for the promised resource until after the promised stream
	streams and the definition of the HEADERS which are very similar to		has closed.
	HTTP, and other areas as well.
	This blending is intentional - the primary goal of this protocol is		The server SHOULD send PUSH_PROMISE (Section 6.6) frames prior to
	to create a low-latency protocol for use with HTTP. Isolating the		sending any HEADERS or DATA frames that reference the promised
	two layers is convenient for description of the protocol and how it		resources. This avoids a race where clients issue requests for
	relates to existing HTTP implementations. However, the ability to		resources prior to receiving any PUSH_PROMISE frames.
	reuse the HTTP/2.0 framing layer is a non goal.
	5.2. Error handling - Framing Layer		For example, if the server receives a request for a document
			containing embedded links to multiple image files, and the server
			chooses to push those additional images to the client, sending push
			promises before the DATA frames that contain the image links ensure
			that the client is able to see the promises before discovering the
			resources. Likewise, if the server pushes resources referenced by
			the header block (for instance, in Link header fields), sending the
			push promises before sending the header block ensures that clients do
			not request those resources.
	Error handling at the HTTP/2.0 layer splits errors into two groups:		PUSH_PROMISE frames MUST NOT be sent by the client. PUSH_PROMISE
	Those that affect an individual HTTP/2.0 stream, and those that do		frames can be sent by the server on any stream that was opened by the
	not.		client. They MUST be sent on a stream that is in either the "open"
			or "half closed (remote)" to the server. PUSH_PROMISE frames can be
			interspersed within the frames that comprise response, with the
			exception that they cannot be interspersed with HEADERS frames that
			comprise a single header block.
	When an error is confined to a single stream, but general framing is		A client can use the SETTINGS_MAX_CONCURRENT_STREAMS setting to limit
	intact, HTTP/2.0 attempts to use the RST_STREAM as a mechanism to		the number of resources that can be concurrently pushed by a server.
	invalidate the stream but move forward without aborting the		Advertising a SETTINGS_MAX_CONCURRENT_STREAMS value of zero disables
	connection altogether.		server push by preventing the server from creating the necessary
			streams.
	For errors occurring outside of a single stream context, HTTP/2.0		The request header fields provided in the PUSH_PROMISE frame SHOULD
	assumes the entire connection is hosed. In this case, the endpoint		include enough information for a client to determine whether a cached
	detecting the error should initiate a connection close.		representation of the resource is already available. If the client
			determines, for any reason, that it does not wish to receive the
			pushed resource from the server, or if the server takes too long to
			begin sending the promised resource, the client can send an
			RST_STREAM frame, using either the CANCEL or REFUSED_STREAM codes,
			and referencing the pushed stream's identifier.
	5.3. One Connection per Domain		Clients receiving a pushed response MUST validate that the server is
			authorized to push the resource using the same-origin policy
			([RFC6454], Section 3). For example, a HTTP/2.0 connection to
			"example.com" is generally [[anchor17: Ed: weaselly use of
			"generally", needs better definition]] not permitted to push a
			response for "www.example.org".
	HTTP/2.0 attempts to use fewer connections than other protocols have		9. Additional HTTP Requirements/Considerations
	traditionally used. The rationale for this behavior is because it is
	very difficult to provide a consistent level of service (e.g. TCP
	slow-start), prioritization, or optimal compression when the client
	is connecting to the server through multiple channels.
	Through lab measurements, we have seen consistent latency benefits by		TODO: SNI, gzip and deflate Content-Encoding, etc..
	using fewer connections from the client. The overall number of
	packets sent by HTTP/2.0 can be as much as 40% less than HTTP.
	Handling large numbers of concurrent connections on the server also
	does become a scalability problem, and HTTP/2.0 reduces this load.
	The use of multiple connections is not without benefit, however.		9.1. Frame Size Limits for HTTP
	Because HTTP/2.0 multiplexes multiple, independent streams onto a
	single stream, it creates a potential for head-of-line blocking
	problems at the transport level. In tests so far, the negative
	effects of head-of-line blocking (especially in the presence of
	packet loss) is outweighed by the benefits of compression and
	prioritization.
	5.4. Fixed vs Variable Length Fields		Frames used for HTTP messages MUST NOT exceed 2^14-1 (16383) octets
			in length, not counting the 8 octet frame header. An endpoint MUST
			treat the receipt of a larger frame as a FRAME_TOO_LARGE error (see
			Section 4.2).
	HTTP/2.0 favors use of fixed length 32bit fields in cases where		9.2. Connection Management
	smaller, variable length encodings could have been used. To some,
	this seems like a tragic waste of bandwidth. HTTP/2.0 chooses the
	simple encoding for speed and simplicity.
	The goal of HTTP/2.0 is to reduce latency on the network. The		HTTP/2.0 connections are persistent. For best performance, it is
	overhead of HTTP/2.0 frames is generally quite low. Each data frame		expected clients will not close connections until it is determined
	is only an 8 byte overhead for a 1452 byte payload (~0.6%). At the		that no further communication with a server is necessary (for
	time of this writing, bandwidth is already plentiful, and there is a		example, when a user navigates away from a particular web page), or
	strong trend indicating that bandwidth will continue to increase.		until the server closes the connection.
	With an average worldwide bandwidth of 1Mbps, and assuming that a
	variable length encoding could reduce the overhead by 50%, the
	latency saved by using a variable length encoding would be less than
	100 nanoseconds. More interesting are the effects when the larger
	encodings force a packet boundary, in which case a round-trip could
	be induced. However, by addressing other aspects of HTTP/2.0 and TCP
	interactions, we believe this is completely mitigated.
	5.5. Server Push		Clients SHOULD NOT open more than one HTTP/2.0 connection to a given
			origin ([RFC6454]) concurrently. A client can create additional
			connections as replacements, either to replace connections that are
			near to exhausting the available stream identifiers (Section 5.1.1),
			or to replace connections that have encountered errors
			(Section 5.4.1).
	A subtle but important point is that server push streams must be		Servers are encouraged to maintain open connections for as long as
	declared before the associated stream is closed. The reason for this		possible, but are permitted to terminate idle connections if
	is so that proxies have a lifetime for which they can discard		necessary. When either endpoint chooses to close the transport-level
	information about previous streams. If a pushed stream could		TCP connection, the terminating endpoint MUST first send a GOAWAY
	associate itself with an already-closed stream, then endpoints would		(Section 6.8) frame so that both endpoints can reliably determine
	not have a specific lifecycle for when they could disavow knowledge		whether previously sent frames have been processed and gracefully
	of the streams which went before.		complete or terminate any necessary remaining tasks.
	6. Security Considerations		10. Security Considerations
	6.1. Server Authority and Same-Origin		10.1. Server Authority and Same-Origin
	This specification uses the same-origin policy ([RFC6454], Section 3)		This specification uses the same-origin policy ([RFC6454], Section 3)
	to determine whether an origin server is permitted to provide		to determine whether an origin server is permitted to provide
	content.		content.
	A server that is contacted using TLS is authenticated based on the		A server that is contacted using TLS is authenticated based on the
	certificate that it offers in the TLS handshake (see [RFC2818],		certificate that it offers in the TLS handshake (see [RFC2818],
	Section 3). A server is considered authoritative for an "https:"		Section 3). A server is considered authoritative for an "https"
	resource if it has been successfully authenticated for the domain		resource if it has been successfully authenticated for the domain
	part of the origin of the resource that it is providing.		part of the origin of the resource that it is providing.
	A server is considered authoritative for an "http:" resource if the		A server is considered authoritative for an "http" resource if the
	connection is established to a resolved IP address for the domain in		connection is established to a resolved IP address for the domain in
	the origin of the resource.		the origin of the resource.
	A client MUST NOT use, in any way, resources provided by a server		A client MUST NOT use, in any way, resources provided by a server
	that is not authoritative for those resources.		that is not authoritative for those resources.
	6.2. Cross-Protocol Attacks		10.2. Cross-Protocol Attacks
	When using TLS, we believe that HTTP/2.0 introduces no new cross-		When using TLS, we believe that HTTP/2.0 introduces no new cross-
	protocol attacks. TLS encrypts the contents of all transmission		protocol attacks. TLS encrypts the contents of all transmission
	(except the handshake itself), making it difficult for attackers to		(except the handshake itself), making it difficult for attackers to
	control the data which could be used in a cross-protocol attack.		control the data which could be used in a cross-protocol attack.
			[[anchor23: Issue: This is no longer true]]
	[[anchor37: Issue: This is no longer true]]		10.3. Cacheability of Pushed Resources
	6.3. Cacheability of Pushed Resources
	Pushed resources are synthesized responses without an explicit		Pushed resources are responses without an explicit request; the
	request; the request for a pushed resource is synthesized from the		request for a pushed resource is synthesized from the request that
	request that triggered the push, plus resource identification		triggered the push, plus resource identification information provided
	information provided by the server. Request header fields are		by the server. Request header fields are necessary for HTTP cache
	necessary for HTTP cache control validations (such as the Vary header		control validations (such as the Vary header field) to work. For
	field) to work. For this reason, caches MUST inherit request header		this reason, caches MUST inherit request header fields from the
	fields from the associated stream for the push. This includes the		associated stream for the push. This includes the Cookie header
	Cookie header field.		field.
	Caching resources that are pushed is possible, based on the guidance		Caching resources that are pushed is possible, based on the guidance
	provided by the origin server in the Cache-Control header field.		provided by the origin server in the Cache-Control header field.
	However, this can cause issues if a single server hosts more than one		However, this can cause issues if a single server hosts more than one
	tenant. For example, a server might offer multiple users each a		tenant. For example, a server might offer multiple users each a
	small portion of its URI space.		small portion of its URI space.
	Where multiple tenants share space on the same server, that server		Where multiple tenants share space on the same server, that server
	MUST ensure that tenants are not able to push representations of		MUST ensure that tenants are not able to push representations of
	resources that they do not have authority over. Failure to enforce		resources that they do not have authority over. Failure to enforce
	this would allow a tenant to provide a representation that would be		this would allow a tenant to provide a representation that would be
	served out of cache, overriding the actual representation that the		served out of cache, overriding the actual representation that the
	authoritative tenant provides.		authoritative tenant provides.
	Pushed resources for which an origin server is not authoritative are		Pushed resources for which an origin server is not authoritative are
	never cached or used.		never cached or used.
	7. Privacy Considerations		11. Privacy Considerations
	7.1. Long Lived Connections
	HTTP/2.0 aims to keep connections open longer between clients and		HTTP/2.0 aims to keep connections open longer between clients and
	servers in order to reduce the latency when a user makes a request.		servers in order to reduce the latency when a user makes a request.
	The maintenance of these connections over time could be used to		The maintenance of these connections over time could be used to
	expose private information. For example, a user using a browser		expose private information. For example, a user using a browser
	hours after the previous user stopped using that browser may be able		hours after the previous user stopped using that browser may be able
	to learn about what the previous user was doing. This is a problem		to learn about what the previous user was doing. This is a problem
	with HTTP in its current form as well, however the short lived		with HTTP in its current form as well, however the short lived
	connections make it less of a risk.		connections make it less of a risk.
	7.2. SETTINGS frame		12. IANA Considerations
	The HTTP/2.0 SETTINGS frame allows servers to store out-of-band
	transmitted information about the communication between client and
	server on the client. Although this is intended only to be used to
	reduce latency, renegade servers could use it as a mechanism to store
	identifying information about the client in future requests.
	Clients implementing privacy modes can disable client-persisted
	SETTINGS storage.
	Clients MUST clear persisted SETTINGS information when clearing the
	cookies.
	8. IANA Considerations
	This document establishes registries for frame types, error codes and		This document establishes registries for frame types, error codes and
	settings.		settings. These new registries are entered in a new "Hypertext
			Transfer Protocol (HTTP) 2.0 Parameters" section.
	8.1. Frame Type Registry		This document also registers the "HTTP2-Settings" header field for
			use in HTTP.
			12.1. Frame Type Registry
	This document establishes a registry for HTTP/2.0 frame types. The		This document establishes a registry for HTTP/2.0 frame types. The
	"HTTP/2.0 Frame Type" registry operates under the "IETF Review"		"HTTP/2.0 Frame Type" registry operates under the "IETF Review"
	policy [RFC5226].		policy [RFC5226].
	Frame types are an 8-bit value. When reviewing new frame type		Frame types are an 8-bit value. When reviewing new frame type
	registrations, special attention is advised for any frame type-		registrations, special attention is advised for any frame type-
	specific flags that are defined. Frame flags can interact with		specific flags that are defined. Frame flags can interact with
	existing flags and could prevent the creation of globally applicable		existing flags and could prevent the creation of globally applicable
	flags.		flags.
	Initial values for the "HTTP/2.0 Frame Type" registry are shown in		Initial values for the "HTTP/2.0 Frame Type" registry are shown in
	Table 1.		Table 1.
	+------------+------------------+---------------------+		+-----------+---------------+---------------------------------------+
	| Frame Type | Name | Flags |		| Frame | Name | Flags |
	+------------+------------------+---------------------+		| Type | | |
	| 0 | DATA | - |		+-----------+---------------+---------------------------------------+
	| 1 | HEADERS+PRIORITY | - |		| 0 | DATA | END_STREAM(1) |
	| 3 | RST_STREAM | - |		| 1 | HEADERS | END_STREAM(1), END_HEADERS(4), |
	| 4 | SETTINGS | CLEAR_PERSISTED(2) |		| | | PRIORITY(8) |
	| 5 | PUSH_PROMISE | - |		| 2 | PRIORITY | - |
	| 6 | PING | PONG(2) |		| 3 | RST_STREAM | - |
	| 7 | GOAWAY | - |		| 4 | SETTINGS | - |
	| 8 | HEADERS | - |		| 5 | PUSH_PROMISE | END_PUSH_PROMISE(1) |
	| 9 | WINDOW_UPDATE | END_FLOW_CONTROL(2) |		| 6 | PING | PONG(1) |
	+------------+------------------+---------------------+		| 7 | GOAWAY | - |
			| 9 | WINDOW_UPDATE | END_FLOW_CONTROL(1) |
			+-----------+---------------+---------------------------------------+
	Table 1		Table 1
	8.2. Error Code Registry		12.2. Error Code Registry
	This document establishes a registry for HTTP/2.0 error codes. The		This document establishes a registry for HTTP/2.0 error codes. The
	"HTTP/2.0 Error Code" registry manages a 32-bit space. The "HTTP/2.0		"HTTP/2.0 Error Code" registry manages a 32-bit space. The "HTTP/2.0
	Error Code" registry operates under the "Expert Review" policy		Error Code" registry operates under the "Expert Review" policy
	[RFC5226].		[RFC5226].
	Registrations for error codes are required to include a description		Registrations for error codes are required to include a description
	of the error code. An expert reviewer is advised to examine new		of the error code. An expert reviewer is advised to examine new
	registrations for possible duplication with existing error codes.		registrations for possible duplication with existing error codes.
	Use of existing registrations is to be encouraged, but not mandated.		Use of existing registrations is to be encouraged, but not mandated.
	skipping to change at page 43, line 30 ¶		skipping to change at page 46, line 48 ¶
	Name: A name for the error code. Specifying an error code name is		Name: A name for the error code. Specifying an error code name is
	optional.		optional.
	Description: A description of the conditions where the error code is		Description: A description of the conditions where the error code is
	applicable.		applicable.
	Specification: An optional reference for a specification that		Specification: An optional reference for a specification that
	defines the error code.		defines the error code.
	An initial set of error code registrations can be found in		An initial set of error code registrations can be found in Section 7.
	Section 3.5.3.
	8.3. Settings Registry		12.3. Settings Registry
	This document establishes a registry for HTTP/2.0 settings. The		This document establishes a registry for HTTP/2.0 settings. The
	"HTTP/2.0 Settings" registry manages a 24-bit space. The "HTTP/2.0		"HTTP/2.0 Settings" registry manages a 24-bit space. The "HTTP/2.0
	Settings" registry operates under the "Expert Review" policy		Settings" registry operates under the "Expert Review" policy
	[RFC5226].		[RFC5226].
	Registrations for settings are required to include a description of		Registrations for settings are required to include a description of
	the setting. An expert reviewer is advised to examine new		the setting. An expert reviewer is advised to examine new
	registrations for possible duplication with existing settings. Use		registrations for possible duplication with existing settings. Use
	of existing registrations is to be encouraged, but not mandated.		of existing registrations is to be encouraged, but not mandated.
	skipping to change at page 44, line 16 ¶		skipping to change at page 47, line 34 ¶
	and semantics.		and semantics.
	Description: A description of the setting. This might include the		Description: A description of the setting. This might include the
	range of values, any applicable units and how to act upon a value		range of values, any applicable units and how to act upon a value
	when it is provided.		when it is provided.
	Specification: An optional reference for a specification that		Specification: An optional reference for a specification that
	defines the setting.		defines the setting.
	An initial set of settings registrations can be found in		An initial set of settings registrations can be found in
	Section 3.8.4.3.		Section 6.5.2.
	9. Acknowledgements		12.4. HTTP2-Settings Header Field Registration
			This section registers the "HTTP2-Settings" header field in the
			Permanent Message Header Field Registry [BCP90].
			Header field name: HTTP2-Settings
			Applicable protocol: http
			Status: standard
			Author/Change controller: IETF
			Specification document(s): RFC XXXX (this document)
			Related information: This header field is only used by an HTTP/2.0
			client for Upgrade-based negotiation.
			13. Acknowledgements
	This document includes substantial input from the following		This document includes substantial input from the following
	individuals:		individuals:
	o Adam Langley, Wan-Teh Chang, Jim Morrison, Mark Nottingham, Alyssa		o Adam Langley, Wan-Teh Chang, Jim Morrison, Mark Nottingham, Alyssa
	Wilk, Costin Manolache, William Chan, Vitaliy Lvin, Joe Chan, Adam		Wilk, Costin Manolache, William Chan, Vitaliy Lvin, Joe Chan, Adam
	Barth, Ryan Hamilton, Gavin Peters, Kent Alstad, Kevin Lindsay,		Barth, Ryan Hamilton, Gavin Peters, Kent Alstad, Kevin Lindsay,
	Paul Amer, Fan Yang, Jonathan Leighton (SPDY contributors).		Paul Amer, Fan Yang, Jonathan Leighton (SPDY contributors).
	o Gabriel Montenegro and Willy Tarreau (Upgrade mechanism)		o Gabriel Montenegro and Willy Tarreau (Upgrade mechanism)
	o William Chan, Salvatore Loreto, Osama Mazahir, Gabriel Montenegro,		o William Chan, Salvatore Loreto, Osama Mazahir, Gabriel Montenegro,
	Jitu Padhye, Roberto Peon, Rob Trace (Flow control)		Jitu Padhye, Roberto Peon, Rob Trace (Flow control)
	o Mark Nottingham, Julian Reschke, James Snell (Editorial)		o Mark Nottingham, Julian Reschke, James Snell, Jeff Pinner
			(Substantial editorial contributions)
	10. References		14. References
	10.1. Normative References		14.1. Normative References
	[HTTP-p1] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol		[COMPRESSION] Ruellan, H. and R. Peon, "HTTP Header Compression",
	(HTTP/1.1): Message Syntax and Routing",		draft-ietf-httpbis-header-compression-00 (work in
	draft-ietf-httpbis-p1-messaging-22 (work in progress),		progress), June 2013.
	February 2013.
	[HTTP-p2] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol		[HTTP-p1] Fielding, R. and J. Reschke, "Hypertext Transfer
	(HTTP/1.1): Semantics and Content",		Protocol (HTTP/1.1): Message Syntax and Routing",
	draft-ietf-httpbis-p2-semantics-22 (work in progress),		draft-ietf-httpbis-p1-messaging-22 (work in progress),
	February 2013.		February 2013.
	[HTTP-p4] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer		[HTTP-p2] Fielding, R. and J. Reschke, "Hypertext Transfer
	Protocol (HTTP/1.1): Conditional Requests",		Protocol (HTTP/1.1): Semantics and Content",
	draft-ietf-httpbis-p4-conditional-22 (work in progress),		draft-ietf-httpbis-p2-semantics-22 (work in progress),
	February 2013.		February 2013.
	[HTTP-p5] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed.,		[HTTP-p4] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
	"Hypertext Transfer Protocol (HTTP/1.1): Range Requests",		Transfer Protocol (HTTP/1.1): Conditional Requests",
	draft-ietf-httpbis-p5-range-22 (work in progress),		draft-ietf-httpbis-p4-conditional-22 (work in
	February 2013.		progress), February 2013.
	[HTTP-p6] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,		[HTTP-p5] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke,
	Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",		Ed., "Hypertext Transfer Protocol (HTTP/1.1): Range
	draft-ietf-httpbis-p6-cache-22 (work in progress),		Requests", draft-ietf-httpbis-p5-range-22 (work in
	February 2013.		progress), February 2013.
	[HTTP-p7] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer		[HTTP-p6] Fielding, R., Ed., Nottingham, M., Ed., and J.
	Protocol (HTTP/1.1): Authentication",		Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1):
	draft-ietf-httpbis-p7-auth-22 (work in progress),		Caching", draft-ietf-httpbis-p6-cache-22 (work in
	February 2013.		progress), February 2013.
	[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,		[HTTP-p7] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
	RFC 793, September 1981.		Transfer Protocol (HTTP/1.1): Authentication",
			draft-ietf-httpbis-p7-auth-22 (work in progress),
			February 2013.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
	Requirement Levels", BCP 14, RFC 2119, March 1997.		RFC 793, September 1981.
	[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
			Requirement Levels", BCP 14, RFC 2119, March 1997.
	[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform		[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
	Resource Identifier (URI): Generic Syntax", STD 66,
	RFC 3986, January 2005.
	[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an		[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter,
	IANA Considerations Section in RFCs", BCP 26, RFC 5226,		"Uniform Resource Identifier (URI): Generic Syntax",
	May 2008.		STD 66, RFC 3986, January 2005.
	[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security		[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
	(TLS) Protocol Version 1.2", RFC 5246, August 2008.		Encodings", RFC 4648, October 2006.
	[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454,		[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing
	December 2011.		an IANA Considerations Section in RFCs", BCP 26,
			RFC 5226, May 2008.
	[TLSALPN] Friedl, S., Popov, A., Langley, A., and E. Stephan,		[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
	"Transport Layer Security (TLS) Application Layer Protocol		Specifications: ABNF", STD 68, RFC 5234, January 2008.
	Negotiation Extension", draft-ietf-tls-applayerprotoneg-01
	(work in progress), April 2013.
	10.2. Informative References		[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer
			Security (TLS) Protocol Version 1.2", RFC 5246,
			August 2008.
	[RFC1323] Jacobson, V., Braden, B., and D. Borman, "TCP Extensions		[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454,
	for High Performance", RFC 1323, May 1992.		December 2011.
	[TALKING] Huang, L-S., Chen, E., Barth, A., Rescorla, E., and C.		[TLSALPN] Friedl, S., Popov, A., Langley, A., and E. Stephan,
			"Transport Layer Security (TLS) Application Layer
			Protocol Negotiation Extension",
			draft-ietf-tls-applayerprotoneg-01 (work in progress),
			April 2013.
	Jackson, "Talking to Yourself for Fun and Profit", 2011,		14.2. Informative References
	<http://w2spconf.com/2011/papers/websocket.pdf>.
			[BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration
			Procedures for Message Header Fields", BCP 90,
			RFC 3864, September 2004.
			[RFC1323] Jacobson, V., Braden, B., and D. Borman, "TCP
			Extensions for High Performance", RFC 1323, May 1992.
			[TALKING] Huang, L-S., Chen, E., Barth, A., Rescorla, E., and C.
			Jackson, "Talking to Yourself for Fun and Profit",
			2011, <http://w2spconf.com/2011/papers/websocket.pdf>.
	Appendix A. Change Log (to be removed by RFC Editor before publication)		Appendix A. Change Log (to be removed by RFC Editor before publication)
	A.1. Since draft-ietf-httpbis-http2-02		A.1. Since draft-ietf-httpbis-http2-03
			Committed major restructuring atrocities.
			Added reference to first header compression draft.
			Added more formal description of frame lifecycle.
			Moved END_STREAM (renamed from FINAL) back to HEADERS/DATA.
			Removed HEADERS+PRIORITY, added optional priority to HEADERS frame.
			Added PRIORITY frame.
			A.2. Since draft-ietf-httpbis-http2-02
	Added continuations to frames carrying header blocks.		Added continuations to frames carrying header blocks.
	Replaced use of "session" with "connection" to avoid confusion with		Replaced use of "session" with "connection" to avoid confusion with
	other HTTP stateful concepts, like cookies.		other HTTP stateful concepts, like cookies.
	Removed "message".		Removed "message".
	Switched to TLS ALPN from NPN.		Switched to TLS ALPN from NPN.
	Editorial changes.		Editorial changes.
	A.2. Since draft-ietf-httpbis-http2-01		A.3. Since draft-ietf-httpbis-http2-01
	Added IANA considerations section for frame types, error codes and		Added IANA considerations section for frame types, error codes and
	settings.		settings.
	Removed data frame compression.		Removed data frame compression.
	Added PUSH_PROMISE.		Added PUSH_PROMISE.
	Added globally applicable flags to framing.		Added globally applicable flags to framing.
	skipping to change at page 47, line 7 ¶		skipping to change at page 51, line 31 ¶
	Restructured frame header. Removed distinction between data and		Restructured frame header. Removed distinction between data and
	control frames.		control frames.
	Altered flow control properties to include session-level limits.		Altered flow control properties to include session-level limits.
	Added note on cacheability of pushed resources and multiple tenant		Added note on cacheability of pushed resources and multiple tenant
	servers.		servers.
	Changed protocol label form based on discussions.		Changed protocol label form based on discussions.
	A.3. Since draft-ietf-httpbis-http2-00		A.4. Since draft-ietf-httpbis-http2-00
	Changed title throughout.		Changed title throughout.
	Removed section on Incompatibilities with SPDY draft#2.		Removed section on Incompatibilities with SPDY draft#2.
	Changed INTERNAL_ERROR on GOAWAY to have a value of 2 <https://		Changed INTERNAL_ERROR on GOAWAY to have a value of 2 <https://
	groups.google.com/forum/?fromgroups#!topic/spdy-dev/cfUef2gL3iU>.		groups.google.com/forum/?fromgroups#!topic/spdy-dev/cfUef2gL3iU>.
	Replaced abstract and introduction.		Replaced abstract and introduction.
	Added section on starting HTTP/2.0, including upgrade mechanism.		Added section on starting HTTP/2.0, including upgrade mechanism.
	Removed unused references.		Removed unused references.
	Added flow control principles (Section 3.6.1) based on <http://		Added flow control principles (Section 5.2.1) based on <http://
	tools.ietf.org/html/draft-montenegro-httpbis-http2-fc-principles-01>.		tools.ietf.org/html/draft-montenegro-httpbis-http2-fc-principles-01>.
	A.4. Since draft-mbelshe-httpbis-spdy-00		A.5. Since draft-mbelshe-httpbis-spdy-00
	Adopted as base for draft-ietf-httpbis-http2.		Adopted as base for draft-ietf-httpbis-http2.
	Updated authors/editors list.		Updated authors/editors list.
	Added status note.		Added status note.
	Authors' Addresses		Authors' Addresses
	Mike Belshe		Mike Belshe
End of changes. 309 change blocks.
	1073 lines changed or deleted		1291 lines changed or added
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