draft-ietf-quic-http-00.txt		draft-ietf-quic-http-01.txt
	QUIC M. Bishop, Ed.		QUIC M. Bishop, Ed.
	Internet-Draft Microsoft		Internet-Draft Microsoft
	Intended status: Standards Track November 28, 2016		Intended status: Standards Track January 14, 2017
	Expires: June 1, 2017		Expires: July 18, 2017
	Hypertext Transfer Protocol (HTTP) over QUIC		Hypertext Transfer Protocol (HTTP) over QUIC
	draft-ietf-quic-http-00		draft-ietf-quic-http-01
	Abstract		Abstract
	The QUIC transport protocol has several features that are desirable		The QUIC transport protocol has several features that are desirable
	in a transport for HTTP/2, such as stream multiplexing, per-stream		in a transport for HTTP, such as stream multiplexing, per-stream flow
	flow control, and low-latency connection establishment. This		control, and low-latency connection establishment. This document
	document describes a mapping of HTTP/2 semantics over QUIC.		describes a mapping of HTTP semantics over QUIC. Specifically, this
	Specifically, this document identifies HTTP/2 features that are		document identifies HTTP/2 features that are subsumed by QUIC, and
	subsumed by QUIC, and describes how the other features can be		describes how the other features can be implemented atop QUIC.
	implemented atop QUIC.
			Note to Readers
			Discussion of this draft takes place on the QUIC working group
			mailing list (quic@ietf.org), which is archived at
			https://mailarchive.ietf.org/arch/search/?email_list=quic .
			Working Group information can be found at https://github.com/quicwg ;
			source code and issues list for this draft can be found at
			https://github.com/quicwg/base-drafts/labels/http .
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	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 June 1, 2017.		This Internet-Draft will expire on July 18, 2017.
	Copyright Notice		Copyright Notice
	Copyright (c) 2016 IETF Trust and the persons identified as the		Copyright (c) 2017 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
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
	1.1. Notational Conventions . . . . . . . . . . . . . . . . . 2		1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
	2. QUIC advertisement . . . . . . . . . . . . . . . . . . . . . 3		2. QUIC Advertisement . . . . . . . . . . . . . . . . . . . . . 3
	3. Connection establishment . . . . . . . . . . . . . . . . . . 3		2.1. QUIC Version Hints . . . . . . . . . . . . . . . . . . . 4
	4. Sending a request on an HTTP/2-over-QUIC connection . . . . . 4		3. Connection Establishment . . . . . . . . . . . . . . . . . . 4
	4.1. Terminating a stream . . . . . . . . . . . . . . . . . . 4		3.1. Draft Version Identification . . . . . . . . . . . . . . 5
	5. Writing data to QUIC streams . . . . . . . . . . . . . . . . 5		4. Stream Mapping and Usage . . . . . . . . . . . . . . . . . . 5
	6. Stream Mapping . . . . . . . . . . . . . . . . . . . . . . . 5		4.1. Stream 3: Connection Control Stream . . . . . . . . . . . 6
	6.1. Reserved Streams . . . . . . . . . . . . . . . . . . . . 5		4.2. HTTP Message Exchanges . . . . . . . . . . . . . . . . . 6
	6.1.1. Stream 3: headers . . . . . . . . . . . . . . . . . . 6		4.2.1. Header Compression . . . . . . . . . . . . . . . . . 7
	6.1.2. Stream states . . . . . . . . . . . . . . . . . . . . 6		4.2.2. The CONNECT Method . . . . . . . . . . . . . . . . . 8
	7. Stream Priorities . . . . . . . . . . . . . . . . . . . . . . 7		4.3. Stream Priorities . . . . . . . . . . . . . . . . . . . . 9
	8. Flow Control . . . . . . . . . . . . . . . . . . . . . . . . 8		4.4. Flow Control . . . . . . . . . . . . . . . . . . . . . . 9
	9. Server Push . . . . . . . . . . . . . . . . . . . . . . . . . 8		4.5. Server Push . . . . . . . . . . . . . . . . . . . . . . . 9
	10. Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . 8		5. HTTP Framing Layer . . . . . . . . . . . . . . . . . . . . . 10
	11. Other HTTP/2 frames . . . . . . . . . . . . . . . . . . . . . 9		5.1. Frame Layout . . . . . . . . . . . . . . . . . . . . . . 10
	11.1. GOAWAY frame . . . . . . . . . . . . . . . . . . . . . . 9		5.2. Frame Definitions . . . . . . . . . . . . . . . . . . . . 11
	11.2. PING frame . . . . . . . . . . . . . . . . . . . . . . . 10		5.2.1. DATA . . . . . . . . . . . . . . . . . . . . . . . . 11
	11.3. PADDING frame . . . . . . . . . . . . . . . . . . . . . 10		5.2.2. HEADERS . . . . . . . . . . . . . . . . . . . . . . . 11
	12. Security Considerations . . . . . . . . . . . . . . . . . . . 10		5.2.3. PRIORITY . . . . . . . . . . . . . . . . . . . . . . 12
	13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10		5.2.4. RST_STREAM . . . . . . . . . . . . . . . . . . . . . 13
	14. Normative References . . . . . . . . . . . . . . . . . . . . 10		5.2.5. SETTINGS . . . . . . . . . . . . . . . . . . . . . . 13
	Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 11		5.2.6. PUSH_PROMISE . . . . . . . . . . . . . . . . . . . . 16
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11		5.2.7. PING . . . . . . . . . . . . . . . . . . . . . . . . 17
			5.2.8. GOAWAY frame . . . . . . . . . . . . . . . . . . . . 17
			5.2.9. WINDOW_UPDATE frame . . . . . . . . . . . . . . . . . 17
			5.2.10. CONTINUATION frame . . . . . . . . . . . . . . . . . 17
			5.2.11. SETTINGS_ACK Frame . . . . . . . . . . . . . . . . . 18
			6. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 19
			6.1. HTTP-Defined QUIC Error Codes . . . . . . . . . . . . . . 19
			6.2. Mapping HTTP/2 Error Codes . . . . . . . . . . . . . . . 20
			7. Security Considerations . . . . . . . . . . . . . . . . . . . 21
			8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
			8.1. Registration of HTTP/QUIC Identification String . . . . . 21
			8.2. Registration of Version Hint Alt-Svc Parameter . . . . . 21
			8.3. Existing Frame Types . . . . . . . . . . . . . . . . . . 22
			8.4. New Frame Types . . . . . . . . . . . . . . . . . . . . . 23
			9. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
			9.1. Normative References . . . . . . . . . . . . . . . . . . 23
			9.2. Informative References . . . . . . . . . . . . . . . . . 24
			Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 24
			Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 24
			B.1. Since draft-ietf-quic-http-00: . . . . . . . . . . . . . 24
			B.2. Since draft-shade-quic-http2-mapping-00: . . . . . . . . 25
			Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 25
	1. Introduction		1. Introduction
	The QUIC transport protocol has several features that are desirable		The QUIC transport protocol has several features that are desirable
	in a transport for HTTP/2, such as stream multiplexing, per-stream		in a transport for HTTP, such as stream multiplexing, per-stream flow
	flow control, and low-latency connection establishment. This		control, and low-latency connection establishment. This document
	document describes a mapping of HTTP/2 semantics over QUIC.		describes a mapping of HTTP semantics over QUIC, drawing heavily on
	Specifically, this document identifies HTTP/2 features that are		the existing TCP mapping, HTTP/2. Specifically, this document
	subsumed by QUIC, and describes how the other features can be		identifies HTTP/2 features that are subsumed by QUIC, and describes
	implemented atop QUIC.		how the other features can be implemented atop QUIC.
	QUIC is described in [QUIC-TRANSPORT]. For a full description of		QUIC is described in [QUIC-TRANSPORT]. For a full description of
	HTTP/2, see [RFC7540].		HTTP/2, see [RFC7540].
	1.1. Notational Conventions		1.1. Notational Conventions
	The words "MUST", "MUST NOT", "SHOULD", and "MAY" are used in this		The words "MUST", "MUST NOT", "SHOULD", and "MAY" are used in this
	document. It's not shouting; when they are capitalized, they have		document. It's not shouting; when they are capitalized, they have
	the special meaning defined in [RFC2119].		the special meaning defined in [RFC2119].
	2. QUIC advertisement		2. QUIC Advertisement
	A server advertises that it can speak HTTP/2-over-QUIC via the Alt-		A server advertises that it can speak HTTP/QUIC via the Alt-Svc
	Svc HTTP response header. It does so by including the header in any		([RFC7838]) HTTP response header (or the semantically equivalent Alt-
	response sent over a non-QUIC (e.g. HTTP/2 over TLS) connection:		Svc HTTP/2 Extension Frame Type), using the ALPN token defined in
			Section 3.
	Alt-Svc: quic=":443"		Thus, a server could indicate in an HTTP/1.1 or HTTP/2 response that
			HTTP/QUIC was available on UDP port 443 by including the following
			header in any response:
	In addition, the list of QUIC versions supported by the server can be		Alt-Svc: hq=":443"
	specified by the v= parameter. For example, if a server supported
	both version 33 and 34 it would specify the following header:
	Alt-Svc: quic=":443"; v="34,33"		2.1. QUIC Version Hints
	On receipt of this header, a client may attempt to establish a QUIC		This document defines the "v" parameter for Alt-Svc, which is used to
	connection on port 443 and, if successful, send HTTP/2 requests using		provide version-negotiation hints to HTTP/QUIC clients. Syntax:
	the mapping described in this document.
	Connectivity problems (e.g. firewall blocking UDP) may result in QUIC		v = version
	connection establishment failure, in which case the client should		version = DQUOTE ( "c" version-string / "x" version-number ) DQUOTE
	gracefully fallback to HTTP/2-over-TLS/TCP.		version-string = token; percent-encoded QUIC version
			version-number = 1*8 HEXDIG; hex-encoded QUIC version
	3. Connection establishment		When multiple versions are supported, the "v" parameter MAY be
			repeated multiple times in a single Alt-Svc entry. For example, if a
			server supported both version "Q034" and version 0x00000001, it would
			specify the following header:
	HTTP/2-over-QUIC connections are established as described in		Alt-Svc: hq=":443";v="x1";v="cQ034"
	[QUIC-TRANSPORT]. The QUIC crypto handshake MUST use TLS [QUIC-TLS].
	While connection-level options pertaining to the core QUIC protocol		Where multiple versions are listed, the order of the values reflects
	are set in the initial crypto handshake [QUIC-TLS]. HTTP/2-specific		the server's preference (with the first value being the most
	settings are conveyed in the HTTP/2 SETTINGS frame. After the QUIC		preferred version).
	connection is established, an HTTP/2 SETTINGS frame may be sent as
	the initial frame of the QUIC headers stream (StreamID 3, See
	Section 6). As in HTTP/2, additional SETTINGS frames may be sent
	mid-connection by either endpoint.
	TODO: Decide whether to acknowledge receipt of SETTINGS through		QUIC versions are four-octet sequences with no additional constraints
	empty SETTINGS frames with ACK bit set, as in HTTP/2, or rely on		on format. Versions containing octets not allowed in tokens
	transport- level acknowledgment.		([RFC7230], Section 3.2.6) MUST be encoded using the hexidecimal
			representation. Versions containing only octets allowed in tokens
			MAY be encoded using either representation.
	Some transport-level options that HTTP/2-over-TCP specifies via the		On receipt of an Alt-Svc header indicating QUIC support, a client MAY
	SETTINGS frame are superseded by QUIC transport parameters in HTTP/2-		attempt to establish a QUIC connection on the indicated port and, if
	over-QUIC. Below is a listing of how each HTTP/2 SETTINGS parameter		successful, send HTTP requests using the mapping described in this
	is mapped:		document. Servers SHOULD list only versions which they support, but
			MAY omit supported versions for any reason.
	SETTINGS_HEADER_TABLE_SIZE: Sent in HTTP/2 SETTINGS frame.		Connectivity problems (e.g. firewall blocking UDP) may result in QUIC
			connection establishment failure, in which case the client should
			gracefully fall back to HTTP/2.
	SETTINGS_ENABLE_PUSH: Sent in HTTP/2 SETTINGS frame (TBD, currently		3. Connection Establishment
	set using QUIC "SPSH" connection option)
	SETTINGS_MAX_CONCURRENT_STREAMS QUIC requires the maximum number of		HTTP/QUIC connections are established as described in
	incoming streams per connection to be specified in the initial		[QUIC-TRANSPORT]. During connection establishment, HTTP/QUIC support
	crypto handshake, using the "MSPC" tag. Specifying		is indicated by selecting the ALPN token "hq" in the crypto
	SETTINGS_MAX_CONCURRENT_STREAMS in the HTTP/2 SETTINGS frame is an		handshake.
	error.
	SETTINGS_INITIAL_WINDOW_SIZE: QUIC requires both stream and		While connection-level options pertaining to the core QUIC protocol
	connection flow control window sizes to be specified in the		are set in the initial crypto handshake, HTTP-specific settings are
	initial crypto handshake, using the "SFCW" and "CFCW" tags,		conveyed in the SETTINGS frame. After the QUIC connection is
	respectively. Specifying SETTINGS_INITIAL_WINDOW_SIZE in the		established, a SETTINGS frame (Section 5.2.5) MUST be sent as the
	HTTP/2 SETTINGS frame is an error.		initial frame of the HTTP control stream (StreamID 3, see Section 4).
	SETTINGS_MAX_FRAME_SIZE: This setting has no equivalent in QUIC.		3.1. Draft Version Identification
	Specifying it in the HTTP/2 SETTINGS frame is an error.
	SETTINGS_MAX_HEADER_LIST_SIZE Sent in HTTP/2 SETTINGS frame.		*RFC Editor's Note:* Please remove this section prior to
			publication of a final version of this document.
	As with HTTP/2-over-TCP, unknown SETTINGS parameters are tolerated		Only implementations of the final, published RFC can identify
	but ignored. SETTINGS parameters are acknowledged by the receiving		themselves as "hq". Until such an RFC exists, implementations MUST
	peer, by sending an empty SETTINGS frame in response with the ACK bit		NOT identify themselves using these strings.
	set.
	4. Sending a request on an HTTP/2-over-QUIC connection		Implementations of draft versions of the protocol MUST add the string
			"-" and the corresponding draft number to the identifier. For
			example, draft-ietf-quic-http-01 is identified using the string "hq-
			01".
	A high level overview of sending an HTTP/2 request on an established		Non-compatible experiments that are based on these draft versions
	QUIC connection is as follows, with further details in later sections		MUST append the string "-" and an experiment name to the identifier.
	of this document. A client should first encode any HTTP headers		For example, an experimental implementation based on draft-ietf-quic-
	using HPACK [RFC7541] and frame them as HTTP/2 HEADERS frames. These		http-09 which reserves an extra stream for unsolicited transmission
	are sent on StreamID 3 (see Section 6). The exact layout of the		of 1980s pop music might identify itself as "hq-09-rickroll". Note
	HEADERS frame is described in Section 6.2 of [RFC7540]. No HTTP/2		that any label MUST conform to the "token" syntax defined in
	padding is required: QUIC provides a PADDING frame for this purpose.		Section 3.2.6 of [RFC7230]. Experimenters are encouraged to
			coordinate their experiments on the quic@ietf.org mailing list.
	While HEADERS are sent on stream 3, the mandatory stream identifier		4. Stream Mapping and Usage
	in each HEADERS frame indicates the QUIC StreamID on which a
	corresponding request body may be sent. If there is no non-header
	data, the specified QUIC data stream will never be used.
	4.1. Terminating a stream		A QUIC stream provides reliable in-order delivery of bytes, but makes
			no guarantees about order of delivery with regard to bytes on other
			streams. On the wire, data is framed into QUIC STREAM frames, but
			this framing is invisible to the HTTP framing layer. A QUIC receiver
			buffers and orders received STREAM frames, exposing the data
			contained within as a reliable byte stream to the application.
	A stream can be terminated in one of three ways:		QUIC reserves Stream 1 for crypto operations (the handshake, crypto
			config updates). Stream 3 is reserved for sending and receiving HTTP
			control frames, and is analogous to HTTP/2's Stream 0.
	o the request/response is headers only, in which case a HEADERS		When HTTP headers and data are sent over QUIC, the QUIC layer handles
	frame with the END_STREAM bit set ends the stream specified in the		most of the stream management. An HTTP request/response consumes a
	HEADERS frame		pair of streams: This means that the client's first request occurs on
			QUIC streams 5 and 7, the second on stream 9 and 11, and so on. The
			server's first push consumes streams 2 and 4. This amounts to the
			second least-significant bit differentiating the two streams in a
			request.
	o the request/response has headers and body but no trailing headers,		The lower-numbered stream is called the message control stream and
	in which case the final QUIC STREAM frame will have the FIN bit		carries frames related to the request/response, including HEADERS.
	set		All request control streams are exempt from connection-level flow
			control. The higher-numbered stream is the data stream and carries
			the request/response body with no additional framing. Note that a
			request or response without a body will cause this stream to be half-
			closed in the corresponding direction without transferring data.
	o the request/response has headers, body, and trailing headers, in		Pairs of streams must be utilized sequentially, with no gaps. The
	which case the final QUIC STREAM frame will not have the FIN bit		data stream MUST be reserved with the QUIC implementation when the
	set, and the trailing HEADERS frame will have the END_STREAM bit		message control stream is opened or reserved, and MUST be closed
	set		after transferring the body, or else closed immediately after sending
			the request headers if there is no body.
	(TODO: Describe mapping of HTTP/2 stream state machine to QUIC stream		HTTP does not need to do any separate multiplexing when using QUIC -
	state machine.)		data sent over a QUIC stream always maps to a particular HTTP
			transaction. Requests and responses are considered complete when the
			corresponding QUIC streams are closed in the appropriate direction.
	5. Writing data to QUIC streams		4.1. Stream 3: Connection Control Stream
	A QUIC stream provides reliable in-order delivery of bytes, within		Since most connection-level concerns from HTTP/2 will be managed by
	that stream. On the wire, data is framed into QUIC STREAM frames,		QUIC, the primary use of Stream 3 will be for SETTINGS and PRIORITY
	but this framing is invisible to the HTTP/2 layer. A QUIC receiver		frames. Stream 3 is exempt from connection-level flow-control.
	buffers and orders received STREAM frames, exposing the data
	contained within as a reliable byte stream to the application.
	Bytes written to Stream 3 must be HTTP/2 HEADERS frames (or other		4.2. HTTP Message Exchanges
	HTTP/2 non-data frames), whereas bytes written to data streams should
	simply be request or response bodies. No further framing is required
	by HTTP/2 (i.e. no HTTP/2 DATA frames are used).
	If data arrives on a data stream before the corresponding HEADERS		A client sends an HTTP request on a new pair of QUIC streams. A
	have arrived on stream 3, then the data is buffered until the HEADERS		server sends an HTTP response on the same streams as the request.
	arrive.
	6. Stream Mapping		An HTTP message (request or response) consists of:
	When HTTP/2 headers and data are sent over QUIC, the QUIC layer		1. for a response only, zero or more header blocks (a sequence of
	handles most of the stream management. HTTP/2 StreamIDs are replaced		HEADERS frames with End Header Block set on the last) on the
	by QUIC StreamIDs. HTTP/2 does not need to do any explicit stream		control stream containing the message headers of informational
	framing when using QUIC - data sent over a QUIC stream simply		(1xx) HTTP responses (see [RFC7230], Section 3.2 and [RFC7231],
	consists of HTTP/2 headers or body. Requests and responses are		Section 6.2),
	considered complete when the QUIC stream is closed in the
	corresponding direction.
	Like HTTP/2, QUIC uses odd-numbered StreamIDs for client initiated		2. one header block on the control stream containing the message
	streams, and even-numbered IDs for server initiated (i.e. server		headers (see [RFC7230], Section 3.2),
	push) streams. Unlike HTTP/2 there are a couple of reserved (or
	dedicated) StreamIDs in QUIC.
	6.1. Reserved Streams		3. the payload body (see [RFC7230], Section 3.3), sent on the data
			stream,
	StreamID 1 is reserved for crypto operations (the handshake, crypto		4. optionally, one header block on the control stream containing the
	config updates), and MUST NOT be used for HTTP/2 headers or body, see		trailer-part, if present (see [RFC7230], Section 4.1.2).
	[QUIC-TRANSPORT]. StreamID 3 is reserved for sending and receiving
	HTTP/2 HEADERS frames. Therefore the first client initiated data
	stream has StreamID 5.
	There are no reserved server initiated StreamIDs, so the first server		The data stream MUST be half-closed immediately after the transfer of
	initiated (i.e. server push) stream has an ID of 2, followed by 4,		the body. If the message does not contain a body, the corresponding
	etc.		data stream MUST still be half-closed without transferring any data.
			The "chunked" transfer encoding defined in Section 4.1 of [RFC7230]
			MUST NOT be used.
	6.1.1. Stream 3: headers		Trailing header fields are carried in a header block following the
			body. Such a header block is a sequence of HEADERS frames with End
			Header Block set on the last frame. Header blocks after the first
			but before the end of the stream are invalid. These MUST be decoded
			to maintain HPACK decoder state, but the resulting output MUST be
			discarded.
	HTTP/2-over-QUIC uses HPACK header compression as described in		An HTTP request/response exchange fully consumes a pair of streams.
	[RFC7541]. HPACK was designed for HTTP/2 with the assumption of in-		After sending a request, a client closes the streams for sending;
	order delivery such as that provided by TCP. A sequence of encoded		after sending a response, the server closes its streams for sending
	header blocks must arrive (and be decoded) at an endpoint in the same		and the QUIC streams are fully closed.
	order in which they were encoded. This ensures that the dynamic
	state at the two endpoints remains in sync.		A server can send a complete response prior to the client sending an
			entire request if the response does not depend on any portion of the
			request that has not been sent and received. When this is true, a
			server MAY request that the client abort transmission of a request
			without error by sending a RST_STREAM with an error code of NO_ERROR
			after sending a complete response and closing its stream. Clients
			MUST NOT discard responses as a result of receiving such a
			RST_STREAM, though clients can always discard responses at their
			discretion for other reasons.
			4.2.1. Header Compression
			HTTP/QUIC uses HPACK header compression as described in [RFC7541].
			HPACK was designed for HTTP/2 with the assumption of in- order
			delivery such as that provided by TCP. A sequence of encoded header
			blocks must arrive (and be decoded) at an endpoint in the same order
			in which they were encoded. This ensures that the dynamic state at
			the two endpoints remains in sync.
	QUIC streams provide in-order delivery of data sent on those streams,		QUIC streams provide in-order delivery of data sent on those streams,
	but there are no guarantees about order of delivery between streams.		but there are no guarantees about order of delivery between streams.
	To achieve in-order delivery of HEADERS frames in QUIC, they are all		To achieve in-order delivery of HEADERS frames in QUIC, the HPACK-
	sent on the reserved Stream 3. Data (request/response bodies) which		bearing frames contain a counter which can be used to ensure in-order
	arrive on other data streams are buffered until the corresponding		processing. Data (request/response bodies) which arrive out of order
	HEADERS arrive and are read out of Stream 3.		are buffered until the corresponding HEADERS arrive.
	This does introduce head-of-line blocking: if the packet containing		This does introduce head-of-line blocking: if the packet containing
	HEADERS for stream N is lost or reordered then stream N+2 cannot be		HEADERS for stream N is lost or reordered then the HEADERS for stream
	processed until they it has been retransmitted successfully, even		N+4 cannot be processed until it has been retransmitted successfully,
	though the HEADERS for stream N+2 may have arrived.		even though the HEADERS for stream N+4 may have arrived.
	Trailing headers (trailers) can also be sent on stream 3. These are		DISCUSS: Keep HPACK with HOLB? Redesign HPACK to be order-
	sent as HTTP/2 HEADERS frames, but MUST have the END_STREAM bit set,		invariant? How much do we need to retain compatibility with
	and MUST include a ":final-offset" pseudo-header. Since QUIC		HTTP/2's HPACK?
	supports out of order delivery, receipt of a HEADERS frame with the
	END_STREAM bit set does not guarantee that the entire request/
	response body has been fully received. Therefore, the extra ":final-
	offset" pseudo-header is included in trailing HEADERS frames to
	indicate the total number of body bytes sent on the corresponding
	data stream. This is used by the QUIC layer to determine when the
	full request has been received and therefore when it is safe to tear
	down local stream state. The ":final-offset" pseudo header is
	stripped from the HEADERS before passing to the HTTP/2 layer.
	6.1.2. Stream states		4.2.2. The CONNECT Method
	The mapping of HTTP/2-over-QUIC with potential out of order delivery		The pseudo-method CONNECT ([RFC7231], Section 4.3.6) is primarily
	of HEADERS frames results in some changes to the HTTP/2 stream state		used with HTTP proxies to establish a TLS session with an origin
	transition diagram ([RFC7540], Section 5.1}}. Specifically the		server for the purposes of interacting with "https" resources. In
	transition from "open" to "half closed (remote)", and the transition		HTTP/1.x, CONNECT is used to convert an entire HTTP connection into a
	from "half closed (local)" to "closed" takes place only when:		tunnel to a remote host. In HTTP/2, the CONNECT method is used to
			establish a tunnel over a single HTTP/2 stream to a remote host for
			similar purposes.
	o the peer has explicitly ended the stream via either		A CONNECT request in HTTP/QUIC functions in the same manner as in
	* an HTTP/2 HEADERS frame with END_STREAM bit set and, in the		HTTP/2. The request MUST be formatted as described in [RFC7540],
	case of trailing headers, the :final-offset pseudo-header		Section 8.3. A CONNECT request that does not conform to these
			restrictions is malformed. The message data stream MUST NOT be
			closed at the end of the request.
	* or a QUIC stream frame with the FIN bit set.		A proxy that supports CONNECT establishes a TCP connection
			([RFC0793]) to the server identified in the ":authority" pseudo-
			header field. Once this connection is successfully established, the
			proxy sends a HEADERS frame containing a 2xx series status code to
			the client, as defined in [RFC7231], Section 4.3.6, on the message
			control stream.
	o and the full request or response body has been received.		All QUIC STREAM frames on the message data stream correspond to data
			sent on the TCP connection. Any QUIC STREAM frame sent by the client
			is transmitted by the proxy to the TCP server; data received from the
			TCP server is written to the data stream by the proxy. Note that the
			size and number of TCP segments is not guaranteed to map predictably
			to the size and number of QUIC STREAM frames.
	7. Stream Priorities		The TCP connection can be closed by either peer. When the client
			half-closes the data stream, the proxy will set the FIN bit on its
			connection to the TCP server. When the proxy receives a packet with
			the FIN bit set, it will half-close the corresponding data stream.
			TCP connections which remain half-closed in a single direction are
			not invalid, but are often handled poorly by servers, so clients
			SHOULD NOT half-close connections on which they are still expecting
			data.
	HTTP/2-over-QUIC uses the HTTP/2 priority scheme described in		A TCP connection error is signaled with RST_STREAM. A proxy treats
	[RFC7540] Section 5.3. In the HTTP/2 priority scheme, a given stream		any error in the TCP connection, which includes receiving a TCP
	can be designated as dependent upon another stream, which expresses		segment with the RST bit set, as a stream error of type
	the preference that the latter stream (the "parent" stream) be		HTTP_CONNECT_ERROR (Section 6.1). Correspondingly, a proxy MUST send
	allocated resources before the former stream (the "dependent"		a TCP segment with the RST bit set if it detects an error with the
	stream). Taken together, the dependencies across all streams in a		stream or the QUIC connection.
	connection form a dependency tree. The structure of the dependency
	tree changes as HTTP/2 HEADERS and PRIORITY frames add, remove, or		4.3. Stream Priorities
	change the dependency links between streams.
			HTTP/QUIC uses the priority scheme described in [RFC7540]
			Section 5.3. In this priority scheme, a given stream can be
			designated as dependent upon another stream, which expresses the
			preference that the latter stream (the "parent" stream) be allocated
			resources before the former stream (the "dependent" stream). Taken
			together, the dependencies across all streams in a connection form a
			dependency tree. The structure of the dependency tree changes as
			HEADERS and PRIORITY frames add, remove, or change the dependency
			links between streams.
	Implicit in this scheme is the notion of in-order delivery of		Implicit in this scheme is the notion of in-order delivery of
	priority changes (i.e., dependency tree mutations): since operations		priority changes (i.e., dependency tree mutations): since operations
	on the dependency tree such as reparenting a subtree are not		on the dependency tree such as reparenting a subtree are not
	commutative, both sender and receiver must apply them in the same		commutative, both sender and receiver must apply them in the same
	order to ensure that both sides have a consistent view of the stream		order to ensure that both sides have a consistent view of the stream
	dependency tree. HTTP/2 specifies priority assignments in PRIORITY		dependency tree. HTTP/2 specifies priority assignments in PRIORITY
	frames and (optionally) in HEADERS frames. To achieve in-order		frames and (optionally) in HEADERS frames. To achieve in-order
	delivery of HTTP/2 priority changes in HTTP/2-over-QUIC, HTTP/2		delivery of priority changes in HTTP/QUIC, PRIORITY frames are sent
	PRIORITY frames, in addition to HEADERS frames, are also sent on		on the connection control stream and the PRIORITY section is removed
	reserved stream 3. The semantics of the Stream Dependency, Weight, E		from the HEADERS frame. The semantics of the Stream Dependency,
	flag, and (for HEADERS frames) PRIORITY flag are the same as in		Weight, E flag, and (for HEADERS frames) PRIORITY flag are the same
	HTTP/2-over-TCP.		as in HTTP/2.
	Since HEADERS and PRIORITY frames are sent on a different stream than
	the STREAM frames for the streams they reference, they may be
	delivered out-of-order with respect to the STREAM frames. There is
	no special handling for this-the receiver should simply assign
	resources according to the most recent stream priority information
	that it has received.
	ALTERNATIVE DESIGN: if the core QUIC protocol implements priorities,		For consistency's sake, all PRIORITY frames MUST refer to the message
	then this document should map the HTTP/2 priorities scheme to that		control stream of the dependent request, not the data stream.
	provided by the core protocol. This would likely involve prohibiting
	the sending of HTTP/2 PRIORITY frames and setting of the PRIORITY
	flag in HTTP/2 HEADERS frames, to avoid conflicting directives.
	8. Flow Control		4.4. Flow Control
	QUIC provides stream and connection level flow control, similar in		QUIC provides stream and connection level flow control, similar in
	principle to HTTP/2's flow control but with some implementation		principle to HTTP/2's flow control but with some implementation
	differences. As flow control is handled by QUIC, the HTTP/2 mapping		differences. As flow control is handled by QUIC, the HTTP mapping
	need not concern itself with maintaining flow control state, or how/		need not concern itself with maintaining flow control state. The
	when to send flow control frames to the peer. The HTTP/2 mapping		HTTP mapping MUST NOT send WINDOW_UPDATE frames at the HTTP level.
	must not send HTTP/2 WINDOW_UPDATE frames.
	The initial flow control window sizes (stream and connection) are
	communicated during the crypto handshake (see Section 3). Setting
	these values to the maximum size (2^31 - 1) effectively disables flow
	control.
	Relatively small initial windows can be used, as QUIC will attempt to
	auto-tune the flow control windows based on usage. See
	[QUIC-TRANSPORT] for more details.
	9. Server Push		4.5. Server Push
	HTTP/2-over-QUIC supports HTTP/2 server push. During connection		HTTP/QUIC supports server push as described in [RFC7540]. During
	establishment, the client indicates whether or it is willing to		connection establishment, the client indicates whether it is willing
	receive server pushes via the SETTINGS_ENABLE_PUSH setting in the		to receive server pushes via the SETTINGS_ENABLE_PUSH setting in the
	HTTP/2 SETTINGS frame (see Section 3), which defaults to 1 (true).		SETTINGS frame (see Section 3), which defaults to 1 (true).
	As with server push for HTTP/2-over-TCP, the server initiates a		As with server push for HTTP/2, the server initiates a server push by
	server push by sending an HTTP/2 PUSH_PROMISE frame containing the		sending a PUSH_PROMISE frame containing the StreamID of the stream to
	StreamID of the stream to be pushed, as well as request header fields		be pushed, as well as request header fields attributed to the
	attributed to the request. The PUSH_PROMISE frame is sent on stream		request. The PUSH_PROMISE frame is sent on the control stream of the
	3, to ensure proper ordering with respect to other HEADERS and non-		associated (client-initiated) request, while the Promised Stream ID
	data frames. Within the PUSH_PROMISE frame, the StreamID in the		field specifies the Stream ID of the control stream for the server-
	common HTTP/2 frame header indicates the associated (client-		initiated request.
	initiated) stream for the new push stream, while the Promised Stream
	ID field specifies the StreamID of the new push stream.
	The server push response is conveyed in the same way as a non-server-		The server push response is conveyed in the same way as a non-server-
	push response, with response headers and (if present) trailers		push response, with response headers and (if present) trailers
	carried by HTTP/2 HEADERS frames sent on reserved stream 3, and		carried by HEADERS frames sent on the control stream, and response
	response body (if any) sent via QUIC stream frames on the stream		body (if any) sent via the corresponding data stream.
	specified in the corresponding PUSH_PROMISE frame.
	10. Error Codes		5. HTTP Framing Layer
			Many framing concepts from HTTP/2 can be elided away on QUIC, because
			the transport deals with them. Because frames are already on a
			stream, they can omit the stream number. Because frames do not block
			multiplexing (QUIC's multiplexing occurs below this layer), the
			support for variable-maximum-length packets can be removed. Because
			stream termination is handled by QUIC, an END_STREAM flag is not
			required.
			Frames are used only on the connection (stream 3) and message
			(streams 5, 9, etc.) control streams. Other streams carry data
			payload and are not framed at the HTTP layer.
			Frame payloads are largely drawn from [RFC7540]. However, QUIC
			includes some features (e.g. flow control) which are also present in
			HTTP/2. In these cases, the HTTP mapping need not re-implement them.
			As a result, some frame types are not required when using QUIC.
			Where an HTTP/2-defined frame is no longer used, the frame ID is
			reserved in order to maximize portability between HTTP/2 and HTTP/
			QUIC implementations. However, equivalent frames between the two
			mappings are not necessarily identical.
			This section describes HTTP framing in QUIC and highlights
			differences from HTTP/2 framing.
			5.1. Frame Layout
			All frames have the following format:
			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
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Length (16) | Type (8) | Flags (8) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Frame Payload (*) ...
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			HTTP/QUIC frame format
			5.2. Frame Definitions
			5.2.1. DATA
			DATA frames do not exist. Frame type 0x0 is reserved.
			5.2.2. HEADERS
			The HEADERS frame (type=0x1) is used to carry part of a header set,
			compressed using HPACK [RFC7541]. Because HEADERS frames from
			different streams will be delivered out-of-order and priority-changes
			are not commutative, the PRIORITY region of HEADERS is not supported.
			A separate PRIORITY frame MUST be used.
			Padding MUST NOT be used. The flags defined are:
			Reserved (0x1): Reserved for HTTP/2 compatibility.
			End Header Block (0x4): This frame concludes a header block.
			Reserved (0x8): Reserved for HTTP/2 compatibility.
			Reserved (0x20): Reserved for HTTP/2 compatibility.
			A HEADERS frame with the Reserved bits set MUST be treated as a
			connection error of type HTTP_MALFORMED_HEADERS.
			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
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Sequence? (16) | Header Block Fragment (*)...
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			HEADERS frame payload
			The HEADERS frame payload has the following fields:
			Sequence Number: Present only on the first frame of a header block
			sequence. This MUST be set to zero on the first header block
			sequence, and incremented on each header block.
			The next frame on the same stream after a HEADERS frame without the
			EHB flag set MUST be another HEADERS frame. A receiver MUST treat
			the receipt of any other type of frame as a stream error of type
			HTTP_INTERRUPTED_HEADERS. (Note that QUIC can intersperse data from
			other streams between frames, or even during transmission of frames,
			so multiplexing is not blocked by this requirement.)
			A full header block is contained in a sequence of zero or more
			HEADERS frames without EHB set, followed by a HEADERS frame with EHB
			set.
			On receipt, header blocks (HEADERS, PUSH_PROMISE) MUST be processed
			by the HPACK decoder in sequence. If a block is missing, all
			subsequent HPACK frames MUST be held until it arrives, or the
			connection terminated.
			5.2.3. PRIORITY
			The PRIORITY (type=0x02) frame specifies the sender-advised priority
			of a stream and is substantially different from [RFC7540]. In order
			to support ordering, it MUST be sent only on the connection control
			stream. The format has been modified to accommodate not being sent
			on-stream and the larger stream ID space of QUIC.
			The flags defined are:
			E (0x01): Indicates that the stream dependency is exclusive (see
			[RFC7540] Section 5.3).
			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
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Prioritized Stream (32) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Dependent Stream (32) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Weight (8) |
			+-+-+-+-+-+-+-+-+
			HEADERS frame payload
			The HEADERS frame payload has the following fields:
			Prioritized Stream: A 32-bit stream identifier for the message
			control stream whose priority is being updated.
			Stream Dependency: A 32-bit stream identifier for the stream that
			this stream depends on (see Section 4.3 and {!RFC7540}}
			Section 5.3).
			Weight: An unsigned 8-bit integer representing a priority weight for
			the stream (see [RFC7540] Section 5.3). Add one to the value to
			obtain a weight between 1 and 256.
			A PRIORITY frame MUST have a payload length of nine octets. A
			PRIORITY frame of any other length MUST be treated as a connection
			error of type HTTP_MALFORMED_PRIORITY.
			5.2.4. RST_STREAM
			RST_STREAM frames do not exist, since QUIC provides stream lifecycle
			management. Frame type 0x3 is reserved.
			5.2.5. SETTINGS
			The SETTINGS frame (type=0x4) conveys configuration parameters that
			affect how endpoints communicate, such as preferences and constraints
			on peer behavior, and is substantially different from [RFC7540].
			Individually, a SETTINGS parameter can also be referred to as a
			"setting".
			SETTINGS parameters are not negotiated; they describe characteristics
			of the sending peer, which can be used by the receiving peer.
			However, a negotiation can be implied by the use of SETTINGS - a peer
			uses SETTINGS to advertise a set of supported values. The recipient
			can then choose which entries from this list are also acceptable and
			proceed with the value it has chosen. (This choice could be
			announced in a field of an extension frame, or in its own value in
			SETTINGS.)
			Different values for the same parameter can be advertised by each
			peer. For example, a client might permit a very large HPACK state
			table while a server chooses to use a small one to conserve memory.
			A SETTINGS frame MAY be sent at any time by either endpoint over the
			lifetime of the connection.
			Each parameter in a SETTINGS frame replaces any existing value for
			that parameter. Parameters are processed in the order in which they
			appear, and a receiver of a SETTINGS frame does not need to maintain
			any state other than the current value of its parameters. Therefore,
			the value of a SETTINGS parameter is the last value that is seen by a
			receiver.
			The SETTINGS frame defines the following flag:
			REQUEST_ACK (0x1): When set, bit 0 indicates that this frame
			contains values which the sender wants to know were understood and
			applied. For more information, see Section 5.2.5.3.
			The payload of a SETTINGS frame consists of zero or more parameters,
			each consisting of an unsigned 16-bit setting identifier and a
			length-prefixed binary value.
			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
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Identifier (16) |B| Length (15) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Contents (?) ...
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			Figure 1: SETTINGS value format
			A zero-length content indicates that the setting value is a Boolean
			given by the B bit. If Length is not zero, the B bit MUST be zero,
			and MUST be ignored by receivers. The initial value of each setting
			is "false" unless otherwise specified by the definition of the
			setting.
			Non-zero-length values MUST be compared against the remaining length
			of the SETTINGS frame. Any value which purports to cross the end of
			the frame MUST cause the SETTINGS frame to be considered malformed
			and trigger a connection error.
			An implementation MUST ignore the contents for any SETTINGS
			identifier it does not understand.
			SETTINGS frames always apply to a connection, never a single stream,
			and MUST only be sent on the connection control stream (Stream 3).
			If an endpoint receives an SETTINGS frame whose stream identifier
			field is anything other than 0x0, the endpoint MUST respond with a
			connection error of type HTTP_SETTINGS_ON_WRONG_STREAM.
			The SETTINGS frame affects connection state. A badly formed or
			incomplete SETTINGS frame MUST be treated as a connection error
			(Section 5.4.1) of type HTTP_MALFORMED_SETTINGS.
			5.2.5.1. Integer encoding
			Settings which are integers are transmitted in network byte order.
			Leading zero octets are permitted, but implementations SHOULD use
			only as many bytes as are needed to represent the value. An integer
			MUST NOT be represented in more bytes than would be used to transfer
			the maximum permitted value.
			5.2.5.2. Defined SETTINGS Parameters
			Some transport-level options that HTTP/2 specifies via the SETTINGS
			frame are superseded by QUIC transport parameters in HTTP/QUIC.
			Below is a listing of how each HTTP/2 SETTINGS parameter is mapped:
			SETTINGS_HEADER_TABLE_SIZE: An integer with a maximum value of 2^32
			- 1.
			SETTINGS_ENABLE_PUSH: Transmitted as a Boolean. The default remains
			"true" as specified in [RFC7540].
			SETTINGS_MAX_CONCURRENT_STREAMS: QUIC requires the maximum number of
			incoming streams per connection to be specified in the initial
			crypto handshake, using the "MSPC" tag. Specifying
			SETTINGS_MAX_CONCURRENT_STREAMS in the SETTINGS frame is an error.
			SETTINGS_INITIAL_WINDOW_SIZE: QUIC requires both stream and
			connection flow control window sizes to be specified in the
			initial crypto handshake, using the "SFCW" and "CFCW" tags,
			respectively. Specifying SETTINGS_INITIAL_WINDOW_SIZE in the
			SETTINGS frame is an error.
			SETTINGS_MAX_FRAME_SIZE: This setting has no equivalent in QUIC.
			Specifying it in the SETTINGS frame is an error.
			SETTINGS_MAX_HEADER_LIST_SIZE: An integer with a maximium value of
			2^32 - 1.
			5.2.5.3. Settings Synchronization
			Some values in SETTINGS benefit from or require an understanding of
			when the peer has received and applied the changed parameter values.
			In order to provide such synchronization timepoints, the recipient of
			a SETTINGS frame MUST apply the updated parameters as soon as
			possible upon receipt. The values in the SETTINGS frame MUST be
			processed in the order they appear, with no other frame processing
			between values. Unsupported parameters MUST be ignored.
			Once all values have been processed, if the REQUEST_ACK flag was set,
			the recipient MUST emit the following frames:
			o On the connection control stream, a SETTINGS_ACK frame
			(Section 5.2.11) listing the identifiers whose values were not
			understood.
			o On each request control stream which is not in the "half-closed
			(local)" or "closed" state, an empty SETTINGS_ACK frame.
			The SETTINGS_ACK frame on the connection control stream contains the
			highest stream number which was open at the time the SETTINGS frame
			was received. All streams with higher numbers can safely be assumed
			to have the new settings in effect when they open.
			For already-open streams including the connection control stream, the
			SETTINGS_ACK frame indicates the point at which the new settings took
			effect, if they did so before the peer half-closed the stream. If
			the peer closed the stream before receiving the SETTINGS frame, the
			previous settings were in effect for the full lifetime of that
			stream.
			In certain conditions, the SETTINGS_ACK frame can be the first frame
			on a given stream - this simply indicates that the new settings apply
			from the beginning of that stream.
			If the sender of a SETTINGS frame with the REQUEST_ACK flag set does
			not receive full acknowledgement within a reasonable amount of time,
			it MAY issue a connection error (Section 6) of type
			HTTP_SETTINGS_TIMEOUT. A full acknowledgement has occurred when:
			o All previous SETTINGS frames have been fully acknowledged,
			o A SETTINGS_ACK frame has been received on the connection control
			stream,
			o All message control streams with a Stream ID through those given
			in the SETTINGS_ACK frame have either closed or received a
			SETTINGS_ACK frame.
			5.2.6. PUSH_PROMISE
			The PUSH_PROMISE frame (type=0x05) is used to carry a request header
			set from server to client, as in HTTP/2. It defines no flags.
			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
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Promised Stream ID (32) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Sequence? (16) | Header Block (*) ...
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			PUSH_PROMISE frame payload
			The payload consists of:
			Promised Stream ID: A 32-bit Stream ID indicating the QUIC stream on
			which the response headers will be sent. (The response body
			stream is implied by the headers stream, as defined in Section 4.)
			HPACK Sequence: A sixteen-bit counter, equivalent to the Sequence
			field in HEADERS
			Payload: HPACK-compressed request headers for the promised response.
			TODOs:
			o QUIC stream space may be enlarged; would need to redefine Promised
			Stream field in this case.
			o No CONTINUATION - HEADERS have EHB; do we need it here?
			5.2.7. PING
			PING frames do not exist, since QUIC provides equivalent
			functionality. Frame type 0x6 is reserved.
			5.2.8. GOAWAY frame
			GOAWAY frames do not exist, since QUIC provides equivalent
			functionality. Frame type 0x7 is reserved.
			5.2.9. WINDOW_UPDATE frame
			WINDOW_UPDATE frames do not exist, since QUIC provides equivalent
			functionality. Frame type 0x8 is reserved.
			5.2.10. CONTINUATION frame
			CONTINUATION frames do not exist, since larger supported HEADERS/
			PUSH_PROMISE frames provide equivalent functionality. Frame type 0x9
			is reserved.
			5.2.11. SETTINGS_ACK Frame
			The SETTINGS_ACK frame (id = 0x0b) acknowledges receipt and
			application of specific values in the peer's SETTINGS frame.
			Depending on the stream where it is sent, it takes two different
			forms.
			On the connection control stream, it contains information about how
			and when the sender has processed the most recently-received SETTINGS
			frame, and has the following payload:
			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
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Highest Local Stream (32) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Highest Remote Stream (32) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Unrecognized Identifiers (*) ...
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			Figure 2: SETTINGS_ACK connection control stream format
			Highest Local Stream (32 bits): The highest locally-initiated Stream
			ID which is not in the "idle" state
			Highest Remote Stream (32 bits): The highest peer-initiated Stream
			ID which is not in the "idle" state
			Unrecognized Identifiers: A list of 16-bit SETTINGS identifiers
			which the sender has not understood and therefore ignored. This
			list MAY be empty.
			On message control streams, the SETTINGS_ACK frame carries no
			payload, and is strictly a synchronization marker for settings
			application. See Section 5.2.5.3 for more detail. A SETTINGS_ACK
			frame with a non-zero length MUST be treated as a connection error of
			type HTTP_MALFORMED_SETTINGS_ACK.
			On the connection control stream, the SETTINGS_ACK frame MUST have a
			length which is a multiple of two octets. A SETTINGS_ACK frame of
			any other length MUST be treated as a connection error of type
			HTTP_MALFORMED_SETTINGS_ACK.
			6. Error Handling
			This section describes the specific error codes defined by HTTP and
			the mapping of HTTP/2 error codes into the QUIC error code space.
			6.1. HTTP-Defined QUIC Error Codes
			QUIC allocates error codes 0x0000-0x3FFF to application protocol
			definition. The following error codes are defined by HTTP for use in
			QUIC RST_STREAM, GOAWAY, and CONNECTION_CLOSE frames.
			HTTP_SETTINGS_TIMEOUT (0x00): After sending a SETTINGS frame which
			requested acknowledgement, the acknowledgement was not completed
			(see Section 5.2.5.3) in a timely manner.
			HTTP_PUSH_REFUSED (0x01): The server has attempted to push content
			which the client will not accept on this connection.
			HTTP_INTERNAL_ERROR (0x02): An internal error has occurred in the
			HTTP stack.
			HTTP_PUSH_ALREADY_IN_CACHE (0x03): The server has attempted to push
			content which the client has cached.
			HTTP_REQUEST_CANCELLED (0x04): The client no longer needs the
			requested data.
			HTTP_HPACK_DECOMPRESSION_FAILED (0x05): HPACK failed to decompress a
			frame and cannot continue.
			HTTP_CONNECT_ERROR (0x06): The connection established in response to
			a CONNECT request was reset or abnormally closed.
			HTTP_EXCESSIVE_LOAD (0x07): The endpoint detected that its peer is
			exhibiting a behavior that might be generating excessive load.
			HTTP_VERSION_FALLBACK (0x08): The requested operation cannot be
			served over HTTP/QUIC. The peer should retry over HTTP/2.
			HTTP_MALFORMED_HEADERS (0x09): A HEADERS frame has been received
			with an invalid format.
			HTTP_MALFORMED_PRIORITY (0x0A): A HEADERS frame has been received
			with an invalid format.
			HTTP_MALFORMED_SETTINGS (0x0B): A HEADERS frame has been received
			with an invalid format.
			HTTP_MALFORMED_PUSH_PROMISE (0x0C): A HEADERS frame has been
			received with an invalid format.
			HTTP_MALFORMED_SETTINGS_ACK (0x0D): A HEADERS frame has been
			received with an invalid format.
			HTTP_INTERRUPTED_HEADERS (0x0E): A HEADERS frame without the End
			Header Block flag was followed by a frame other than HEADERS.
			HTTP_SETTINGS_ON_WRONG_STREAM (0x0F): A SETTINGS frame was received
			on a request control stream.
			6.2. Mapping HTTP/2 Error Codes
	The HTTP/2 error codes defined in Section 7 of [RFC7540] map to QUIC		The HTTP/2 error codes defined in Section 7 of [RFC7540] map to QUIC
	error codes as follows:		error codes as follows:
	NO_ERROR (0x0): Maps to QUIC_NO_ERROR		NO_ERROR (0x0): QUIC_NO_ERROR
	PROTOCOL_ERROR (0x1): No single mapping?
	INTERNAL_ERROR (0x2) QUIC_INTERNAL_ERROR? (not currently defined in		PROTOCOL_ERROR (0x1): No single mapping. See new HTTP_MALFORMED_*
	core protocol spec)		error codes defined in Section 6.1.
	FLOW_CONTROL_ERROR (0x3): QUIC_FLOW_CONTROL_RECEIVED_TOO_MUCH_DATA?		INTERNAL_ERROR (0x2) HTTP_INTERNAL_ERROR in Section 6.1.
	(not currently defined in core protocol spec)
	SETTINGS_TIMEOUT (0x4): (depends on whether we support SETTINGS		FLOW_CONTROL_ERROR (0x3): Not applicable, since QUIC handles flow
	acks)		control. Would provoke a QUIC_FLOW_CONTROL_RECEIVED_TOO_MUCH_DATA
			from the QUIC layer.
	STREAM_CLOSED (0x5): QUIC_STREAM_DATA_AFTER_TERMINATION		SETTINGS_TIMEOUT (0x4): HTTP_SETTINGS_TIMEOUT in Section 6.1.
	FRAME_SIZE_ERROR (0x6) QUIC_INVALID_FRAME_DATA		STREAM_CLOSED (0x5): Not applicable, since QUIC handles stream
			management. Would provoke a QUIC_STREAM_DATA_AFTER_TERMINATION
			from the QUIC layer.
	REFUSED_STREAM (0x7): ?		FRAME_SIZE_ERROR (0x6) No single mapping. See new error codes
			defined in Section 6.1.
	CANCEL (0x8): ?		REFUSED_STREAM (0x7): Not applicable, since QUIC handles stream
			management. Would provoke a QUIC_TOO_MANY_OPEN_STREAMS from the
			QUIC layer.
	COMPRESSION_ERROR (0x9): QUIC_DECOMPRESSION_FAILURE (not currently		CANCEL (0x8): HTTP_REQUEST_CANCELLED in Section 6.1.
	defined in core spec)
	CONNECT_ERROR (0xa): ? (depends whether we decide to support		COMPRESSION_ERROR (0x9): HTTP_HPACK_DECOMPRESSION_FAILED in
	CONNECT)		Section 6.1.
	ENHANCE_YOUR_CALM (0xb): ?		CONNECT_ERROR (0xa): HTTP_CONNECT_ERROR in Section 6.1.
	INADEQUATE_SECURITY (0xc): QUIC_HANDSHAKE_FAILED,		ENHANCE_YOUR_CALM (0xb): HTTP_EXCESSIVE_LOAD in Section 6.1.
	QUIC_CRYPTO_NO_SUPPORT
	HTTP_1_1_REQUIRED (0xd): ?		INADEQUATE_SECURITY (0xc): Not applicable, since QUIC is assumed to
			provide sufficient security on all connections.
			HTTP_1_1_REQUIRED (0xd): HTTP_VERSION_FALLBACK in Section 6.1.
	TODO: fill in missing error code mappings.		TODO: fill in missing error code mappings.
	11. Other HTTP/2 frames		7. Security Considerations
	QUIC includes some features (e.g. flow control) which are also		The security considerations of HTTP over QUIC should be comparable to
	present in HTTP/2. In these cases the HTTP/2 mapping need not re-		those of HTTP/2.
	implement them. As a result some HTTP/2 frame types are not required
	when using QUIC, as they either are directly implemented in the QUIC
	layer, or their functionality is provided via other means. This
	section of the document describes these cases.
	11.1. GOAWAY frame		The modified SETTINGS format contains nested length elements, which
			could pose a security risk to an uncautious implementer. A SETTINGS
			frame parser MUST ensure that the length of the frame exactly matches
			the length of the settings it contains.
	QUIC has its own GOAWAY frame, and QUIC implementations may to expose		8. IANA Considerations
	the sending of a GOAWAY to the application. The semantics of sending
	a GOAWAY in QUIC are identical to HTTP/2: an endpoint sending a
	GOAWAY will continue processing open streams, but will not accept
	newly created streams.
	QUIC's GOAWAY frame is described in detail in the [QUIC-TRANSPORT].		8.1. Registration of HTTP/QUIC Identification String
	11.2. PING frame		This document creates a new registration for the identification of
			HTTP/QUIC in the "Application Layer Protocol Negotiation (ALPN)
			Protocol IDs" registry established in [RFC7301].
	QUIC has its own PING frame, which is currently exposed to the		The "hq" string identifies HTTP/QUIC:
	application. QUIC clients send periodic PINGs to servers if there
	are no currently active data streams on the connection.
	QUIC's PING frame is described in detail in the [QUIC-TRANSPORT].		Protocol: HTTP over QUIC
	11.3. PADDING frame		Identification Sequence: 0x68 0x71 ("hq")
	There is no HTTP/2 padding in this mapping; padding is instead		Specification: This document
	provided at the QUIC layer by including QUIC PADDING frames in a
	packet payload. An HTTP/2 over QUIC mapping should treat any HTTP/2
	level padding as an error, to avoid any possibility of inconsistent
	flow control states between endpoints (e.g. client sends HTTP/2
	padding, counts it against flow control, server ignores).
	12. Security Considerations		8.2. Registration of Version Hint Alt-Svc Parameter
	The security considerations of HTTP over QUIC should be comparable to		This document creates a new registration for version-negotiation
	those of HTTP/2.		hints in the "Hypertext Transfer Protocol (HTTP) Alt-Svc Parameter"
			registry established in [RFC7838].
	13. IANA Considerations		Parameter: "v"
	This document has no IANA actions. Yet.		Specification: This document, Section 2.1
	14. Normative References		8.3. Existing Frame Types
			This document adds two new columns to the "HTTP/2 Frame Type"
			registry defined in [RFC7540]:
			Supported Protocols: Indicates which associated protocols use the
			frame type. Values MUST be one of:
			* "HTTP/2 only"
			* "HTTP/QUIC only"
			* "Both"
			HTTP/QUIC Specification: Indicates where this frame's behavior over
			QUIC is defined; required if the frame is supported over QUIC.
			Values for existing registrations are assigned by this document:
			+---+---------------+---------------------+-------------------------+
			| | Frame Type | Supported Protocols | HTTP/QUIC Specification |
			+---+---------------+---------------------+-------------------------+
			| | DATA | HTTP/2 only | N/A |
			| | | | |
			| | HEADERS | Both | Section 5.2.2 |
			| | | | |
			| | PRIORITY | Both | Section 5.2.3 |
			| | | | |
			| | RST_STREAM | HTTP/2 only | N/A |
			| | | | |
			| | SETTINGS | Both | Section 5.2.5 |
			| | | | |
			| | PUSH_PROMISE | Both | Section 5.2.6 |
			| | | | |
			| | PING | HTTP/2 only | N/A |
			| | | | |
			| | GOAWAY | HTTP/2 only | N/A |
			| | | | |
			| | WINDOW_UPDATE | HTTP/2 only | N/A |
			| | | | |
			| | CONTINUATION | HTTP/2 only | N/A |
			+---+---------------+---------------------+-------------------------+
			The "Specification" column is renamed to "HTTP/2 specification" and
			is only required if the frame is supported over HTTP/2.
			8.4. New Frame Types
			This document adds one new entry to the "HTTP/2 Frame Type" registry
			defined in [RFC7540]:
			Frame Type: SETTINGS_ACK
			Code: 0x0b
			HTTP/2 Specification: N/A
			Supported Protocols: HTTP/QUIC only
			HTTP/QUIC Specification: Section 5.2.11
			9. References
			9.1. Normative References
	[QUIC-TLS]		[QUIC-TLS]
	Thomson, M., Ed. and S. Turner, Ed, Ed., "Using Transport		Thomson, M., Ed. and S. Turner, Ed, Ed., "Using Transport
	Layer Security (TLS) to Secure QUIC", November 2016.		Layer Security (TLS) to Secure QUIC".
	[QUIC-TRANSPORT]		[QUIC-TRANSPORT]
	Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based		Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
	Multiplexed and Secure Transport", November 2016.		Multiplexed and Secure Transport".
			[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
			RFC 793, DOI 10.17487/RFC0793, September 1981,
			<http://www.rfc-editor.org/info/rfc793>.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
			[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
			Protocol (HTTP/1.1): Message Syntax and Routing",
			RFC 7230, DOI 10.17487/RFC7230, June 2014,
			<http://www.rfc-editor.org/info/rfc7230>.
			[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
			Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
			DOI 10.17487/RFC7231, June 2014,
			<http://www.rfc-editor.org/info/rfc7231>.
	[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext		[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
	Transfer Protocol Version 2 (HTTP/2)", RFC 7540,		Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
	DOI 10.17487/RFC7540, May 2015,		DOI 10.17487/RFC7540, May 2015,
	<http://www.rfc-editor.org/info/rfc7540>.		<http://www.rfc-editor.org/info/rfc7540>.
	[RFC7541] Peon, R. and H. Ruellan, "HPACK: Header Compression for		[RFC7541] Peon, R. and H. Ruellan, "HPACK: Header Compression for
	HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015,		HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015,
	<http://www.rfc-editor.org/info/rfc7541>.		<http://www.rfc-editor.org/info/rfc7541>.
			[RFC7838] Nottingham, M., McManus, P., and J. Reschke, "HTTP
			Alternative Services", RFC 7838, DOI 10.17487/RFC7838,
			April 2016, <http://www.rfc-editor.org/info/rfc7838>.
			9.2. Informative References
			[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
			"Transport Layer Security (TLS) Application-Layer Protocol
			Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
			July 2014, <http://www.rfc-editor.org/info/rfc7301>.
	Appendix A. Contributors		Appendix A. Contributors
	The original authors of this specification were Robbie Shade and Mike		The original authors of this specification were Robbie Shade and Mike
	Warres.		Warres.
			Appendix B. Change Log
			*RFC Editor's Note:* Please remove this section prior to
			publication of a final version of this document.
			B.1. Since draft-ietf-quic-http-00:
			o Changed "HTTP/2-over-QUIC" to "HTTP/QUIC" throughout
			o Changed from using HTTP/2 framing within Stream 3 to new framing
			format and two-stream-per-request model
			o Adopted SETTINGS format from draft-bishop-httpbis-extended-
			settings-01
			o Reworked SETTINGS_ACK to account for indeterminate inter-stream
			order.
			o Described CONNECT pseudo-method
			o Updated ALPN token and Alt-Svc guidance
			o Application-layer-defined error codes
			B.2. Since draft-shade-quic-http2-mapping-00:
			o Adopted as base for draft-ietf-quic-http.
			o Updated authors/editors list.
	Author's Address		Author's Address
	Mike Bishop (editor)		Mike Bishop (editor)
	Microsoft		Microsoft
	Email: Mike.Bishop@microsoft.com		Email: Michael.Bishop@microsoft.com
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