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Versions: (draft-shade-quic-http2-mapping) 00 01 02 03 04

QUIC                                                      M. Bishop, Ed.
Internet-Draft                                                 Microsoft
Intended status: Standards Track                            May 21, 2017
Expires: November 22, 2017


              Hypertext Transfer Protocol (HTTP) over QUIC
                        draft-ietf-quic-http-03

Abstract

   The QUIC transport protocol has several features that are desirable
   in a transport for HTTP, such as stream multiplexing, per-stream flow
   control, and low-latency connection establishment.  This document
   describes a mapping of HTTP semantics over QUIC.  This document also
   identifies HTTP/2 features that are subsumed by QUIC, and describes
   how HTTP/2 extensions can be ported to 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

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 22, 2017.







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Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
   2.  QUIC Advertisement  . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  QUIC Version Hints  . . . . . . . . . . . . . . . . . . .   4
   3.  Connection Establishment  . . . . . . . . . . . . . . . . . .   4
     3.1.  Draft Version Identification  . . . . . . . . . . . . . .   5
   4.  Stream Mapping and Usage  . . . . . . . . . . . . . . . . . .   5
     4.1.  Stream 1: Connection Control Stream . . . . . . . . . . .   6
     4.2.  HTTP Message Exchanges  . . . . . . . . . . . . . . . . .   6
       4.2.1.  Header Compression  . . . . . . . . . . . . . . . . .   7
       4.2.2.  The CONNECT Method  . . . . . . . . . . . . . . . . .   8
     4.3.  Stream Priorities . . . . . . . . . . . . . . . . . . . .   9
     4.4.  Server Push . . . . . . . . . . . . . . . . . . . . . . .   9
   5.  HTTP Framing Layer  . . . . . . . . . . . . . . . . . . . . .  10
     5.1.  Frame Layout  . . . . . . . . . . . . . . . . . . . . . .  10
     5.2.  Frame Definitions . . . . . . . . . . . . . . . . . . . .  10
       5.2.1.  HEADERS . . . . . . . . . . . . . . . . . . . . . . .  10
       5.2.2.  PRIORITY  . . . . . . . . . . . . . . . . . . . . . .  11
       5.2.3.  SETTINGS  . . . . . . . . . . . . . . . . . . . . . .  12
       5.2.4.  PUSH_PROMISE  . . . . . . . . . . . . . . . . . . . .  15
   6.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .  15
     6.1.  HTTP-Defined QUIC Error Codes . . . . . . . . . . . . . .  16
   7.  Considerations for Transitioning from HTTP/2  . . . . . . . .  17
     7.1.  HTTP Frame Types  . . . . . . . . . . . . . . . . . . . .  17
     7.2.  HTTP/2 SETTINGS Parameters  . . . . . . . . . . . . . . .  18
     7.3.  HTTP/2 Error Codes  . . . . . . . . . . . . . . . . . . .  19
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  20
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
     9.1.  Registration of HTTP/QUIC Identification String . . . . .  21
     9.2.  Registration of QUIC Version Hint Alt-Svc Parameter . . .  21
     9.3.  Existing Frame Types  . . . . . . . . . . . . . . . . . .  21



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     9.4.  Settings Parameters . . . . . . . . . . . . . . . . . . .  22
     9.5.  Error Codes . . . . . . . . . . . . . . . . . . . . . . .  23
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  25
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  25
     10.2.  Informative References . . . . . . . . . . . . . . . . .  26
   Appendix A.  Contributors . . . . . . . . . . . . . . . . . . . .  26
   Appendix B.  Change Log . . . . . . . . . . . . . . . . . . . . .  26
     B.1.  Since draft-ietf-quic-http-02 . . . . . . . . . . . . . .  26
     B.2.  Since draft-ietf-quic-http-01 . . . . . . . . . . . . . .  27
     B.3.  Since draft-ietf-quic-http-00 . . . . . . . . . . . . . .  27
     B.4.  Since draft-shade-quic-http2-mapping-00 . . . . . . . . .  28
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  28

1.  Introduction

   The QUIC transport protocol has several features that are desirable
   in a transport for HTTP, such as stream multiplexing, per-stream flow
   control, and low-latency connection establishment.  This document
   describes a mapping of HTTP semantics over QUIC, drawing heavily on
   the existing TCP mapping, HTTP/2.  Specifically, this document
   identifies HTTP/2 features that are subsumed by QUIC, and describes
   how the other features can be implemented atop QUIC.

   QUIC is described in [QUIC-TRANSPORT].  For a full description of
   HTTP/2, see [RFC7540].

1.1.  Notational Conventions

   The words "MUST", "MUST NOT", "SHOULD", and "MAY" are used in this
   document.  It's not shouting; when they are capitalized, they have
   the special meaning defined in [RFC2119].

2.  QUIC Advertisement

   An HTTP origin advertises the availability of an equivalent HTTP/QUIC
   endpoint via the Alt-Svc HTTP response header or the HTTP/2 ALTSVC
   frame ([RFC7838]), using the ALPN token defined in Section 3.

   For example, an origin could indicate in an HTTP/1.1 or HTTP/2
   response that HTTP/QUIC was available on UDP port 50781 at the same
   hostname by including the following header in any response:

   Alt-Svc: hq=":50781"

   On receipt of an Alt-Svc header indicating HTTP/QUIC support, a
   client MAY attempt to establish a QUIC connection to the indicated
   host and port and, if successful, send HTTP requests using the
   mapping described in this document.



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   Connectivity problems (e.g. firewall blocking UDP) can result in QUIC
   connection establishment failure, in which case the client SHOULD
   continue using the existing connection or try another alternative
   endpoint offered by the origin.

   Servers MAY serve HTTP/QUIC on any UDP port.  Servers MUST use the
   same port across all IP addresses that serve a single domain, and
   SHOULD NOT change this port.

2.1.  QUIC Version Hints

   This document defines the "quic" parameter for Alt-Svc, which MAY be
   used to provide version-negotiation hints to HTTP/QUIC clients.  QUIC
   versions are four-octet sequences with no additional constraints on
   format.  Syntax:

   quic = version-number
   version-number = 1*8HEXDIG; hex-encoded QUIC version

   Leading zeros SHOULD be omitted for brevity.  When multiple versions
   are supported, the "quic" parameter MAY be repeated multiple times in
   a single Alt-Svc entry.  For example, if a server supported both
   version 0x00000001 and the version rendered in ASCII as "Q034", it
   could specify the following header:

   Alt-Svc: hq=":49288";quic=1;quic=51303334

   Where multiple versions are listed, the order of the values reflects
   the server's preference (with the first value being the most
   preferred version).  Origins SHOULD list only versions which are
   supported by the alternative, but MAY omit supported versions for any
   reason.

3.  Connection Establishment

   HTTP/QUIC connections are established as described in
   [QUIC-TRANSPORT].  During connection establishment, HTTP/QUIC support
   is indicated by selecting the ALPN token "hq" in the crypto
   handshake.

   While connection-level options pertaining to the core QUIC protocol
   are set in the initial crypto handshake, HTTP-specific settings are
   conveyed in the SETTINGS frame.  After the QUIC connection is
   established, a SETTINGS frame (Section 5.2.3) MUST be sent as the
   initial frame of the HTTP control stream (Stream ID 1, see
   Section 4).  The server MUST NOT send data on any other stream until
   the client's SETTINGS frame has been received.




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3.1.  Draft Version Identification

      *RFC Editor's Note:* Please remove this section prior to
      publication of a final version of this document.

   Only implementations of the final, published RFC can identify
   themselves as "hq".  Until such an RFC exists, implementations MUST
   NOT identify themselves using this string.

   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".

   Non-compatible experiments that are based on these draft versions
   MUST append the string "-" and an experiment name to the identifier.
   For example, an experimental implementation based on draft-ietf-quic-
   http-09 which reserves an extra stream for unsolicited transmission
   of 1980s pop music might identify itself as "hq-09-rickroll".  Note
   that any label MUST conform to the "token" syntax defined in
   Section 3.2.6 of [RFC7230].  Experimenters are encouraged to
   coordinate their experiments on the quic@ietf.org mailing list.

4.  Stream Mapping and Usage

   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.

   QUIC reserves Stream 0 for crypto operations (the handshake, crypto
   config updates).  Stream 1 is reserved for sending and receiving HTTP
   control frames, and is analogous to HTTP/2's Stream 0.  This
   connection control stream is considered critical to the HTTP
   connection.  If the connection control stream is closed for any
   reason, this MUST be treated as a connection error of type
   QUIC_CLOSED_CRITICAL_STREAM.

   When HTTP headers and data are sent over QUIC, the QUIC layer handles
   most of the stream management.  An HTTP request/response consumes a
   pair of streams: This means that the client's first request occurs on
   QUIC streams 3 and 5, the second on stream 7 and 9, 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.




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   The lower-numbered stream is called the message control stream and
   carries frames related to the request/response, including HEADERS.
   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.

   Because the message control stream contains HPACK data which
   manipulates connection-level state, the message control stream MUST
   NOT be closed with a stream-level error.  If an implementation
   chooses to reject a request with a QUIC error code, it MUST trigger a
   QUIC RST_STREAM on the data stream only.  An implementation MAY close
   (FIN) a message control stream without completing a full HTTP message
   if the data stream has been abruptly closed.  Data on message control
   streams MUST be fully consumed, or the connection terminated.

   All message control streams are considered critical to the HTTP
   connection.  If a message control stream is terminated abruptly for
   any reason, this MUST be treated as a connection error of type
   HTTP_RST_CONTROL_STREAM.  When a message control stream terminates
   cleanly, if the last frame on the stream was truncated, this MUST be
   treated as a connection error (see HTTP_MALFORMED_* in Section 6.1).

   Pairs of streams must be utilized sequentially, with no gaps.  The
   data stream is opened at the same time as the message control stream
   is opened and is closed after transferring the body.  The data stream
   is closed immediately after sending the request headers if there is
   no body.

   HTTP does not need to do any separate multiplexing when using QUIC -
   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.

4.1.  Stream 1: Connection Control Stream

   Since most connection-level concerns will be managed by QUIC, the
   primary use of Stream 1 will be for the SETTINGS frame when the
   connection opens and for PRIORITY frames subsequently.

4.2.  HTTP Message Exchanges

   A client sends an HTTP request on a new pair of QUIC streams.  A
   server sends an HTTP response on the same streams as the request.

   An HTTP message (request or response) consists of:





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   1.  one header block (see Section 5.2.1) on the control stream
       containing the message headers (see [RFC7230], Section 3.2),

   2.  the payload body (see [RFC7230], Section 3.3), sent on the data
       stream,

   3.  optionally, one header block on the control stream containing the
       trailer-part, if present (see [RFC7230], Section 4.1.2).

   In addition, prior to sending the message header block indicated
   above, a response may contain zero or more header blocks on the
   control stream containing the message headers of informational (1xx)
   HTTP responses (see [RFC7230], Section 3.2 and [RFC7231],
   Section 6.2).

   The data stream MUST be half-closed immediately after the transfer of
   the body.  If the message does not contain a body, the corresponding
   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.

   Trailing header fields are carried in an additional header block on
   the message control stream.  Such a header block is a sequence of
   HEADERS frames with End Header Block set on the last frame.  Senders
   MUST send only one header block in the trailers section; receivers
   MUST decode any subsequent header blocks in order to maintain HPACK
   decoder state, but the resulting output MUST be discarded.

   An HTTP request/response exchange fully consumes a pair of streams.
   After sending a request, a client closes the streams for sending;
   after sending a response, the server closes its streams for sending
   and the QUIC streams are fully closed.

   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



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   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,
   but there are no guarantees about order of delivery between streams.
   To achieve in-order delivery of HEADERS frames in QUIC, the HPACK-
   bearing frames contain a counter which can be used to ensure in-order
   processing.  Data (request/response bodies) which arrive out of order
   are buffered until the corresponding HEADERS arrive.

   This does introduce head-of-line blocking: if the packet containing
   HEADERS for stream N is lost or reordered then the HEADERS for stream
   N+4 cannot be processed until it has been retransmitted successfully,
   even though the HEADERS for stream N+4 may have arrived.

   DISCUSS:  Keep HPACK with HOLB?  Redesign HPACK to be order-
      invariant?  How much do we need to retain compatibility with
      HTTP/2's HPACK?

4.2.2.  The CONNECT Method

   The pseudo-method CONNECT ([RFC7231], Section 4.3.6) is primarily
   used with HTTP proxies to establish a TLS session with an origin
   server for the purposes of interacting with "https" resources.  In
   HTTP/1.x, CONNECT is used to convert an entire HTTP connection into a
   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.

   A CONNECT request in HTTP/QUIC functions in the same manner as in
   HTTP/2.  The request MUST be formatted as described in [RFC7540],
   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.

   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.

   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




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   size and number of TCP segments is not guaranteed to map predictably
   to the size and number of QUIC STREAM frames.

   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.

   A TCP connection error is signaled with RST_STREAM.  A proxy treats
   any error in the TCP connection, which includes receiving a TCP
   segment with the RST bit set, as a stream error of type
   HTTP_CONNECT_ERROR (Section 6.1).  Correspondingly, a proxy MUST send
   a TCP segment with the RST bit set if it detects an error with the
   stream or the QUIC connection.

4.3.  Stream Priorities

   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
   PRIORITY frames add, remove, or change the dependency links between
   streams.

   For consistency's sake, all PRIORITY frames MUST refer to the message
   control stream of the dependent request, not the data stream.

4.4.  Server Push

   HTTP/QUIC supports server push as described in [RFC7540].  During
   connection establishment, the client indicates whether it is willing
   to receive server pushes via the SETTINGS_DISABLE_PUSH setting in the
   SETTINGS frame (see Section 3), which defaults to 1 (true).

   As with server push for HTTP/2, the server initiates a server push by
   sending a PUSH_PROMISE frame containing the Stream ID of the stream
   to be pushed, as well as request header fields attributed to the
   request.  The PUSH_PROMISE frame is sent on the control stream of the
   associated (client-initiated) request, while the Promised Stream ID
   field specifies the Stream ID of the control stream for the server-
   initiated request.



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   The server push response is conveyed in the same way as a non-server-
   push response, with response headers and (if present) trailers
   carried by HEADERS frames sent on the control stream, and response
   body (if any) sent via the corresponding data stream.

5.  HTTP Framing Layer

   Frames are used only on the connection (stream 1) and message
   (streams 3, 7, etc.) control streams.  Other streams carry data
   payload and are not framed at the HTTP layer.

   This section describes HTTP framing in QUIC and highlights some
   differences from HTTP/2 framing.  For more detail on differences from
   HTTP/2, see Section 7.1.

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 (*)                     ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: HTTP/QUIC frame format

5.2.  Frame Definitions

5.2.1.  HEADERS

   The HEADERS frame (type=0x1) is used to carry part of a header set,
   compressed using HPACK [RFC7541].

   One flag is defined:

   End Header Block (0x4):  This frame concludes a header block.

   A HEADERS frame with any other flags set MUST be treated as a
   connection error of type HTTP_MALFORMED_HEADERS.









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       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 (*)...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 2: 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.

   When the Sequence counter reaches its maximum value (0xFFFF), the
   next increment returns it to zero.  An endpoint MUST NOT wrap the
   Sequence counter to zero until the previous zero-value header block
   has been confirmed received.

5.2.2.  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 semantics of the Stream Dependency, Weight, and E flag are the
   same as in HTTP/2.

   The flags defined are:




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   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)  |
      +-+-+-+-+-+-+-+-+

                     Figure 3: PRIORITY 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.

5.2.3.  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.)



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   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.

   Parameters MUST NOT occur more than once.  A receiver MAY treat the
   presence of the same parameter more than once as a connection error
   of type HTTP_MALFORMED_SETTINGS.

   The SETTINGS frame defines no flags.

   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)        |         Length (16)           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Contents (?)                       ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 4: SETTINGS value format

   A zero-length content indicates that the setting value is a Boolean
   and true.  False is indicated by the absence 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 of type HTTP_MALFORMED_SETTINGS.

   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.
   A SETTINGS frame MUST be sent as the first frame of the connection
   control stream (see Section 4) by each peer, and MUST NOT be sent
   subsequently or on any other stream.  If an endpoint receives an
   SETTINGS frame on a different stream, the endpoint MUST respond with
   a connection error of type HTTP_SETTINGS_ON_WRONG_STREAM.  If an
   endpoint receives a second SETTINGS frame, the endpoint MUST respond
   with a connection error of type HTTP_MULTIPLE_SETTINGS.

   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.




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5.2.3.1.  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.

5.2.3.2.  Defined SETTINGS Parameters

   The following settings are defined in HTTP/QUIC:

   SETTINGS_HEADER_TABLE_SIZE (0x1):  An integer with a maximum value of
      2^32 - 1.

   SETTINGS_DISABLE_PUSH (0x2):  Transmitted as a Boolean; replaces
      SETTINGS_ENABLE_PUSH

   SETTINGS_MAX_HEADER_LIST_SIZE (0x6):  An integer with a maximum value
      of 2^32 - 1.

5.2.3.3.  Usage in 0-RTT

   When a 0-RTT QUIC connection is being used, the client's initial
   requests will be sent before the arrival of the server's SETTINGS
   frame.  Clients SHOULD cache at least the following settings about
   servers:

   o  SETTINGS_HEADER_TABLE_SIZE

   o  SETTINGS_MAX_HEADER_LIST_SIZE

   Clients MUST comply with cached settings until the server's current
   settings are received.  If a client does not have cached values, it
   SHOULD assume the following values:

   o  SETTINGS_HEADER_TABLE_SIZE: 0 octets

   o  SETTINGS_MAX_HEADER_LIST_SIZE: 16,384 octets

   Servers MAY continue processing data from clients which exceed its
   current configuration during the initial flight.  In this case, the
   client MUST apply the new settings immediately upon receipt.

   If the connection is closed because these or other constraints were
   violated during the 0-RTT flight (e.g. with
   HTTP_HPACK_DECOMPRESSION_FAILED), clients MAY establish a new
   connection and retry any 0-RTT requests using the settings sent by



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   the server on the closed connection.  (This assumes that only
   requests that are safe to retry are sent in 0-RTT.)  If the
   connection was closed before the SETTINGS frame was received, clients
   SHOULD discard any cached values and use the defaults above on the
   next connection.

5.2.4.  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 (*)    ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 5: 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.

6.  Error Handling

   QUIC allows the application to abruptly terminate individual streams
   or the entire connection when an error is encountered.  These are
   referred to as "stream errors" or "connection errors" and are
   described in more detail in [QUIC-TRANSPORT].

   HTTP/QUIC requires that only data streams be terminated abruptly.
   Terminating a message control stream will result in an error of type
   HTTP_RST_CONTROL_STREAM.

   This section describes HTTP-specific error codes which can be used to
   express the cause of a connection or stream error.






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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_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 PRIORITY frame has been received
      with an invalid format.

   HTTP_MALFORMED_SETTINGS (0x0B):  A SETTINGS frame has been received
      with an invalid format.

   HTTP_MALFORMED_PUSH_PROMISE (0x0C):  A PUSH_PROMISE 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.




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   HTTP_MULTIPLE_SETTINGS (0x10):  More than one SETTINGS frame was
      received.

   HTTP_RST_CONTROL_STREAM (0x11):  A message control stream closed
      abruptly.

7.  Considerations for Transitioning from HTTP/2

   HTTP/QUIC is strongly informed by HTTP/2, and bears many
   similarities.  This section points out important differences from
   HTTP/2 and describes how to map HTTP/2 extensions into HTTP/QUIC.

7.1.  HTTP Frame Types

   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.

   Frame payloads are largely drawn from [RFC7540].  However, QUIC
   includes many features (e.g. flow control) which are also present in
   HTTP/2.  In these cases, the HTTP mapping does not re-implement them.
   As a result, several HTTP/2 frame types are not required in HTTP/
   QUIC.  Where an HTTP/2-defined frame is no longer used, the frame ID
   has been reserved in order to maximize portability between HTTP/2 and
   HTTP/QUIC implementations.  However, even equivalent frames between
   the two mappings are not identical.

   Many of the differences arise from the fact that HTTP/2 provides an
   absolute ordering between frames across all streams, while QUIC
   provides this guarantee on each stream only.  As a result, if a frame
   type makes assumptions that frames from different streams will still
   be received in the order sent, HTTP/QUIC will break them.

   For example, implicit in the HTTP/2 prioritization scheme is the
   notion of in-order delivery of priority changes (i.e., dependency
   tree mutations): since operations on the dependency tree such as
   reparenting a subtree are not commutative, both sender and receiver
   must apply them in the same order to ensure that both sides have a
   consistent view of the stream dependency tree.  HTTP/2 specifies
   priority assignments in PRIORITY frames and (optionally) in HEADERS
   frames.  To achieve in-order delivery of priority changes in HTTP/
   QUIC, PRIORITY frames are sent on the connection control stream and
   the PRIORITY section is removed from the HEADERS frame.




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   Other than this issue, frame type HTTP/2 extensions are typically
   portable to QUIC simply by replacing Stream 0 in HTTP/2 with Stream 1
   in HTTP/QUIC.

   Below is a listing of how each HTTP/2 frame type is mapped:

   DATA (0x0):  Instead of DATA frames, HTTP/QUIC uses a separate data
      stream.  See Section 4.

   HEADERS (0x1):  As described above, the PRIORITY region of HEADERS is
      not supported.  A separate PRIORITY frame MUST be used.  Padding
      is not defined in HTTP/QUIC frames.  See Section 5.2.1.

   PRIORITY (0x2):  As described above, the PRIORITY frame is sent on
      the connection control stream.  See Section 5.2.2.

   RST_STREAM (0x3):  RST_STREAM frames do not exist, since QUIC
      provides stream lifecycle management.

   SETTINGS (0x4):  SETTINGS frames are sent only at the beginning of
      the connection.  See Section 5.2.3 and Section 7.2.

   PUSH_PROMISE (0x5):  See Section 5.2.4.

   PING (0x6):  PING frames do not exist, since QUIC provides equivalent
      functionality.

   GOAWAY (0x7):  GOAWAY frames do not exist, since QUIC provides
      equivalent functionality.

   WINDOW_UPDATE (0x8):  WINDOW_UPDATE frames do not exist, since QUIC
      provides flow control.

   CONTINUATION (0x9):  CONTINUATION frames do not exist; instead,
      larger HEADERS/PUSH_PROMISE frames than HTTP/2 are permitted, and
      HEADERS frames can be used in series.

   The IANA registry of frame types has been updated in Section 9.3 to
   include references to the definition for each frame type in HTTP/2
   and in HTTP/QUIC.  Frames not defined as available in HTTP/QUIC
   SHOULD NOT be sent and SHOULD be ignored as unknown on receipt.

7.2.  HTTP/2 SETTINGS Parameters

   An important difference from HTTP/2 is that settings are sent once,
   at the beginning of the connection, and thereafter cannot change.
   This eliminates many corner cases around synchronization of changes.




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   Some transport-level options that HTTP/2 specifies via the SETTINGS
   frame are superseded by QUIC transport parameters in HTTP/QUIC.  The
   HTTP-level options that are retained in HTTP/QUIC have the same value
   as in HTTP/2.

   Below is a listing of how each HTTP/2 SETTINGS parameter is mapped:

   SETTINGS_HEADER_TABLE_SIZE:  See Section 5.2.3.2.

   SETTINGS_ENABLE_PUSH:  See SETTINGS_DISABLE_PUSH in Section 5.2.3.2.

   SETTINGS_MAX_CONCURRENT_STREAMS:  QUIC requires the maximum number of
      incoming streams per connection to be specified in the initial
      transport handshake.  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 transport handshake.  Specifying
      SETTINGS_INITIAL_WINDOW_SIZE in the SETTINGS frame is an error.

   SETTINGS_MAX_FRAME_SIZE:  This setting has no equivalent in HTTP/
      QUIC.  Specifying it in the SETTINGS frame is an error.

   SETTINGS_MAX_HEADER_LIST_SIZE:  See Section 5.2.3.2.

   Settings defined by extensions to HTTP/2 MAY be expressed as integers
   with a maximum value of 2^32-1, if they are applicable to HTTP/QUIC,
   but SHOULD have a specification describing their usage.  Fields for
   this purpose have been added to the IANA registry in Section 9.4.

7.3.  HTTP/2 Error Codes

   QUIC has the same concepts of "stream" and "connection" errors that
   HTTP/2 provides.  However, because the error code space is shared
   between multiple components, there is no direct portability of HTTP/2
   error codes.

   The HTTP/2 error codes defined in Section 7 of [RFC7540] map to QUIC
   error codes as follows:

   NO_ERROR (0x0):  QUIC_NO_ERROR

   PROTOCOL_ERROR (0x1):  No single mapping.  See new HTTP_MALFORMED_*
      error codes defined in Section 6.1.

   INTERNAL_ERROR (0x2)  HTTP_INTERNAL_ERROR in Section 6.1.




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   FLOW_CONTROL_ERROR (0x3):  Not applicable, since QUIC handles flow
      control.  Would provoke a QUIC_FLOW_CONTROL_RECEIVED_TOO_MUCH_DATA
      from the QUIC layer.

   SETTINGS_TIMEOUT (0x4):  Not applicable, since no acknowledgement of
      SETTINGS is defined.

   STREAM_CLOSED (0x5):  Not applicable, since QUIC handles stream
      management.  Would provoke a QUIC_STREAM_DATA_AFTER_TERMINATION
      from the QUIC layer.

   FRAME_SIZE_ERROR (0x6)  No single mapping.  See new error codes
      defined in Section 6.1.

   REFUSED_STREAM (0x7):  Not applicable, since QUIC handles stream
      management.  Would provoke a QUIC_TOO_MANY_OPEN_STREAMS from the
      QUIC layer.

   CANCEL (0x8):  HTTP_REQUEST_CANCELLED in Section 6.1.

   COMPRESSION_ERROR (0x9):  HTTP_HPACK_DECOMPRESSION_FAILED in
      Section 6.1.

   CONNECT_ERROR (0xa):  HTTP_CONNECT_ERROR in Section 6.1.

   ENHANCE_YOUR_CALM (0xb):  HTTP_EXCESSIVE_LOAD in Section 6.1.

   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.

   Error codes defined by HTTP/2 extensions need to be re-registered for
   HTTP/QUIC if still applicable.  See Section 9.5.

8.  Security Considerations

   The security considerations of HTTP over QUIC should be comparable to
   those of HTTP/2.

   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.







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9.  IANA Considerations

9.1.  Registration of HTTP/QUIC Identification String

   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].

   The "hq" string identifies HTTP/QUIC:

   Protocol:  HTTP over QUIC

   Identification Sequence:  0x68 0x71 ("hq")

   Specification:  This document

9.2.  Registration of QUIC Version Hint Alt-Svc Parameter

   This document creates a new registration for version-negotiation
   hints in the "Hypertext Transfer Protocol (HTTP) Alt-Svc Parameter"
   registry established in [RFC7838].

   Parameter:  "quic"

   Specification:  This document, Section 2.1

9.3.  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:







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     +---------------+---------------------+-------------------------+
     | Frame Type    | Supported Protocols | HTTP/QUIC Specification |
     +---------------+---------------------+-------------------------+
     | DATA          |     HTTP/2 only     | N/A                     |
     |               |                     |                         |
     | HEADERS       |         Both        | Section 5.2.1           |
     |               |                     |                         |
     | PRIORITY      |         Both        | Section 5.2.2           |
     |               |                     |                         |
     | RST_STREAM    |     HTTP/2 only     | N/A                     |
     |               |                     |                         |
     | SETTINGS      |         Both        | Section 5.2.3           |
     |               |                     |                         |
     | PUSH_PROMISE  |         Both        | Section 5.2.4           |
     |               |                     |                         |
     | 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.

9.4.  Settings Parameters

   This document adds two new columns to the "HTTP/2 Settings" registry
   defined in [RFC7540]:

   Supported Protocols:  Indicates which associated protocols use the
      setting.  Values MUST be one of:

      *  "HTTP/2 only"

      *  "HTTP/QUIC only"

      *  "Both"

   HTTP/QUIC Specification:  Indicates where this setting's behavior
      over QUIC is defined; required if the frame is supported over
      QUIC.

   Values for existing registrations are assigned by this document:





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   +-------------------------+------------------+----------------------+
   | Setting Name            |    Supported     | HTTP/QUIC            |
   |                         |    Protocols     | Specification        |
   +-------------------------+------------------+----------------------+
   | HEADER_TABLE_SIZE       |       Both       | Section 5.2.3.2      |
   |                         |                  |                      |
   | ENABLE_PUSH /           |       Both       | Section 5.2.3.2      |
   | DISABLE_PUSH            |                  |                      |
   |                         |                  |                      |
   | MAX_CONCURRENT_STREAMS  |   HTTP/2 Only    | N/A                  |
   |                         |                  |                      |
   | INITIAL_WINDOW_SIZE     |   HTTP/2 Only    | N/A                  |
   |                         |                  |                      |
   | MAX_FRAME_SIZE          |   HTTP/2 Only    | N/A                  |
   |                         |                  |                      |
   | MAX_HEADER_LIST_SIZE    |       Both       | Section 5.2.3.2      |
   +-------------------------+------------------+----------------------+

   The "Specification" column is renamed to "HTTP/2 Specification" and
   is only required if the setting is supported over HTTP/2.

9.5.  Error Codes

   This document establishes a registry for HTTP/QUIC error codes.  The
   "HTTP/QUIC Error Code" registry manages a 30-bit space.  The "HTTP/
   QUIC Error Code" registry operates under the "Expert Review" policy
   [RFC5226].

   Registrations for error codes are required to include a description
   of the error code.  An expert reviewer is advised to examine new
   registrations for possible duplication with existing error codes.
   Use of existing registrations is to be encouraged, but not mandated.

   New registrations are advised to provide the following information:

   Name:  A name for the error code.  Specifying an error code name is
      optional.

   Code:  The 30-bit error code value.

   Description:  A brief description of the error code semantics, longer
      if no detailed specification is provided.

   Specification:  An optional reference for a specification that
      defines the error code.

   The entries in the following table are registered by this document.




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   +------------------------------+-----+--------------+---------------+
   | Name                         | Cod | Description  | Specification |
   |                              | e   |              |               |
   +------------------------------+-----+--------------+---------------+
   | HTTP_PUSH_REFUSED            | 0x0 | Client       | Section 6.1   |
   |                              | 1   | refused      |               |
   |                              |     | pushed       |               |
   |                              |     | content      |               |
   |                              |     |              |               |
   | HTTP_INTERNAL_ERROR          | 0x0 | Internal     | Section 6.1   |
   |                              | 2   | error        |               |
   |                              |     |              |               |
   | HTTP_PUSH_ALREADY_IN_CACHE   | 0x0 | Pushed       | Section 6.1   |
   |                              | 3   | content      |               |
   |                              |     | already      |               |
   |                              |     | cached       |               |
   |                              |     |              |               |
   | HTTP_REQUEST_CANCELLED       | 0x0 | Data no      | Section 6.1   |
   |                              | 4   | longer       |               |
   |                              |     | needed       |               |
   |                              |     |              |               |
   | HTTP_HPACK_DECOMPRESSION_FAI | 0x0 | HPACK cannot | Section 6.1   |
   | LED                          | 5   | continue     |               |
   |                              |     |              |               |
   | HTTP_CONNECT_ERROR           | 0x0 | TCP reset or | Section 6.1   |
   |                              | 6   | error on     |               |
   |                              |     | CONNECT      |               |
   |                              |     | request      |               |
   |                              |     |              |               |
   | HTTP_EXCESSIVE_LOAD          | 0x0 | Peer         | Section 6.1   |
   |                              | 7   | generating   |               |
   |                              |     | excessive    |               |
   |                              |     | load         |               |
   |                              |     |              |               |
   | HTTP_VERSION_FALLBACK        | 0x0 | Retry over   | Section 6.1   |
   |                              | 8   | HTTP/2       |               |
   |                              |     |              |               |
   | HTTP_MALFORMED_HEADERS       | 0x0 | Invalid      | Section 6.1   |
   |                              | 9   | HEADERS      |               |
   |                              |     | frame        |               |
   |                              |     |              |               |
   | HTTP_MALFORMED_PRIORITY      | 0x0 | Invalid      | Section 6.1   |
   |                              | A   | PRIORITY     |               |
   |                              |     | frame        |               |
   |                              |     |              |               |
   | HTTP_MALFORMED_SETTINGS      | 0x0 | Invalid      | Section 6.1   |
   |                              | B   | SETTINGS     |               |
   |                              |     | frame        |               |



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   |                              |     |              |               |
   | HTTP_MALFORMED_PUSH_PROMISE  | 0x0 | Invalid      | Section 6.1   |
   |                              | C   | PUSH_PROMISE |               |
   |                              |     | frame        |               |
   |                              |     |              |               |
   | HTTP_INTERRUPTED_HEADERS     | 0x0 | Incomplete   | Section 6.1   |
   |                              | E   | HEADERS      |               |
   |                              |     | block        |               |
   |                              |     |              |               |
   | HTTP_SETTINGS_ON_WRONG_STREA | 0x0 | SETTINGS     | Section 6.1   |
   | M                            | F   | frame on a   |               |
   |                              |     | request      |               |
   |                              |     | control      |               |
   |                              |     | stream       |               |
   |                              |     |              |               |
   | HTTP_MULTIPLE_SETTINGS       | 0x1 | Multiple     | Section 6.1   |
   |                              | 0   | SETTINGS     |               |
   |                              |     | frames       |               |
   |                              |     |              |               |
   | HTTP_RST_CONTROL_STREAM      | 0x1 | Message      | Section 6.1   |
   |                              | 1   | control      |               |
   |                              |     | stream was   |               |
   |                              |     | RST          |               |
   +------------------------------+-----+--------------+---------------+

10.  References

10.1.  Normative References

   [QUIC-TRANSPORT]
              Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", draft-ietf-quic-
              transport (work in progress), May 2017.

   [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
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <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>.




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   [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
              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
              DOI 10.17487/RFC7540, May 2015,
              <http://www.rfc-editor.org/info/rfc7540>.

   [RFC7541]  Peon, R. and H. Ruellan, "HPACK: Header Compression for
              HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015,
              <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>.

10.2.  Informative References

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [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

   The original authors of this specification were Robbie Shade and Mike
   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-02

   o  Track changes in transport draft








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B.2.  Since draft-ietf-quic-http-01

   o  SETTINGS changes (#181):

      *  SETTINGS can be sent only once at the start of a connection; no
         changes thereafter

      *  SETTINGS_ACK removed

      *  Settings can only occur in the SETTINGS frame a single time

      *  Boolean format updated

   o  Alt-Svc parameter changed from "v" to "quic"; format updated
      (#229)

   o  Closing the connection control stream or any message control
      stream is a fatal error (#176)

   o  HPACK Sequence counter can wrap (#173)

   o  0-RTT guidance added

   o  Guide to differences from HTTP/2 and porting HTTP/2 extensions
      added (#127,#242)

B.3.  Since draft-ietf-quic-http-00

   o  Changed "HTTP/2-over-QUIC" to "HTTP/QUIC" throughout (#11,#29)

   o  Changed from using HTTP/2 framing within Stream 3 to new framing
      format and two-stream-per-request model (#71,#72,#73)

   o  Adopted SETTINGS format from draft-bishop-httpbis-extended-
      settings-01

   o  Reworked SETTINGS_ACK to account for indeterminate inter-stream
      order (#75)

   o  Described CONNECT pseudo-method (#95)

   o  Updated ALPN token and Alt-Svc guidance (#13,#87)

   o  Application-layer-defined error codes (#19,#74)







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B.4.  Since draft-shade-quic-http2-mapping-00

   o  Adopted as base for draft-ietf-quic-http

   o  Updated authors/editors list

Author's Address

   Mike Bishop (editor)
   Microsoft

   Email: Michael.Bishop@microsoft.com







































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