QUIC                                                      M. Bishop, Ed.
Internet-Draft                                                    Akamai
Intended status: Standards Track                        October 03, 24, 2018
Expires: April 6, 27, 2019

              Hypertext Transfer Protocol (HTTP) over QUIC
                        draft-ietf-quic-http-15
                        draft-ietf-quic-http-16

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 [1].

   Working Group information can be found at https://github.com/quicwg
   [2]; source code and issues list for this draft can be found at
   https://github.com/quicwg/base-drafts/labels/-http [3].

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 https://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 April 6, 27, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   publication of this document.  Please review these documents
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   4
   2.  Connection Setup and Management . . . . . . . . . . . . . . .   4   5
     2.1.  Draft Version Identification  . . . . . . . . . . . . . .   4   5
     2.2.  Discovering an HTTP/QUIC Endpoint . . . . . . . . . . . .   5
       2.2.1.  QUIC Version Hints  . . . . . . . . . . . . . . . . .   5   6
     2.3.  Connection Establishment  . . . . . . . . . . . . . . . .   6
     2.4.  Connection Reuse  . . . . . . . . . . . . . . . . . . . .   7
   3.  Stream Mapping and Usage  . . . . . . . . . . . . . . . . . .   7
     3.1.  HTTP Message Exchanges  Bidirectional Streams . . . . . . . . . . . . . . . . . .   8
       3.1.1.  Header Formatting and Compression
     3.2.  Unidirectional Streams  . . . . . . . . . .   9
       3.1.2.  The CONNECT Method . . . . . . .   8
       3.2.1.  Control Streams . . . . . . . . . .  10
       3.1.3.  Request Cancellation . . . . . . . . .   9
       3.2.2.  Push Streams  . . . . . . .  11
     3.2.  Request Prioritization . . . . . . . . . . . . .   9
       3.2.3.  Reserved Stream Types . . . .  11
       3.2.1.  Placeholders . . . . . . . . . . . .  10
   4.  HTTP Framing Layer  . . . . . . . .  12
       3.2.2.  Priority Tree Maintenance . . . . . . . . . . . . .  10
     4.1.  Frame Layout  .  12
     3.3.  Unidirectional Streams . . . . . . . . . . . . . . . . .  13
       3.3.1.  Reserved Stream Types . . . .  10
     4.2.  Frame Definitions . . . . . . . . . . . .  14
       3.3.2.  Control Streams . . . . . . . .  11
       4.2.1.  DATA  . . . . . . . . . . .  14
       3.3.3.  Server Push . . . . . . . . . . . . .  11
       4.2.2.  HEADERS . . . . . . . .  15
   4.  HTTP Framing Layer . . . . . . . . . . . . . . .  12
       4.2.3.  PRIORITY  . . . . . .  16
     4.1.  Frame Layout . . . . . . . . . . . . . . . .  12
       4.2.4.  CANCEL_PUSH . . . . . .  16
     4.2.  Frame Definitions . . . . . . . . . . . . . . .  14
       4.2.5.  SETTINGS  . . . . .  17
       4.2.1.  Reserved Frame Types . . . . . . . . . . . . . . . .  17
       4.2.2.  DATA .  15
       4.2.6.  PUSH_PROMISE  . . . . . . . . . . . . . . . . . . . .  17
       4.2.7.  GOAWAY  . . .  17
       4.2.3.  HEADERS . . . . . . . . . . . . . . . . . . . .  18
       4.2.8.  MAX_PUSH_ID . . .  17
       4.2.4.  PRIORITY . . . . . . . . . . . . . . . . . .  19
       4.2.9.  Reserved Frame Types  . . . .  18
       4.2.5.  CANCEL_PUSH . . . . . . . . . . . .  19
   5.  HTTP Request Lifecycle  . . . . . . . . .  20
       4.2.6.  SETTINGS . . . . . . . . . .  20
     5.1.  HTTP Message Exchanges  . . . . . . . . . . . .  21
       4.2.7.  PUSH_PROMISE . . . . .  20
       5.1.1.  Header Formatting and Compression . . . . . . . . . .  21
       5.1.2.  Request Cancellation  . . . . .  23
       4.2.8.  GOAWAY . . . . . . . . . . .  22
     5.2.  The CONNECT Method  . . . . . . . . . . . .  24
       4.2.9.  MAX_PUSH_ID . . . . . . .  22
     5.3.  Request Prioritization  . . . . . . . . . . . . . .  25
   5.  Connection Closure . . .  23
       5.3.1.  Placeholders  . . . . . . . . . . . . . . . . . .  25
     5.1.  Idle Connections . .  24
       5.3.2.  Priority Tree Maintenance . . . . . . . . . . . . . .  24
     5.4.  Server Push . . . .  26
     5.2.  Connection Shutdown . . . . . . . . . . . . . . . . . . .  26
     5.3.  Immediate Application  25
   6.  Connection Closure  . . . . . . . . . . . . . .  27
     5.4.  Transport Closure . . . . . . . .  26
     6.1.  Idle Connections  . . . . . . . . . . . .  28
   6.  Error Handling . . . . . . . .  26
     6.2.  Connection Shutdown . . . . . . . . . . . . . . .  28
     6.1.  HTTP/QUIC Error Codes . . . .  27
     6.3.  Immediate Application Closure . . . . . . . . . . . . . .  28
   7.  Extensions to HTTP/QUIC
     6.4.  Transport Closure . . . . . . . . . . . . . . . . . . .  30
   8.  Considerations for Transitioning from HTTP/2 .  28
   7.  Extensions to HTTP/QUIC . . . . . . .  30
     8.1.  Streams . . . . . . . . . . . .  29
   8.  Error Handling  . . . . . . . . . . . . .  31
     8.2.  HTTP Frame Types . . . . . . . . . .  29
     8.1.  HTTP/QUIC Error Codes . . . . . . . . . .  31
     8.3.  HTTP/2 SETTINGS Parameters  . . . . . . . . . . . . . . .  33
     8.4.  HTTP/2 Error Codes  . . . . . . . . . . . . . . . . . . .  34  30
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  35  31
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  35  32
     10.1.  Registration of HTTP/QUIC Identification String  . . . .  35  32
     10.2.  Registration of QUIC Version Hint Alt-Svc Parameter  . .  36  32
     10.3.  Frame Types  . . . . . . . . . . . . . . . . . . . . . .  36  32
     10.4.  Settings Parameters  . . . . . . . . . . . . . . . . . .  37  33
     10.5.  Error Codes  . . . . . . . . . . . . . . . . . . . . . .  38  34
     10.6.  Stream Types . . . . . . . . . . . . . . . . . . . . . .  41  37
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  42  38
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  42  38
     11.2.  Informative References . . . . . . . . . . . . . . . . .  43  39
     11.3.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . .  43  39
   Appendix A.  Considerations for Transitioning from HTTP/2 . . . .  39
     A.1.  Streams . . . . . . . . . . . . . . . . . . . . . . . . .  40
     A.2.  HTTP Frame Types  . . . . . . . . . . . . . . . . . . . .  40
     A.3.  HTTP/2 SETTINGS Parameters  . . . . . . . . . . . . . . .  42
     A.4.  HTTP/2 Error Codes  . . . . . . . . . . . . . . . . . . .  43
   Appendix B.  Change Log . . . . . . . . . . . . . . . . . . . . .  43
     A.1.  44
     B.1.  Since draft-ietf-quic-http-15 . . . . . . . . . . . . . .  44
     B.2.  Since draft-ietf-quic-http-14 . . . . . . . . . . . . . .  43
     A.2.  44
     B.3.  Since draft-ietf-quic-http-13 . . . . . . . . . . . . . .  44
     A.3.
     B.4.  Since draft-ietf-quic-http-12 . . . . . . . . . . . . . .  44
     A.4.  45
     B.5.  Since draft-ietf-quic-http-11 . . . . . . . . . . . . . .  44
     A.5.  45
     B.6.  Since draft-ietf-quic-http-10 . . . . . . . . . . . . . .  44
     A.6.  45
     B.7.  Since draft-ietf-quic-http-09 . . . . . . . . . . . . . .  45
     A.7.
     B.8.  Since draft-ietf-quic-http-08 . . . . . . . . . . . . . .  45
     A.8.  46
     B.9.  Since draft-ietf-quic-http-07 . . . . . . . . . . . . . .  45
     A.9.  46
     B.10. Since draft-ietf-quic-http-06 . . . . . . . . . . . . . .  45
     A.10.  46
     B.11. Since draft-ietf-quic-http-05 . . . . . . . . . . . . . .  45
     A.11.  46
     B.12. Since draft-ietf-quic-http-04 . . . . . . . . . . . . . .  45
     A.12.  46
     B.13. Since draft-ietf-quic-http-03 . . . . . . . . . . . . . .  46
     A.13.  47
     B.14. Since draft-ietf-quic-http-02 . . . . . . . . . . . . . .  46
     A.14.  47
     B.15. Since draft-ietf-quic-http-01 . . . . . . . . . . . . . .  46
     A.15.  47
     B.16. Since draft-ietf-quic-http-00 . . . . . . . . . . . . . .  46
     A.16.  47
     B.17. Since draft-shade-quic-http2-mapping-00 . . . . . . . . .  47  48
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  47  48
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  47  48

1.  Introduction

   The QUIC transport protocol has several features that

   HTTP semantics are desirable
   in a transport used for HTTP, such as stream multiplexing, per-stream flow
   control, and low-latency connection establishment.  This document
   describes a mapping broad range of HTTP semantics over QUIC, drawing heavily services on the existing
   Internet.  These semantics have commonly been used with two different
   TCP mapping, mappings, HTTP/1.1 and HTTP/2.  Specifically, this document
   identifies  HTTP/2 introduced a framing and
   multiplexing layer to improve latency without modifying the transport
   layer.  However, TCP's lack of visibility into parallel requests in
   both mappings limited the possible performance gains.

   The QUIC transport protocol incorporates stream multiplexing and per-
   stream flow control, similar to that provided by the HTTP/2 framing
   layer.  By providing reliability at the stream level and congestion
   control across the entire connection, it has the capability to
   improve the performance of HTTP compared to a TCP mapping.  QUIC also
   incorporates TLS 1.3 at the transport layer, offering comparable
   security to running TLS over TCP, but with improved connection setup
   latency.

   This document describes a mapping of HTTP semantics over the QUIC
   transport protocol, drawing heavily on design of HTTP/2.  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 key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   Field definitions are given in Augmented Backus-Naur Form (ABNF), as
   defined in [RFC5234].

   This document uses the variable-length integer encoding from
   [QUIC-TRANSPORT].

   Protocol elements called "frames" exist in both this document and
   [QUIC-TRANSPORT].  Where frames from [QUIC-TRANSPORT] are referenced,
   the frame name will be prefaced with "QUIC."  For example, "QUIC
   APPLICATION_CLOSE frames."  References without this preface refer to
   frames defined in Section 4.2.

2.  Connection Setup and Management

2.1.  Draft Version Identification

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

   HTTP/QUIC uses the token "hq" to identify itself in ALPN and Alt-Svc.
   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.

2.2.  Discovering an HTTP/QUIC Endpoint

   An HTTP origin advertises the availability of an equivalent HTTP/QUIC
   endpoint via the Alt-Svc HTTP response header field or the HTTP/2
   ALTSVC frame ([ALTSVC]), using the ALPN token defined in Section 2.3.

   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 field in any response:

   Alt-Svc: hq=":50781"

   On receipt of an Alt-Svc record 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.

   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, since an alternative
   always includes an explicit port.

2.2.1.  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.  Leading zeros SHOULD be omitted for brevity.

   Syntax:

   quic = DQUOTE version-number [ "," version-number ] * DQUOTE
   version-number = 1*8HEXDIG; hex-encoded QUIC version

   Where multiple versions are listed, the order of the values reflects
   the server's preference (with the first value being the most
   preferred version).  Reserved versions MAY be listed, but unreserved
   versions which are not supported by the alternative SHOULD NOT be
   present in the list.  Origins MAY omit supported versions for any
   reason.

   Clients MUST ignore any included versions which they do not support.
   The "quic" parameter MUST NOT occur more than once; clients SHOULD
   process only the first occurrence.

   For example, suppose a server supported both version 0x00000001 and
   the version rendered in ASCII as "Q034".  If it also opted to include
   the reserved versions version (from Section 4 3 of [QUIC-TRANSPORT]) 0x0 and 0x1abadaba,
   it could specify the following header field:

   Alt-Svc: hq=":49288";quic="1,1abadaba,51303334,0" hq=":49288";quic="1,1abadaba,51303334"

   A client acting on this header field would drop the reserved versions
   (because it does not support them), version
   (not supported), then attempt to connect to the alternative using the
   first version in the list which it does
   support. support, if any.

2.3.  Connection Establishment

   HTTP/QUIC relies on QUIC as the underlying transport.  The QUIC
   version being used MUST use TLS version 1.3 or greater as its
   handshake protocol.  HTTP/QUIC clients MUST indicate the target
   domain name during the TLS handshake.  This may be done using the
   Server Name Indication (SNI) [RFC6066] extension to TLS or using some
   other mechanism.

   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 TLS handshake.  Support for
   other application-layer protocols MAY be offered in the same
   handshake.

   While connection-level options pertaining to the core QUIC protocol
   are set in the initial crypto handshake, HTTP/QUIC-specific settings
   are conveyed in the SETTINGS frame.  After the QUIC connection is
   established, a SETTINGS frame (Section 4.2.6) 4.2.5) MUST be sent by each
   endpoint as the initial frame of their respective HTTP control stream
   (see Section 3.3.2). 3.2.1).  The server MUST NOT send data on process any other
   stream request streams
   or send responses until the client's SETTINGS frame has been
   received.

2.4.  Connection Reuse

   Once a connection exists to a server endpoint, this connection MAY be
   reused for requests with multiple different URI authority components.
   The client MAY send any requests for which the client considers the
   server authoritative.

   An authoritative HTTP/QUIC endpoint is typically discovered because
   the client has received an Alt-Svc record from the request's origin
   which nominates the endpoint as a valid HTTP Alternative Service for
   that origin.  As required by [RFC7838], clients MUST check that the
   nominated server can present a valid certificate for the origin
   before considering it authoritative.  Clients MUST NOT assume that an
   HTTP/QUIC endpoint is authoritative for other origins without an
   explicit signal.

   A server that does not wish clients to reuse connections for a
   particular origin can indicate that it is not authoritative for a
   request by sending a 421 (Misdirected Request) status code in
   response to the request (see Section 9.1.2 of [RFC7540]).

   The considerations discussed in Section 9.1 of [RFC7540] also apply
   to the management of HTTP/QUIC connections.

3.  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  The transport
   layer buffers and orders received QUIC STREAM frames, exposing the
   data contained within as a reliable byte stream to the application.

   QUIC streams can be either unidirectional, carrying data only from
   initiator to receiver, or bidirectional.  Streams can be initiated by
   either the client or the server.  For more detail on QUIC streams,
   see [QUIC-TRANSPORT], Section 9.

   When HTTP headers and data are sent over QUIC, the QUIC layer handles
   most of the stream management.  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 or connection context.

3.1.  Bidirectional Streams

   All client-initiated bidirectional streams are used for HTTP requests
   and responses.  A bidirectional stream ensures that the response can
   be readily correlated with the request.  This means that the client's
   first request occurs on QUIC stream 0, with subsequent requests on
   stream 4, 8, and so on.  In order to permit these streams to open, an
   HTTP/QUIC client SHOULD send non-zero values for the QUIC transport
   parameters "initial_max_stream_data_bidi_local".  An HTTP/QUIC server
   SHOULD send non-zero values for the QUIC transport parameters
   "initial_max_stream_data_bidi_remote" and "initial_max_bidi_streams".
   It is recommended that "initial_max_bidi_streams" be no smaller than
   100, so as to not unnecessarily limit parallelism.

   These streams carry frames related to the request/response (see
   Section 4.2). 5.1).  When a stream terminates cleanly, if the last frame on
   the stream was truncated, this MUST be treated as a connection error
   (see HTTP_MALFORMED_FRAME in Section 6.1). 8.1).  Streams which terminate
   abruptly may be reset at any point in the frame.

   HTTP/QUIC does not use server-initiated bidirectional streams.  The
   use of unidirectional streams is discussed in Section 3.3.  Both streams;
   clients and servers SHOULD send MUST omit or specify a value of three or greater zero for the QUIC transport
   parameter "initial_max_uni_streams".

   HTTP does not need to do any separate multiplexing when using QUIC -
   data sent over "initial_max_bidi_streams".

3.2.  Unidirectional Streams

   Unidirectional streams, in either direction, are used for a range of
   purposes.  The purpose is indicated by a QUIC stream always maps to type, which is sent
   as a particular HTTP
   transaction.  Requests single octet header at the start of the stream.  The format and responses are considered complete when
   structure of data that follows this header is determined by the
   corresponding QUIC
   stream is closed type.

    0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+
   |Stream Type (8)|
   +-+-+-+-+-+-+-+-+

                  Figure 1: Unidirectional Stream Header

   Some stream types are reserved (Section 3.2.3).  Two stream types are
   defined in the appropriate direction.

3.1.  HTTP Message Exchanges

   A client sends an HTTP request on this document: control streams (Section 3.2.1) and push
   streams (Section 3.2.2).  Other stream types can be defined by
   extensions to HTTP/QUIC.

   Both clients and servers SHOULD send a client-initiated bidirectional value of three or greater for
   the QUIC stream.  A server sends an HTTP response on transport parameter "initial_max_uni_streams".

   If the same stream as
   the request.

   An HTTP message (request or response) consists of:

   1.  one header block (see Section 4.2.3) containing indicates a stream type which is not supported
   by the message
       header (see [RFC7230], Section 3.2),

   2. recipient, the payload body (see [RFC7230], Section 3.3), sent as a series remainder of DATA frames (see Section 4.2.2),

   3.  optionally, one header block 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 containing stream cannot be consumed as
   the message headers semantics are unknown.  Recipients of informational (1xx) HTTP responses (see
   [RFC7230], Section 3.2 and [RFC7231], Section 6.2).

   A server unknown stream types MAY interleave one or more PUSH_PROMISE frames (see
   Section 4.2.7) with the frames of
   trigger a response message.  These
   PUSH_PROMISE frames are not part of the response; see Section 3.3.3
   for more details.

   The "chunked" transfer encoding defined in Section 4.1 QUIC STOP_SENDING frame with an error code of [RFC7230]
   HTTP_UNKNOWN_STREAM_TYPE, but MUST NOT consider such streams to be used.

   Trailing header fields are carried in an additional header block
   following the body.  Senders MUST
   error of any kind.

   Implementations MAY send only one header block in stream types before knowing whether the
   trailers section; receivers peer
   supports them.  However, stream types which could modify the state or
   semantics of existing protocol components, including QPACK or other
   extensions, MUST discard any subsequent header
   blocks.

   An HTTP request/response exchange fully consumes a bidirectional QUIC
   stream.  After sending a request, a client closes NOT be sent until the peer is known to support them.

3.2.1.  Control Streams

   The control stream for
   sending; after sending is indicated by a response, the server closes the stream for
   sending and the QUIC type of "0x43" (ASCII
   'C').  Data on this stream is fully closed.

   A server can send consists of HTTP/QUIC frames, as defined
   in Section 4.2.

   Each side MUST initiate a complete response prior to the client sending an
   entire request if single control stream at the response does not depend on any portion beginning of
   the
   request that has not been sent connection and received.  When send its SETTINGS frame as the first frame on this is true, a
   server MAY request that
   stream.  If the client abort transmission first frame of the control stream is any other frame
   type, this MUST be treated as a request
   without error by triggering a QUIC STOP_SENDING with connection error code
   HTTP_EARLY_RESPONSE, sending a complete response, and cleanly closing
   its streams.  Clients of type
   HTTP_MISSING_SETTINGS.  Only one control stream per peer is
   permitted; receipt of a second stream which claims to be a control
   stream MUST NOT discard complete responses be treated as a result connection error of having their request terminated abruptly, though clients can
   always discard responses at their discretion for other reasons.

   Changes to type
   HTTP_WRONG_STREAM_COUNT.  If the state of a request stream, including receiving a
   RST_STREAM with control stream is closed at any
   point, this MUST be treated as a connection error code, do not affect the state of the
   server's response.  Servers do not abort type
   HTTP_CLOSED_CRITICAL_STREAM.

   A pair of unidirectional streams is used rather than a response in progress
   solely due single
   bidirectional stream.  This allows either peer to a state change send data as soon
   they are able.  Depending on whether 0-RTT is enabled on the request stream.  However, if
   connection, either client or server might be able to send stream data
   first after the
   request cryptographic handshake completes.

3.2.2.  Push Streams

   A push stream terminates without containing is indicated by a usable HTTP request, stream type of "0x50" (ASCII 'P'),
   followed by the server SHOULD abort its response with Push ID of the error code
   HTTP_INCOMPLETE_REQUEST.

3.1.1.  Header Formatting and Compression

   HTTP header fields carry information promise that it fulfills, encoded as a series of key-value pairs.
   For a listing
   variable-length integer.  The remaining data on this stream consists
   of registered HTTP header fields, see the "Message
   Header Field" registry maintained at
   https://www.iana.org/assignments/message-headers [4].

   Just HTTP/QUIC frames, as defined in previous versions of HTTP, header field names are strings
   of ASCII characters that are compared in a case-insensitive fashion.
   Properties of HTTP header field names Section 4.2, and values fulfills a
   promised server push.  Server push and Push IDs are discussed in
   more detail described in
   Section 3.2 of [RFC7230], though the wire rendering in
   HTTP/QUIC differs.  As in HTTP/2, header field names MUST be
   converted to lowercase prior to their encoding.  A request or
   response containing uppercase header field names 5.4.

   Only servers can push; if a server receives a client-initiated push
   stream, this MUST be treated as
   malformed.

   As in HTTP/2, HTTP/QUIC uses special pseudo-header fields beginning
   with ':' character (ASCII 0x3a) to convey the target URI, the method a stream error of the request, and the status code for the response.  These pseudo-
   header fields are defined type
   HTTP_WRONG_STREAM_DIRECTION.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Stream Type (8)|                  Push ID (i)                ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 2: Push Stream Header

   Each Push ID MUST only be used once in Section 8.1.2.3 and 8.1.2.4 of
   [RFC7540].  Pseudo-header fields are not HTTP a push stream header.  If a
   push stream header fields.
   Endpoints MUST NOT generate pseudo-header fields other than those
   defined includes a Push ID that was used in [RFC7540].  The restrictions on another push
   stream header, the use of pseudo-header
   fields in Section 8.1.2.1 of [RFC7540] also apply to HTTP/QUIC.

   HTTP/QUIC uses QPACK header compression client MUST treat this as described in [QPACK], a
   variation connection error of HPACK which allows the flexibility to avoid header-
   compression-induced head-of-line blocking.  See that document for
   additional details.

3.1.2.  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
   type HTTP_DUPLICATE_PUSH.

3.2.3.  Reserved Stream Types

   Stream types 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 format "0x1f * N" are reserved to a remote host for
   similar purposes.

   A CONNECT request in HTTP/QUIC functions in exercise the same manner as in
   HTTP/2.  The request MUST be formatted as described in [RFC7540],
   Section 8.3.  A CONNECT request
   requirement that does not conform to these
   restrictions unknown types be ignored.  These streams have no
   semantic meaning, and can be sent when application-layer padding is malformed.  The
   desired.  They MAY also be sent on connections where no request stream data
   is currently being transferred.  Endpoints MUST NOT be half-
   closed at the end of the request.

   A proxy that supports CONNECT establishes a TCP connection
   ([RFC0793]) consider these
   streams to have any meaning upon receipt.

   The payload and length of the server identified stream are selected in any manner 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.

   All DATA frames
   implementation chooses.

4.  HTTP Framing Layer

   Frames are used on the control stream, request stream correspond to data sent on the
   TCP connection.  Any DATA frame sent by streams, and push
   streams.  This section describes HTTP framing in QUIC.  For a
   comparison with HTTP/2 frames, see Appendix A.2.

4.1.  Frame Layout

   All frames have the client is transmitted by 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 (i)                        ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Type (8)   |               Frame Payload (*)             ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 3: HTTP/QUIC frame format

   A frame includes the proxy to following fields:

   Length:  A variable-length integer that describes the TCP server; data received from length of the TCP server is
   packaged into DATA frames
      Frame Payload.  This length does not include the Type field.

   Type:  An 8-bit type for the frame.

   Frame Payload:  A payload, the semantics of which are determined by
      the proxy.  Note Type field.

   Each frame's payload MUST contain exactly the identified fields.  A
   frame that contains additional octets after the identified fields or
   a frame that terminates before the size and
   number end of TCP segments is not guaranteed to map predictably to the
   size and number identified fields MUST
   be treated as a connection error of HTTP type HTTP_MALFORMED_FRAME.

4.2.  Frame Definitions

4.2.1.  DATA

   DATA frames (type=0x0) convey arbitrary, variable-length sequences of
   octets associated with an HTTP request or QUIC STREAM frames.

   The TCP connection can response payload.

   DATA frames MUST be closed by either peer.  When the client
   ends the associated with an HTTP request stream (that is, or response.  If
   a DATA frame is received on either control stream, the receive stream at the proxy
   enters the "Data Recvd" state), the proxy will set the FIN bit on its
   connection to the TCP server.  When the proxy receives a packet recipient MUST
   respond with
   the FIN bit set, it will terminate the send stream that it sends to
   client.  TCP connections which remain half-closed in a single
   direction are not invalid, but are often handled poorly by servers,
   so clients SHOULD NOT close a stream for sending while they still
   expect to receive data from the target of the CONNECT.

   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 (Section 8) of type
   HTTP_CONNECT_ERROR (Section 6.1).  Correspondingly, a proxy
   HTTP_WRONG_STREAM.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Payload (*)                         ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 4: DATA frame payload

   DATA frames MUST send contain a TCP segment non-zero-length payload.  If a DATA frame
   is received with a payload length of zero, the RST bit set if it detects an error recipient MUST respond
   with the
   stream or the QUIC connection.

3.1.3.  Request Cancellation

   Either client or server can cancel requests by aborting the a stream
   (QUIC RST_STREAM or STOP_SENDING frames, as appropriate) with an error code of HTTP_REQUEST_CANCELLED (Section 6.1).  When the client
   cancels a response, it indicates that this response is no longer of
   interest.  Clients SHOULD cancel requests by aborting both directions 8) of type HTTP_MALFORMED_FRAME.

4.2.2.  HEADERS

   The HEADERS frame (type=0x1) is used to carry a stream.

   When the server cancels its response stream header block,
   compressed using
   HTTP_REQUEST_CANCELLED, it indicates that no application processing
   was performed.  The client QPACK.  See [QPACK] for more details.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Header Block (*)                      ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 5: HEADERS frame payload

   HEADERS frames can treat requests cancelled by the server
   as though they had never been sent at all, thereby allowing them to only be retried later sent on a new connection.  Servers MUST NOT use request / push streams.

4.2.3.  PRIORITY

   The PRIORITY (type=0x02) frame specifies the
   HTTP_REQUEST_CANCELLED status for requests which were partially or
   fully processed.

   Note: sender-advised priority
   of a stream.  In this context, "processed" means that some data from the
      stream was passed order to some higher layer of software ensure that might have
      taken some action as a result.

   If a stream prioritization is cancelled after receiving processed in
   a complete response, the
   client MAY ignore the cancellation and use consistent order, PRIORITY frames MUST be sent on the response.  However, if
   a control
   stream.  A PRIORITY frame sent on any other stream is cancelled after receiving a partial response, the
   response SHOULD NOT MUST be used.  Automatically retrying such requests is
   not possible, unless this is otherwise permitted (e.g., idempotent
   actions like GET, PUT, or DELETE).

3.2.  Request Prioritization

   HTTP/QUIC uses a priority scheme similar to that described in
   [RFC7540], Section 5.3.  In this priority scheme, a given stream can
   be designated as dependent upon another request, which expresses the
   preference that the latter stream (the "parent" request) be allocated
   resources before the former stream (the "dependent" request).  Taken
   together, the dependencies across all requests in treated as
   a connection form a
   dependency tree.  The structure error of the dependency tree changes as type HTTP_WRONG_STREAM.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |PT |DT |Empty|E|          Prioritized Element ID (i)         ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Element Dependency ID (i)                   ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Weight (8)  |
   +-+-+-+-+-+-+-+-+

                     Figure 6: PRIORITY frames add, remove, or change the dependency links between
   requests. frame payload

   The PRIORITY frame Section 4.2.4 identifies a prioritized element.
   The elements payload has the following fields:

   Prioritized Type:  A two-bit field indicating the type of element
      being prioritized.

   Dependency Type:  A two-bit field indicating the type of element
      being depended on.

   Empty:  A three-bit field which can MUST be prioritized are:

   o  Requests, identified by zero when sent and MUST be
      ignored on receipt.

   Exclusive:  A flag which indicates that the ID stream dependency is
      exclusive (see [RFC7540], Section 5.3).

   Prioritized Element ID:  A variable-length integer that identifies
      the element being prioritized.  Depending on the value of
      Prioritized Type, this contains the Stream ID of a request stream

   o  Pushes, identified by stream,
      the Push ID of the a promised resource
      (Section 4.2.7)

   o  Placeholders, identified by resource, or a Placeholder ID

   An element can depend on another element or on the root of the tree. a
      placeholder.

   Element Dependency ID:  A reference to an variable-length integer that identifies the
      element on which is no longer in the tree is treated
   as a reference to dependency is being expressed.  Depending on
      the root value of Dependency Type, this contains the tree.

   Only Stream ID of a client can send PRIORITY frames.  A server MUST NOT send
      request stream, the Push ID of a
   PRIORITY frame.

3.2.1.  Placeholders

   In HTTP/2, certain implementations used closed or unused streams as
   placeholders in describing promised resource, the relative priority
      Placeholder ID of requests.
   However, this created confusion as servers could not reliably
   identify which elements a placeholder, or is ignored.  For details of the
      dependencies, see Section 5.3 and [RFC7540], Section 5.3.

   Weight:  An unsigned 8-bit integer representing a priority tree could safely be
   discarded.  Clients could potentially reference closed streams long
   after weight for
      the server had discarded state, leading stream (see [RFC7540], Section 5.3).  Add one to disparate views of the prioritization the client had attempted value to express.

   In HTTP/QUIC,
      obtain a number of placeholders are explicitly permitted by weight between 1 and 256.

   A PRIORITY frame identifies an element to prioritize, and an element
   upon which it depends.  A Prioritized ID or Dependency ID identifies
   a client-initiated request using the corresponding stream ID, a
   server push using a Push ID (see Section 4.2.6), or a placeholder
   using a Placeholder ID (see Section 5.3.1).

   The values for the "SETTINGS_NUM_PLACEHOLDERS" setting.  Because
   the server commits to maintain these IDs in Prioritized Element Type and Element Dependency
   Type imply the tree, clients can use
   them with confidence that interpretation of the server will not have discarded the
   state.

   Placeholders are identified by an associated Element ID between zero and one less than
   the number fields.

          +-----------+------------------+---------------------+
          | Type Bits | Type Description | Element ID Contents |
          +-----------+------------------+---------------------+
          | 00        | Request stream   | Stream ID           |
          |           |                  |                     |
          | 01        | Push stream      | Push ID             |
          |           |                  |                     |
          | 10        | Placeholder      | Placeholder ID      |
          |           |                  |                     |
          | 11        | Root of placeholders the server has permitted.

3.2.2.  Priority Tree Maintenance

   Servers can aggressively prune inactive regions from tree | Ignored             |
          +-----------+------------------+---------------------+

   Note that the priority
   tree, because placeholders will be used to "root" any persistent
   structure root of the tree which the client cares about retaining.  For
   prioritization purposes, cannot be referenced using a node Stream ID
   of 0, as in the tree is considered "inactive"
   when the corresponding [RFC7540]; QUIC stream has been closed for at least two round-
   trip times (using any reasonable estimate available on 0 carries a valid HTTP request.
   The root of the server).
   This delay helps mitigate race conditions where tree cannot be reprioritized.  A PRIORITY frame that
   prioritizes the server has pruned
   a node root of the client believed was still active and used tree MUST be treated as a Stream
   Dependency.

   Specifically, the server MAY at any time:

   o  Identify and discard branches connection
   error of type HTTP_MALFORMED_FRAME.

   When a PRIORITY frame claims to reference a request, the tree containing only inactive
      nodes (i.e. associated
   ID MUST identify a node client-initiated bidirectional stream.  A server
   MUST treat receipt of PRIORITY frame with only a Stream ID of any other inactive nodes
   type as descendants,
      along with those descendants)

   o  Identify and condense interior regions a connection error of the tree containing only
      inactive nodes, allocating weight appropriately

       x                x                 x
       |                |                 |
       P                P                 P
      / \               |                 |
     I   I     ==>      I      ==>        A
        / \             |                 |
       A   I            A                 A
       |                |
       A type HTTP_MALFORMED_FRAME.

   A

                Figure 1: Example PRIORITY frame that references a non-existent Push ID or a
   Placeholder ID greater than the server's limit MUST be treated as a
   HTTP_MALFORMED_FRAME error.

4.2.4.  CANCEL_PUSH

   The CANCEL_PUSH frame (type=0x3) is used to request cancellation of Priority Tree Pruning

   In a
   server push prior to the example in Figure 1, "P" represents push stream being created.  The CANCEL_PUSH
   frame identifies a Placeholder, "A"
   represents an active node, and "I" represents an inactive node.  In server push by Push ID (see Section 4.2.6),
   encoded as a variable-length integer.

   When a server receives this frame, it aborts sending the first step, response for
   the identified server discards two inactive branches (each a
   single node).  In push.  If the second step, server has not yet started to
   send the server condenses an interior
   inactive node.  Note that these transformations will result in no
   change in push, it can use the resources allocated receipt of a CANCEL_PUSH frame
   to avoid opening a particular active push stream.

   Clients SHOULD assume  If the push stream has been opened
   by the server, the server is actively performing such pruning
   and SHOULD NOT declare send a dependency QUIC RST_STREAM frame on a that
   stream it knows and cease transmission of the response.

   A server can send this frame to have been
   closed.

3.3.  Unidirectional Streams

   Unidirectional streams, in either direction, are used for indicate that it will not be
   fulfilling a range promise prior to creation of
   purposes.  The purpose is indicated by a push stream.  Once the
   push stream type, which is sent
   as a single octet header at has been created, sending CANCEL_PUSH has no effect on
   the start state of the push stream.  The format and
   structure  A QUIC RST_STREAM frame SHOULD be used
   instead to abort transmission of data that follows this header the server push response.

   A CANCEL_PUSH frame is determined by sent on the control stream.  Sending a
   CANCEL_PUSH frame on a stream other than the control stream type. MUST be
   treated as a stream error of type HTTP_WRONG_STREAM.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+
   |Stream Type (8)|
   +-+-+-+-+-+-+-+-+ 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Push ID (i)                        ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 2: Unidirectional Stream Header

   Some stream types are reserved (Section 3.3.1).  Two stream types are
   defined in this document: control streams (Section 3.3.2) and 7: CANCEL_PUSH frame payload

   The CANCEL_PUSH frame carries a Push ID encoded as a variable-length
   integer.  The Push ID identifies the server push
   streams (Section 3.3.3).  Other stream types can be defined by
   extensions to HTTP/QUIC. that is being
   cancelled (see Section 4.2.6).

   If the stream header indicates client receives a stream type which is CANCEL_PUSH frame, that frame might identify
   a Push ID that has not supported yet been mentioned by the recipient, the remainder of the stream cannot be consumed as
   the semantics are unknown.  Recipients of unknown stream types MAY
   trigger a QUIC STOP_SENDING PUSH_PROMISE frame.

   An endpoint MUST treat a CANCEL_PUSH frame with an which does not contain
   exactly one properly-formatted variable-length integer as a
   connection error code of
   HTTP_UNKNOWN_STREAM_TYPE, but MUST NOT consider type HTTP_MALFORMED_FRAME.

4.2.5.  SETTINGS

   The SETTINGS frame (type=0x4) conveys configuration parameters that
   affect how endpoints communicate, such streams as preferences and constraints
   on peer behavior.  Individually, a SETTINGS parameter can also be
   referred to as a "setting"; the identifier and value of each setting
   parameter can be an
   error referred to as a "setting identifier" and a "setting
   value".

   SETTINGS parameters are not negotiated; they describe characteristics
   of any kind.

   Implementations MAY send stream types before knowing whether the peer
   supports them.  However, stream types sending peer, which could modify can be used by the state or
   semantics of existing protocol components, including QPACK or other
   extensions, MUST NOT receiving peer.
   However, a negotiation can be sent until implied by the use of SETTINGS - a peer is known
   uses SETTINGS to support them.

3.3.1.  Reserved Stream Types

   Stream types advertise a set of the format "0x1f * N" are reserved to exercise the
   requirement that unknown types be ignored.  These streams have no
   semantic meaning, and supported values.  The recipient
   can be sent when application-layer padding is
   desired.  They MAY then choose which entries from this list are also be sent on connections where no request data
   is currently being transferred.  Endpoints MUST NOT consider these
   streams to have any meaning upon receipt.

   The payload acceptable and length of
   proceed with the stream are selected value it has chosen.  (This choice could be
   announced in any manner the
   implementation chooses.

3.3.2.  Control Streams

   The control stream is indicated by a stream type field of "0x43" (ASCII
   'C').  Data on this stream consists of HTTP/QUIC frames, as defined an extension frame, or in Section 4.2.

   Each side MUST initiate a single control stream at the beginning of
   the connection and send its SETTINGS frame as own value in
   SETTINGS.)

   Different values for the first frame on this
   stream.  If same parameter can be advertised by each
   peer.  For example, a client might be willing to consume a very large
   response header, while servers are more cautious about request size.

   Parameters MUST NOT occur more than once.  A receiver MAY treat the first frame
   presence of the control stream is any other frame
   type, this MUST be treated same parameter more than once as a connection error
   of type
   HTTP_MISSING_SETTINGS.  Only one control stream per peer is
   permitted; receipt HTTP_MALFORMED_FRAME.

   The payload of a second stream SETTINGS frame consists of zero or more parameters,
   each consisting of an unsigned 16-bit setting identifier and a value
   which claims to uses the QUIC variable-length integer encoding.

    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)       |           Value (i)         ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 8: SETTINGS parameter format

   Each value MUST be a control
   stream compared against the remaining length of the
   SETTINGS frame.  A variable-length integer value which cannot fit
   within the remaining length of the SETTINGS frame MUST cause the
   SETTINGS frame to be treated as considered malformed and trigger a connection
   error of type
   HTTP_WRONG_STREAM_COUNT.  If HTTP_MALFORMED_FRAME.

   An implementation MUST ignore the control stream is closed at any
   point, this MUST be treated as contents for any SETTINGS
   identifier it does not understand.

   SETTINGS frames always apply to a connection error of type
   HTTP_CLOSED_CRITICAL_STREAM.

   A pair of unidirectional streams is used rather than connection, never a single
   bidirectional stream.  This allows either peer to send data
   A SETTINGS frame MUST be sent as soon
   they are able.  Depending on whether 0-RTT is enabled on the
   connection, either client or server might be able to send stream data first after the cryptographic handshake completes.

3.3.3.  Server Push

   HTTP/QUIC server push is similar to what is described in HTTP/2
   [RFC7540], but uses different mechanisms.

   The PUSH_PROMISE frame (Section 4.2.7) is of each control
   stream (see Section 3.2.1) by each peer, and MUST NOT be sent
   subsequently or on any other stream.  If an endpoint receives a
   SETTINGS frame on a different stream, the client-
   initiated bidirectional stream that carried the request that
   generated the push.  This allows the server push to be associated endpoint MUST respond with
   a request.  Ordering connection error of type HTTP_WRONG_STREAM.  If an endpoint
   receives a PUSH_PROMISE in relation to certain
   parts of second SETTINGS frame, the response is important (see Section 8.2.1 endpoint MUST respond with a
   connection error of [RFC7540]). type HTTP_MALFORMED_FRAME.

   The PUSH_PROMISE SETTINGS frame does not reference a stream; it contains a
   Push ID that uniquely identifies a server push.  This allows affects connection state.  A badly formed or
   incomplete SETTINGS frame MUST be treated as a server
   to fulfill promises in the order that best suits its needs. connection error
   (Section 8) of type HTTP_MALFORMED_FRAME.

4.2.5.1.  Defined SETTINGS Parameters

   The same
   Push ID can be used following settings are defined in multiple PUSH_PROMISE frames (see
   Section 4.2.7).  When a server later fulfills a promise, the server
   push response HTTP/QUIC:

   SETTINGS_NUM_PLACEHOLDERS (0x3):  This value SHOULD be non-zero.  The
      default value is conveyed on a push stream.

   A push stream 16.

   SETTINGS_MAX_HEADER_LIST_SIZE (0x6):  The default value is indicated by a stream type unlimited.

   Setting identifiers of "0x50" (ASCII 'P'),
   followed by the Push ID of format "0x?a?a" are reserved to exercise
   the promise requirement that it fulfills, encoded as a
   variable-length integer.  The remaining data on this stream consists
   of HTTP/QUIC frames, as unknown identifiers be ignored.  Such settings
   have no defined meaning.  Endpoints SHOULD include at least one such
   setting in Section 4.2, and carries their SETTINGS frame.  Endpoints MUST NOT consider such
   settings to have any meaning upon receipt.

   Because the
   response side of an HTTP message exchange as described in
   Section 3.1.  The header setting has no defined meaning, the value of the request message is carried setting
   can be any value the implementation selects.

   Additional settings MAY be defined by extensions to HTTP/QUIC.

4.2.5.2.  Initialization

   When a
   PUSH_PROMISE frame (see Section 4.2.7) on the request stream which
   generated 0-RTT QUIC connection is being used, the push.  Promised client's initial
   requests MUST conform to will be sent before the
   requirements in Section 8.2 arrival of [RFC7540].

   Only servers can push; if a the server's SETTINGS
   frame.  Clients MUST store the settings the server receives a client-initiated push
   stream, this provided in the
   session being resumed and MUST be treated as a stream error of type
   HTTP_WRONG_STREAM_DIRECTION.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Stream Type (8)|                  Push ID (i)                ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 3: Push Stream Header

   Server push is only enabled on a comply with stored settings until the
   server's current settings are received.  Remembered settings apply to
   the new connection when a client sends a
   MAX_PUSH_ID until the server's SETTINGS frame (see Section 4.2.9). is received.

   A server cannot use server
   push until it receives a MAX_PUSH_ID frame.  A client sends
   additional MAX_PUSH_ID frames to control can remember the number of pushes settings that a
   server can promise. it advertised, or store an
   integrity-protected copy of the values in the ticket and recover the
   information when accepting 0-RTT data.  A server SHOULD use Push IDs sequentially,
   starting at 0. uses the HTTP/QUIC
   settings values in determining whether to accept 0-RTT data.

   A client MUST treat receipt of a push stream with a
   Push ID that server MAY accept 0-RTT and subsequently provide different settings
   in its SETTINGS frame.  If 0-RTT data is greater than accepted by the maximum Push ID as a connection
   error of type HTTP_PUSH_LIMIT_EXCEEDED.

   Each Push ID server, its
   SETTINGS frame MUST only be used once in a push stream header.  If a
   push stream header includes a Push ID NOT reduce any limits or alter any values that was used in another push
   stream header,
   might be violated by the client MUST treat this as with its 0-RTT data.

   When a 1-RTT QUIC connection error of
   type HTTP_DUPLICATE_PUSH.

   If a promised server push is not needed by the client, being used, the client
   SHOULD MUST NOT send a CANCEL_PUSH frame.  If
   requests prior to receiving and processing the push stream is already open,
   a QUIC STOP_SENDING server's SETTINGS
   frame.

4.2.6.  PUSH_PROMISE

   The PUSH_PROMISE frame with an appropriate error code can be (type=0x05) is used
   instead (e.g., HTTP_PUSH_REFUSED, HTTP_PUSH_ALREADY_IN_CACHE; see
   Section 6).  This asks the server not to transfer the data and
   indicates that it will be discarded upon receipt.

4.  HTTP Framing Layer

   Frames are used on the control stream, carry a promised
   request streams, and push
   streams.  This section describes HTTP framing in QUIC and highlights
   some differences from HTTP/2 framing.  For more detail on differences header set from HTTP/2, see Section 8.2.

4.1.  Frame Layout

   All frames have the following format: server to client, as in HTTP/2.

    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                          Push ID (i)                        ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Type (8)   |               Frame Payload                       Header Block (*)                      ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 4: HTTP/QUIC frame format

   A 9: PUSH_PROMISE frame includes the following fields:

   Length: payload

   The payload consists of:

   Push ID:  A variable-length integer that describes the length of the
      Frame Payload.  This length does not include identifies the Type field.

   Type:  An 8-bit type server push
      operation.  A Push ID is used in push stream headers
      (Section 5.4), CANCEL_PUSH frames (Section 4.2.4), and PRIORITY
      frames (Section 4.2.3).

   Header Block:  QPACK-compressed request header fields for the frame.

   Frame Payload:
      promised response.  See [QPACK] for more details.

   A payload, server MUST NOT use a Push ID that is larger than the semantics client has
   provided in a MAX_PUSH_ID frame (Section 4.2.8).  A client MUST treat
   receipt of which are determined by a PUSH_PROMISE that contains a larger Push ID than the Type field.

4.2.  Frame Definitions

4.2.1.  Reserved Frame Types

   Frame types
   client has advertised as a connection error of type
   HTTP_MALFORMED_FRAME.

   A server MAY use the format "0xb + (0x1f * N)" are reserved to exercise
   the requirement same Push ID in multiple PUSH_PROMISE frames.
   This allows the server to use the same server push in response to
   multiple concurrent requests.  Referencing the same server push
   ensures that unknown types be ignored.  These frames have no
   semantic meaning, and a PUSH_PROMISE can be sent when application-layer padding is
   desired.  They MAY also made in relation to every response
   in which server push might be sent on connections where no request data
   is currently being transferred.  Endpoints MUST NOT consider these needed without duplicating pushes.

   A server that uses the same Push ID in multiple PUSH_PROMISE frames to have any meaning upon receipt.
   MUST include the same header fields each time.  The payload and length octets of the frames are selected in any manner
   header block MAY be different due to differing encoding, but the
   implementation chooses.

4.2.2.  DATA

   DATA frames (type=0x0) convey arbitrary, variable-length sequences of
   octets associated with an HTTP request or response payload.

   DATA frames
   header fields and their values MUST be associated with an HTTP request or response.  If
   a DATA frame identical.  Note that ordering
   of header fields is received on either control stream, the recipient significant.  A client MUST
   respond treat receipt of a
   PUSH_PROMISE with conflicting header field values for the same Push
   ID as a connection error (Section 6) of type
   HTTP_WRONG_STREAM.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Payload (*)                         ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 5: DATA frame payload

   DATA frames MUST contain a non-zero-length payload.  If a DATA frame HTTP_MALFORMED_FRAME.

   Allowing duplicate references to the same Push ID is received with primarily to
   reduce duplication caused by concurrent requests.  A server SHOULD
   avoid reusing a payload length of zero, the recipient MUST respond
   with Push ID over a stream error (Section 6) of type HTTP_MALFORMED_FRAME.

4.2.3.  HEADERS long period.  Clients are likely to
   consume server push responses and not retain them for reuse over
   time.  Clients that see a PUSH_PROMISE that uses a Push ID that they
   have since consumed and discarded are forced to ignore the
   PUSH_PROMISE.

4.2.7.  GOAWAY

   The HEADERS GOAWAY frame (type=0x1) (type=0x7) is used to carry initiate graceful shutdown of
   a header block,
   compressed using QPACK.  See [QPACK] for more details. connection by a server.  GOAWAY allows a server to stop accepting
   new requests while still finishing processing of previously received
   requests.  This enables administrative actions, like server
   maintenance.  GOAWAY by itself does not close a connection.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Header Block (*)                          Stream ID (i)                      ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 6: HEADERS 10: GOAWAY frame payload

   HEADERS frames can only be sent on request / push streams.

4.2.4.  PRIORITY

   The PRIORITY (type=0x02) GOAWAY frame specifies the sender-advised priority
   of carries a QUIC Stream ID for a client-initiated
   bidirectional stream and is substantially different in format from [RFC7540].
   In order to ensure that prioritization is processed in encoded as a consistent
   order, PRIORITY frames MUST be sent on the control stream. variable-length integer.  A
   PRIORITY client
   MUST treat receipt of a GOAWAY frame sent on containing a Stream ID of any
   other stream MUST be treated type as a
   HTTP_WRONG_STREAM error.

   The format has been modified to accommodate connection error of type HTTP_MALFORMED_FRAME.

   Clients do not being sent on a
   request stream, need to allow for identification of send GOAWAY to initiate a graceful shutdown;
   they simply stop making new requests.  A server pushes, and the
   larger stream ID space of QUIC.  The semantics MUST treat receipt of the Stream
   Dependency, Weight, and E flag are otherwise the same as in HTTP/2.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |PT |DT |Empty|E|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Prioritized Element ID (i)                  ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Element Dependency ID (i)                   ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Weight (8)  |
   +-+-+-+-+-+-+-+-+

                     Figure 7: PRIORITY
   a GOAWAY frame payload as a connection error (Section 8) of type
   HTTP_UNEXPECTED_GOAWAY.

   The PRIORITY GOAWAY frame payload has the following fields:

   Prioritized Type:  A two-bit field indicating the type of element
      being prioritized.

   Dependency Type:  A two-bit field indicating applies to the type of element
      being depended on.

   Empty:  A three-bit field which MUST be zero when sent and connection, not a specific stream.
   An endpoint MUST be
      ignored treat a GOAWAY frame on receipt.

   Exclusive:  A flag which indicates that a stream other than the
   control stream dependency is
      exclusive (see [RFC7540], as a connection error (Section 8) of type
   HTTP_WRONG_STREAM.

   See Section 5.3).

   Prioritized Element ID:  A variable-length integer that identifies
      the element being prioritized.  Depending 6.2 for more information on the value use of
      Prioritized Type, this contains the Stream ID of a request stream, GOAWAY frame.

4.2.8.  MAX_PUSH_ID

   The MAX_PUSH_ID frame (type=0xD) is used by clients to control the Push ID
   number of a promised resource, or a Placeholder ID of a
      placeholder.

   Element Dependency ID:  A variable-length integer server pushes that identifies the
      element on which a dependency is being expressed.  Depending on server can initiate.  This sets the
   maximum value of Dependency Type, this contains the Stream ID of for a
      request stream, the Push ID of a promised resource, or a
      Placeholder ID of that the server can use in a placeholder.  For details PUSH_PROMISE
   frame.  Consequently, this also limits the number of dependencies, see
      Section 3.2 and [RFC7540], Section 5.3.

   Weight:  An unsigned 8-bit integer representing a priority weight for push streams
   that the stream (see [RFC7540], Section 5.3).  Add one server can initiate in addition to the value to
      obtain limit set by the QUIC
   MAX_STREAM_ID frame.

   The MAX_PUSH_ID frame is always sent on a weight between 1 and 256.

   A PRIORITY control stream.  Receipt of
   a MAX_PUSH_ID frame identifies an element to prioritize, and an element
   upon which it depends. on any other stream MUST be treated as a
   connection error of type HTTP_WRONG_STREAM.

   A Prioritized ID or Dependency ID identifies server MUST NOT send a client-initiated request using MAX_PUSH_ID frame.  A client MUST treat the corresponding stream ID,
   receipt of a
   server push using MAX_PUSH_ID frame as a connection error of type
   HTTP_MALFORMED_FRAME.

   The maximum Push ID (see Section 4.2.7), or is unset when a placeholder
   using connection is created, meaning
   that a Placeholder ID (see Section 3.2.1).

   The values for the Prioritized Element Type and Element Dependency
   Type imply server cannot push until it receives a MAX_PUSH_ID frame.  A
   client that wishes to manage the interpretation number of promised server pushes can
   increase the associated Element maximum Push ID fields.

          +-----------+------------------+---------------------+
          | Type Bits | Type Description | Element ID Contents |
          +-----------+------------------+---------------------+
          | 00        | Request stream   | Stream ID           |
          |           |                  |                     |
          | 01        | Push stream by sending MAX_PUSH_ID frames as the
   server fulfills or cancels server pushes.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Push ID             |
          |           |                  |                     |
          | 10        | Placeholder      | Placeholder ID      |
          |           |                  |                     |
          | 11        | Root of the tree | Ignored             |
          +-----------+------------------+---------------------+

   Note (i)                        ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 11: MAX_PUSH_ID frame payload

   The MAX_PUSH_ID frame carries a single variable-length integer that
   identifies the root of the tree cannot be referenced using maximum value for a Stream Push ID
   of 0, as in [RFC7540]; QUIC stream 0 carries a valid HTTP request.
   The root of that the tree cannot be reprioritized. server can use
   (see Section 4.2.6).  A PRIORITY MAX_PUSH_ID frame that
   prioritizes cannot reduce the root maximum
   Push ID; receipt of the tree a MAX_PUSH_ID that contains a smaller value than
   previously received MUST be treated as a connection error of type
   HTTP_MALFORMED_FRAME.

   When a PRIORITY frame claims to reference a request, the associated
   ID MUST identify a client-initiated bidirectional stream.

   A server MUST treat receipt of PRIORITY a MAX_PUSH_ID frame with payload that does not contain
   a Stream ID of any other
   type single variable-length integer as a connection error of type
   HTTP_MALFORMED_FRAME.

   A PRIORITY frame that references a non-existent Push ID or a
   Placeholder ID greater than

4.2.9.  Reserved Frame Types

   Frame types of the server's limit MUST be treated as a
   HTTP_MALFORMED_FRAME error.

   A PRIORITY frame MUST contain only format "0xb + (0x1f * N)" are reserved to exercise
   the identified fields.  A PRIORITY
   frame that contains more or fewer fields, or a PRIORITY frame requirement that
   includes a truncated integer encoding MUST unknown types be treated as a connection
   error of type HTTP_MALFORMED_FRAME.

4.2.5.  CANCEL_PUSH

   The CANCEL_PUSH frame (type=0x3) ignored (Section 7).  These
   frames have no semantic value, and can be sent when application-layer
   padding is used to desired.  They MAY also be sent on connections where no
   request cancellation of
   server push prior to the push stream data is currently being created. transferred.  Endpoints MUST NOT
   consider these frames to have any meaning upon receipt.

   The CANCEL_PUSH
   frame identifies a server push payload and length of the frames are selected in any manner the
   implementation chooses.

5.  HTTP Request Lifecycle

5.1.  HTTP Message Exchanges

   A client sends an HTTP request by Push ID (see Section 4.2.7)
   using a variable-length integer.

   When on a client-initiated bidirectional
   QUIC stream.  A server receives this frame, it aborts sending the sends an HTTP response for
   the identified server push.  If on the server has not yet started to
   send same stream as
   the server push, it can use request.

   An HTTP message (request or response) consists of:

   1.  the receipt of message header (see [RFC7230], Section 3.2), sent as a CANCEL_PUSH single
       HEADERS frame
   to avoid opening a stream.  If the push stream has been opened by the
   server, (see Section 4.2.2),

   2.  the server SHOULD send payload body (see [RFC7230], Section 3.3), sent as a QUIC RST_STREAM frame on those
   streams and cease transmission series
       of DATA frames (see Section 4.2.1),

   3.  optionally, one HEADERS frame containing the response.

   A server can send this frame to indicate that it won't trailer-part, if
       present (see [RFC7230], Section 4.1.2).

   A server MAY interleave one or more PUSH_PROMISE frames (see
   Section 4.2.6) with the frames of a response message.  These
   PUSH_PROMISE frames are not part of the response; see Section 5.4 for
   more details.

   The "chunked" transfer encoding defined in Section 4.1 of [RFC7230]
   MUST NOT be sending used.

   Trailing header fields are carried in an additional header block
   following the body.  Senders MUST send only one header block in the
   trailers section; receivers MUST discard any subsequent header
   blocks.

   A response MAY consist of multiple messages when and only when one or
   more informational responses (1xx, see [RFC7231], Section 6.2)
   precede a final response prior to creation of the same request.  Non-final responses do
   not contain a push payload body or trailers.

   An HTTP request/response exchange fully consumes a bidirectional QUIC
   stream.  Once  After sending a request, a client closes the push stream
   has been created, for
   sending; after sending CANCEL_PUSH has no effect on a final response, the state of server closes the stream
   for sending and the push stream.  A QUIC RST_STREAM frame SHOULD be used instead to
   cancel transmission of stream is fully closed.  Requests and
   responses are considered complete when the server push response.

   A CANCEL_PUSH frame corresponding QUIC stream
   is sent on closed in the control stream.  Sending appropriate direction.

   A server can send a
   CANCEL_PUSH frame complete response prior to the client sending an
   entire request if the response does not depend on a stream other than any portion of the control stream MUST be
   treated as
   request that has not been sent and received.  When this is true, a stream error of type HTTP_WRONG_STREAM.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Push ID (i)                        ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 8: CANCEL_PUSH frame payload

   The CANCEL_PUSH frame carries a Push ID encoded as a variable-length
   integer.  The Push ID identifies the
   server push MAY request that is being
   cancelled (see Section 4.2.7).

   If the client receives a CANCEL_PUSH frame, that frame might identify abort transmission of a Push ID that has not yet been mentioned request
   without error by triggering a PUSH_PROMISE frame.

   An endpoint MUST treat a CANCEL_PUSH QUIC STOP_SENDING frame which does not contain
   exactly one properly-formatted variable-length integer as a
   connection with error of type HTTP_MALFORMED_FRAME.

4.2.6.  SETTINGS

   The SETTINGS frame (type=0x4) conveys configuration parameters that
   affect how endpoints communicate, such as preferences and constraints
   on peer behavior, and is different from [RFC7540].  Individually, code
   HTTP_EARLY_RESPONSE, sending a
   SETTINGS parameter can also be referred to complete response, and cleanly closing
   its stream.  Clients MUST NOT discard complete responses as a "setting".

   SETTINGS parameters are not negotiated; they describe characteristics result
   of the sending peer, which having their request terminated abruptly, though clients can be used by
   always discard responses at their discretion for other reasons.

   Changes to the state of a request stream, including receiving peer.
   However, a negotiation can be implied by
   RST_STREAM with any error code, do not affect the use state of SETTINGS - the
   server's response.  Servers do not abort a peer
   uses SETTINGS response in progress
   solely due to advertise a set of supported values.  The recipient
   can then choose which entries from this list are also acceptable and
   proceed with state change on the value it has chosen.  (This choice could be
   announced in request stream.  However, if the
   request stream terminates without containing a field of an extension frame, or in usable HTTP request,
   the server SHOULD abort its own value in
   SETTINGS.)

   Different values for response with the same parameter can be advertised by each
   peer.  For example, error code
   HTTP_INCOMPLETE_REQUEST.

5.1.1.  Header Formatting and Compression

   HTTP message headers carry information as a client might be willing to consume series of key-value
   pairs, called header fields.  For a very large
   response header, while servers are more cautious about request size.

   Parameters MUST NOT occur more than once.  A receiver MAY treat the
   presence listing of registered HTTP header
   fields, see the same parameter more than once "Message Header Field" registry maintained at
   https://www.iana.org/assignments/message-headers [4].

   Just as a connection error in previous versions of type HTTP_MALFORMED_FRAME.

   The payload HTTP, header field names are strings
   of ASCII characters that are compared in a SETTINGS frame consists case-insensitive fashion.
   Properties of zero or HTTP header field names and values are discussed in
   more parameters,
   each consisting detail in Section 3.2 of an unsigned 16-bit setting identifier and a value
   which uses [RFC7230], though the QUIC variable-length integer wire rendering in
   HTTP/QUIC differs.  As in HTTP/2, header field names MUST be
   converted to lowercase prior to their encoding.

    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)       |           Value (i)         ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 9: SETTINGS value format

   Each value  A request or
   response containing uppercase header field names MUST be compared against the remaining length of treated as
   malformed.

   As in HTTP/2, HTTP/QUIC uses special pseudo-header fields beginning
   with the
   SETTINGS frame.  Any value which purports ':' character (ASCII 0x3a) to cross convey the end of target URI, the
   frame MUST cause
   method of the SETTINGS frame to be considered malformed request, and
   trigger a connection error of type HTTP_MALFORMED_FRAME.

   An implementation MUST ignore the contents status code 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 either control
   stream (see response.  These
   pseudo-header fields are defined in Section 3) by each peer, 8.1.2.3 and 8.1.2.4 of
   [RFC7540].  Pseudo-header fields are not HTTP header fields.
   Endpoints MUST NOT be sent
   subsequently or on any generate pseudo-header fields other stream.  If an endpoint receives a
   SETTINGS frame than those
   defined in [RFC7540].  The restrictions on a different stream, the endpoint MUST respond with use of pseudo-header
   fields in Section 8.1.2.1 of [RFC7540] also apply to HTTP/QUIC.

   HTTP/QUIC uses QPACK header compression as described in [QPACK], a connection error
   variation of type HTTP_WRONG_STREAM.  If an endpoint
   receives HPACK which allows the flexibility to avoid header-
   compression-induced head-of-line blocking.  See that document for
   additional details.

   An HTTP/QUIC implementation MAY impose a second SETTINGS frame, limit on the endpoint MUST respond with maximum size of
   the header it will accept on an individual HTTP message.  This limit
   is conveyed as a
   connection error number of type HTTP_MALFORMED_FRAME. octets in the
   "SETTINGS_MAX_HEADER_LIST_SIZE" parameter.  The SETTINGS frame affects connection state.  A badly formed or
   incomplete SETTINGS frame MUST be treated as size of a connection error
   (Section 6) header list
   is calculated based on the uncompressed size of type HTTP_MALFORMED_FRAME.

4.2.6.1.  Defined SETTINGS Parameters

   The following settings are defined header fields,
   including the length of the name and value in HTTP/QUIC:

   SETTINGS_NUM_PLACEHOLDERS (0x3):  This octets plus an overhead
   of 32 octets for each header field.  Encountering a message header
   larger than this value SHOULD be non-zero.  The
      default value is 16.

   SETTINGS_MAX_HEADER_LIST_SIZE (0x6):  The default value is unlimited.

   Settings values treated as a stream error of type
   "HTTP_EXCESSIVE_LOAD".

5.1.2.  Request Cancellation

   Either client or server can cancel requests by aborting the format "0x?a?a" are reserved to exercise stream
   (QUIC RST_STREAM and/or STOP_SENDING frames, as appropriate) with an
   error code of HTTP_REQUEST_CANCELLED (Section 8.1).  When the
   requirement client
   cancels a response, it indicates that unknown parameters be ignored.  Such settings have this response is no defined meaning.  Endpoints longer of
   interest.  Implementations SHOULD include at least one such
   setting in their SETTINGS frame.  Endpoints MUST NOT consider such
   settings to have any meaning upon receipt.

   Because the setting has no defined meaning, the value cancel requests by aborting both
   directions of a stream.

   When the setting server aborts its response stream using
   HTTP_REQUEST_CANCELLED, it indicates that no application processing
   was performed.  The client can be any value the implementation selects.

   Additional settings MAY be defined treat requests cancelled by extensions the server
   as though they had never been sent at all, thereby allowing them to HTTP/QUIC.

4.2.6.2.  Initial SETTINGS Values

   When
   be retried later on a 0-RTT QUIC connection is being used, new connection.  Servers MUST NOT use the client's initial
   HTTP_REQUEST_CANCELLED status for requests will be sent before which were partially or
   fully processed.

   Note:  In this context, "processed" means that some data from the arrival
      stream was passed to some higher layer of software that might have
      taken some action as a result.

   If a stream is cancelled after receiving a complete response, the server's SETTINGS
   frame.  Clients MUST store
   client MAY ignore the settings cancellation and use the server provided in response.  However, if
   a stream is cancelled after receiving a partial response, the
   response SHOULD NOT be used.  Automatically retrying such requests is
   not possible, unless this is otherwise permitted (e.g., idempotent
   actions like GET, PUT, or DELETE).

5.2.  The CONNECT Method

   The pseudo-method CONNECT ([RFC7231], Section 4.3.6) is primarily
   used with HTTP proxies to establish a TLS session being resumed and MUST comply with stored settings until an origin
   server for the
   server's current settings are received.  Remembered settings apply purposes of interacting with "https" resources.  In
   HTTP/1.x, CONNECT is used to
   the new convert an entire HTTP connection until into a
   tunnel to a remote host.  In HTTP/2, the server's SETTINGS frame CONNECT method is received. used to
   establish a tunnel over a single HTTP/2 stream to a remote host for
   similar purposes.

   A server can remember the settings that it advertised, or store an
   integrity-protected copy of the values CONNECT request in the ticket and recover the
   information when accepting 0-RTT data.  A server uses the HTTP/QUIC
   settings values in determining whether to accept 0-RTT data.

   A server MAY accept 0-RTT and subsequently provide different settings functions in its SETTINGS frame.  If 0-RTT data is accepted by the server, its
   SETTINGS frame same manner as in
   HTTP/2.  The request MUST NOT reduce any limits or alter any values be formatted as described in [RFC7540],
   Section 8.3.  A CONNECT request that
   might does not conform to these
   restrictions is malformed.  The request stream MUST NOT be violated by closed at
   the client with its 0-RTT data.

   When end of the request.

   A proxy that supports CONNECT establishes a 1-RTT QUIC TCP connection is being used, the client MUST NOT send
   requests prior
   ([RFC0793]) to receiving and processing the server's SETTINGS
   frame.

4.2.7.  PUSH_PROMISE

   The PUSH_PROMISE frame (type=0x05) server identified in the ":authority" pseudo-
   header field.  Once this connection is used to carry successfully established, the
   proxy sends a request header
   set from server HEADERS frame containing a 2xx series status code to
   the client, as defined in HTTP/2.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Push ID (i)                        ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Header Block (*)                      ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 10: PUSH_PROMISE [RFC7231], Section 4.3.6.

   All DATA frames on the stream correspond to data sent or received on
   the TCP connection.  Any DATA frame payload

   The payload consists of:

   Push ID:  A variable-length integer that identifies sent by the client is transmitted
   by the proxy to the TCP server; data received from the TCP server push
      request.  A push ID is used in push stream header (Section 3.3.3),
      CANCEL_PUSH frames (Section 4.2.5), and PRIORITY
   packaged into DATA frames
      (Section 4.2.4).

   Header Block:  QPACK-compressed request header fields for by the
      promised response.  See [QPACK] for more details.

   A server MUST NOT use a Push ID proxy.  Note that is larger than the client has
   provided in a MAX_PUSH_ID frame (Section 4.2.9).  A client MUST treat
   receipt size and
   number of a PUSH_PROMISE that contains a larger Push ID than TCP segments is not guaranteed to map predictably to the
   client has advertised as a connection error
   size and number of type
   HTTP_MALFORMED_FRAME.

   A server MAY use the same Push ID in multiple PUSH_PROMISE HTTP DATA or QUIC STREAM frames.
   This allows

   The TCP connection can be closed by either peer.  When the server to use client
   ends the same server push in response to
   multiple concurrent requests.  Referencing request stream (that is, the same server push
   ensures that a PUSH_PROMISE can be made in relation to every response
   in which server push might be needed without duplicating pushes.

   A server that uses receive stream at the same Push ID in multiple PUSH_PROMISE frames
   MUST include proxy
   enters the same header fields each time.  The octets of "Data Recvd" state), the
   header block MAY be different due proxy will set the FIN bit on its
   connection to differing encoding, but the
   header fields and their values MUST be identical.  Note that ordering
   of header fields is significant.  A client MUST treat receipt of TCP server.  When the proxy receives a
   PUSH_PROMISE packet with conflicting header field values for
   the same Push
   ID as a connection error of type HTTP_MALFORMED_FRAME.

   Allowing duplicate references to FIN bit set, it will terminate the same Push ID is primarily send stream that it sends to
   reduce duplication caused by concurrent requests.  A server SHOULD
   avoid reusing a Push ID over
   the client.  TCP connections which remain half-closed in a long period.  Clients single
   direction are likely to
   consume server push responses and not retain them for reuse over
   time.  Clients that see a PUSH_PROMISE that uses a Push ID that they
   have since consumed and discarded invalid, but are forced to ignore the
   PUSH_PROMISE.

4.2.8.  GOAWAY

   The GOAWAY frame (type=0x7) is used to initiate graceful shutdown of
   a connection often handled poorly by servers,
   so clients SHOULD NOT close a server.  GOAWAY allows a server to stop accepting
   new requests stream for sending while they still finishing processing
   expect to receive data from the target of previously received
   requests.  This enables administrative actions, like server
   maintenance.  GOAWAY by itself does not close a connection.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Stream ID (i)                      ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 11: GOAWAY frame payload

   The GOAWAY frame carries a QUIC Stream ID for a client-initiated
   bidirectional stream encoded as a variable-length integer. the CONNECT.

   A client
   MUST treat receipt of a GOAWAY frame containing a Stream ID of TCP connection error is signaled with RST_STREAM.  A proxy treats
   any
   other type error in the TCP connection, which includes receiving a TCP
   segment with the RST bit set, as a connection stream error of type HTTP_MALFORMED_FRAME.

   Clients do not need to
   HTTP_CONNECT_ERROR (Section 8.1).  Correspondingly, a proxy MUST send GOAWAY to initiate
   a graceful shutdown;
   they simply stop making new requests.  A server MUST treat receipt of
   a GOAWAY frame as a connection TCP segment with the RST bit set if it detects an error (Section 6) of type
   HTTP_UNEXPECTED_GOAWAY.

   The GOAWAY frame applies to with the connection, not a specific stream.
   An endpoint MUST treat
   stream or the QUIC connection.

5.3.  Request Prioritization

   HTTP/QUIC uses a GOAWAY frame on priority scheme similar to that described in
   [RFC7540], Section 5.3.  In this priority scheme, a given stream other than can
   be designated as dependent upon another request, which expresses the
   control
   preference that the latter stream as (the "parent" request) be allocated
   resources before the former stream (the "dependent" request).  Taken
   together, the dependencies across all requests in a connection error (Section 6) form a
   dependency tree.  The structure of type
   HTTP_WRONG_STREAM.

   See Section 5.2 for more information on the use of dependency tree changes as
   PRIORITY frames add, remove, or change the GOAWAY frame.

4.2.9.  MAX_PUSH_ID dependency links between
   requests.

   The MAX_PUSH_ID PRIORITY frame (type=0xD) is used Section 4.2.3 identifies a prioritized element.
   The elements which can be prioritized are:

   o  Requests, identified by clients to control the
   number ID of server pushes that the server can initiate.  This sets request stream

   o  Pushes, identified by the
   maximum value for a Push ID that of the server can use in promised resource
      (Section 4.2.6)

   o  Placeholders, identified by a PUSH_PROMISE
   frame.  Consequently, this also limits Placeholder ID

   An element can depend on another element or on the number root of push streams
   that the server can initiate tree.
   A reference to an element which is no longer in addition the tree is treated
   as a reference to the limit set by root of the QUIC
   MAX_STREAM_ID frame.

   The MAX_PUSH_ID frame is always sent on a control stream.  Receipt of
   a MAX_PUSH_ID frame on any other stream MUST be treated tree.

5.3.1.  Placeholders

   In HTTP/2, certain implementations used closed or unused streams as a
   connection error of type HTTP_WRONG_STREAM.

   A server MUST NOT send a MAX_PUSH_ID frame.  A client MUST treat
   placeholders in describing the
   receipt relative priority of a MAX_PUSH_ID frame requests.
   However, this created confusion as a connection error servers could not reliably
   identify which elements of type
   HTTP_MALFORMED_FRAME.

   The maximum Push ID is unset when a connection is created, meaning
   that a the priority tree could safely be
   discarded.  Clients could potentially reference closed streams long
   after the server cannot push until it receives a MAX_PUSH_ID frame.  A
   client that wishes had discarded state, leading to manage disparate views of
   the prioritization the client had attempted to express.

   In HTTP/QUIC, a number of promised server pushes can
   increase the maximum Push ID placeholders are explicitly permitted by sending a MAX_PUSH_ID frame as
   the server fulfills or cancels server pushes.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          Push ID (i)                        ...
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 12: MAX_PUSH_ID frame payload

   The MAX_PUSH_ID frame carries a single variable-length integer that
   identifies using the maximum value for a Push ID that "SETTINGS_NUM_PLACEHOLDERS" setting.  Because
   the server commits to maintain these IDs in the tree, clients can use
   (see Section 4.2.7).  A MAX_PUSH_ID frame cannot reduce the maximum
   Push ID; receipt of a MAX_PUSH_ID
   them with confidence that contains a smaller value than
   previously received MUST be treated as a connection error of type
   HTTP_MALFORMED_FRAME.

   A the server MUST treat a MAX_PUSH_ID frame payload that does will not contain
   a single variable-length integer as a connection error of type
   HTTP_MALFORMED_FRAME.

5.  Connection Closure

   Once established, an HTTP/QUIC connection can be used for many
   requests and responses over time until have discarded the connection is closed.
   Connection closure can happen in any of several different ways.

5.1.  Idle Connections

   Each QUIC endpoint declares
   state.

   Placeholders are identified by an idle timeout during the handshake.  If
   the connection remains idle (no packets received) for longer ID between zero and one less than
   this duration,
   the peer will assume that number of placeholders the connection server has been
   closed.  HTTP/QUIC implementations permitted.

5.3.2.  Priority Tree Maintenance

   Servers can aggressively prune inactive regions from the priority
   tree, because placeholders will need be used to open "root" any persistent
   structure of the tree which the client cares about retaining.  For
   prioritization purposes, a new connection
   for new requests if node in the existing connection tree is considered "inactive"
   when the corresponding stream has been idle closed for longer
   than at least two round-
   trip times (using any reasonable estimate available on the server's advertised idle timeout, and SHOULD do so if
   approaching server).
   This delay helps mitigate race conditions where the idle timeout.

   HTTP clients are expected to use QUIC PING frames to keep connections
   open while there are responses outstanding for requests or server
   pushes.  If has pruned
   a node the client is not expecting believed was still active and used as a response from Stream
   Dependency.

   Specifically, the server,
   allowing an idle connection to time out is preferred over expending
   effort maintaining a connection that might not be needed.  A gateway server MAY use PING to maintain connections in anticipation at any time:

   o  Identify and discard branches of need rather
   than incur the latency cost of connection establishment to servers.
   Servers SHOULD NOT use PING frames to keep a connection open.

5.2.  Connection Shutdown

   Even when tree containing only inactive
      nodes (i.e. a connection is not idle, either endpoint can decide to
   stop using the connection node with only other inactive nodes as descendants,
      along with those descendants)

   o  Identify and let condense interior regions of the connection close gracefully.
   Since clients drive request generation, clients perform a connection
   shutdown by not sending additional requests on tree containing only
      inactive nodes, allocating weight appropriately

       x                x                 x
       |                |                 |
       P                P                 P
      / \               |                 |
     I   I     ==>      I      ==>        A
        / \             |                 |
       A   I            A                 A
       |                |
       A                A

                Figure 12: Example of Priority Tree Pruning

   In the connection;
   responses example in Figure 12, "P" represents a Placeholder, "A"
   represents an active node, and pushed responses associated to previous requests will
   continue to completion.  Servers perform "I" represents an inactive node.  In
   the same function by
   communicating with clients.

   Servers initiate first step, the shutdown of a connection by sending server discards two inactive branches (each a GOAWAY
   frame (Section 4.2.8).  The GOAWAY frame indicates that client-
   initiated requests on lower stream IDs were or might be processed in
   this connection, while requests on
   single node).  In the second step, the indicated stream ID and
   greater were not accepted.  This enables client and server to agree
   on which requests were accepted prior to condenses an interior
   inactive node.  Note that these transformations will result in no
   change in the connection shutdown.
   This identifier MAY be lower than resources allocated to a particular active stream.

   Clients SHOULD assume the server is actively performing such pruning
   and SHOULD NOT declare a dependency on a stream limit it knows to have been
   closed.

5.4.  Server Push

   HTTP/QUIC server push is similar to what is described in HTTP/2
   [RFC7540], but uses different mechanisms.

   Each server push is identified by a
   QUIC MAX_STREAM_ID frame, and MAY unique Push ID.  The same Push ID
   can be zero if no requests were
   processed.  Servers SHOULD NOT increase used in one or more PUSH_PROMISE frames (see Section 4.2.6),
   then included with the QUIC MAX_STREAM_ID limit
   after sending push stream which ultimately fulfills those
   promises.

   Server push is only enabled on a GOAWAY connection when a client sends a
   MAX_PUSH_ID frame (see Section 4.2.8).  A server cannot use server
   push until it receives a MAX_PUSH_ID frame.

   Once sent,  A client sends
   additional MAX_PUSH_ID frames to control the number of pushes that a
   server can promise.  A server SHOULD use Push IDs sequentially,
   starting at 0.  A client MUST cancel requests sent on streams treat receipt of a push stream with an
   identifier higher a
   Push ID that is greater than the indicated last Stream ID.  Clients MUST
   NOT send new requests maximum Push ID as a connection
   error of type HTTP_PUSH_LIMIT_EXCEEDED.

   The header of the request message is carried by a PUSH_PROMISE frame
   (see Section 4.2.6) on the connection after receiving GOAWAY,
   although requests might already be in transit.  A new connection can
   be established for new requests.

   If the client has sent requests on streams with a higher Stream ID
   than indicated in the GOAWAY frame, those requests are considered
   cancelled (Section 3.1.3).  Clients SHOULD reset any streams above
   this ID with the error code HTTP_REQUEST_CANCELLED.  Servers MAY also
   cancel requests on streams below the indicated ID if these requests
   were not processed.

   Requests on Stream IDs less than request stream which generated the Stream ID in push.
   This allows the GOAWAY frame
   might have been processed; their status cannot server push to be known until they
   are completed successfully, reset individually, or the connection
   terminates.

   Servers SHOULD send associated with a GOAWAY frame when the closing client request.
   Ordering of a connection
   is known PUSH_PROMISE in advance, even if relation to certain parts of the advance notice
   response is small, so that important (see Section 8.2.1 of [RFC7540]).  Promised
   requests MUST conform to the
   remote peer can know whether requirements in Section 8.2 of
   [RFC7540].

   When a stream has been partially processed or
   not.  For example, if an HTTP client sends server later fulfills a POST at promise, the same time
   that a server closes push response is
   conveyed on a QUIC connection, push stream (see Section 3.2.2).  The push stream
   identifies the client cannot know if Push ID of the
   server started to process promise that POST it fulfills, then contains
   a response to the promised request if using the same format described
   for responses in Section 5.1.

   If a promised server does push is not needed by the client, the client
   SHOULD send a GOAWAY frame to indicate what streams it might have acted on.

   A client that is unable to retry requests loses all requests that are
   in flight when the server closes CANCEL_PUSH frame.  If the connection.  A server MAY send
   multiple GOAWAY frames indicating different push stream IDs, but MUST NOT
   increase the value they send in the last Stream ID, since clients
   might already have retried unprocessed requests on another
   connection.  A server that is attempting to gracefully shut down already open
   or opens after sending the CANCEL_PUSH frame, a
   connection SHOULD send an initial GOAWAY QUIC STOP_SENDING
   frame with the last Stream
   ID set to the current value of QUIC's MAX_STREAM_ID and SHOULD NOT
   increase the MAX_STREAM_ID thereafter. an appropriate error code can also be used (e.g.,
   HTTP_PUSH_REFUSED, HTTP_PUSH_ALREADY_IN_CACHE; see Section 8).  This signals to
   asks the client
   that a shutdown is imminent server not to transfer additional data and indicates that initiating further requests is
   prohibited.  After allowing time for any in-flight requests (at least
   one round-trip time), the server MAY send another GOAWAY frame with it
   will be discarded upon receipt.

6.  Connection Closure

   Once established, an updated last Stream ID.  This ensures that a HTTP/QUIC connection can be
   cleanly shut down without losing requests.

   Once all accepted used for many
   requests have been processed, the server can permit and responses over time until the connection to become idle, or MAY initiate an immediate is closed.
   Connection closure can happen in any of the connection.  An several different ways.

6.1.  Idle Connections

   Each QUIC endpoint that completes a graceful shutdown
   SHOULD use declares an idle timeout during the HTTP_NO_ERROR code when closing handshake.  If
   the connection.

5.3.  Immediate Application Closure

   An HTTP/QUIC implementation can immediately close the QUIC connection
   at any time.  This results in sending a QUIC APPLICATION_CLOSE frame
   to the peer; the error code in remains idle (no packets received) for longer than
   this frame indicates to duration, the peer why will assume that the connection is being has been
   closed.  See Section 6 for error codes which
   can be used when closing a connection.

   Before closing the connection, a GOAWAY MAY be sent to allow the
   client  HTTP/QUIC implementations will need to retry some requests.  Including the GOAWAY frame in the
   same packet as the QUIC APPLICATION_CLOSE frame improves open a new connection
   for new requests if the chances
   of existing connection has been idle for longer
   than the frame being received by clients.

5.4.  Transport Closure

   For various reasons, server's advertised idle timeout, and SHOULD do so if
   approaching the idle timeout.

   HTTP clients are expected to use QUIC transport could indicate PING frames to keep connections
   open while there are responses outstanding for requests or server
   pushes.  If the
   application layer that client is not expecting a response from the server,
   allowing an idle connection has terminated.  This to time out is preferred over expending
   effort maintaining a connection that might not be
   due needed.  A gateway
   MAY use PING to an explicit closure by the peer, a transport-level error, or a
   change maintain connections in network topology which interrupts connectivity.

   If anticipation of need rather
   than incur the latency cost of connection establishment to servers.
   Servers SHOULD NOT use PING frames to keep a connection terminates without open.

6.2.  Connection Shutdown

   Even when a GOAWAY frame, clients MUST
   assume that any request which was sent, whether in whole or in part,
   might have been processed.

6.  Error Handling

   QUIC allows the application to abruptly terminate (reset) 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].

   This section describes HTTP/QUIC-specific error codes which not idle, either endpoint can be
   used decide to express
   stop using the cause of a connection or stream error.

6.1.  HTTP/QUIC Error Codes

   The following error codes are defined for use in QUIC RST_STREAM,
   STOP_SENDING, and APPLICATION_CLOSE frames when using HTTP/QUIC.

   STOPPING (0x00):  This value is reserved let the connection close gracefully.
   Since clients drive request generation, clients perform a connection
   shutdown by not sending additional requests on the transport connection;
   responses and pushed responses associated to be used
      in response previous requests will
   continue to QUIC STOP_SENDING frames.

   HTTP_NO_ERROR (0x01):  No error.  This is used when completion.  Servers perform the same function by
   communicating with clients.

   Servers initiate the shutdown of a connection or
      stream needs to be closed, but there is no error to signal.

   HTTP_PUSH_REFUSED (0x02): by sending a GOAWAY
   frame (Section 4.2.7).  The server has attempted to push content
      which the client will not accept GOAWAY frame indicates that client-
   initiated requests on this connection.

   HTTP_INTERNAL_ERROR (0x03):  An internal error has occurred lower stream IDs were or might be processed in
   this connection, while requests on the
      HTTP stack.

   HTTP_PUSH_ALREADY_IN_CACHE (0x04):  The indicated stream ID and
   greater were not accepted.  This enables client and server has attempted to push
      content agree
   on which requests were accepted prior to the client has cached.

   HTTP_REQUEST_CANCELLED (0x05):  The client no longer needs connection shutdown.
   This identifier MAY be lower than the
      requested data.

   HTTP_INCOMPLETE_REQUEST (0x06):  The client's stream terminated
      without containing a fully-formed request.

   HTTP_CONNECT_ERROR (0x07):  The connection established in response to limit identified by a CONNECT request was reset or abnormally closed.

   HTTP_EXCESSIVE_LOAD (0x08):  The endpoint detected that its peer is
      exhibiting
   QUIC MAX_STREAM_ID frame, and MAY be zero if no requests were
   processed.  Servers SHOULD NOT increase the QUIC MAX_STREAM_ID limit
   after sending a behavior that GOAWAY frame.

   Once sent, the server MUST cancel requests sent on streams with an
   identifier higher than the indicated last Stream ID.  Clients MUST
   NOT send new requests on the connection after receiving GOAWAY,
   although requests might already be generating excessive load.

   HTTP_VERSION_FALLBACK (0x09):  The requested operation cannot be
      served over HTTP/QUIC.  The peer should retry over HTTP/1.1.

   HTTP_WRONG_STREAM (0x0A): in transit.  A frame was received new connection can
   be established for new requests.

   If the client has sent requests on streams with a stream where it
      is not permitted.

   HTTP_PUSH_LIMIT_EXCEEDED (0x0B):  A Push higher Stream ID greater
   than indicated in the current
      maximum Push GOAWAY frame, those requests are considered
   cancelled (Section 5.1.2).  Clients SHOULD reset any streams above
   this ID was referenced.

   HTTP_DUPLICATE_PUSH (0x0C):  A Push with the error code HTTP_REQUEST_CANCELLED.  Servers MAY also
   cancel requests on streams below the indicated ID was referenced in two
      different stream headers.

   HTTP_UNKNOWN_STREAM_TYPE (0x0D):  A unidirectional stream header
      contained an unknown stream type.

   HTTP_WRONG_STREAM_COUNT (0x0E):  A unidirectional stream type was
      used more times if these requests
   were not processed.

   Requests on Stream IDs less than is permitted by that type.

   HTTP_CLOSED_CRITICAL_STREAM (0x0F):  A stream required by the
      connection was closed Stream ID in the GOAWAY frame
   might have been processed; their status cannot be known until they
   are completed successfully, reset individually, or reset.

   HTTP_WRONG_STREAM_DIRECTION (0x0010):  A unidirectional stream type
      was used by a peer which is not permitted to do so.

   HTTP_EARLY_RESPONSE (0x0011):  The remainder of the client's request
      is not needed to produce connection
   terminates.

   Servers SHOULD send a response.  For use in STOP_SENDING
      only.

   HTTP_MISSING_SETTINGS (0x0012):  No SETTINGS GOAWAY frame was received at when the beginning closing of the control stream.

   HTTP_GENERAL_PROTOCOL_ERROR (0x00FF):  Peer violated protocol
      requirements in a way which doesn't match a more specific error
      code, or endpoint declines to use the more specific error code.

   HTTP_MALFORMED_FRAME (0x01XX):  An error in a specific frame type.
      The frame type connection
   is included as known in advance, even if the last octet of advance notice is small, so that the error code.
   remote peer can know whether a stream has been partially processed or
   not.  For example, if an error in HTTP client sends a MAX_PUSH_ID frame would be indicated
      with the code (0x10D).

7.  Extensions to HTTP/QUIC

   HTTP/QUIC permits extension of the protocol.  Within POST at the limitations
   described in this section, protocol extensions can be used to provide
   additional services or alter any aspect of same time
   that a server closes a QUIC connection, the protocol.  Extensions
   are effective only within client cannot know if the scope of a single HTTP/QUIC connection.

   This applies
   server started to process that POST request if the protocol elements defined in this document.  This server does not affect the existing options for extending HTTP, such as
   defining new methods, status codes, or header fields.

   Extensions are permitted to use new frame types (Section 4.2), new
   settings (Section 4.2.6.1), new error codes (Section 6), or new
   unidirectional stream types (Section 3.3).  Registries are
   established for managing these extension points:
   send a GOAWAY frame types
   (Section 10.3), settings (Section 10.4), error codes (Section 10.5),
   and stream types (Section 10.6).

   Implementations MUST ignore unknown or unsupported values in all
   extensible protocol elements.  Implementations MUST discard frames
   and unidirectional to indicate what streams that it might have unknown or unsupported types.
   This means acted on.

   A client that any of these extension points can be safely used by
   extensions without prior arrangement or negotiation.

   Extensions is unable to retry requests loses all requests that could change are
   in flight when the semantics of existing protocol
   components MUST be negotiated before being used.  For example, an
   extension that changes server closes the layout of connection.  A server MAY send
   multiple GOAWAY frames indicating different stream IDs, but MUST NOT
   increase the HEADERS frame cannot be used
   until value they send in the peer has given a positive signal last Stream ID, since clients
   might already have retried unprocessed requests on another
   connection.  A server that this is acceptable.
   In this case, it could also be necessary attempting to coordinate when the
   revised layout comes into effect.

   This document doesn't mandate gracefully shut down a specific method for negotiating the
   use of
   connection SHOULD send an extension but notes that a setting (Section 4.2.6.1) could
   be used for that purpose.  If both peers initial GOAWAY frame with the last Stream
   ID set a value that indicates
   willingness to use the extension, then the extension can be used.  If current value of QUIC's MAX_STREAM_ID and SHOULD NOT
   increase the MAX_STREAM_ID thereafter.  This signals to the client
   that a setting shutdown is used imminent and that initiating further requests is
   prohibited.  After allowing time for extension negotiation, any in-flight requests (at least
   one round-trip time), the default value MUST
   be defined in such server MAY send another GOAWAY frame with
   an updated last Stream ID.  This ensures that a fashion connection can be
   cleanly shut down without losing requests.

   Once all accepted requests have been processed, the server can permit
   the connection to become idle, or MAY initiate an immediate closure
   of the connection.  An endpoint that completes a graceful shutdown
   SHOULD use the extension is disabled if HTTP_NO_ERROR code when closing the
   setting is omitted.

8.  Considerations for Transitioning from HTTP/2 connection.

6.3.  Immediate Application Closure

   An HTTP/QUIC is strongly informed by HTTP/2, and bears many
   similarities.  This section describes implementation can immediately close the approach taken to design
   HTTP/QUIC, points out important differences from HTTP/2, and
   describes how QUIC connection
   at any time.  This results in sending a QUIC APPLICATION_CLOSE frame
   to map HTTP/2 extensions into HTTP/QUIC.

   HTTP/QUIC begins from the premise that HTTP/2 peer; the error code reuse in this frame indicates to the peer why
   the connection is being closed.  See Section 8 for error codes which
   can be used when closing a useful
   feature, but not connection.

   Before closing the connection, a hard requirement.  HTTP/QUIC departs from HTTP/2
   primarily where necessary GOAWAY MAY be sent to accommodate allow the differences
   client to retry some requests.  Including the GOAWAY frame in behavior
   between the
   same packet as the QUIC and TCP (lack APPLICATION_CLOSE frame improves the chances
   of ordering, support for streams).  We
   intend to avoid gratuitous changes which make it difficult or
   impossible the frame being received by clients.

6.4.  Transport Closure

   For various reasons, the QUIC transport could indicate to build extensions with the same semantics applicable
   application layer that the connection has terminated.  This might be
   due to
   both protocols at once.

   These departures are noted an explicit closure by the peer, a transport-level error, or a
   change in this section.

8.1.  Streams

   HTTP/QUIC permits use of network topology which interrupts connectivity.

   If a larger number of streams (2^62-1) than
   HTTP/2.  The considerations about exhaustion of stream identifier
   space apply, though the space is significantly larger such that it is
   likely connection terminates without a GOAWAY frame, clients MUST
   assume that other limits any request which was sent, whether in QUIC are reached first, such as whole or in part,
   might have been processed.

7.  Extensions to HTTP/QUIC

   HTTP/QUIC permits extension of the limit
   on protocol.  Within the connection flow control window.

8.2.  HTTP Frame Types

   Many framing concepts from HTTP/2 limitations
   described in this section, protocol extensions can be elided away on QUIC, because used to provide
   additional services or alter any aspect of the transport deals with them.  Because frames protocol.  Extensions
   are already on effective only within the scope of a
   stream, they can omit single HTTP/QUIC connection.

   This applies to the stream number.  Because frames do not block
   multiplexing (QUIC's multiplexing occurs below protocol elements defined in this layer), document.  This
   does not affect the
   support existing options for variable-maximum-length packets can be removed.  Because
   stream termination is handled by QUIC, an END_STREAM flag is not
   required.  This permits the removal of the Flags field from the
   generic frame layout.

   Frame payloads are largely drawn from [RFC7540].  However, QUIC
   includes many features (e.g. flow control) which extending HTTP, such as
   defining new methods, status codes, or header fields.

   Extensions are also present in
   HTTP/2.  In these cases, the HTTP mapping does not re-implement them.
   As a result, several HTTP/2 permitted to use new frame types (Section 4.2), new
   settings (Section 4.2.5.1), new error codes (Section 8), or new
   unidirectional stream types (Section 3.2).  Registries are not required in HTTP/
   QUIC.  Where an HTTP/2-defined frame is no longer used, the
   established for managing these extension points: frame ID
   has been reserved in order to maximize portability between HTTP/2 types
   (Section 10.3), settings (Section 10.4), error codes (Section 10.5),
   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 types (Section 10.6).

   Implementations MUST ignore unknown or unsupported values in all
   extensible protocol elements.  Implementations MUST discard frames from different
   and unidirectional streams will still that have unknown or unsupported types.
   This means that any of these extension points can be received in safely used by
   extensions without prior arrangement or negotiation.

   Extensions that could change the order sent, HTTP/QUIC will break them. semantics of existing protocol
   components MUST be negotiated before being used.  For example, implicit in an
   extension that changes 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 layout 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 control stream and frame cannot be used
   until the PRIORITY
   section peer has given a positive signal that this is removed from acceptable.
   In this case, it could also be necessary to coordinate when the HEADERS frame.

   Likewise, HPACK was designed with
   revised layout comes into effect.

   This document doesn't mandate a specific method for negotiating the assumption of in-order
   delivery.  A sequence
   use of encoded header blocks must arrive (and be
   decoded) at an endpoint in the same order in which they were encoded.
   This ensures extension but notes that the dynamic state at the two endpoints remains in
   sync.  As a result, HTTP/QUIC uses setting (Section 4.2.5.1) could
   be used for that purpose.  If both peers set a modified version of HPACK,
   described in [QPACK].

   Frame type definitions in HTTP/QUIC often value that indicates
   willingness to use the QUIC variable-
   length integer encoding.  In particular, Stream IDs use this
   encoding, which allow for a larger range of possible values than extension, then the
   encoding extension can be used.  If
   a setting is used for extension negotiation, the default value MUST
   be defined in HTTP/2.  Some frames in HTTP/QUIC use an identifier
   rather than such a Stream ID (e.g.  Push IDs in PRIORITY frames).
   Redefinition of fashion that the encoding of extension frame types might be
   necessary is disabled if the encoding includes a Stream ID.

   Because the Flags field
   setting is not present in generic HTTP/QUIC frames,
   those frames which depend on omitted.

8.  Error Handling

   QUIC allows the presence of flags need application to allocate
   space for flags as part of their frame payload.

   Other than this issue, frame type HTTP/2 extensions abruptly terminate (reset) individual
   streams or the entire connection when an error is encountered.  These
   are typically
   portable referred to QUIC simply by replacing Stream 0 as "stream errors" or "connection errors" and are
   described in HTTP/2 with more detail in [QUIC-TRANSPORT].  An endpoint MAY choose
   to treat a
   control stream in HTTP/QUIC.  HTTP/QUIC extensions will not assume
   ordering, but would not be harmed by ordering, and would error as a connection error.

   This section describes HTTP/QUIC-specific error codes which can be portable
   used to HTTP/2 in express the same manner.

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

   DATA (0x0):  Padding is not a connection or stream error.

8.1.  HTTP/QUIC Error Codes

   The following error codes are defined for use in HTTP/QUIC frames.  See
      Section 4.2.2.

   HEADERS (0x1):  As described above, the PRIORITY region of HEADERS QUIC RST_STREAM,
   STOP_SENDING, and APPLICATION_CLOSE frames when using HTTP/QUIC.

   STOPPING (0x00):  This value is
      not supported.  A separate PRIORITY frame MUST reserved by the transport to be used.  Padding
      is not defined used
      in HTTP/QUIC response to QUIC STOP_SENDING frames.  See Section 4.2.3.

   PRIORITY (0x2):  As described above, the PRIORITY frame is sent on
      the control stream and can reference either a Stream ID or a Push
      ID.  See Section 4.2.4.

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

   HTTP_NO_ERROR (0x01):  No error.  This is used
      for the CANCEL_PUSH frame (Section 4.2.5).

   SETTINGS (0x4):  SETTINGS frames are sent only at the beginning of
      the connection.  See Section 4.2.6 and Section 8.3.

   PUSH_PROMISE (0x5):  The PUSH_PROMISE does not reference a stream;
      instead when the push connection or
      stream references the PUSH_PROMISE frame using a
      Push ID.  See Section 4.2.7.

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

   GOAWAY (0x7):  GOAWAY needs to be closed, but there is sent only from no error to signal.

   HTTP_PUSH_REFUSED (0x02):  The server has attempted to push content
      which the client and does will not
      contain an accept on this connection.

   HTTP_INTERNAL_ERROR (0x03):  An internal error code.  See Section 4.2.8.

   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 has occurred in series.

   Frame types defined by extensions to HTTP/2 need to be separately
   registered for HTTP/QUIC if still applicable. the
      HTTP stack.

   HTTP_PUSH_ALREADY_IN_CACHE (0x04):  The IDs of frames
   defined in [RFC7540] have been reserved for simplicity.  See
   Section 10.3.

8.3.  HTTP/2 SETTINGS Parameters

   An important difference from HTTP/2 is that settings are sent once,
   at server has attempted to push
      content which the beginning of client has cached.

   HTTP_REQUEST_CANCELLED (0x05):  The client no longer needs the connection, and thereafter cannot change.
   This eliminates many corner cases around synchronization of changes.

   Some transport-level options that HTTP/2 specifies via the SETTINGS
   frame are superseded by QUIC transport parameters
      requested data.

   HTTP_INCOMPLETE_REQUEST (0x06):  The client's stream terminated
      without containing a fully-formed request.

   HTTP_CONNECT_ERROR (0x07):  The connection established in HTTP/QUIC. response to
      a CONNECT request was reset or abnormally closed.

   HTTP_EXCESSIVE_LOAD (0x08):  The
   HTTP-level options endpoint detected that are retained in HTTP/QUIC have its peer is
      exhibiting a behavior that might be generating excessive load.

   HTTP_VERSION_FALLBACK (0x09):  The requested operation cannot be
      served over HTTP/QUIC.  The peer should retry over HTTP/1.1.

   HTTP_WRONG_STREAM (0x0A):  A frame was received on a stream where it
      is not permitted.

   HTTP_PUSH_LIMIT_EXCEEDED (0x0B):  A Push ID greater than the same value
   as current
      maximum Push ID was referenced.

   HTTP_DUPLICATE_PUSH (0x0C):  A Push ID was referenced in HTTP/2.

   Below two
      different stream headers.

   HTTP_UNKNOWN_STREAM_TYPE (0x0D):  A unidirectional stream header
      contained an unknown stream type.

   HTTP_WRONG_STREAM_COUNT (0x0E):  A unidirectional stream type was
      used more times than is permitted by that type.

   HTTP_CLOSED_CRITICAL_STREAM (0x0F):  A stream required by the
      connection was closed or reset.

   HTTP_WRONG_STREAM_DIRECTION (0x0010):  A unidirectional stream type
      was used by a listing of how each HTTP/2 SETTINGS parameter peer which is mapped:

   SETTINGS_HEADER_TABLE_SIZE:  See Section 4.2.6.1.

   SETTINGS_ENABLE_PUSH:  This not permitted to do so.

   HTTP_EARLY_RESPONSE (0x0011):  The remainder of the client's request
      is removed not needed to produce a response.  For use in favor STOP_SENDING
      only.

   HTTP_MISSING_SETTINGS (0x0012):  No SETTINGS frame was received at
      the beginning of the MAX_PUSH_ID control stream.

   HTTP_GENERAL_PROTOCOL_ERROR (0x00FF):  Peer violated protocol
      requirements in a way which provides doesn't match a more granular control over server push.

   SETTINGS_MAX_CONCURRENT_STREAMS:  QUIC controls the largest open
      Stream ID as part of its flow control logic.  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 specific error
      code, or endpoint declines to be specified in use the
      initial transport handshake.  Specifying
      SETTINGS_INITIAL_WINDOW_SIZE more specific error code.

   HTTP_MALFORMED_FRAME (0x01XX):  An error in the SETTINGS a specific frame is an error.

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

   SETTINGS_MAX_HEADER_LIST_SIZE:  See Section 4.2.6.1.

   In HTTP/QUIC, setting values are variable-length integers (6, 14, 30,
   or 62 bits long) rather than fixed-length 32-bit fields included as in HTTP/2.
   This will often produce a shorter encoding, but can produce a longer
   encoding for settings which use the full 32-bit space.  Settings
   ported from HTTP/2 might choose to redefine the format last octet of their
   settings to avoid using the 62-bit encoding.

   Settings need to be defined separately for HTTP/2 and HTTP/QUIC.  The
   IDs of settings defined error code.
      For example, an error in [RFC7540] have been reserved for
   simplicity.  See Section 10.4.

8.4.  HTTP/2 Error Codes

   QUIC has the same concepts of "stream" and "connection" errors that
   HTTP/2 provides.  However, because a MAX_PUSH_ID frame would be indicated
      with the error code space is shared
   between multiple components, there is no direct portability (0x10D).

9.  Security Considerations

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

   The with TLS.  Note that where HTTP/2 error codes defined employs PADDING
   frames and Padding fields in Section 7 of [RFC7540] map other frames to the make a connection more
   resistant to traffic analysis, HTTP/QUIC error codes as follows:

   NO_ERROR (0x0):  HTTP_NO_ERROR in Section 6.1.

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

   INTERNAL_ERROR (0x2):  HTTP_INTERNAL_ERROR in Section 6.1.

   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_QPACK_DECOMPRESSION_FAILED in [QPACK].

   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 need to be defined for HTTP/2 and HTTP/QUIC separately.
   See Section 10.5.

9.  Security Considerations

   The security considerations of HTTP/QUIC should be comparable to
   those of HTTP/2 with TLS.  Note that where HTTP/2 employs PADDING
   frames to make a connection more resistant to traffic analysis, HTTP/
   QUIC can rely on QUIC's own QUIC PADDING
   frames or employ the reserved frame and stream types discussed in
   Section 4.2.1 4.2.9 and Section 3.3.1. 3.2.3.

   When HTTP Alternative Services is used for discovery for HTTP/QUIC
   endpoints, the security considerations of [ALTSVC] also apply.

   The modified SETTINGS format contains

   Several protocol elements contain nested length elements, which typically
   in the form of frames with an explicit length containing variable-
   length integers.  This could pose a security risk to an incautious
   implementer.  A SETTINGS
   frame parser  An implementation MUST ensure that the length of the a
   frame exactly matches the length of the settings fields it contains.

10.  IANA Considerations

10.1.  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/QUIC

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

   Specification:  This document

10.2.  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 2.2.1

10.3.  Frame Types

   This document establishes a registry for HTTP/QUIC frame type codes.
   The "HTTP/QUIC Frame Type" registry manages an 8-bit space.  The
   "HTTP/QUIC Frame Type" registry operates under either of the "IETF
   Review" or "IESG Approval" policies [RFC8126] for values from 0x00 up
   to and including 0xef, with values from 0xf0 up to and including 0xff
   being reserved for Experimental Use.

   While this registry is separate from the "HTTP/2 Frame Type" registry
   defined in [RFC7540], it is preferable that the assignments parallel
   each other.  If an entry is present in only one registry, every
   effort SHOULD be made to avoid assigning the corresponding value to
   an unrelated operation.

   New entries in this registry require the following information:

   Frame Type:  A name or label for the frame type.

   Code:  The 8-bit code assigned to the frame type.

   Specification:  A reference to a specification that includes a
      description of the frame layout and its semantics, including any
      parts of the frame that are conditionally present.

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

                  +--------------+------+---------------+
                  | Frame Type   | Code | Specification |
                  +--------------+------+---------------+
                  | DATA         | 0x0  | Section 4.2.2 4.2.1 |
                  |              |      |               |
                  | HEADERS      | 0x1  | Section 4.2.3 4.2.2 |
                  |              |      |               |
                  | PRIORITY     | 0x2  | Section 4.2.4 4.2.3 |
                  |              |      |               |
                  | CANCEL_PUSH  | 0x3  | Section 4.2.5 4.2.4 |
                  |              |      |               |
                  | SETTINGS     | 0x4  | Section 4.2.6 4.2.5 |
                  |              |      |               |
                  | PUSH_PROMISE | 0x5  | Section 4.2.7 4.2.6 |
                  |              |      |               |
                  | Reserved     | 0x6  | N/A           |
                  |              |      |               |
                  | GOAWAY       | 0x7  | Section 4.2.8 4.2.7 |
                  |              |      |               |
                  | Reserved     | 0x8  | N/A           |
                  |              |      |               |
                  | Reserved     | 0x9  | N/A           |
                  |              |      |               |
                  | MAX_PUSH_ID  | 0xD  | Section 4.2.9 4.2.8 |
                  +--------------+------+---------------+

   Additionally, each code of the format "0xb + (0x1f * N)" for values
   of N in the range (0..7) (that is, "0xb", "0x2a", "0x49", "0x68",
   "0x87", "0xa6", "0xc5", and "0xe4"), the following values should be
   registered:

   Frame Type:  Reserved - GREASE

   Specification:  Section 4.2.1 4.2.9

10.4.  Settings Parameters

   This document establishes a registry for HTTP/QUIC settings.  The
   "HTTP/QUIC Settings" registry manages a 16-bit space.  The "HTTP/QUIC
   Settings" registry operates under the "Expert Review" policy
   [RFC8126] for values in the range from 0x0000 to 0xefff, with values
   between and 0xf000 and 0xffff being reserved for Experimental Use.

   The designated experts are the same as those for the "HTTP/2
   Settings" registry defined in [RFC7540].

   While this registry is separate from the "HTTP/2 Settings" registry
   defined in [RFC7540], it is preferable that the assignments parallel
   each other.  If an entry is present in only one registry, every
   effort SHOULD be made to avoid assigning the corresponding value to
   an unrelated operation.

   New registrations are advised to provide the following information:

   Name:  A symbolic name for the setting.  Specifying a setting name is
      optional.

   Code:  The 16-bit code assigned to the setting.

   Specification:  An optional reference to a specification that
      describes the use of the setting.

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

             +----------------------+------+-----------------+
             | Setting Name         | Code | Specification   |
             +----------------------+------+-----------------+
             | Reserved             | 0x2  | N/A             |
             |                      |      |                 |
             | NUM_PLACEHOLDERS     | 0x3  | Section 4.2.6.1 4.2.5.1 |
             |                      |      |                 |
             | Reserved             | 0x4  | N/A             |
             |                      |      |                 |
             | Reserved             | 0x5  | N/A             |
             |                      |      |                 |
             | MAX_HEADER_LIST_SIZE | 0x6  | Section 4.2.6.1 4.2.5.1 |
             +----------------------+------+-----------------+

   Additionally, each code of the format "0x?a?a" where each "?" is any
   four bits (that is, "0x0a0a", "0x0a1a", etc. through "0xfafa"), the
   following values should be registered:

   Name:  Reserved - GREASE

   Specification:  Section 4.2.6.1 4.2.5.1

10.5.  Error Codes

   This document establishes a registry for HTTP/QUIC error codes.  The
   "HTTP/QUIC Error Code" registry manages a 16-bit space.  The "HTTP/
   QUIC Error Code" registry operates under the "Expert Review" policy
   [RFC8126].

   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 16-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.

   +-------------------------+-------+---------------+-----------------+
   | Name                    | Code  | Description   | Specification   |
   +-------------------------+-------+---------------+-----------------+
   | STOPPING                | 0x000 | Reserved by   | [QUIC-TRANSPORT |
   |                         | 0     | QUIC          | ]               |
   |                         |       |               |                 |
   | HTTP_NO_ERROR           | 0x000 | No error      | Section 6.1 8.1     |
   |                         | 1     |               |                 |
   |                         |       |               |                 |
   | HTTP_PUSH_REFUSED       | 0x000 | Client        | Section 6.1 8.1     |
   |                         | 2     | refused       |                 |
   |                         |       | pushed        |                 |
   |                         |       | content       |                 |
   |                         |       |               |                 |
   | HTTP_INTERNAL_ERROR     | 0x000 | Internal      | Section 6.1 8.1     |
   |                         | 3     | error         |                 |
   |                         |       |               |                 |
   | HTTP_PUSH_ALREADY_IN_CA | 0x000 | Pushed        | Section 6.1 8.1     |
   | CHE                     | 4     | content       |                 |
   |                         |       | already       |                 |
   |                         |       | cached        |                 |
   |                         |       |               |                 |
   | HTTP_REQUEST_CANCELLED  | 0x000 | Data no       | Section 6.1 8.1     |
   |                         | 5     | longer needed |                 |
   |                         |       |               |                 |
   | HTTP_INCOMPLETE_REQUEST | 0x000 | Stream        | Section 6.1 8.1     |
   |                         | 6     | terminated    |                 |
   |                         |       | early         |                 |
   |                         |       |               |                 |
   | HTTP_CONNECT_ERROR      | 0x000 | TCP reset or  | Section 6.1 8.1     |
   |                         | 7     | error on      |                 |
   |                         |       | CONNECT       |                 |
   |                         |       | request       |                 |
   |                         |       |               |                 |
   | HTTP_EXCESSIVE_LOAD     | 0x000 | Peer          | Section 6.1 8.1     |
   |                         | 8     | generating    |                 |
   |                         |       | excessive     |                 |
   |                         |       | load          |                 |
   |                         |       |               |                 |
   | HTTP_VERSION_FALLBACK   | 0x000 | Retry over    | Section 6.1 8.1     |
   |                         | 9     | HTTP/1.1      |                 |
   |                         |       |               |                 |
   | HTTP_WRONG_STREAM       | 0x000 | A frame was   | Section 6.1 8.1     |
   |                         | A     | sent on the   |                 |
   |                         |       | wrong stream  |                 |
   |                         |       |               |                 |
   | HTTP_PUSH_LIMIT_EXCEEDE | 0x000 | Maximum Push  | Section 6.1 8.1     |
   | D                       | B     | ID exceeded   |                 |
   |                         |       |               |                 |
   | HTTP_DUPLICATE_PUSH     | 0x000 | Push ID was   | Section 6.1 8.1     |
   |                         | C     | fulfilled     |                 |
   |                         |       | multiple      |                 |
   |                         |       | times         |                 |
   |                         |       |               |                 |
   | HTTP_UNKNOWN_STREAM_TYP | 0x000 | Unknown unidi | Section 6.1 8.1     |
   | E                       | D     | rectional     |                 |
   |                         |       | stream type   |                 |
   |                         |       |               |                 |
   | HTTP_WRONG_STREAM_COUNT | 0x000 | Too many unid | Section 6.1 8.1     |
   |                         | E     | irectional    |                 |
   |                         |       | streams       |                 |
   |                         |       |               |                 |
   | HTTP_CLOSED_CRITICAL_ST | 0x000 | Critical      | Section 6.1 8.1     |
   | REAM                    | F     | stream was    |                 |
   |                         |       | closed        |                 |
   |                         |       |               |                 |
   | HTTP_WRONG_STREAM_DIREC | 0x001 | Unidirectiona | Section 6.1 8.1     |
   | TION                    | 0     | l stream in   |                 |
   |                         |       | wrong         |                 |
   |                         |       | direction     |                 |
   |                         |       |               |                 |
   | HTTP_EARLY_RESPONSE     | 0x001 | Remainder of  | Section 6.1 8.1     |
   |                         | 1     | request not   |                 |
   |                         |       | needed        |                 |
   |                         |       |               |                 |
   | HTTP_MISSING_SETTINGS   | 0x001 | No SETTINGS   | Section 6.1 8.1     |
   |                         | 2     | frame         |                 |
   |                         |       | received      |                 |
   |                         |       |               |                 |
   | HTTP_MALFORMED_FRAME    | 0x01X | Error in      | Section 6.1 8.1     |
   |                         | X     | frame         |                 |
   |                         |       | formatting or |                 |
   |                         |       | use           |                 |
   +-------------------------+-------+---------------+-----------------+

10.6.  Stream Types

   This document establishes a registry for HTTP/QUIC unidirectional
   stream types.  The "HTTP/QUIC Stream Type" registry manages an 8-bit
   space.  The "HTTP/QUIC Stream Type" registry operates under either of
   the "IETF Review" or "IESG Approval" policies [RFC8126] for values
   from 0x00 up to and including 0xef, with values from 0xf0 up to and
   including 0xff being reserved for Experimental Use.

   New entries in this registry require the following information:

   Stream Type:  A name or label for the stream type.

   Code:  The 8-bit code assigned to the stream type.

   Specification:  A reference to a specification that includes a
      description of the stream type, including the layout semantics of
      its payload.

   Sender:  Which endpoint on a connection may initiate a stream of this
      type.  Values are "Client", "Server", or "Both".

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

            +----------------+------+---------------+--------+
            | Stream Type    | Code | Specification | Sender |
            +----------------+------+---------------+--------+
            | Control Stream | 0x43 | Section 3.3.2 3.2.1 | Both   |
            |                |      |               |        |
            | Push Stream    | 0x50 | Section 3.3.3 5.4   | Server |
            +----------------+------+---------------+--------+

   Additionally, for each code of the format "0x1f * N" for values of N
   in the range (0..8) (that is, "0x00", "0x1f", "0x3e", "0x5d", "0x7c",
   "0x9b", "0xba", "0xd9", "0xf8"), the following values should be
   registered:

   Stream Type:  Reserved - GREASE

   Specification:  Section 3.3.1 3.2.3

   Sender:  Both

11.  References

11.1.  Normative References

   [ALTSVC]   Nottingham, M., McManus, P., and J. Reschke, "HTTP
              Alternative Services", RFC 7838, DOI 10.17487/RFC7838,
              April 2016, <https://www.rfc-editor.org/info/rfc7838>.

   [QPACK]    Krasic, C., Bishop, M., and A. Frindell, Ed., "QPACK:
              Header Compression for HTTP over QUIC", draft-ietf-quic-
              qpack-03
              qpack-04 (work in progress), October 2018.

   [QUIC-TRANSPORT]
              Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", draft-ietf-quic-
              transport-14
              transport-16 (work in progress), October 2018.

   [RFC0793]  Postel, J., "Transmission Control Protocol", STD 7,
              RFC 793, DOI 10.17487/RFC0793, September 1981,
              <https://www.rfc-editor.org/info/rfc793>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

   [RFC6066]  Eastlake 3rd, D., "Transport Layer Security (TLS)
              Extensions: Extension Definitions", RFC 6066,
              DOI 10.17487/RFC6066, January 2011,
              <https://www.rfc-editor.org/info/rfc6066>.

   [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,
              <https://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,
              <https://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,
              <https://www.rfc-editor.org/info/rfc7540>.

   [RFC7838]  Nottingham, M., McManus, P., and J. Reschke, "HTTP
              Alternative Services", RFC 7838, DOI 10.17487/RFC7838,
              April 2016, <https://www.rfc-editor.org/info/rfc7838>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

11.2.  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, <https://www.rfc-editor.org/info/rfc7301>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

11.3.  URIs

   [1] https://mailarchive.ietf.org/arch/search/?email_list=quic

   [2] https://github.com/quicwg

   [3] https://github.com/quicwg/base-drafts/labels/-http

   [4] https://www.iana.org/assignments/message-headers

Appendix A.  Considerations for Transitioning from HTTP/2

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

   HTTP/QUIC begins from the premise that similarity to HTTP/2 is
   preferable, but not a hard requirement.  HTTP/QUIC departs from
   HTTP/2 primarily where necessary to accommodate the differences in
   behavior between QUIC and TCP (lack of ordering, support for
   streams).  We intend to avoid gratuitous changes which make it
   difficult or impossible to build extensions with the same semantics
   applicable to both protocols at once.

   These departures are noted in this section.

A.1.  Streams

   HTTP/QUIC permits use of a larger number of streams (2^62-1) than
   HTTP/2.  The considerations about exhaustion of stream identifier
   space apply, though the space is significantly larger such that it is
   likely that other limits in QUIC are reached first, such as the limit
   on the connection flow control window.

A.2.  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.  This permits the removal of the Flags field from the
   generic frame layout.

   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 control stream and the PRIORITY
   section is removed from the HEADERS frame.

   Likewise, HPACK was designed with the assumption of in-order
   delivery.  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.  As a result, HTTP/QUIC uses a modified version of HPACK,
   described in [QPACK].

   Frame type definitions in HTTP/QUIC often use the QUIC variable-
   length integer encoding.  In particular, Stream IDs use this
   encoding, which allow for a larger range of possible values than the
   encoding used in HTTP/2.  Some frames in HTTP/QUIC use an identifier
   rather than a Stream ID (e.g.  Push IDs in PRIORITY frames).
   Redefinition of the encoding of extension frame types might be
   necessary if the encoding includes a Stream ID.

   Because the Flags field is not present in generic HTTP/QUIC frames,
   those frames which depend on the presence of flags need to allocate
   space for flags as part of their frame payload.

   Other than this issue, frame type HTTP/2 extensions are typically
   portable to QUIC simply by replacing Stream 0 in HTTP/2 with a
   control stream in HTTP/QUIC.  HTTP/QUIC extensions will not assume
   ordering, but would not be harmed by ordering, and would be portable
   to HTTP/2 in the same manner.

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

   DATA (0x0):  Padding is not defined in HTTP/QUIC frames.  See
      Section 4.2.1.

   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 4.2.2.

   PRIORITY (0x2):  As described above, the PRIORITY frame is sent on
      the control stream and can reference a variety of identifiers.
      See Section 4.2.3.

   RST_STREAM (0x3):  RST_STREAM frames do not exist, since QUIC
      provides stream lifecycle management.  The same code point is used
      for the CANCEL_PUSH frame (Section 4.2.4).

   SETTINGS (0x4):  SETTINGS frames are sent only at the beginning of
      the connection.  See Section 4.2.5 and Appendix A.3.

   PUSH_PROMISE (0x5):  The PUSH_PROMISE does not reference a stream;
      instead the push stream references the PUSH_PROMISE frame using a
      Push ID.  See Section 4.2.6.

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

   GOAWAY (0x7):  GOAWAY is sent only from server to client and does not
      contain an error code.  See Section 4.2.7.

   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.

   Frame types defined by extensions to HTTP/2 need to be separately
   registered for HTTP/QUIC if still applicable.  The IDs of frames
   defined in [RFC7540] have been reserved for simplicity.  See
   Section 10.3.

A.3.  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.

   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 [QPACK].

   SETTINGS_ENABLE_PUSH:  This is removed in favor of the MAX_PUSH_ID
      which provides a more granular control over server push.

   SETTINGS_MAX_CONCURRENT_STREAMS:  QUIC controls the largest open
      Stream ID as part of its flow control logic.  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 4.2.5.1.

   In HTTP/QUIC, setting values are variable-length integers (6, 14, 30,
   or 62 bits long) rather than fixed-length 32-bit fields as in HTTP/2.
   This will often produce a shorter encoding, but can produce a longer
   encoding for settings which use the full 32-bit space.  Settings
   ported from HTTP/2 might choose to redefine the format of their
   settings to avoid using the 62-bit encoding.

   Settings need to be defined separately for HTTP/2 and HTTP/QUIC.  The
   IDs of settings defined in [RFC7540] have been reserved for
   simplicity.  See Section 10.4.

A.4.  HTTP/2 Error Codes

   QUIC has the same concepts of "stream" and "connection" errors that
   HTTP/2 provides.  However, there is no direct portability of HTTP/2
   error codes.

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

   NO_ERROR (0x0):  HTTP_NO_ERROR in Section 8.1.

   PROTOCOL_ERROR (0x1):  No single mapping.  See new
      HTTP_MALFORMED_FRAME error codes defined in Section 8.1.

   INTERNAL_ERROR (0x2):  HTTP_INTERNAL_ERROR in Section 8.1.

   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):  HTTP_MALFORMED_FRAME error codes defined in
      Section 8.1.

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

   CANCEL (0x8):  HTTP_REQUEST_CANCELLED in Section 8.1.

   COMPRESSION_ERROR (0x9):  Multiple error codes are defined in
      [QPACK].

   CONNECT_ERROR (0xa):  HTTP_CONNECT_ERROR in Section 8.1.

   ENHANCE_YOUR_CALM (0xb):  HTTP_EXCESSIVE_LOAD in Section 8.1.

   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 8.1.

   Error codes need to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF be defined for Syntax
              Specifications: ABNF", STD 68, RFC 5234,
              DOI 10.17487/RFC5234, January 2008,
              <https://www.rfc-editor.org/info/rfc5234>.

   [RFC6066]  Eastlake 3rd, D., "Transport Layer Security (TLS)
              Extensions: Extension Definitions", RFC 6066,
              DOI 10.17487/RFC6066, January 2011,
              <https://www.rfc-editor.org/info/rfc6066>.

   [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,
              <https://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,
              <https://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,
              <https://www.rfc-editor.org/info/rfc7540>.

   [RFC7838]  Nottingham, M., McManus, P., and J. Reschke, "HTTP
              Alternative Services", RFC 7838, DOI 10.17487/RFC7838,
              April 2016, <https://www.rfc-editor.org/info/rfc7838>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

11.2.  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, <https://www.rfc-editor.org/info/rfc7301>.

   [RFC8126]  Cotton, M., Leiba, B., HTTP/2 and T. Narten, "Guidelines for
              Writing an IANA Considerations HTTP/QUIC separately.
   See Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

11.3.  URIs

   [1] https://mailarchive.ietf.org/arch/search/?email_list=quic

   [2] https://github.com/quicwg

   [3] https://github.com/quicwg/base-drafts/labels/-http

   [4] https://www.iana.org/assignments/message-headers 10.5.

Appendix A. B.  Change Log

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

A.1.

B.1.  Since draft-ietf-quic-http-15

   Substantial editorial reorganization; no technical changes.

B.2.  Since draft-ietf-quic-http-14

   o  Recommend sensible values for QUIC transport parameters
      (#1720,#1806)

   o  Define error for missing SETTINGS frame (#1697,#1808)

   o  Setting values are variable-length integers (#1556,#1807) and do
      not have separate maximum values (#1820)

   o  Expanded discussion of connection closure (#1599,#1717,#1712)

   o  HTTP_VERSION_FALLBACK falls back to HTTP/1.1 (#1677,#1685)

A.2.

B.3.  Since draft-ietf-quic-http-13

   o  Reserved some frame types for grease (#1333, #1446)
   o  Unknown unidirectional stream types are tolerated, not errors;
      some reserved for grease (#1490, #1525)

   o  Require settings to be remembered for 0-RTT, prohibit reductions
      (#1541, #1641)

   o  Specify behavior for truncated requests (#1596, #1643)

A.3.

B.4.  Since draft-ietf-quic-http-12

   o  TLS SNI extension isn't mandatory if an alternative method is used
      (#1459, #1462, #1466)

   o  Removed flags from HTTP/QUIC frames (#1388, #1398)

   o  Reserved frame types and settings for use in preserving
      extensibility (#1333, #1446)

   o  Added general error code (#1391, #1397)

   o  Unidirectional streams carry a type byte and are extensible
      (#910,#1359)

   o  Priority mechanism now uses explicit placeholders to enable
      persistent structure in the tree (#441,#1421,#1422)

A.4.

B.5.  Since draft-ietf-quic-http-11

   o  Moved QPACK table updates and acknowledgments to dedicated streams
      (#1121, #1122, #1238)

A.5.

B.6.  Since draft-ietf-quic-http-10

   o  Settings need to be remembered when attempting and accepting 0-RTT
      (#1157, #1207)

A.6.

B.7.  Since draft-ietf-quic-http-09

   o  Selected QCRAM for header compression (#228, #1117)

   o  The server_name TLS extension is now mandatory (#296, #495)

   o  Specified handling of unsupported versions in Alt-Svc (#1093,
      #1097)

A.7.

B.8.  Since draft-ietf-quic-http-08

   o  Clarified connection coalescing rules (#940, #1024)

A.8.

B.9.  Since draft-ietf-quic-http-07

   o  Changes for integer encodings in QUIC (#595,#905)

   o  Use unidirectional streams as appropriate (#515, #240, #281, #886)

   o  Improvement to the description of GOAWAY (#604, #898)

   o  Improve description of server push usage (#947, #950, #957)

A.9.

B.10.  Since draft-ietf-quic-http-06

   o  Track changes in QUIC error code usage (#485)

A.10.

B.11.  Since draft-ietf-quic-http-05

   o  Made push ID sequential, add MAX_PUSH_ID, remove
      SETTINGS_ENABLE_PUSH (#709)

   o  Guidance about keep-alive and QUIC PINGs (#729)

   o  Expanded text on GOAWAY and cancellation (#757)

A.11.

B.12.  Since draft-ietf-quic-http-04

   o  Cite RFC 5234 (#404)

   o  Return to a single stream per request (#245,#557)

   o  Use separate frame type and settings registries from HTTP/2 (#81)

   o  SETTINGS_ENABLE_PUSH instead of SETTINGS_DISABLE_PUSH (#477)

   o  Restored GOAWAY (#696)

   o  Identify server push using Push ID rather than a stream ID
      (#702,#281)

   o  DATA frames cannot be empty (#700)

A.12.

B.13.  Since draft-ietf-quic-http-03

   None.

A.13.

B.14.  Since draft-ietf-quic-http-02

   o  Track changes in transport draft

A.14.

B.15.  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)

A.15.

B.16.  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)

A.16.

B.17.  Since draft-shade-quic-http2-mapping-00

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

   o  Updated authors/editors list

Acknowledgements

   The original authors of this specification were Robbie Shade and Mike
   Warres.

   A substantial portion of Mike's contribution was supported by
   Microsoft during his employment there.

Author's Address

   Mike Bishop (editor)
   Akamai

   Email: mbishop@evequefou.be