wdiff draft-ietf-quic-http-04.txt draft-ietf-quic-http-05.txt

QUIC M. Bishop, Ed.
Internet-Draft Microsoft
Intended status: Standards Track June 13, 2017
Expires: December August 15, 2017
Expires: February 16, 2018

Hypertext Transfer Protocol (HTTP) over QUIC
draft-ietf-quic-http-04
draft-ietf-quic-http-05

Abstract

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

Note to Readers

Discussion of this draft takes place on the QUIC working group
mailing list (quic@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/search/?email_list=quic.

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

Status of This Memo

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

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

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

This Internet-Draft will expire on December 15, 2017. February 16, 2018.

This document is subject to BCP 78 and the IETF Trust's Legal
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(http://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. QUIC Advertisement . . . . . . . . . . . . . . . . . . . . . 3
2.1. QUIC Version Hints . . . . . . . . . . . . . . . . . . . 4
3. Connection Establishment . . . . . . . . . . . . . . . . . . 4 5
3.1. Draft Version Identification . . . . . . . . . . . . . . 5
4. Stream Mapping and Usage . . . . . . . . . . . . . . . . . . 5
4.1. Stream 1: Connection Control Stream . . . . . . . . . . . . . . . . 6
4.2. HTTP Message Exchanges . . . . . . . . . . . . . . . . . 6
4.2.1. Header Compression . . . . . . . . . . . . . . . . . 7
4.2.2. The CONNECT Method . . . . . . . . . . . . . . . . . 8
4.3. Stream Priorities . . . Request Prioritization . . . . . . . . . . . . . . . . . 9
4.4. Server Push . . . . . . . . . . . . . . . . . . . . . . . 9
5. HTTP Framing Layer . . . . . . . . . . . . . . . . . . . . . 10
5.1. Frame Layout . . . . . . . . . . . . . . . . . . . . . . 10
5.2. Frame Definitions . . . . . . . . . . . . . . . . . . . . 10 11
5.2.1. HEADERS DATA . . . . . . . . . . . . . . . . . . . . . . . 10 . 11
5.2.2. PRIORITY HEADERS . . . . . . . . . . . . . . . . . . . . . . . 11
5.2.3. SETTINGS PRIORITY . . . . . . . . . . . . . . . . . . . . . . 12 11
5.2.4. CANCEL_PUSH . . . . . . . . . . . . . . . . . . . . . 13
5.2.5. SETTINGS . . . . . . . . . . . . . . . . . . . . . . 14
5.2.6. PUSH_PROMISE . . . . . . . . . . . . . . . . . . . . 15 16
5.2.7. GOAWAY . . . . . . . . . . . . . . . . . . . . . . . 17
6. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 15 19
6.1. HTTP-Defined QUIC Error Codes . . . . . . . . . . . . . . 16 19
7. Considerations for Transitioning from HTTP/2 . . . . . . . . 17 21
7.1. HTTP Frame Types . . . . . . . . . . . . . . . . . . . . 17 21
7.2. HTTP/2 SETTINGS Parameters . . . . . . . . . . . . . . . 18 23
7.3. HTTP/2 Error Codes . . . . . . . . . . . . . . . . . . . 19 24
8. Security Considerations . . . . . . . . . . . . . . . . . . . 20 25
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 25
9.1. Registration of HTTP/QUIC Identification String . . . . . 21 25
9.2. Registration of QUIC Version Hint Alt-Svc Parameter . . . 21 25
9.3. Existing Frame Types . . . . . . . . . . . . . . . . . . 21 . . . . . 25
9.4. Settings Parameters . . . . . . . . . . . . . . . . . . . 22 26
9.5. Error Codes . . . . . . . . . . . . . . . . . . . . . . . 23 27
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 29
10.1. Normative References . . . . . . . . . . . . . . . . . . 25 30
10.2. Informative References . . . . . . . . . . . . . . . . . 26 31
Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 26 31
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 26 31
B.1. Since draft-ietf-quic-http-02 draft-ietf-quic-http-04 . . . . . . . . . . . . . . 26 31
B.2. Since draft-ietf-quic-http-01 draft-ietf-quic-http-03 . . . . . . . . . . . . . . 27 31
B.3. Since draft-ietf-quic-http-00 draft-ietf-quic-http-02 . . . . . . . . . . . . . . 27 31
B.4. Since draft-ietf-quic-http-01 . . . . . . . . . . . . . . 32
B.5. Since draft-ietf-quic-http-00 . . . . . . . . . . . . . . 32
B.6. Since draft-shade-quic-http2-mapping-00 . . . . . . . . . 28 33
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 28 33

1. Introduction

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

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

1.1. Notational Conventions

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

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

2. QUIC Advertisement

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

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

Alt-Svc: hq=":50781"

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

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

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

2.1. QUIC Version Hints

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

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

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

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

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

3. Connection Establishment

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

While connection-level options pertaining to the core QUIC protocol
are set in the initial crypto handshake, HTTP-specific settings are
conveyed in the SETTINGS frame. After the QUIC connection is
established, a SETTINGS frame (Section 5.2.3) 5.2.5) MUST be sent as the
initial frame of the HTTP control stream (Stream ID 1, see
Section 4). The server MUST NOT send data on any other stream until
the client's SETTINGS frame has been received.

3.1. Draft Version Identification

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

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

Implementations of draft versions of the protocol MUST add the string
"-" and the corresponding draft number to the identifier. For
example, draft-ietf-quic-http-01 is identified using the string "hq-
01".

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

4. Stream Mapping and Usage

A QUIC stream provides reliable in-order delivery of bytes, but makes
no guarantees about order of delivery with regard to bytes on other
streams. On the wire, data is framed into QUIC STREAM frames, but
this framing is invisible to the HTTP framing layer. A QUIC receiver
buffers and orders received STREAM frames, exposing the data
contained within as a reliable byte stream to the application.

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

When HTTP headers and data are sent over QUIC, the QUIC layer handles
most of the stream management. An HTTP request/response consumes a
pair of streams:
single stream: This means that the client's first request occurs on
QUIC streams 3 and 5, stream 3, the second on stream 7 and 9, 5, and so on. The server's first
push consumes streams 2 and 4. This amounts to the
second least-significant bit differentiating the two streams in a
request.

The lower-numbered stream is called the message control 2.

This stream and carries frames related to the request/response, including HEADERS.
The higher-numbered stream is the data stream and carries the request/response body with no additional framing. Note that a
request or response without a body will cause this stream to be half-
closed in the corresponding direction without transferring data.

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

All message control streams are considered critical to the HTTP
connection. If a message control stream is terminated abruptly for
any reason, this MUST be treated as a connection error of type
HTTP_RST_CONTROL_STREAM. (see
Section 5.2). When a message control stream terminates cleanly, if the last frame on
the stream was truncated, this MUST be treated as a connection error
(see HTTP_MALFORMED_* in Section 6.1).

Pairs of streams must Streams which terminate
abruptly may be utilized reset at any point in the frame.

Streams SHOULD be used sequentially, with no gaps. The
data stream is opened at the same time as the message control stream
is opened and is closed after transferring the body. The data Streams used for
pushed resources MAY be initiated out-of-order, but stream
is closed immediately after sending the request headers if there is
no body. IDs SHOULD
be allocated to promised resources sequentially.

HTTP does not need to do any separate multiplexing when using QUIC -
data sent over a QUIC stream always maps to a particular HTTP
transaction. Requests and responses are considered complete when the
corresponding QUIC streams are stream is closed in the appropriate direction.

4.1. Stream 1: Connection Control Stream

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

4.2. HTTP Message Exchanges

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

An HTTP message (request or response) consists of:

1. one header block (see Section 5.2.1) on the control stream 5.2.2) containing the message
headers (see [RFC7230], Section 3.2),

2. the payload body (see [RFC7230], Section 3.3), sent on the data
stream, as a series
of DATA frames (see Section 5.2.1),

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

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

The data stream MUST be half-closed immediately after the transfer of
the body. If the message does not contain a body, the corresponding
data stream MUST still be half-closed without transferring any data.
The "chunked" transfer encoding defined in Section 4.1 of [RFC7230]
MUST NOT be used.

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

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

A server can send a complete response prior to the client sending an
entire request if the response does not depend on any portion of the
request that has not been sent and received. When this is true, a
server MAY request that the client abort transmission of a request
without error by sending triggering a RST_STREAM QUIC STOP_SENDING with an error code of NO_ERROR
after
HTTP_EARLY_RESPONSE, sending a complete response response, and cleanly closing
its stream. streams. Clients MUST NOT discard complete responses as a result
of receiving such a
RST_STREAM, having their request terminated abruptly, though clients can
always discard responses at their discretion for other reasons.
Servers MUST NOT abort a response in progress as a result of
receiving a solicited RST_STREAM.

4.2.1. Header Compression

HTTP/QUIC uses HPACK header compression as described in [RFC7541].
HPACK was designed for HTTP/2 with the assumption of in-order
delivery such as that provided by TCP. A sequence of encoded header
blocks must arrive (and be decoded) at an endpoint in the same order
in which they were encoded. This ensures that the dynamic state at
the two endpoints remains in sync.

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

This does introduce head-of-line blocking: if HPACK without this
assumption. In the packet containing
HEADERS for stream N is lost or reordered then meantime, by fixing the HEADERS for stream
N+4 cannot be processed until it has been retransmitted successfully,
even though size of the HEADERS for stream N+4 may have arrived.

DISCUSS: Keep HPACK with HOLB? Redesign dynamic table
at zero, HPACK to can be order-
invariant? How much do we need to retain compatibility with
HTTP/2's HPACK? used in an unordered environment.

4.2.2. The CONNECT Method

The pseudo-method CONNECT ([RFC7231], Section 4.3.6) is primarily
used with HTTP proxies to establish a TLS session with an origin
server for the purposes of interacting with "https" resources. In
HTTP/1.x, CONNECT is used to convert an entire HTTP connection into a
tunnel to a remote host. In HTTP/2, the CONNECT method is used to
establish a tunnel over a single HTTP/2 stream to a remote host for
similar purposes.

A CONNECT request in HTTP/QUIC functions in the same manner as in
HTTP/2. The request MUST be formatted as described in [RFC7540],
Section 8.3. A CONNECT request that does not conform to these
restrictions is malformed. The message data stream MUST NOT be
closed at the end of the request.

A proxy that supports CONNECT establishes a TCP connection
([RFC0793]) to the server identified in the ":authority" pseudo-
header field. Once this connection is successfully established, the
proxy sends a HEADERS frame containing a 2xx series status code to
the client, as defined in [RFC7231], Section 4.3.6, on the message
control stream. 4.3.6.

All QUIC STREAM DATA frames on the message data request stream correspond to data sent on the
TCP connection. Any QUIC STREAM DATA frame sent by the client is transmitted by
the proxy to the TCP server; data received from the TCP server is written to the data stream
packaged into DATA frames by the proxy. Note that the size and
number of TCP segments is not guaranteed to map predictably to the
size and number of HTTP DATA or QUIC STREAM frames.

The TCP connection can be closed by either peer. When the client
half-closes the data request stream, the proxy will set the FIN bit on its
connection to the TCP server. When the proxy receives a packet with
the FIN bit set, it will half-close the corresponding data stream. TCP
connections which remain half-closed in a single direction are not
invalid, but are often handled poorly by servers, so clients SHOULD
NOT half-close connections on which they are still expecting data.

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

4.3. Stream Priorities Request Prioritization

HTTP/QUIC uses the priority scheme described in [RFC7540] [RFC7540],
Section 5.3. In this priority scheme, a given stream request can be
designated as dependent upon another stream, request, which expresses the
preference that the latter stream (the "parent" stream) request) be allocated
resources before the former stream (the "dependent" stream). request). Taken
together, the dependencies across all streams requests in a connection form a
dependency tree. The structure of the dependency tree changes as
PRIORITY frames add, remove, or change the dependency links between
streams.

For consistency's sake, all
requests.

HTTP/2 defines its priorities in terms of streams whereas HTTP over
QUIC identifies requests. The PRIORITY frames MUST refer to frame Section 5.2.3
identifies a request either by identifying the message
control stream of that carries a
request or by using a Push ID (Section 5.2.6). Other than the dependent request, not means
of identifying requests, the data stream. prioritization system is identical to
that in HTTP/2.

Only a client can send PRIORITY frames. A server MUST NOT send a
PRIORITY frame.

4.4. Server Push

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

As with server push for HTTP/2, the server initiates a server push by
sending a PUSH_PROMISE frame containing the Stream ID of the stream
to be pushed, as well as that includes request header fields
attributed to the request. The PUSH_PROMISE frame is sent on a
response stream. Unlike HTTP/2, the control stream of the
associated (client-initiated) request, while the Promised Stream ID
field specifies PUSH_PROMISE does not reference
a stream; when a server fulfills a promise, the Stream ID of stream that carries
the control stream for headers references the server-
initiated request. PUSH_PROMISE. This allows a server
to fulfill promises in the order that best suits its needs.

The server push response is conveyed on a push stream. A push stream
is a server-initiated stream. A push stream includes a header (see
Figure 1) that identifies the PUSH_PROMISE that it fulfills. This
header consists of a 32-bit Push ID, which identifies a server push
(see Section 5.2.6).

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 (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: Push Stream Header

Each Push ID MUST only be used once in a push stream header. If a
push stream header includes a Push ID that was used in another push
stream header, the same way client MUST treat this as a non-server- connection error of
type HTTP_DUPLICATE_PUSH. The same Push ID can be used in multiple
PUSH_PROMISE frames (see Section 5.2.6).

After the push response, stream header, a push contains a response
(Section 4.2), with response headers and headers, a response body (if present) any)
carried by DATA frames, then trailers (if any) carried by HEADERS frames sent on
frames.

If a promised server push is not needed by the control stream, and response
body (if any) sent via client, the client
SHOULD send a CANCEL_PUSH frame; if the push stream is already open,
a QUIC STOP_SENDING frame with an appropriate error code can be used
instead (e.g., HTTP_PUSH_REFUSED, HTTP_PUSH_ALREADY_IN_CACHE; see
Section 6). This asks the server not to transfer the corresponding data stream. and
indicates that it will be discarded upon receipt.

5. HTTP Framing Layer

Frames are used only on the connection (stream 1) and message
(streams 3, 7, etc.) control streams. Other streams carry data
payload and are not framed at the HTTP layer. each stream. This section describes HTTP framing
in QUIC and highlights some differences from HTTP/2 framing. For
more detail on differences from HTTP/2, see Section 7.1.

5.1. Frame Layout

All frames have the following format:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (16) | Type (8) | Flags (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Frame Payload (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: 2: HTTP/QUIC frame format

5.2. Frame Definitions

5.2.1. DATA

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

The DATA frame defines no flags.

DATA frames MUST be associated with an HTTP request or response. If
a DATA frame is received on the control stream, the recipient MUST
respond with a connection error (Section 6) of type
HTTP_WRONG_STREAM.

DATA frames MUST contain a non-zero-length payload. If a DATA frame
is received with a payload length of zero, the recipient MUST respond
with a stream error (Section 6) of type HTTP_MALFORMED_DATA.

5.2.2. HEADERS

The HEADERS frame (type=0x1) is used to carry part of a header set,
compressed using HPACK [RFC7541]. Section 4.2.1.

One flag is defined:

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

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

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence? (16) | Header Block Fragment (*)...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 2: HEADERS frame payload

The HEADERS frame payload has the following fields:

Sequence Number: Present only on the first frame of a header block
sequence. This MUST be set to zero on the first header block
sequence, and incremented on each header block.

The next frame on the same stream after a HEADERS frame without the
EHB flag set MUST be another HEADERS frame. A receiver MUST treat
the receipt of any other type of frame as a stream error of type
HTTP_INTERRUPTED_HEADERS. (Note that QUIC can intersperse data from
other streams between frames, or even during transmission of frames,
so multiplexing is not blocked by this requirement.)

A full header block is contained in a sequence of zero or more
HEADERS frames without EHB set, followed by a HEADERS frame with EHB
set.

On receipt, header blocks (HEADERS, PUSH_PROMISE) MUST be processed
by the HPACK decoder in sequence. If a block is missing, all
subsequent HPACK frames MUST be held until it arrives, or the
connection terminated.

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

5.2.2.

5.2.3. PRIORITY

The PRIORITY (type=0x02) frame specifies the sender-advised priority
of a stream and is substantially different in format from [RFC7540].
In order to support ordering, it ensure that prioritization is processed in a consistent
order, PRIORITY frames MUST be sent only on the connection control stream. A
PRIORITY frame sent on any other stream MUST be treated as a
HTTP_WRONG_STREAM error.

The format has been modified to accommodate not being sent
on-stream on a
request stream, to allow for identification of server pushes, and the
larger stream ID space of QUIC. The semantics of the Stream
Dependency, Weight, and E flag are otherwise the same as in HTTP/2.

The flags defined are:

PUSH_PRIORITIZED (0x04): Indicates that the Prioritized Stream is a
server push rather than a request.

PUSH_DEPENDENT (0x02): Indicates a dependency on a server push.

E (0x01): Indicates that the stream dependency is exclusive (see
[RFC7540]
[RFC7540], Section 5.3).

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prioritized Stream Request ID (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Dependent Stream Dependency ID (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Weight (8) |
+-+-+-+-+-+-+-+-+

Figure 3: PRIORITY frame payload

The HEADERS PRIORITY frame payload has the following fields:

Prioritized Stream: Request ID: A 32-bit stream identifier for a request. This
contains the message
control stream whose priority ID of a request stream when the
PUSH_PRIORITIZED flag is being updated. clear, or a Push ID when the
PUSH_PRIORITIZED flag is set.

Stream Dependency: Dependency ID: A 32-bit stream identifier for a dependent
request. This contains the stream that
this ID of a request stream when the
PUSH_DEPENDENT flag is clear, or a Push ID when the PUSH_DEPENDENT
flag is set. A request stream depends ID of 0 indicates a dependency on (see
the root stream. For details of dependencies, see Section 4.3 and {!RFC7540}}
[RFC7540], Section 5.3). 5.3.

Weight: An unsigned 8-bit integer representing a priority weight for
the stream (see [RFC7540] [RFC7540], Section 5.3). Add one to the value to
obtain a weight between 1 and 256.

A PRIORITY frame identifies a request to priotize, and a request upon
which that request is dependent. A Prioritized Request ID or Stream
Dependency ID identifies a client-initiated request using the
corresponding stream ID when the corresponding PUSH_PRIORITIZED or
PUSH_DEPENDENT flag is not set. Setting the PUSH_PRIORITIZED or
PUSH_DEPENDENT flag causes the Prioritized Request ID or Stream
Dependency ID (respectively) to identify a server push using a Push
ID (see Section 5.2.6 for details).

A PRIORITY frame MAY identify a Stream Dependency ID using a stream
ID of 0; as in [RFC7540], this makes the request dependent on the
root of the dependency tree.

Stream ID 0 and stream ID 1 cannot be reprioritized. A Prioritized
Request ID that identifies Stream 0 or 1 MUST have be treated as a payload
connection error of type HTTP_MALFORMED_PRIORITY.

A PRIORITY frame that does not reference a request MUST be treated as
a HTTP_MALFORMED_PRIORITY error, unless it references stream ID 0. A
PRIORITY that sets a PUSH_PRIORITIZED or PUSH_DEPENDENT flag, but
then references a non-existent Push ID MUST be treated as a
HTTP_MALFORMED_PRIORITY error.

The length of nine a PRIORITY frame is 9 octets. A PRIORITY frame of with
any other length MUST be treated as a connection error of type
HTTP_MALFORMED_PRIORITY.

5.2.3.

5.2.4. CANCEL_PUSH

The CANCEL_PUSH frame (type=0x3) is used to request cancellation of
server push prior to the push stream being created. The CANCEL_PUSH
frame identifies a server push request by Push ID (see
Section 5.2.6).

When a server receives this frame, it aborts sending the response for
the identified server push. If the server has not yet started to
send the server push, it can use the receipt of a CANCEL_PUSH frame
to avoid opening a stream. If the push stream has been opened by the
server, the server SHOULD sent a QUIC RST_STREAM frame on those
streams and cease transmission of the response.

A server can send this frame to indicate that it won't be sending a
response prior to creation of a push stream. Once the push stream
has been created, sending CANCEL_PUSH has no effect on the state of
the push stream. A QUIC RST_STREAM frame SHOULD be used instead to
cancel transmission of the server push response.

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

The CANCEL_PUSH frame has no defined flags.

The CANCEL_PUSH frame carries a 32-bit Push ID that identifies the
server push that is being cancelled (see Section 5.2.6).

If the client receives a CANCEL_PUSH frame, that frame might identify
a Push ID that has not yet been mentioned by a PUSH_PROMISE frame.

A server MUST treat a CANCEL_PUSH frame payload that is other than 4
octets in length as a connection error of type
HTTP_MALFORMED_CANCEL_PUSH.

5.2.5. SETTINGS

The SETTINGS frame (type=0x4) conveys configuration parameters that
affect how endpoints communicate, such as preferences and constraints
on peer behavior, and is substantially different from [RFC7540]. Individually, a
SETTINGS parameter can also be referred to as a "setting".

SETTINGS parameters are not negotiated; they describe characteristics
of the sending peer, which can be used by the receiving peer.
However, a negotiation can be implied by the use of SETTINGS - a peer
uses SETTINGS to advertise a set of supported values. The recipient
can then choose which entries from this list are also acceptable and
proceed with the value it has chosen. (This choice could be
announced in a field of an extension frame, or in its own value in
SETTINGS.)

Different values for the same parameter can be advertised by each
peer. For example, a client might permit a be willing to consume very large HPACK state
table
response headers, while a server chooses to use a small one to conserve memory. servers are more cautious about request size.

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

The SETTINGS frame defines no flags.

The payload of a SETTINGS frame consists of zero or more parameters,
each consisting of an unsigned 16-bit setting identifier and a
length-prefixed binary value.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier (16) | Length (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Contents (?) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 4: SETTINGS value format

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

Non-zero-length values MUST be compared against the remaining length
of the SETTINGS frame. Any value which purports to cross the end of
the frame MUST cause the SETTINGS frame to be considered malformed
and trigger a connection error of type HTTP_MALFORMED_SETTINGS.

An implementation MUST ignore the contents for any SETTINGS
identifier it does not understand.

SETTINGS frames always apply to a connection, never a single stream.
A SETTINGS frame MUST be sent as the first frame of the connection control
stream (see Section 4) by each peer, and MUST NOT be sent
subsequently or on any other stream. If an endpoint receives an
SETTINGS frame on a different stream, the endpoint MUST respond with
a connection error of type HTTP_SETTINGS_ON_WRONG_STREAM. HTTP_WRONG_STREAM. If an endpoint
receives a second SETTINGS frame, the endpoint MUST respond with a
connection error of type HTTP_MULTIPLE_SETTINGS.

The SETTINGS frame affects connection state. A badly formed or
incomplete SETTINGS frame MUST be treated as a connection error
(Section 5.4.1) 6) of type HTTP_MALFORMED_SETTINGS.

5.2.3.1.

5.2.5.1. Integer encoding

Settings which are integers are transmitted in network byte order.
Leading zero octets are permitted, but implementations SHOULD use
only as many bytes as are needed to represent the value. An integer
MUST NOT be represented in more bytes than would be used to transfer
the maximum permitted value.

5.2.3.2.

5.2.5.2. Defined SETTINGS Parameters

The following settings are defined in HTTP/QUIC:

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

SETTINGS_DISABLE_PUSH This value MUST be zero.

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

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

5.2.3.3. 1

5.2.5.3. Usage in 0-RTT

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

o SETTINGS_HEADER_TABLE_SIZE

o SETTINGS_MAX_HEADER_LIST_SIZE

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

o SETTINGS_HEADER_TABLE_SIZE: 0 octets

o SETTINGS_MAX_HEADER_LIST_SIZE: 16,384 octets

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

If the connection is closed because these or other constraints were
violated during the 0-RTT flight (e.g. with
HTTP_HPACK_DECOMPRESSION_FAILED), clients MAY establish a new
connection and retry any 0-RTT requests using the settings sent by
the server on the closed connection. (This assumes that only
requests that are safe to retry are sent in 0-RTT.) If the
connection was closed before the SETTINGS frame was received, clients
SHOULD discard any cached values and use the defaults above on the
next connection.

5.2.4.

5.2.6. PUSH_PROMISE

The PUSH_PROMISE frame (type=0x05) is used to carry a request header
set from server to client, as in HTTP/2. It The PUSH_PROMISE frame
defines no flags.

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Promised Stream Push ID (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence? (16) | Header Block (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 5: PUSH_PROMISE frame payload

The payload consists of:

Promised Stream

Push ID: A 32-bit Stream identifier for the server push request. A push ID indicating
is used in push stream header (Section 4.4), CANCEL_PUSH frames
(Section 5.2.4), and PRIORITY frames (Section 5.2.3).

Header Block: HPACK-compressed request headers for the promised
response.

A server MAY use the 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 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 the same Push ID in multiple PUSH_PROMISE frames
MUST include the same header fields each time. The octets of the
header block MAY be different due 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 a
PUSH_PROMISE with conflicting header field values for the same Push
ID as a connection error of type HTTP_MALFORMED_PUSH_PROMISE.

Allowing duplicate references to the same Push ID is primarily to
reduce duplication caused by concurrent requests. A server SHOULD
avoid reusing a Push ID over a 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.

5.2.7. GOAWAY

The GOAWAY frame (type=0x7) is used to initiate graceful shutdown of
a 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. (Note
that clients do not need to send GOAWAY to gracefully close a
connection; they simply stop making new requests.)

The GOAWAY frame does not define any flags, and the payload is a QUIC
stream identifier. The GOAWAY frame applies to the connection, not a
specific stream. An endpoint MUST treat a GOAWAY frame on a stream
other than the control stream as a connection error (Section 6) of
type HTTP_WRONG_STREAM.

New client requests might already have been sent before the client
receives the server's GOAWAY frame. The GOAWAY frame contains the
stream identifier of the last client-initiated request that was or
might be processed in this connection, which enables client and
server to agree on which requests were accepted prior to the response headers will
connection shutdown. This identifier MAY be sent. (The response body lower than the stream is implied
limit identified by a QUIC MAX_STREAM_ID frame, and MAY be zero if no
requests were processed. Servers SHOULD NOT increase the headers stream,
MAX_STREAM_ID limit after sending a GOAWAY frame.

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

Once sent, the server will refuse requests sent on streams with an
identifier higher than the included last stream identifier. Clients
MUST NOT send new requests on the connection after receiving GOAWAY,
although requests might already be in Section 4.)

HPACK Sequence: transit. A sixteen-bit counter, equivalent new connection can
be established for new requests.

If the client has sent requests on streams with a higher stream
identifier than indicated in the GOAWAY frame, those requests were
not and will not be processed. Endpoints SHOULD reset any streams
above this ID with the error code HTTP_REQUEST_CANCELLED. Servers
MAY also reset streams below the indicated ID with
HTTP_REQUEST_CANCELLED if the associated requests were not processed.

The client can treat requests cancelled by the server as though they
had never been sent at all, thereby allowing them to be retried later
on a new connection. Automatically retrying other requests is not
possible, unless this is otherwise permitted (e.g. idempotent actions
like GET, PUT, or DELETE). Requests on stream IDs less than or equal
to the Sequence
field stream ID in HEADERS

Payload: HPACK-compressed the GOAWAY frame might have been processed; their
status cannot be known until they are completed successfully, reset,
or the connection terminates.

Servers SHOULD send a GOAWAY frame when the closing of a connection
is known in advance, even if the advance notice is small, so that the
remote peer can know whether a stream has been partially processed or
not. For example, if an HTTP client sends a POST at the same time
that a server closes a QUIC connection, the client cannot know if the
server started to process that POST request headers if the server does not
send a GOAWAY frame to indicate what streams it might have acted on.

For unexpected closures caused by error conditions, a QUIC
CONNECTION_CLOSE frame MUST be used. However, a GOAWAY MAY be sent
first to provide additional detail to clients. If a connection
terminates without a GOAWAY frame, the last stream identifier is
effectively the highest possible stream identifier (as determined by
QUIC's MAX_STREAM_ID).

An endpoint MAY send multiple GOAWAY frames if circumstances change.
For instance, an endpoint that sends GOAWAY without an error code
during graceful shutdown could subsequently encounter an error
condition. The last stream identifier from the last GOAWAY frame
received indicates which streams could have been acted upon.
Endpoints MUST NOT increase the value they send in the last stream
identifier, since the peers might already have retried unprocessed
requests on another connection.

A client that is unable to retry requests loses all requests that are
in flight when the server closes the connection. A server that is
attempting to gracefully shut down a connection SHOULD send an
initial GOAWAY frame with the last stream identifier set to the
current value of QUIC's MAX_STREAM_ID and SHOULD NOT increase the
MAX_STREAM_ID thereafter. This signals to the client that a shutdown
is imminent and that initiating further requests is prohibited.
After allowing time for any in-flight requests (at least one round-
trip time), the promised response. server MAY send another GOAWAY frame with an updated
last stream identifier. This ensures that a connection can be
cleanly shut down without losing requests.

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].

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

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

6.1. HTTP-Defined QUIC Error Codes

QUIC allocates error codes 0x0000-0x3FFF to application protocol
definition. The following error codes are defined by HTTP for use in
QUIC RST_STREAM, GOAWAY, RST_STREAM and CONNECTION_CLOSE frames.

HTTP_PUSH_REFUSED (0x01): The server has attempted to push content
which the client will not accept on this connection.

HTTP_INTERNAL_ERROR (0x02): An internal error has occurred in the
HTTP stack.

HTTP_PUSH_ALREADY_IN_CACHE (0x03): The server has attempted to push
content which the client has cached.

HTTP_REQUEST_CANCELLED (0x04): The client no longer needs the
requested data.

HTTP_HPACK_DECOMPRESSION_FAILED (0x05): HPACK failed to decompress a
frame and cannot continue.

HTTP_CONNECT_ERROR (0x06): The connection established in response to
a CONNECT request was reset or abnormally closed.

HTTP_EXCESSIVE_LOAD (0x07): The endpoint detected that its peer is
exhibiting a behavior that might be generating excessive load.

HTTP_VERSION_FALLBACK (0x08): The requested operation cannot be
served over HTTP/QUIC. The peer should retry over HTTP/2.

HTTP_MALFORMED_HEADERS (0x09): A HEADERS frame has been received
with an invalid format.

HTTP_MALFORMED_PRIORITY (0x0A): A PRIORITY frame has been received
with an invalid format.

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

HTTP_MALFORMED_PUSH_PROMISE (0x0C): A PUSH_PROMISE frame has been
received with an invalid format.

HTTP_MALFORMED_DATA (0x0D): A DATA frame has been received with an
invalid format.

HTTP_INTERRUPTED_HEADERS (0x0E): A HEADERS frame without the End
Header Block flag was followed by a frame other than HEADERS.

HTTP_SETTINGS_ON_WRONG_STREAM

HTTP_WRONG_STREAM (0x0F): A SETTINGS frame was received on a request control stream. stream where it is
not permitted.

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

HTTP_RST_CONTROL_STREAM

HTTP_DUPLICATE_PUSH (0x11): A message control stream closed
abruptly. Multiple push streams used the same Push
ID.

7. 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 HTTP/2, and
describes how to map HTTP/2 extensions into HTTP/QUIC.

HTTP/QUIC begins from the premise that HTTP/2 code reuse is a useful
feature, 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.

7.1. HTTP Frame Types

Many framing concepts from HTTP/2 can be elided away on QUIC, because
the transport deals with them. Because frames are already on a
stream, they can omit the stream number. Because frames do not block
multiplexing (QUIC's multiplexing occurs below this layer), the
support for variable-maximum-length packets can be removed. Because
stream termination is handled by QUIC, an END_STREAM flag is not
required.

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

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

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

Other than this issue, frame type HTTP/2 extensions are typically
portable to QUIC simply by replacing Stream 0 in HTTP/2 with Stream 1
in HTTP/QUIC. 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): Instead of DATA frames, Padding is not defined in HTTP/QUIC uses a separate data
stream. frames. See
Section 4. 5.2.1.

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 5.2.1. 5.2.2.

PRIORITY (0x2): As described above, the PRIORITY frame is sent on
the connection control stream. See Section 5.2.2. 5.2.3.

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 5.2.4).

SETTINGS (0x4): SETTINGS frames are sent only at the beginning of
the connection. See Section 5.2.3 5.2.5 and Section 7.2.

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 5.2.4. 5.2.6.

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

GOAWAY (0x7): GOAWAY frames do is sent only from server to client and does not exist, since QUIC provides
equivalent functionality.
contain an error code. See Section 5.2.7.

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, and
HEADERS frames can be used in series.

The IANA registry of frame

Frame types has been updated in Section 9.3 defined by extensions to
include references HTTP/2 need to the definition be separately
registered for each frame type in HTTP/2
and in HTTP/QUIC. Frames not HTTP/QUIC if still applicable. The IDs of frames
defined as available in HTTP/QUIC
SHOULD NOT be sent and SHOULD be ignored as unknown on receipt. [RFC7540] have been reserved for simplicity. See
Section 9.3.

7.2. HTTP/2 SETTINGS Parameters

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

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

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

SETTINGS_HEADER_TABLE_SIZE: See Section 5.2.3.2. 5.2.5.2.

SETTINGS_ENABLE_PUSH: See SETTINGS_DISABLE_PUSH in Section 5.2.3.2. 5.2.5.2.

SETTINGS_MAX_CONCURRENT_STREAMS: QUIC requires controls the maximum number largest open
stream ID as part of
incoming streams per connection to be specified in the initial
transport handshake. 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 5.2.3.2. 5.2.5.2.

Settings defined by extensions need to HTTP/2 MAY be expressed as integers
with a maximum value of 2^32-1, if they are applicable to HTTP/QUIC,
but SHOULD have a specification describing their usage. Fields defined separately for
this purpose HTTP/2 and HTTP/QUIC. The
IDs of settings defined in [RFC7540] have been added to the IANA registry in reserved for
simplicity. See Section 9.4.

7.3. HTTP/2 Error Codes

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

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

NO_ERROR (0x0): QUIC_NO_ERROR

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

INTERNAL_ERROR (0x2) (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_HPACK_DECOMPRESSION_FAILED in
Section 6.1.

CONNECT_ERROR (0xa): HTTP_CONNECT_ERROR in Section 6.1.

ENHANCE_YOUR_CALM (0xb): HTTP_EXCESSIVE_LOAD in Section 6.1.

INADEQUATE_SECURITY (0xc): Not applicable, since QUIC is assumed to
provide sufficient security on all connections.

HTTP_1_1_REQUIRED (0xd): HTTP_VERSION_FALLBACK in Section 6.1.

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

8. Security Considerations

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

The modified SETTINGS format contains nested length elements, which
could pose a security risk to an uncautious implementer. A SETTINGS
frame parser MUST ensure that the length of the frame exactly matches
the length of the settings it contains.

9. IANA Considerations

9.1. Registration of HTTP/QUIC Identification String

This document creates a new registration for the identification of
HTTP/QUIC in the "Application Layer Protocol Negotiation (ALPN)
Protocol IDs" registry established in [RFC7301].

The "hq" string identifies HTTP/QUIC:

Protocol: HTTP over QUIC

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

Specification: This document

9.2. Registration of QUIC Version Hint Alt-Svc Parameter

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

Parameter: "quic"

Specification: This document, Section 2.1

9.3. Existing Frame Types

This document adds two new columns to 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 [RFC5226] for values between 0x00
and 0xef, with values between 0xf0 and 0xff being reserved for
Experimental Use.

While this registry is separate from the "HTTP/2 Frame Type" registry
defined in [RFC7540]:

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

* "HTTP/2 only"

* "HTTP/QUIC only"

* "Both"

HTTP/QUIC

Specification: Indicates where this frame's behavior over
QUIC is defined; required if A reference to a specification that includes a
description of the frame is supported over QUIC.

Values for existing registrations layout, its semantics, and flags that the
frame type uses, including any parts of the frame that are assigned
conditionally present based on the value of flags.

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

+---------------+---------------------+-------------------------+ document.

The "Specification" column is renamed to "HTTP/2 specification" and
is only required if the frame is supported over HTTP/2.
+--------------+------+---------------+

9.4. Settings Parameters

This document adds two new columns 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

[RFC5226] 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]:

Supported Protocols: Indicates which associated protocols use [RFC7540].

While this registry is separate from the
setting. Values MUST be one of:

* "HTTP/2 only"

* "HTTP/QUIC only"

* "Both"

HTTP/QUIC Specification: Indicates where this setting's behavior
over QUIC Settings" registry
defined in [RFC7540], it is defined; required if preferable that the frame assignments parallel
each other. If an entry is supported over
QUIC.

Values for existing 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:

+-------------------------+------------------+----------------------+ document.

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

9.5. Error Codes

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

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

New registrations are advised to provide the following information:

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

Code: The 30-bit error code value.

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

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

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

10. References
10.1. Normative References

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

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

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

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

[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>.

[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<http://www.rfc-editor.org/info/rfc7231>.

[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<http://www.rfc-editor.org/info/rfc7540>.

[RFC7541] Peon, R. and H. Ruellan, "HPACK: Header Compression for
HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015,
<http://www.rfc-editor.org/info/rfc7541>.

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

10.2. Informative References

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

[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <http://www.rfc-editor.org/info/rfc7301>.

Appendix A. Contributors

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

Appendix B. Change Log

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

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

B.2. Since draft-ietf-quic-http-03

None.

B.3. Since draft-ietf-quic-http-02

o Track changes in transport draft

B.2.

B.4. Since draft-ietf-quic-http-01

o SETTINGS changes (#181):

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

* SETTINGS_ACK removed

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

* Boolean format updated

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

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

o HPACK Sequence counter can wrap (#173)

o 0-RTT guidance added

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

B.3.

B.5. 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)

B.4.

B.6. Since draft-shade-quic-http2-mapping-00

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

o Updated authors/editors list

Author's Address

Mike Bishop (editor)
Microsoft

Email: Michael.Bishop@microsoft.com