Hypertext Transfer Protocol (HTTP) over QUIC
draft-ietf-quic-http-16
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 9114.
|
|
|---|---|---|---|
| Author | Mike Bishop | ||
| Last updated | 2018-10-23 (Latest revision 2018-10-03) | ||
| Replaces | draft-shade-quic-http2-mapping | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
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by Reese Enghardt
Ready w/issues
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| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 9114 (Proposed Standard) | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-quic-http-16
QUIC M. Bishop, Ed.
Internet-Draft Akamai
Intended status: Standards Track October 24, 2018
Expires: April 27, 2019
Hypertext Transfer Protocol (HTTP) over QUIC
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 27, 2019.
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Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
2. Connection Setup and Management . . . . . . . . . . . . . . . 5
2.1. Draft Version Identification . . . . . . . . . . . . . . 5
2.2. Discovering an HTTP/QUIC Endpoint . . . . . . . . . . . . 5
2.2.1. QUIC Version Hints . . . . . . . . . . . . . . . . . 6
2.3. Connection Establishment . . . . . . . . . . . . . . . . 6
2.4. Connection Reuse . . . . . . . . . . . . . . . . . . . . 7
3. Stream Mapping and Usage . . . . . . . . . . . . . . . . . . 7
3.1. Bidirectional Streams . . . . . . . . . . . . . . . . . . 8
3.2. Unidirectional Streams . . . . . . . . . . . . . . . . . 8
3.2.1. Control Streams . . . . . . . . . . . . . . . . . . . 9
3.2.2. Push Streams . . . . . . . . . . . . . . . . . . . . 9
3.2.3. Reserved Stream Types . . . . . . . . . . . . . . . . 10
4. HTTP Framing Layer . . . . . . . . . . . . . . . . . . . . . 10
4.1. Frame Layout . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Frame Definitions . . . . . . . . . . . . . . . . . . . . 11
4.2.1. DATA . . . . . . . . . . . . . . . . . . . . . . . . 11
4.2.2. HEADERS . . . . . . . . . . . . . . . . . . . . . . . 12
4.2.3. PRIORITY . . . . . . . . . . . . . . . . . . . . . . 12
4.2.4. CANCEL_PUSH . . . . . . . . . . . . . . . . . . . . . 14
4.2.5. SETTINGS . . . . . . . . . . . . . . . . . . . . . . 15
4.2.6. PUSH_PROMISE . . . . . . . . . . . . . . . . . . . . 17
4.2.7. GOAWAY . . . . . . . . . . . . . . . . . . . . . . . 18
4.2.8. MAX_PUSH_ID . . . . . . . . . . . . . . . . . . . . . 19
4.2.9. Reserved Frame Types . . . . . . . . . . . . . . . . 19
5. HTTP Request Lifecycle . . . . . . . . . . . . . . . . . . . 20
5.1. HTTP Message Exchanges . . . . . . . . . . . . . . . . . 20
5.1.1. Header Formatting and Compression . . . . . . . . . . 21
5.1.2. Request Cancellation . . . . . . . . . . . . . . . . 22
5.2. The CONNECT Method . . . . . . . . . . . . . . . . . . . 22
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5.3. Request Prioritization . . . . . . . . . . . . . . . . . 23
5.3.1. Placeholders . . . . . . . . . . . . . . . . . . . . 24
5.3.2. Priority Tree Maintenance . . . . . . . . . . . . . . 24
5.4. Server Push . . . . . . . . . . . . . . . . . . . . . . . 25
6. Connection Closure . . . . . . . . . . . . . . . . . . . . . 26
6.1. Idle Connections . . . . . . . . . . . . . . . . . . . . 26
6.2. Connection Shutdown . . . . . . . . . . . . . . . . . . . 27
6.3. Immediate Application Closure . . . . . . . . . . . . . . 28
6.4. Transport Closure . . . . . . . . . . . . . . . . . . . . 28
7. Extensions to HTTP/QUIC . . . . . . . . . . . . . . . . . . . 29
8. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 29
8.1. HTTP/QUIC Error Codes . . . . . . . . . . . . . . . . . . 30
9. Security Considerations . . . . . . . . . . . . . . . . . . . 31
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
10.1. Registration of HTTP/QUIC Identification String . . . . 32
10.2. Registration of QUIC Version Hint Alt-Svc Parameter . . 32
10.3. Frame Types . . . . . . . . . . . . . . . . . . . . . . 32
10.4. Settings Parameters . . . . . . . . . . . . . . . . . . 33
10.5. Error Codes . . . . . . . . . . . . . . . . . . . . . . 34
10.6. Stream Types . . . . . . . . . . . . . . . . . . . . . . 37
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 38
11.1. Normative References . . . . . . . . . . . . . . . . . . 38
11.2. Informative References . . . . . . . . . . . . . . . . . 39
11.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . 44
B.1. Since draft-ietf-quic-http-15 . . . . . . . . . . . . . . 44
B.2. Since draft-ietf-quic-http-14 . . . . . . . . . . . . . . 44
B.3. Since draft-ietf-quic-http-13 . . . . . . . . . . . . . . 44
B.4. Since draft-ietf-quic-http-12 . . . . . . . . . . . . . . 45
B.5. Since draft-ietf-quic-http-11 . . . . . . . . . . . . . . 45
B.6. Since draft-ietf-quic-http-10 . . . . . . . . . . . . . . 45
B.7. Since draft-ietf-quic-http-09 . . . . . . . . . . . . . . 45
B.8. Since draft-ietf-quic-http-08 . . . . . . . . . . . . . . 46
B.9. Since draft-ietf-quic-http-07 . . . . . . . . . . . . . . 46
B.10. Since draft-ietf-quic-http-06 . . . . . . . . . . . . . . 46
B.11. Since draft-ietf-quic-http-05 . . . . . . . . . . . . . . 46
B.12. Since draft-ietf-quic-http-04 . . . . . . . . . . . . . . 46
B.13. Since draft-ietf-quic-http-03 . . . . . . . . . . . . . . 47
B.14. Since draft-ietf-quic-http-02 . . . . . . . . . . . . . . 47
B.15. Since draft-ietf-quic-http-01 . . . . . . . . . . . . . . 47
B.16. Since draft-ietf-quic-http-00 . . . . . . . . . . . . . . 47
B.17. Since draft-shade-quic-http2-mapping-00 . . . . . . . . . 48
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 48
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Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 48
1. Introduction
HTTP semantics are used for a broad range of services on the
Internet. These semantics have commonly been used with two different
TCP mappings, HTTP/1.1 and HTTP/2. 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.
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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.
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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 version (from Section 3 of [QUIC-TRANSPORT]) 0x1abadaba,
it could specify the following header field:
Alt-Svc: hq=":49288";quic="1,1abadaba,51303334"
A client acting on this header field would drop the reserved version
(not supported), then attempt to connect to the alternative using the
first version in the list which it does 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
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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 4.2.5) MUST be sent by each
endpoint as the initial frame of their respective HTTP control stream
(see Section 3.2.1). The server MUST NOT process any 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. 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
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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 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 8.1). Streams which terminate
abruptly may be reset at any point in the frame.
HTTP/QUIC does not use server-initiated bidirectional streams;
clients MUST omit or specify a value of zero for the QUIC transport
parameter "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 stream type, which is sent
as a single octet header at the start of the stream. The format and
structure of data that follows this header is determined by the
stream type.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|Stream Type (8)|
+-+-+-+-+-+-+-+-+
Figure 1: Unidirectional Stream Header
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Some stream types are reserved (Section 3.2.3). Two stream types are
defined in 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 value of three or greater for
the QUIC transport parameter "initial_max_uni_streams".
If the stream header indicates a stream type which is not supported
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 frame with an error code of
HTTP_UNKNOWN_STREAM_TYPE, but MUST NOT consider such streams to be an
error of any kind.
Implementations MAY send stream types before knowing whether the peer
supports them. However, stream types which could modify the state or
semantics of existing protocol components, including QPACK or other
extensions, MUST NOT be sent until the peer is known to support them.
3.2.1. Control Streams
The control stream is indicated by a stream type of "0x43" (ASCII
'C'). Data on this stream consists of HTTP/QUIC frames, as defined
in Section 4.2.
Each side MUST initiate a single control stream at the beginning of
the connection and send its SETTINGS frame as the first frame on this
stream. If the first frame of the control stream is any other frame
type, this MUST be treated as a connection error 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 be treated as a connection error of type
HTTP_WRONG_STREAM_COUNT. If the control stream is closed at any
point, this MUST be treated as a connection error of type
HTTP_CLOSED_CRITICAL_STREAM.
A pair of unidirectional streams is used rather than a single
bidirectional stream. This allows either peer to send data 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.
3.2.2. Push Streams
A push stream is indicated by a stream type of "0x50" (ASCII 'P'),
followed by the Push ID of the promise that it fulfills, encoded as a
variable-length integer. The remaining data on this stream consists
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of HTTP/QUIC frames, as defined in Section 4.2, and fulfills a
promised server push. Server push and Push IDs are described in
Section 5.4.
Only servers can push; if a server receives a client-initiated push
stream, this 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 2: 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 client MUST treat this as a connection error of
type HTTP_DUPLICATE_PUSH.
3.2.3. Reserved Stream Types
Stream types of the format "0x1f * N" are reserved to exercise the
requirement that unknown types be ignored. These streams have no
semantic meaning, and can be sent when application-layer padding is
desired. They MAY 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 and length of the stream are selected in any manner the
implementation chooses.
4. HTTP Framing Layer
Frames are used on the control stream, request 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 following format:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (8) | Frame Payload (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: HTTP/QUIC frame format
A frame includes the following fields:
Length: A variable-length integer that describes the length of the
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 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 end of the identified fields MUST
be treated as a connection error of 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 response payload.
DATA frames MUST be associated with an HTTP request or response. If
a DATA frame is received on either control stream, the recipient MUST
respond with a connection error (Section 8) 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 4: DATA frame payload
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 8) of type HTTP_MALFORMED_FRAME.
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4.2.2. HEADERS
The HEADERS frame (type=0x1) is used to carry a header block,
compressed using 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 only be sent on request / push streams.
4.2.3. PRIORITY
The PRIORITY (type=0x02) frame specifies the sender-advised priority
of a stream. In order to ensure that prioritization is processed in
a consistent order, PRIORITY frames MUST be sent on the control
stream. A PRIORITY frame sent on any other stream MUST be treated as
a connection 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|PT |DT |Empty|E| Prioritized Element ID (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Element Dependency ID (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Weight (8) |
+-+-+-+-+-+-+-+-+
Figure 6: PRIORITY frame payload
The PRIORITY 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 the type of element
being depended on.
Empty: A three-bit field which MUST be zero when sent and MUST be
ignored on receipt.
Exclusive: A flag which indicates that the stream dependency is
exclusive (see [RFC7540], Section 5.3).
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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,
the Push ID of a promised resource, or a Placeholder ID of a
placeholder.
Element Dependency ID: A variable-length integer that identifies the
element on which a dependency is being expressed. Depending on
the value of Dependency Type, this contains the Stream ID of a
request stream, the Push ID of a promised resource, the
Placeholder ID of a placeholder, or is ignored. For details of
dependencies, see Section 5.3 and [RFC7540], Section 5.3.
Weight: An unsigned 8-bit integer representing a priority weight for
the stream (see [RFC7540], Section 5.3). Add one to the value to
obtain a weight between 1 and 256.
A PRIORITY frame 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 Prioritized Element Type and Element Dependency
Type imply the interpretation of the associated Element ID 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 the tree | Ignored |
+-----------+------------------+---------------------+
Note that the root of the tree cannot be referenced using a Stream ID
of 0, as in [RFC7540]; QUIC stream 0 carries a valid HTTP request.
The root of the tree cannot be reprioritized. A PRIORITY frame that
prioritizes the root of the tree 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 frame with a Stream ID of any other
type as a connection error of type HTTP_MALFORMED_FRAME.
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A 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 a
server push prior to the push stream being created. The CANCEL_PUSH
frame identifies a 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 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 push stream. If the push stream has been opened
by the server, the server SHOULD send a QUIC RST_STREAM frame on that
stream and cease transmission of the response.
A server can send this frame to indicate that it will not be
fulfilling a promise 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 abort 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.
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 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 that is being
cancelled (see Section 4.2.6).
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.
An endpoint MUST treat a CANCEL_PUSH frame which does not contain
exactly one properly-formatted variable-length integer as a
connection error of type HTTP_MALFORMED_FRAME.
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4.2.5. SETTINGS
The SETTINGS frame (type=0x4) conveys configuration parameters that
affect how endpoints communicate, such 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 referred to as a "setting identifier" and a "setting
value".
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 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
presence of the same parameter more than once as a connection error
of type HTTP_MALFORMED_FRAME.
The payload of a SETTINGS frame consists of zero or more parameters,
each consisting of an unsigned 16-bit setting identifier and a value
which 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 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 considered malformed and trigger a connection
error of type HTTP_MALFORMED_FRAME.
An implementation MUST ignore the contents for any SETTINGS
identifier it does not understand.
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SETTINGS frames always apply to a connection, never a single stream.
A SETTINGS frame MUST be sent as the first frame 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 endpoint MUST respond with
a connection error of type HTTP_WRONG_STREAM. If an endpoint
receives a second SETTINGS frame, the endpoint MUST respond with a
connection error of type HTTP_MALFORMED_FRAME.
The SETTINGS frame affects connection state. A badly formed or
incomplete SETTINGS frame MUST be treated as a connection error
(Section 8) of type HTTP_MALFORMED_FRAME.
4.2.5.1. Defined SETTINGS Parameters
The following settings are defined in HTTP/QUIC:
SETTINGS_NUM_PLACEHOLDERS (0x3): This value SHOULD be non-zero. The
default value is 16.
SETTINGS_MAX_HEADER_LIST_SIZE (0x6): The default value is unlimited.
Setting identifiers of the format "0x?a?a" are reserved to exercise
the requirement that unknown identifiers be ignored. Such settings
have no defined meaning. Endpoints 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 of the 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 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 MUST store the settings the server provided in the
session being resumed and MUST comply with stored settings until the
server's current settings are received. Remembered settings apply to
the new connection until the server's SETTINGS frame is received.
A server can remember the settings that 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 uses the HTTP/QUIC
settings values in determining whether to accept 0-RTT data.
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A server MAY accept 0-RTT and subsequently provide different settings
in its SETTINGS frame. If 0-RTT data is accepted by the server, its
SETTINGS frame MUST NOT reduce any limits or alter any values that
might be violated by the client with its 0-RTT data.
When a 1-RTT QUIC connection is being used, the client MUST NOT send
requests prior to receiving and processing the server's SETTINGS
frame.
4.2.6. PUSH_PROMISE
The PUSH_PROMISE frame (type=0x05) is used to carry a promised
request header set from 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Push ID (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Header Block (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: PUSH_PROMISE frame payload
The payload consists of:
Push ID: A variable-length integer that identifies the 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
promised response. See [QPACK] for more details.
A server MUST NOT use a Push ID that is larger than the client has
provided in a MAX_PUSH_ID frame (Section 4.2.8). A client MUST treat
receipt of a PUSH_PROMISE that contains a larger Push ID than the
client has advertised as a connection error of type
HTTP_MALFORMED_FRAME.
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
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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_FRAME.
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.
4.2.7. 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.
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 10: GOAWAY frame payload
The GOAWAY frame carries a QUIC Stream ID for a client-initiated
bidirectional stream encoded as a variable-length integer. A client
MUST treat receipt of a GOAWAY frame containing a Stream ID of any
other type as a connection error of type HTTP_MALFORMED_FRAME.
Clients do not need to 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 error (Section 8) of type
HTTP_UNEXPECTED_GOAWAY.
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 8) of type
HTTP_WRONG_STREAM.
See Section 6.2 for more information on the use of the GOAWAY frame.
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4.2.8. MAX_PUSH_ID
The MAX_PUSH_ID frame (type=0xD) is used by clients to control the
number of server pushes that the server can initiate. This sets the
maximum value for a Push ID that the server can use in a PUSH_PROMISE
frame. Consequently, this also limits the number of push streams
that the server can initiate in addition to the limit set by 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 as a
connection error of type HTTP_WRONG_STREAM.
A server MUST NOT send a MAX_PUSH_ID frame. A client MUST treat the
receipt of a MAX_PUSH_ID frame as a connection error of type
HTTP_MALFORMED_FRAME.
The maximum Push ID is unset when a connection is created, meaning
that a server cannot push until it receives a MAX_PUSH_ID frame. A
client that wishes to manage the number of promised server pushes can
increase the maximum Push ID 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 (i) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: MAX_PUSH_ID frame payload
The MAX_PUSH_ID frame carries a single variable-length integer that
identifies the maximum value for a Push ID that the server can use
(see Section 4.2.6). A MAX_PUSH_ID frame cannot reduce the maximum
Push ID; receipt of a MAX_PUSH_ID that contains a smaller value than
previously received MUST be treated as a connection error of type
HTTP_MALFORMED_FRAME.
A server MUST treat a MAX_PUSH_ID frame payload that does not contain
a single variable-length integer as a connection error of type
HTTP_MALFORMED_FRAME.
4.2.9. Reserved Frame Types
Frame types of the format "0xb + (0x1f * N)" are reserved to exercise
the requirement that unknown types be ignored (Section 7). These
frames have no semantic value, and can be sent when application-layer
padding is desired. They MAY also be sent on connections where no
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request data is currently being transferred. Endpoints MUST NOT
consider these frames to have any meaning upon receipt.
The 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 on a client-initiated bidirectional
QUIC stream. A server sends an HTTP response on the same stream as
the request.
An HTTP message (request or response) consists of:
1. the message header (see [RFC7230], Section 3.2), sent as a single
HEADERS frame (see Section 4.2.2),
2. the payload body (see [RFC7230], Section 3.3), sent as a series
of DATA frames (see Section 4.2.1),
3. optionally, one HEADERS frame containing the 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 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 to the same request. Non-final responses do
not contain a payload body or trailers.
An HTTP request/response exchange fully consumes a bidirectional QUIC
stream. After sending a request, a client closes the stream for
sending; after sending a final response, the server closes the stream
for sending and the QUIC stream is fully closed. Requests and
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responses are considered complete when the corresponding QUIC stream
is closed in the appropriate direction.
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 triggering a QUIC STOP_SENDING frame with error code
HTTP_EARLY_RESPONSE, sending a complete response, and cleanly closing
its stream. Clients MUST NOT discard complete responses as a result
of having their request terminated abruptly, though clients can
always discard responses at their discretion for other reasons.
Changes to the state of a request stream, including receiving a
RST_STREAM with any error code, do not affect the state of the
server's response. Servers do not abort a response in progress
solely due to a state change on the request stream. However, if the
request stream terminates without containing a usable HTTP request,
the server SHOULD abort its response with the error code
HTTP_INCOMPLETE_REQUEST.
5.1.1. Header Formatting and Compression
HTTP message headers carry information as a series of key-value
pairs, called header fields. For a listing of registered HTTP header
fields, see the "Message Header Field" registry maintained at
https://www.iana.org/assignments/message-headers [4].
Just as 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 and values are discussed in
more detail 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 MUST be treated as
malformed.
As in HTTP/2, HTTP/QUIC uses special pseudo-header fields beginning
with the ':' character (ASCII 0x3a) to convey the target URI, the
method of the request, and the status code for the response. These
pseudo-header fields are defined in Section 8.1.2.3 and 8.1.2.4 of
[RFC7540]. Pseudo-header fields are not HTTP header fields.
Endpoints MUST NOT generate pseudo-header fields other than those
defined in [RFC7540]. The restrictions on 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 as described in [QPACK], a
variation of HPACK which allows the flexibility to avoid header-
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compression-induced head-of-line blocking. See that document for
additional details.
An HTTP/QUIC implementation MAY impose a limit on the maximum size of
the header it will accept on an individual HTTP message. This limit
is conveyed as a number of octets in the
"SETTINGS_MAX_HEADER_LIST_SIZE" parameter. The size of a header list
is calculated based on the uncompressed size of header fields,
including the length of the name and value in octets plus an overhead
of 32 octets for each header field. Encountering a message header
larger than this value SHOULD be 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 stream
(QUIC RST_STREAM and/or STOP_SENDING frames, as appropriate) with an
error code of HTTP_REQUEST_CANCELLED (Section 8.1). When the client
cancels a response, it indicates that this response is no longer of
interest. Implementations SHOULD cancel requests by aborting both
directions of a stream.
When the server aborts its response stream using
HTTP_REQUEST_CANCELLED, it indicates that no application processing
was performed. 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. Servers MUST NOT use the
HTTP_REQUEST_CANCELLED status for requests which were partially or
fully processed.
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 a result.
If a stream is cancelled after receiving a complete response, the
client MAY ignore the cancellation and use the 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 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
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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 request 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.
All DATA frames on the stream correspond to data sent or received on
the TCP connection. Any DATA frame sent by the client is transmitted
by the proxy to the TCP server; data received from the TCP server is
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
ends the request stream (that is, 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 with
the FIN bit set, it will terminate the send stream that it sends to
the 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 of type
HTTP_CONNECT_ERROR (Section 8.1). 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.
5.3. 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 a connection form a
dependency tree. The structure of the dependency tree changes as
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PRIORITY frames add, remove, or change the dependency links between
requests.
The PRIORITY frame Section 4.2.3 identifies a prioritized element.
The elements which can be prioritized are:
o Requests, identified by the ID of the request stream
o Pushes, identified by the Push ID of the promised resource
(Section 4.2.6)
o Placeholders, identified by a Placeholder ID
An element can depend on another element or on the root of the tree.
A reference to an element which is no longer in the tree is treated
as a reference to the root of the tree.
5.3.1. Placeholders
In HTTP/2, certain implementations used closed or unused streams as
placeholders in describing the relative priority of requests.
However, this created confusion as servers could not reliably
identify which elements of the priority tree could safely be
discarded. Clients could potentially reference closed streams long
after the server had discarded state, leading to disparate views of
the prioritization the client had attempted to express.
In HTTP/QUIC, a number of placeholders are explicitly permitted by
the server using the "SETTINGS_NUM_PLACEHOLDERS" setting. Because
the server commits to maintain these IDs in the tree, clients can use
them with confidence that the server will not have discarded the
state.
Placeholders are identified by an ID between zero and one less than
the number of placeholders the server has permitted.
5.3.2. Priority Tree Maintenance
Servers can aggressively prune inactive regions from the priority
tree, because placeholders will be used to "root" any persistent
structure of the tree which the client cares about retaining. For
prioritization purposes, a node in the tree is considered "inactive"
when the corresponding stream has been closed for at least two round-
trip times (using any reasonable estimate available on the server).
This delay helps mitigate race conditions where the server has pruned
a node the client believed was still active and used as a Stream
Dependency.
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Specifically, the server MAY at any time:
o Identify and discard branches of the tree containing only inactive
nodes (i.e. a node with only other inactive nodes as descendants,
along with those descendants)
o Identify and condense interior regions 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 A
Figure 12: Example of Priority Tree Pruning
In the example in Figure 12, "P" represents a Placeholder, "A"
represents an active node, and "I" represents an inactive node. In
the first step, the server discards two inactive branches (each a
single node). In the second step, the server condenses an interior
inactive node. Note that these transformations will result in no
change in the 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 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 unique Push ID. The same Push ID
can be used in one or more PUSH_PROMISE frames (see Section 4.2.6),
then included with the push stream which ultimately fulfills those
promises.
Server push is only enabled on a 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. 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 treat receipt of a push stream with a
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Push ID that is greater than the 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 request stream which generated the push.
This allows the server push to be associated with a client request.
Ordering of a PUSH_PROMISE in relation to certain parts of the
response is important (see Section 8.2.1 of [RFC7540]). Promised
requests MUST conform to the requirements in Section 8.2 of
[RFC7540].
When a server later fulfills a promise, the server push response is
conveyed on a push stream (see Section 3.2.2). The push stream
identifies the Push ID of the promise that it fulfills, then contains
a response to the promised request using the same format described
for responses in Section 5.1.
If a promised server push is not needed by the client, the client
SHOULD send a CANCEL_PUSH frame. If the push stream is already open
or opens after sending the CANCEL_PUSH frame, a QUIC STOP_SENDING
frame with an appropriate error code can also be used (e.g.,
HTTP_PUSH_REFUSED, HTTP_PUSH_ALREADY_IN_CACHE; see Section 8). This
asks the server not to transfer additional data and indicates that it
will be discarded upon receipt.
6. Connection Closure
Once established, an HTTP/QUIC connection can be used for many
requests and responses over time until the connection is closed.
Connection closure can happen in any of several different ways.
6.1. Idle Connections
Each QUIC endpoint declares an idle timeout during the handshake. If
the connection remains idle (no packets received) for longer than
this duration, the peer will assume that the connection has been
closed. HTTP/QUIC implementations will need to open a new connection
for new requests if the existing connection has been idle for longer
than the server's advertised idle timeout, and SHOULD do so if
approaching 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 the client is not expecting a response from the server,
allowing an idle connection to time out is preferred over expending
effort maintaining a connection that might not be needed. A gateway
MAY use PING to maintain connections in anticipation of need rather
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than incur the latency cost of connection establishment to servers.
Servers SHOULD NOT use PING frames to keep a connection open.
6.2. Connection Shutdown
Even when a connection is not idle, either endpoint can decide to
stop using the connection and let the connection close gracefully.
Since clients drive request generation, clients perform a connection
shutdown by not sending additional requests on the connection;
responses and pushed responses associated to previous requests will
continue to completion. Servers perform the same function by
communicating with clients.
Servers initiate the shutdown of a connection by sending a GOAWAY
frame (Section 4.2.7). The GOAWAY frame indicates that client-
initiated requests on lower stream IDs were or might be processed in
this connection, while requests on the indicated stream ID and
greater were not accepted. This enables client and server to agree
on which requests were accepted prior to the connection shutdown.
This identifier MAY be lower than the stream limit identified by a
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 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 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 5.1.2). 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 the Stream ID in the GOAWAY frame
might have been processed; their status cannot be known until they
are completed successfully, reset individually, 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
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server started to process that POST request if the server does not
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 the connection. A server MAY send
multiple GOAWAY frames indicating different 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 a
connection SHOULD send an initial GOAWAY 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. 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 server MAY send another GOAWAY frame with
an updated last Stream ID. This ensures that a 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 HTTP_NO_ERROR code when closing the connection.
6.3. 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 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 connection.
Before closing the connection, a GOAWAY MAY be sent to allow the
client to retry some requests. Including the GOAWAY frame in the
same packet as the QUIC APPLICATION_CLOSE frame improves the chances
of the frame being received by clients.
6.4. Transport Closure
For various reasons, the QUIC transport could indicate to the
application layer that the connection has terminated. This might be
due to an explicit closure by the peer, a transport-level error, or a
change in network topology which interrupts connectivity.
If a connection terminates without a GOAWAY frame, clients MUST
assume that any request which was sent, whether in whole or in part,
might have been processed.
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7. Extensions to HTTP/QUIC
HTTP/QUIC permits extension of the protocol. Within the limitations
described in this section, protocol extensions can be used to provide
additional services or alter any aspect of the protocol. Extensions
are effective only within the scope of a single HTTP/QUIC connection.
This applies to the protocol elements defined in this document. This
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 4.2.5.1), new error codes (Section 8), or new
unidirectional stream types (Section 3.2). Registries are
established for managing these extension points: 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 streams that have unknown or unsupported types.
This means that any of these extension points can be safely used by
extensions without prior arrangement or negotiation.
Extensions that could change the semantics of existing protocol
components MUST be negotiated before being used. For example, an
extension that changes the layout of the HEADERS frame cannot be used
until the peer has given a positive signal that this is acceptable.
In this case, it could also be necessary to coordinate when the
revised layout comes into effect.
This document doesn't mandate a specific method for negotiating the
use of an extension but notes that a setting (Section 4.2.5.1) could
be used for that purpose. If both peers set a value that indicates
willingness to use the extension, then the extension can be used. If
a setting is used for extension negotiation, the default value MUST
be defined in such a fashion that the extension is disabled if the
setting is omitted.
8. 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]. An endpoint MAY choose
to treat a stream error as a connection error.
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This section describes HTTP/QUIC-specific error codes which can be
used to express the cause of a connection or stream error.
8.1. 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 by the transport to be used
in response to QUIC STOP_SENDING frames.
HTTP_NO_ERROR (0x01): No error. This is used when the connection or
stream needs to be closed, but there is no error to signal.
HTTP_PUSH_REFUSED (0x02): The server has attempted to push content
which the client will not accept on this connection.
HTTP_INTERNAL_ERROR (0x03): An internal error has occurred in the
HTTP stack.
HTTP_PUSH_ALREADY_IN_CACHE (0x04): The server has attempted to push
content which the client has cached.
HTTP_REQUEST_CANCELLED (0x05): The client no longer needs 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
a CONNECT request was reset or abnormally closed.
HTTP_EXCESSIVE_LOAD (0x08): The endpoint detected that 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 current
maximum Push ID was referenced.
HTTP_DUPLICATE_PUSH (0x0C): A Push ID was referenced in two
different stream headers.
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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 peer which is not permitted to do so.
HTTP_EARLY_RESPONSE (0x0011): The remainder of the client's request
is not needed to produce a response. For use in STOP_SENDING
only.
HTTP_MISSING_SETTINGS (0x0012): No SETTINGS frame was received at
the beginning 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 is included as the last octet of the error code.
For example, an error in a MAX_PUSH_ID frame would be indicated
with the code (0x10D).
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 and Padding fields in other frames to make a connection more
resistant to traffic analysis, HTTP/QUIC can rely on QUIC PADDING
frames or employ the reserved frame and stream types discussed in
Section 4.2.9 and Section 3.2.3.
When HTTP Alternative Services is used for discovery for HTTP/QUIC
endpoints, the security considerations of [ALTSVC] also apply.
Several protocol elements contain nested length elements, typically
in the form of frames with an explicit length containing variable-
length integers. This could pose a security risk to an incautious
implementer. An implementation MUST ensure that the length of a
frame exactly matches the length of the fields it contains.
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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.
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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 4.2.1 |
| | | |
| HEADERS | 0x1 | Section 4.2.2 |
| | | |
| PRIORITY | 0x2 | Section 4.2.3 |
| | | |
| CANCEL_PUSH | 0x3 | Section 4.2.4 |
| | | |
| SETTINGS | 0x4 | Section 4.2.5 |
| | | |
| PUSH_PROMISE | 0x5 | Section 4.2.6 |
| | | |
| Reserved | 0x6 | N/A |
| | | |
| GOAWAY | 0x7 | Section 4.2.7 |
| | | |
| Reserved | 0x8 | N/A |
| | | |
| Reserved | 0x9 | N/A |
| | | |
| MAX_PUSH_ID | 0xD | Section 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 4.2.9
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.
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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 4.2.5.1 |
| | | |
| Reserved | 0x4 | N/A |
| | | |
| Reserved | 0x5 | N/A |
| | | |
| MAX_HEADER_LIST_SIZE | 0x6 | Section 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 4.2.5.1
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/
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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 8.1 |
| | 1 | | |
| | | | |
| HTTP_PUSH_REFUSED | 0x000 | Client | Section 8.1 |
| | 2 | refused | |
| | | pushed | |
| | | content | |
| | | | |
| HTTP_INTERNAL_ERROR | 0x000 | Internal | Section 8.1 |
| | 3 | error | |
| | | | |
| HTTP_PUSH_ALREADY_IN_CA | 0x000 | Pushed | Section 8.1 |
| CHE | 4 | content | |
| | | already | |
| | | cached | |
| | | | |
| HTTP_REQUEST_CANCELLED | 0x000 | Data no | Section 8.1 |
| | 5 | longer needed | |
| | | | |
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| HTTP_INCOMPLETE_REQUEST | 0x000 | Stream | Section 8.1 |
| | 6 | terminated | |
| | | early | |
| | | | |
| HTTP_CONNECT_ERROR | 0x000 | TCP reset or | Section 8.1 |
| | 7 | error on | |
| | | CONNECT | |
| | | request | |
| | | | |
| HTTP_EXCESSIVE_LOAD | 0x000 | Peer | Section 8.1 |
| | 8 | generating | |
| | | excessive | |
| | | load | |
| | | | |
| HTTP_VERSION_FALLBACK | 0x000 | Retry over | Section 8.1 |
| | 9 | HTTP/1.1 | |
| | | | |
| HTTP_WRONG_STREAM | 0x000 | A frame was | Section 8.1 |
| | A | sent on the | |
| | | wrong stream | |
| | | | |
| HTTP_PUSH_LIMIT_EXCEEDE | 0x000 | Maximum Push | Section 8.1 |
| D | B | ID exceeded | |
| | | | |
| HTTP_DUPLICATE_PUSH | 0x000 | Push ID was | Section 8.1 |
| | C | fulfilled | |
| | | multiple | |
| | | times | |
| | | | |
| HTTP_UNKNOWN_STREAM_TYP | 0x000 | Unknown unidi | Section 8.1 |
| E | D | rectional | |
| | | stream type | |
| | | | |
| HTTP_WRONG_STREAM_COUNT | 0x000 | Too many unid | Section 8.1 |
| | E | irectional | |
| | | streams | |
| | | | |
| HTTP_CLOSED_CRITICAL_ST | 0x000 | Critical | Section 8.1 |
| REAM | F | stream was | |
| | | closed | |
| | | | |
| HTTP_WRONG_STREAM_DIREC | 0x001 | Unidirectiona | Section 8.1 |
| TION | 0 | l stream in | |
| | | wrong | |
| | | direction | |
| | | | |
| HTTP_EARLY_RESPONSE | 0x001 | Remainder of | Section 8.1 |
| | 1 | request not | |
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| | | needed | |
| | | | |
| HTTP_MISSING_SETTINGS | 0x001 | No SETTINGS | Section 8.1 |
| | 2 | frame | |
| | | received | |
| | | | |
| HTTP_MALFORMED_FRAME | 0x01X | Error in | Section 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 3.2.1 | Both |
| | | | |
| Push Stream | 0x50 | Section 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:
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Stream Type: Reserved - GREASE
Specification: Section 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-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-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 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>.
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[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014,
<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.
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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
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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).
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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
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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.
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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 be defined for HTTP/2 and HTTP/QUIC separately.
See Section 10.5.
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-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)
B.3. Since draft-ietf-quic-http-13
o Reserved some frame types for grease (#1333, #1446)
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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)
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)
B.5. Since draft-ietf-quic-http-11
o Moved QPACK table updates and acknowledgments to dedicated streams
(#1121, #1122, #1238)
B.6. Since draft-ietf-quic-http-10
o Settings need to be remembered when attempting and accepting 0-RTT
(#1157, #1207)
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)
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B.8. Since draft-ietf-quic-http-08
o Clarified connection coalescing rules (#940, #1024)
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)
B.10. Since draft-ietf-quic-http-06
o Track changes in QUIC error code usage (#485)
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)
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)
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B.13. Since draft-ietf-quic-http-03
None.
B.14. Since draft-ietf-quic-http-02
o Track changes in transport draft
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)
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)
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o Updated ALPN token and Alt-Svc guidance (#13,#87)
o Application-layer-defined error codes (#19,#74)
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
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