Internet DRAFT - draft-schinazi-masque-h3-datagram
draft-schinazi-masque-h3-datagram
Network Working Group D. Schinazi
Internet-Draft Google LLC
Intended status: Standards Track L. Pardue
Expires: 9 July 2021 Cloudflare
5 January 2021
Using QUIC Datagrams with HTTP/3
draft-schinazi-masque-h3-datagram-04
Abstract
The QUIC DATAGRAM extension provides application protocols running
over QUIC with a mechanism to send unreliable data while leveraging
the security and congestion-control properties of QUIC. However,
QUIC DATAGRAM frames do not provide a means to demultiplex
application contexts. This document defines how to use QUIC DATAGRAM
frames when the application protocol running over QUIC is HTTP/3 by
adding an identifier at the start of the frame payload. This allows
HTTP messages to convey related information using unreliable DATAGRAM
frames, ensuring those frames are properly associated with an HTTP
message.
Discussion of this work is encouraged to happen on the MASQUE IETF
mailing list (masque@ietf.org (mailto:masque@ietf.org)) or on the
GitHub repository which contains the draft:
https://github.com/DavidSchinazi/draft-h3-datagram.
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-
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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 9 July 2021.
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Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions and Definitions . . . . . . . . . . . . . . . 3
2. Flow Identifiers . . . . . . . . . . . . . . . . . . . . . . 3
3. Flow Identifier Allocation . . . . . . . . . . . . . . . . . 3
4. HTTP/3 DATAGRAM Frame Format . . . . . . . . . . . . . . . . 4
5. The H3_DATAGRAM HTTP/3 SETTINGS Parameter . . . . . . . . . . 4
6. Datagram-Flow-Id Header Field Definition . . . . . . . . . . 5
7. HTTP Intermediaries . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9.1. HTTP SETTINGS Parameter . . . . . . . . . . . . . . . . . 7
9.2. HTTP Header Field . . . . . . . . . . . . . . . . . . . . 8
9.3. Flow Identifier Parameters . . . . . . . . . . . . . . . 8
10. Normative References . . . . . . . . . . . . . . . . . . . . 8
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
The QUIC DATAGRAM extension [DGRAM] provides application protocols
running over QUIC [QUIC] with a mechanism to send unreliable data
while leveraging the security and congestion-control properties of
QUIC. However, QUIC DATAGRAM frames do not provide a means to
demultiplex application contexts. This document defines how to use
QUIC DATAGRAM frames when the application protocol running over QUIC
is HTTP/3 [H3] by adding an identifier at the start of the frame
payload. This allows HTTP messages to convey related information
using unreliable DATAGRAM frames, ensuring those frames are properly
associated with an HTTP message.
This design mimics the use of Stream Types in HTTP/3, which provide a
demultiplexing identifier at the start of each unidirectional stream.
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Discussion of this work is encouraged to happen on the MASQUE IETF
mailing list (masque@ietf.org (mailto:masque@ietf.org)) or on the
GitHub repository which contains the draft:
https://github.com/DavidSchinazi/draft-h3-datagram.
1.1. Conventions and Definitions
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.
2. Flow Identifiers
Flow identifiers represent bidirectional flows of datagrams within a
single QUIC connection. These are conceptually similar to streams in
the sense that they allow multiplexing of application data. Flows
lack any of the ordering or reliability guarantees of streams.
Beyond this, a sender SHOULD ensure that DATAGRAM frames within a
single flow are transmitted in order relative to one another. If
multiple DATAGRAM frames can be packed into a single QUIC packet, the
sender SHOULD group them by flow identifier to promote fate-sharing
within a specific flow and improve the ability to process batches of
datagram messages efficiently on the receiver.
3. Flow Identifier Allocation
Implementations of HTTP/3 that support the DATAGRAM extension MUST
provide a flow identifier allocation service. That service will
allow applications co-located with HTTP/3 to request a unique flow
identifier that they can subsequently use for their own purposes.
The HTTP/3 implementation will then parse the flow identifier of
incoming DATAGRAM frames and use it to deliver the frame to the
appropriate application.
Even-numbered flow identifiers are client-initiated, while odd-
numbered flow identifiers are server-initiated. This means that an
HTTP/3 client implementation of the flow identifier allocation
service MUST only provide even-numbered identifiers, while a server
implementation MUST only provide odd-numbered identifiers. Note
that, once allocated, any flow identifier can be used by both client
and server - only allocation carries separate namespaces to avoid
requiring synchronization.
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The flow allocation service SHOULD also provide a mechanism for
applications to indicate they have completed their usage of a flow
identifier and will no longer be using that flow identifier, this
process is called "retiring" a flow identifier. Applications MUST
NOT retire a flow identifier until after they have received
confirmation that the peer has also stopped using that flow
identifier. The flow identifier allocation service MAY reuse
previously retired flow identifiers once they have ascertained that
there are no packets with DATAGRAM frames using that flow identifier
still in flight. Reusing flow identifiers can improve performance by
transmitting the flow identifier using a shorter variable-length
integer encoding.
4. HTTP/3 DATAGRAM Frame Format
When used with HTTP/3, the Datagram Data field of QUIC DATAGRAM
frames uses the following format (using the notation from the
"Notational Conventions" section of [QUIC]):
HTTP/3 DATAGRAM Frame {
Flow Identifier (i),
HTTP/3 Datagram Payload (..),
}
Figure 1: HTTP/3 DATAGRAM Frame Format
Flow Identifier: A variable-length integer indicating the Flow
Identifier of the datagram (see Section 2).
HTTP/3 Datagram Payload: The payload of the datagram, whose
semantics are defined by individual applications. Note that this
field can be empty.
Endpoints MUST treat receipt of a DATAGRAM frame whose payload is too
short to parse the flow identifier as an HTTP/3 connection error of
type H3_GENERAL_PROTOCOL_ERROR.
5. The H3_DATAGRAM HTTP/3 SETTINGS Parameter
Implementations of HTTP/3 that support this mechanism can indicate
that to their peer by sending the H3_DATAGRAM SETTINGS parameter with
a value of 1. The value of the H3_DATAGRAM SETTINGS parameter MUST
be either 0 or 1. A value of 0 indicates that this mechanism is not
supported. An endpoint that receives the H3_DATAGRAM SETTINGS
parameter with a value that is neither 0 or 1 MUST terminate the
connection with error H3_SETTINGS_ERROR.
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An endpoint that sends the H3_DATAGRAM SETTINGS parameter with a
value of 1 MUST send the max_datagram_frame_size QUIC Transport
Parameter [DGRAM]. An endpoint that receives the H3_DATAGRAM
SETTINGS parameter with a value of 1 on a QUIC connection that did
not also receive the max_datagram_frame_size QUIC Transport Parameter
MUST terminate the connection with error H3_SETTINGS_ERROR.
When clients use 0-RTT, they MAY store the value of the server's
H3_DATAGRAM SETTINGS parameter. Doing so allows the client to use
HTTP/3 datagrams in 0-RTT packets. When servers decide to accept
0-RTT data, they MUST send a H3_DATAGRAM SETTINGS parameter greater
than or equal to the value they sent to the client in the connection
where they sent them the NewSessionTicket message. If a client
stores the value of the H3_DATAGRAM SETTINGS parameter with their
0-RTT state, they MUST validate that the new value of the H3_DATAGRAM
SETTINGS parameter sent by the server in the handshake is greater
than or equal to the stored value; if not, the client MUST terminate
the connection with error H3_SETTINGS_ERROR. In all cases, the
maximum permitted value of the H3_DATAGRAM SETTINGS parameter is 1.
6. Datagram-Flow-Id Header Field Definition
"Datagram-Flow-Id" is a List Structured Field [STRUCT-FIELD], whose
members MUST all be Items of type Integer. Its ABNF is:
Datagram-Flow-Id = sf-list
The "Datagram-Flow-Id" header field is used to associate one or more
datagram flow identifiers with an HTTP message. As a simple example
using a single identifier, the definition of an HTTP method could
instruct the client to use its flow identifier allocation service to
allocate a new flow identifier, and then the client will add the
"Datagram-Flow-Id" header field to its request to communicate that
value to the server. In this example, the resulting header field
could look like:
Datagram-Flow-Id = 2
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List members are flow identifier elements, which can be named or
unnamed. One element in the list is allowed to be unnamed, but all
but one elements MUST carry a name. The name of an element is
encoded in the key of the first parameter of that element (parameters
are defined in Section 3.1.2 of [STRUCT-FIELD]). Each name MUST NOT
appear more than once in the list. The value of the first parameter
of each named element (whose corresponding key conveys the element
name) MUST be of type Boolean and equal to true. The value of the
first parameter of the unnamed element MUST NOT be of type Boolean.
The ordering of the list does not carry any semantics. For example,
an HTTP method that wishes to use four datagram flow identifiers for
the lifetime of its request stream could look like this:
Datagram-Flow-Id = 42, 44; ecn-ect0, 46; ecn-ect1, 48; ecn-ce
In this example, 42 is the unnamed flow identifier, 44 represents the
name "ecn-ect0", 46 represents "ecn-ect1", and 48 represents "ecn-
ce". Note that, since the list ordering does not carry semantics,
this example can be equivalently encoded as:
Datagram-Flow-Id = 44; ecn-ect0, 42, 48; ecn-ce, 46; ecn-ect1
Even if a sender attempts to communicate the meaning of a flow
identifier before it uses it in an HTTP/3 datagram, it is possible
that its peer will receive an HTTP/3 datagram with a flow identifier
that it does not know as it has not yet received the corresponding
"Datagram-Flow-Id" header field. (For example, this could happen if
the QUIC STREAM frame that contains the "Datagram-Flow-Id" header
field is reordered and arrives afer the DATAGRAM frame.) Endpoints
MUST NOT treat that scenario as an error; they MUST either silently
discard the datagram or buffer it until they receive the "Datagram-
Flow-Id" header field.
Distinct HTTP requests MAY refer to the same flow identifier in their
respective "Datagram-Flow-Id" header fields.
Note that integer structured fields can only encode values up to
10^15-1, therefore the maximum possible value of an element of the
"Datagram-Flow-Id" header field is lower then the theoretical maximum
value of a flow identifier which is 2^62-1 due to the QUIC variable
length integer encoding. If the flow identifier allocation service
of an endpoint runs out of values lower than 10^15-1, the endpoint
MUST fail the flow identifier allocation. An HTTP message that
carries a "Datagram-Flow-Id" header field with a flow identifier
value above 10^15-1 is malformed (see Section 8.1.2.6 of [H2]).
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7. HTTP Intermediaries
HTTP/3 DATAGRAM flow identifiers are specific to a given HTTP/3
connection. However, in some cases, an HTTP request may travel
across multiple HTTP connections if there are HTTP intermediaries
involved; see Section 2.3 of [RFC7230].
If an intermediary has sent the H3_DATAGRAM SETTINGS parameter with a
value of 1 on its client-facing connection, it MUST inspect all HTTP
requests from that connection and check for the presence of the
"Datagram-Flow-Id" header field. If the HTTP method of the request
is not supported by the intermediary, it MUST remove the "Datagram-
Flow-Id" header field before forwarding the request. If the
intermediary supports the method, it MUST either remove the header
field or adhere to the requirements leveraged by that method on
intermediaries.
If an intermediary has sent the H3_DATAGRAM SETTINGS parameter with a
value of 1 on its server-facing connection, it MUST inspect all HTTP
responses from that connection and check for the presence of the
"Datagram-Flow-Id" header field. If the HTTP method of the request
is not supported by the intermediary, it MUST remove the "Datagram-
Flow-Id" header field before forwarding the response. If the
intermediary supports the method, it MUST either remove the header
field or adhere to the requirements leveraged by that method on
intermediaries.
If an intermediary processes distinct HTTP requests that refer to the
same flow identifier in their respective "Datagram-Flow-Id" header
fields, it MUST ensure that those requests are routed to the same
backend.
8. Security Considerations
This document does not have additional security considerations beyond
those defined in [QUIC] and [DGRAM].
9. IANA Considerations
9.1. HTTP SETTINGS Parameter
This document will request IANA to register the following entry in
the "HTTP/3 Settings" registry:
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+--------------+-------+---------------+---------+
| Setting Name | Value | Specification | Default |
+==============+=======+===============+=========+
| H3_DATAGRAM | 0x276 | This Document | 0 |
+--------------+-------+---------------+---------+
9.2. HTTP Header Field
This document will request IANA to register the "Datagram-Flow-Id"
header field in the "Permanent Message Header Field Names" registry
maintained at <https://www.iana.org/assignments/message-headers>.
+-------------------+----------+--------+---------------+
| Header Field Name | Protocol | Status | Reference |
+-------------------+----------+--------+---------------+
| Datagram-Flow-Id | http | std | This document |
+-------------------+----------+--------+---------------+
9.3. Flow Identifier Parameters
This document will request IANA to create an "HTTP Datagram Flow
Identifier Parameters" registry. Registrations in this registry MUST
include the following fields:
Key: The key of a parameter that is associated with a datagram flow
identifier list member (see Section 6). Keys MUST be valid
structured field parameter keys (see Section 3.1.2 of
[STRUCT-FIELD]).
Description: A brief description of the parameter semantics, which
MAY be a summary if a specification reference is provided.
Is Name: This field MUST be either Yes or No. Yes indicates that
this parameter is the name of a named element (see Section 6). No
indicates that it is a parameter that is not a name.
Reference: An optional reference to a specification for the
parameter. This field MAY be empty.
Registrations follow the "First Come First Served" policy (see
Section 4.4 of [IANA-POLICY]) where two registrations MUST NOT have
the same Key. This registry is initially empty.
10. Normative References
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[DGRAM] Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable
Datagram Extension to QUIC", Work in Progress, Internet-
Draft, draft-ietf-quic-datagram-01, 24 August 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-quic-
datagram-01.txt>.
[H2] 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>.
[H3] Bishop, M., "Hypertext Transfer Protocol Version 3
(HTTP/3)", Work in Progress, Internet-Draft, draft-ietf-
quic-http-33, 15 December 2020, <http://www.ietf.org/
internet-drafts/draft-ietf-quic-http-33.txt>.
[IANA-POLICY]
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>.
[QUIC] Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
and Secure Transport", Work in Progress, Internet-Draft,
draft-ietf-quic-transport-33, 13 December 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-quic-
transport-33.txt>.
[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>.
[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>.
[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>.
[STRUCT-FIELD]
Nottingham, M. and P. Kamp, "Structured Field Values for
HTTP", Work in Progress, Internet-Draft, draft-ietf-
httpbis-header-structure-19, 3 June 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-httpbis-
header-structure-19.txt>.
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Acknowledgments
The DATAGRAM flow identifier was previously part of the DATAGRAM
frame definition itself, the author would like to acknowledge the
authors of that document and the members of the IETF MASQUE working
group for their suggestions. Additionally, the author would like to
thank Martin Thomson for suggesting the use of an HTTP/3 SETTINGS
parameter.
Authors' Addresses
David Schinazi
Google LLC
1600 Amphitheatre Parkway
Mountain View, California 94043,
United States of America
Email: dschinazi.ietf@gmail.com
Lucas Pardue
Cloudflare
Email: lucaspardue.24.7@gmail.com
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