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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
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   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Simplified BSD License.

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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