Internet-Draft HTTP Datagram Prioritization July 2021
Pardue Expires 14 January 2022 [Page]
Workgroup:
MASQUE
Internet-Draft:
draft-pardue-masque-dgram-priority-00
Published:
Intended Status:
Standards Track
Expires:
Author:
L. Pardue
Cloudflare

HTTP Datagram Prioritization

Abstract

Application protocols using the QUIC transport protocol rely on streams, and optionally the DATAGRAM extension, to carry application data. Streams and datagrams can be multiplexed but QUIC provides no interoperable prioritization scheme or signaling mechanism itself. The HTTP Extensible Prioritization scheme describes how to prioritize streams in HTTP/2 and HTTP/3. This document adopts the scheme to support HTTP datagrams.

Note tho Readers

RFC EDITOR: please remove this section before publication

Source code and issues list for this draft can be found at https://github.com/LPardue/draft-pardue-masque-dgram-priority.

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 14 January 2022.

Table of Contents

1. Introduction

Application protocols using the QUIC transport protocol [QUIC] rely on streams, and optionally the DATAGRAM extension [DATAGRAM], to carry application data. Streams and datagrams can be multiplexed but QUIC provides no interoperable prioritization scheme or signaling mechanism itself. The HTTP Extensible Prioritization scheme [I-D.ietf-httpbis-priority] describes how to prioritize streams in HTTP/2 and HTTP/3. This document adopts the scheme to support HTTP datagrams [I-D.ietf-masque-h3-datagram].

The Extensible Priorities scheme for HTTP describes how clients can send priority signals related to requests in order to suggest how a server allocates resources to serving responses. When the protocol is HTTP/2, responses are carried on streams. When the protocol is HTTP/3, responses are carries on QUIC streams.

While QUIC streams support multiplexing natively via use of a stream identifier, the QUIC DATAGRAM extension does not provide any such identifier. [I-D.ietf-masque-h3-datagram] defines a set of identifiers that can be controlled and accessed by HTTP. When the protocol is HTTP/2 or HTTP/3, one identifer relates to a request stream. A second, optional, identifer relates to an abstract context. [I-D.ietf-masque-h3-datagram] does not define any means for multiplexed datagram prioritization.

This document describes how the Extensible Priorities scheme applies to HTTP datagrams. Signals sent by clients related to requests can also be considered input to server scheduling decisions regarding HTTP datagrams.

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.

2. Signalling Datagram Priority

The Extensible Prioritization scheme [I-D.ietf-httpbis-priority] provides a framework for communicating and acting upon priority parameters. It defines the urgency and incremental parameters and provides guidance to implementers about how to act on these parameters, in combination with other inputs, to make resource allocation and scheduling choices. Urgency communicates the client-view of request importance and incremental communicates how the client intends to process response data as it arrives. Parameters are communicated in HTTP headers or version-specific frames. Omitting a priority signal indicates to the server to apply default priorities. The core scheme is extensible, new parameters can be defined to augment the base ones.

2.1. Datagram Urgency

The datagram-urgency parameter (du) takes an integer between 0 and 7, in descending order of priority. This range matches the base urgency (u) paramenter range.

The value is encoded as an sf-integer. The default value is 3.

This parameter indicates the sender's recommendation, based on the expectation that the server would transmit HTTP datagrams in the order of their urgency values if possible. The smaller the value, the higher the precedence.

The following example shows a request for a CSS file with the urgency set to 0, any associated datagrams will be delivered with the lower urgency of 2:

:method = GET
:scheme = https
:authority = example.net
:path = /style.css
priority = u=0, du=2

3. Scheduling guidance

TBD - bikeshed

4. Security Considerations

TBD

5. IANA Considerations

TBD

6. References

6.1. Normative References

[DATAGRAM]
Pauly, T., Kinnear, E., and D. Schinazi, "An Unreliable Datagram Extension to QUIC", Work in Progress, Internet-Draft, draft-ietf-quic-datagram-02, , <https://www.ietf.org/archive/id/draft-ietf-quic-datagram-02.txt>.
[I-D.ietf-httpbis-priority]
Oku, K. and L. Pardue, "Extensible Prioritization Scheme for HTTP", Work in Progress, Internet-Draft, draft-ietf-httpbis-priority-03, , <https://www.ietf.org/archive/id/draft-ietf-httpbis-priority-03.txt>.
[I-D.ietf-masque-h3-datagram]
Schinazi, D. and L. Pardue, "Using QUIC Datagrams with HTTP/3", Work in Progress, Internet-Draft, draft-ietf-masque-h3-datagram-02, , <https://www.ietf.org/archive/id/draft-ietf-masque-h3-datagram-02.txt>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.

6.2. Informative References

[QUIC]
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, , <https://www.rfc-editor.org/info/rfc9000>.

Appendix A. Acknowledgements

This document is inspired by discussion by many people across HTTP, QUIC and MASQUE WGs.

Author's Address

Lucas Pardue
Cloudflare