HTTP Datagram Prioritization

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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.¶

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.¶

: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¶

Appendix A. Acknowledgements

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

Author's Address