Extensible Prioritization Scheme for HTTP
draft-kazuho-httpbis-priority-04
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HTTP K. Oku
Internet-Draft Fastly
Intended status: Standards Track L. Pardue
Expires: May 23, 2020 Cloudflare
November 20, 2019
Extensible Prioritization Scheme for HTTP
draft-kazuho-httpbis-priority-04
Abstract
This document describes a scheme for prioritizing HTTP responses.
This scheme expresses the priority of each HTTP response using
absolute values, rather than as a relative relationship between a
group of HTTP responses.
This document defines the Priority header field for communicating the
initial priority in an HTTP version-independent manner, as well as
HTTP/2 and HTTP/3 frames for reprioritizing the responses. These
share a common format structure that is designed to provide future
extensibility.
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
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Drafts is at https://datatracker.ietf.org/drafts/current/.
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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 May 23, 2020.
Copyright Notice
Copyright (c) 2019 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
Oku & Pardue Expires May 23, 2020 [Page 1]
Internet-Draft Extensible Prioritization Scheme for HTTP November 2019
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. Motivation for Replacing HTTP/2 Priorities . . . . . . . . . 4
2.1. Disabling HTTP/2 Priorities . . . . . . . . . . . . . . . 5
3. Priority Parameters . . . . . . . . . . . . . . . . . . . . . 6
3.1. urgency . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1.1. prerequisite . . . . . . . . . . . . . . . . . . . . 7
3.1.2. default . . . . . . . . . . . . . . . . . . . . . . . 7
3.1.3. supplementary . . . . . . . . . . . . . . . . . . . . 7
3.1.4. background . . . . . . . . . . . . . . . . . . . . . 8
3.2. incremental . . . . . . . . . . . . . . . . . . . . . . . 8
3.3. Defining New Parameters . . . . . . . . . . . . . . . . . 9
4. The Priority HTTP Header Field . . . . . . . . . . . . . . . 9
5. Reprioritization . . . . . . . . . . . . . . . . . . . . . . 9
5.1. HTTP/2 PRIORITY_UPDATE Frame . . . . . . . . . . . . . . 10
5.2. HTTP/3 PRIORITY_UPDATE Frame . . . . . . . . . . . . . . 11
6. Merging Client- and Server-Driven Parameters . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7.1. Fairness . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1.1. Coalescing Intermediaries . . . . . . . . . . . . . . 13
7.1.2. HTTP/1.x Back Ends . . . . . . . . . . . . . . . . . 14
7.1.3. Intentional Introduction of Unfairness . . . . . . . 15
8. Considerations . . . . . . . . . . . . . . . . . . . . . . . 15
8.1. Why use an End-to-End Header Field? . . . . . . . . . . . 15
8.2. Why do Urgencies Have Meanings? . . . . . . . . . . . . . 15
8.3. Can an Intermediary Send its own Signal? . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . 17
10.2. Informative References . . . . . . . . . . . . . . . . . 18
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 19
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 19
B.1. Since draft-kazuho-httpbis-priority-03 . . . . . . . . . 20
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