Extensible Prioritization Scheme for HTTP
draft-ietf-httpbis-priority-03

Document Type Active Internet-Draft (httpbis WG)
Authors Kazuho Oku  , Lucas Pardue 
Last updated 2021-01-11
Replaces draft-kazuho-httpbis-priority
Stream Internent Engineering Task Force (IETF)
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HTTP                                                              K. Oku
Internet-Draft                                                    Fastly
Intended status: Standards Track                               L. Pardue
Expires: 15 July 2021                                         Cloudflare
                                                         11 January 2021

               Extensible Prioritization Scheme for HTTP
                     draft-ietf-httpbis-priority-03

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.

Note to Readers

   _RFC EDITOR: please remove this section before publication_

   Discussion of this draft takes place on the HTTP working group
   mailing list (ietf-http-wg@w3.org), which is archived at
   https://lists.w3.org/Archives/Public/ietf-http-wg/
   (https://lists.w3.org/Archives/Public/ietf-http-wg/).

   Working Group information can be found at https://httpwg.org/
   (https://httpwg.org/); source code and issues list for this draft can
   be found at https://github.com/httpwg/http-extensions/labels/
   priorities (https://github.com/httpwg/http-extensions/labels/
   priorities).

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/.

Oku & Pardue              Expires 15 July 2021                  [Page 1]
Internet-Draft               HTTP Priorities                January 2021

   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 15 July 2021.

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/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   4
   2.  Motivation for Replacing HTTP/2 Priorities  . . . . . . . . .   4
     2.1.  Disabling HTTP/2 Priorities . . . . . . . . . . . . . . .   5
   3.  Priority Parameters . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Urgency . . . . . . . . . . . . . . . . . . . . . . . . .   7
     3.2.  Incremental . . . . . . . . . . . . . . . . . . . . . . .   8
     3.3.  Defining New Parameters . . . . . . . . . . . . . . . . .   8
       3.3.1.  Registration  . . . . . . . . . . . . . . . . . . . .   9
   4.  The Priority HTTP Header Field  . . . . . . . . . . . . . . .   9
   5.  Reprioritization  . . . . . . . . . . . . . . . . . . . . . .  10
   6.  The PRIORITY_UPDATE Frame . . . . . . . . . . . . . . . . . .  10
     6.1.  HTTP/2 PRIORITY_UPDATE Frame  . . . . . . . . . . . . . .  11
     6.2.  HTTP/3 PRIORITY_UPDATE Frame  . . . . . . . . . . . . . .  12
   7.  Merging Client- and Server-Driven Parameters  . . . . . . . .  13
   8.  Client Scheduling . . . . . . . . . . . . . . . . . . . . . .  14
   9.  Server Scheduling . . . . . . . . . . . . . . . . . . . . . .  14
   10. Fairness  . . . . . . . . . . . . . . . . . . . . . . . . . .  16
     10.1.  Coalescing Intermediaries  . . . . . . . . . . . . . . .  16
     10.2.  HTTP/1.x Back Ends . . . . . . . . . . . . . . . . . . .  17
     10.3.  Intentional Introduction of Unfairness . . . . . . . . .  17
   11. Why use an End-to-End Header Field? . . . . . . . . . . . . .  17
   12. Security Considerations . . . . . . . . . . . . . . . . . . .  18
   13. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  19
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  20
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