Extensible Prioritization Scheme for HTTP
draft-ietf-httpbis-priority-01

Document Type Active Internet-Draft (httpbis WG)
Last updated 2020-07-12
Replaces draft-kazuho-httpbis-priority
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HTTP                                                              K. Oku
Internet-Draft                                                    Fastly
Intended status: Standards Track                               L. Pardue
Expires: January 14, 2021                                     Cloudflare
                                                           July 13, 2020

               Extensible Prioritization Scheme for HTTP
                     draft-ietf-httpbis-priority-01

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/ [1].

   Working Group information can be found at https://httpwg.org/ [2];
   source code and issues list for this draft can be found at
   https://github.com/httpwg/http-extensions/labels/priorities [3].

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

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   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 January 14, 2021.

Copyright Notice

   Copyright (c) 2020 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  . . . . . . . . . . . . . . . . .   3
   2.  Motivation for Replacing HTTP/2 Priorities  . . . . . . . . .   4
     2.1.  Disabling HTTP/2 Priorities . . . . . . . . . . . . . . .   5
   3.  Priority Parameters . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Urgency . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Incremental . . . . . . . . . . . . . . . . . . . . . . .   7
     3.3.  Defining New Parameters . . . . . . . . . . . . . . . . .   8
   4.  The Priority HTTP Header Field  . . . . . . . . . . . . . . .   8
   5.  Reprioritization  . . . . . . . . . . . . . . . . . . . . . .   8
     5.1.  HTTP/2 PRIORITY_UPDATE Frame  . . . . . . . . . . . . . .   9
     5.2.  HTTP/3 PRIORITY_UPDATE Frame  . . . . . . . . . . . . . .  10
   6.  Merging Client- and Server-Driven Parameters  . . . . . . . .  11
   7.  Client Scheduling . . . . . . . . . . . . . . . . . . . . . .  12
   8.  Fairness  . . . . . . . . . . . . . . . . . . . . . . . . . .  12
     8.1.  Coalescing Intermediaries . . . . . . . . . . . . . . . .  13
     8.2.  HTTP/1.x Back Ends  . . . . . . . . . . . . . . . . . . .  13
     8.3.  Intentional Introduction of Unfairness  . . . . . . . . .  14
   9.  Why use an End-to-End Header Field? . . . . . . . . . . . . .  14
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  15
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  16
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  16
     12.2.  Informative References . . . . . . . . . . . . . . . . .  17
     12.3.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . .  18
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .  18

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