Declaring Support for HTTP/2 Priorities
draft-lassey-priority-setting-00

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HTTP                                                           B. Lassey
Internet-Draft                                                    Google
Intended status: Standards Track                               L. Pardue
Expires: January 26, 2020                                     Cloudflare
                                                           July 25, 2019

                Declaring Support for HTTP/2 Priorities
                    draft-lassey-priority-setting-00

Abstract

   HTTP/2 provides a prioritization scheme but experience has shown that
   implementation support varies.  This document defines an HTTP/2
   setting that endpoints can use as an affirmative signal to indicate
   their support for HTTP/2 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
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   This Internet-Draft will expire on January 26, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  The SETTINGS_ENABLE_HTTP2_PRIORITIES SETTINGS Parameter . . .   2
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  A New HTTP/2 Setting  . . . . . . . . . . . . . . . . . .   3
   5.  Normative References  . . . . . . . . . . . . . . . . . . . .   3
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   3

1.  Introduction

   The HTTP/2 specification defines a priority scheme in [RFC7540],
   Section 5.3, which some implementers have opted not to fully support.
   The lack of signalling about the status of the implementation has
   caused several implementations to implement heuristics to detect when
   the clients they are connected to do not support priorities as
   defined and take steps to compensate for that.  The intent of this
   draft is to provide and affirmative signalling mechanism for each
   client to communicate whether or not it supports and will use the
   priority scheme as defined in [RFC7540], Section 5.3.

2.  Terminology

   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.

3.  The SETTINGS_ENABLE_HTTP2_PRIORITIES SETTINGS Parameter

   This document adds a new SETTINGS parameter to those defined by
   [RFC7540], Section 6.5.2.

   The new parameter name is SETTINGS_ENABLE_HTTP2_PRIORITIES.  The
   value of the parameter MUST be 0 or 1 to indicate not supporting or
   supporting HTTP/2 priorities respectively.  If either side sends the
   parameter with a value of 0, clients SHOULD NOT send priority frames
   and servers SHOULD NOT make any assumptions based on the presence or
   lack thereof of priority frames.  If both sides send the parameter
   with a value of 1, then both parties MAY use HTTP/2 priorities as
   they see fit.  A sender MUST NOT send the parameter with the value of
   0 after previously sending a value of 1.  If a client or server does
   not send the setting, the peer SHOULD NOT make any assumptions about
   its support for HTTP/2 priorities.

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4.  IANA Considerations

4.1.  A New HTTP/2 Setting

   This document registers an entry in the "HTTP/2 Settings" registry
   that was established by Section 11.3 of [RFC7540].
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