Hypertext Transfer Protocol Version 2 (HTTP/2)
draft-thomson-httpbis-http2bis-00

Document Type Active Internet-Draft (individual)
Author Martin Thomson 
Last updated 2020-08-28
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HTTPbis                                                  M. Thomson, Ed.
Internet-Draft                                                   Mozilla
Obsoletes: 7540 (if approved)                             28 August 2020
Intended status: Standards Track                                        
Expires: 1 March 2021

             Hypertext Transfer Protocol Version 2 (HTTP/2)
                   draft-thomson-httpbis-http2bis-00

Abstract

   This specification describes an optimized expression of the semantics
   of the Hypertext Transfer Protocol (HTTP), referred to as HTTP
   version 2 (HTTP/2).  HTTP/2 enables a more efficient use of network
   resources and a reduced perception of latency by introducing header
   field compression and allowing multiple concurrent exchanges on the
   same connection.  It also introduces unsolicited push of
   representations from servers to clients.

   This specification is an alternative to, but does not obsolete, the
   HTTP/1.1 message syntax.  HTTP's existing semantics remain unchanged.

Discussion Venues

   Discussion of this document takes place on the HTTPBIS Working Group
   mailing list (ietf-http-wg@w3.org), which is archived at
   https://lists.w3.org/Archives/Public/ietf-http-wg/.

   This note is to be removed before publishing as an RFC.

   Source for this draft and an issue tracker can be found at
   https://github.com/martinthomson/http2-spec.

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/.

   Internet-Drafts are draft documents valid for a maximum of six months
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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."

Thomson                   Expires 1 March 2021                  [Page 1]
Internet-Draft                   HTTP/2                      August 2020

   This Internet-Draft will expire on 1 March 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
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  HTTP/2 Protocol Overview  . . . . . . . . . . . . . . . . . .   5
     2.1.  Document Organization . . . . . . . . . . . . . . . . . .   6
     2.2.  Conventions and Terminology . . . . . . . . . . . . . . .   6
   3.  Starting HTTP/2 . . . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  HTTP/2 Version Identification . . . . . . . . . . . . . .   7
     3.2.  Starting HTTP/2 for "http" URIs . . . . . . . . . . . . .   8
       3.2.1.  HTTP2-Settings Header Field . . . . . . . . . . . . .   9
     3.3.  Starting HTTP/2 for "https" URIs  . . . . . . . . . . . .  10
     3.4.  Starting HTTP/2 with Prior Knowledge  . . . . . . . . . .  10
     3.5.  HTTP/2 Connection Preface . . . . . . . . . . . . . . . .  11
   4.  HTTP Frames . . . . . . . . . . . . . . . . . . . . . . . . .  12
     4.1.  Frame Format  . . . . . . . . . . . . . . . . . . . . . .  12
     4.2.  Frame Size  . . . . . . . . . . . . . . . . . . . . . . .  13
     4.3.  Header Compression and Decompression  . . . . . . . . . .  14
   5.  Streams and Multiplexing  . . . . . . . . . . . . . . . . . .  15
     5.1.  Stream States . . . . . . . . . . . . . . . . . . . . . .  15
       5.1.1.  Stream Identifiers  . . . . . . . . . . . . . . . . .  21
       5.1.2.  Stream Concurrency  . . . . . . . . . . . . . . . . .  21
     5.2.  Flow Control  . . . . . . . . . . . . . . . . . . . . . .  22
       5.2.1.  Flow-Control Principles . . . . . . . . . . . . . . .  22
       5.2.2.  Appropriate Use of Flow Control . . . . . . . . . . .  23
     5.3.  Stream Priority . . . . . . . . . . . . . . . . . . . . .  24
       5.3.1.  Stream Dependencies . . . . . . . . . . . . . . . . .  25
       5.3.2.  Dependency Weighting  . . . . . . . . . . . . . . . .  26
       5.3.3.  Reprioritization  . . . . . . . . . . . . . . . . . .  26
       5.3.4.  Prioritization State Management . . . . . . . . . . .  27
       5.3.5.  Default Priorities  . . . . . . . . . . . . . . . . .  28
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