Header Compression for HTTP/QUIC
draft-bishop-quic-http-and-qpack-02

Document Type Active Internet-Draft (individual)
Last updated 2017-02-08
Stream (None)
Intended RFC status (None)
Formats plain text xml pdf html bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
QUIC Working Group                                             M. Bishop
Internet-Draft                                                 Microsoft
Intended status: Standards Track                        February 8, 2017
Expires: August 12, 2017

                    Header Compression for HTTP/QUIC
                  draft-bishop-quic-http-and-qpack-02

Abstract

   HTTP/2 [RFC7540] uses HPACK [RFC7541] for header compression.
   However, HPACK relies on the in-order message-based semantics of the
   HTTP/2 framing layer in order to function.  Messages can only be
   successfully decoded if processed by the decoder in the same order as
   generated by the encoder.  This draft refines HPACK to loosen the
   ordering requirements for use over QUIC [I-D.ietf-quic-transport].

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 http://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
   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 August 12, 2017.

Copyright Notice

   Copyright (c) 2017 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
   (http://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

Bishop                   Expires August 12, 2017                [Page 1]
Internet-Draft                    QPACK                    February 2017

   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  QPACK . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Basic model . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Changes to Static and Dynamic Tables  . . . . . . . . . .   4
       2.2.1.  Changes to Header Table Size  . . . . . . . . . . . .   4
       2.2.2.  Dynamic Table State Synchronization . . . . . . . . .   5
     2.3.  Format of Header Management stream  . . . . . . . . . . .   6
       2.3.1.  Insert  . . . . . . . . . . . . . . . . . . . . . . .   6
       2.3.2.  Delete  . . . . . . . . . . . . . . . . . . . . . . .   7
       2.3.3.  Delete-Ack  . . . . . . . . . . . . . . . . . . . . .  10
     2.4.  Format of Encoded Headers on Message Streams  . . . . . .  10
       2.4.1.  Indexed Header Field Representation . . . . . . . . .  10
       2.4.2.  Literal Header Field Representation . . . . . . . . .  11
   3.  Use in HTTP/QUIC  . . . . . . . . . . . . . . . . . . . . . .  12
   4.  Performance Considerations  . . . . . . . . . . . . . . . . .  12
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .  14
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   HPACK has a number of features that were intended to provide
   performance advantages to HTTP/2, but which don't live well in an
   out-of-order environment such as that provided by QUIC.

   The largest challenge is the fact that elements are referenced by a
   very fluid index.  Not only is the index implicit when an item is
   added to the header table, the index will change without notice as
   other items are added to the header table.  Static entries occupy the
   first 61 values, followed by dynamic entries.  A newly-added dynamic
   entry would cause older dynamic entries to be evicted, and the
   retained items are then renumbered beginning with 62.  This means
   that, without processing all preceding header sets, no index into the
   dynamic table can be interpreted, and the index of a given entry
   cannot be predicted.

   Any solution to the above will almost certainly fall afoul of the
Show full document text