Header Compression for HTTP over QUIC
draft-krasic-quic-qcram-00

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QUIC                                                           C. Krasic
Internet-Draft                                                    Google
Intended status: Standards Track                          March 27, 2017
Expires: September 28, 2017

                 Header Compression for HTTP over QUIC
                       draft-krasic-quic-qcram-00

Abstract

   The design of the core QUIC transport and the mapping of HTTP
   semantics over it subsume many HTTP/2 features, prominent among them
   stream multiplexing and HTTP header compression.  A key advantage of
   the QUIC transport is that provides stream multiplexing free of HoL
   blocking between streams, while in HTTP/2 multiplexed streams can
   suffer HoL blocking primarily due to HTTP/2's layering above TCP.
   However, assuming HPACK is used for header compression, HTTP over
   QUIC is still vulnerable to HoL blocking, because of how HPACK
   exploits header redundancies between multiplexed HTTP transactions.
   This draft defines QCRAM, a variation of HPACK and mechanisms in the
   QUIC HTTP mapping that allow QUIC implementations the flexibility to
   avoid header-compression induced HoL blocking.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on September 28, 2017.

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   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

Krasic                 Expires September 28, 2017               [Page 1]
Internet-Draft                    QCRAM                       March 2017

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  QCRAM overview  . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Example of HoL blocking . . . . . . . . . . . . . . . . .   3
     2.2.  How QCRAM avoids HoL blocking . . . . . . . . . . . . . .   3
       2.2.1.  Header Blocks, Fragments, Frames, Packets...  . . . .   4
       2.2.2.  Absolute Indexing . . . . . . . . . . . . . . . . . .   4
   3.  Changes to HPACK and HTTP over QUIC . . . . . . . . . . . . .   5
     3.1.  HPACK changes . . . . . . . . . . . . . . . . . . . . . .   5
       3.1.1.  Indexed representations . . . . . . . . . . . . . . .   5
       3.1.2.  Indexing  . . . . . . . . . . . . . . . . . . . . . .   6
       3.1.3.  Table evictions . . . . . . . . . . . . . . . . . . .   6
     3.2.  HTTP Mapping changes  . . . . . . . . . . . . . . . . . .   6
   4.  Performance considerations  . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The QUIC transport protocol was designed from the outset to support
   HTTP semantics, and its design subsumes most of the features of
   HTTP/2.  Two of those features, stream multiplexing and header
   compression come into some conflict in QUIC.  A key goal of the
   design of QUIC is to improve stream multiplexing relative to HTTP/2,
   by eliminating HoL (head of line) blocking that can occur in HTTP/2.
   HoL blocking can happen because HTTP/2 streams are multiplexed onto a
   single TCP connection with its in-order semantics.  QUIC can maintain
   independence between streams because it implements core transport
   functionality in a fully stream-aware manner.  However, the HTTP over
   QUIC mapping is still subject HoL blocking if HPACK is used directly
   as in HTTP/2.  HPACK exploits multiplexing for greater compression,
   shrinking the representation of headers that have appeared earlier on
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