HTTP Browser Hints
draft-nottingham-http-browser-hints-03

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Network Working Group                                      M. Nottingham
Internet-Draft                                             June 20, 2012
Intended status: Informational
Expires: December 22, 2012

                           HTTP Browser Hints
                 draft-nottingham-http-browser-hints-03

Abstract

   Over time, Web browsers have adapted how they use HTTP based upon
   common server configurations and behaviours.  While this is necessary
   in the common case, it can be detrimental for performance and
   interoperability.

   This document establishes a mechanism whereby origin servers can make
   available hints for browsers about their preferences and
   capabilities, without imposing overhead on their interactions or
   requiring support for them.

   This is intended to allow browsers to safely optimise connections to
   servers.

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
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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 December 22, 2012.

Copyright Notice

   Copyright (c) 2012 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

Nottingham              Expires December 22, 2012               [Page 1]
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   (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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  A file format for Browser Hints  . . . . . . . . . . . . . . .  3
     3.1.  The 'prefixlist' Value Type  . . . . . . . . . . . . . . .  4
   4.  Discovering Browser Hints for a Web site . . . . . . . . . . .  4
   5.  Pre-defined Browser Hints  . . . . . . . . . . . . . . . . . .  5
     5.1.  max-conns  . . . . . . . . . . . . . . . . . . . . . . . .  5
     5.2.  pconn-ip . . . . . . . . . . . . . . . . . . . . . . . . .  5
     5.3.  ip-balance . . . . . . . . . . . . . . . . . . . . . . . .  6
     5.4.  connect-timeout  . . . . . . . . . . . . . . . . . . . . .  6
     5.5.  read-timeout . . . . . . . . . . . . . . . . . . . . . . .  6
     5.6.  max-pipeline-depth . . . . . . . . . . . . . . . . . . . .  7
     5.7.  small-hdrs . . . . . . . . . . . . . . . . . . . . . . . .  7
     5.8.  relative-referer . . . . . . . . . . . . . . . . . . . . .  7
     5.9.  chunk-req-bodies . . . . . . . . . . . . . . . . . . . . .  7
     5.10. omit-cookies . . . . . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
     7.1.  The 'browser-hints' Well-Known URI . . . . . . . . . . . .  8
     7.2.  The HTTP Browser Hints Registry  . . . . . . . . . . . . .  8
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     8.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     8.2.  Informative References . . . . . . . . . . . . . . . . . .  9
   Appendix A.  Acknowledgements  . . . . . . . . . . . . . . . . . .  9
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10

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1.  Introduction

   HTTP [RFC2616] clients -- especially browsers -- typically use
   hardcoded values or heuristics to determine how many TCP connections
   to use to a server, based on common-case server behaviours and
   limitations.

   Likewise, they often send voluminous request headers (e.g., in User-
   Agent and Allow) because they fear that changing those headers'
   values will break some sites that depend upon specific values.

   These are just two examples of common, conservative behaviour by
   browsers that is good for interoperability, but potentially bad for
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