HTTP Representation Variants
draft-ietf-httpbis-variants-03

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HTTP                                                       M. Nottingham
Internet-Draft                                                    Fastly
Updates: 7234 (if approved)                                 July 1, 2018
Intended status: Standards Track
Expires: January 2, 2019

                      HTTP Representation Variants
                     draft-ietf-httpbis-variants-03

Abstract

   This specification introduces an alternative way to communicate a
   secondary cache key for a HTTP resource, using the HTTP "Variants"
   and "Variant-Key" response header fields.  Its aim is to make HTTP
   proactive content negotiation more cache-friendly.

Note to Readers

   _RFC EDITOR: please remove this section before publication_

   Discussion of this draft takes place on the HTTP working group
   mailing list (ietf-http-wg@w3.org), which is archived at
   https://lists.w3.org/Archives/Public/ietf-http-wg/ [1].

   Working Group information can be found at https://httpwg.github.io/
   [2]; source code and issues list for this draft can be found at
   https://github.com/httpwg/http-extensions/labels/variants [3].

   There is a prototype implementation of the algorithms herein at
   https://github.com/mnot/variants-toy [4].

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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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 2, 2019.

Nottingham               Expires January 2, 2019                [Page 1]
Internet-Draft        HTTP Representation Variants             July 2018

Copyright Notice

   Copyright (c) 2018 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 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
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   4
   2.  The "Variants" HTTP Header Field  . . . . . . . . . . . . . .   5
     2.1.  Relationship to Vary  . . . . . . . . . . . . . . . . . .   6
   3.  The "Variant-Key" HTTP Header Field . . . . . . . . . . . . .   7
     3.1.  Generating a Variant-Key List . . . . . . . . . . . . . .   7
   4.  Cache Behaviour . . . . . . . . . . . . . . . . . . . . . . .   8
     4.1.  Compute Possible Keys . . . . . . . . . . . . . . . . . .   9
     4.2.  Check Vary  . . . . . . . . . . . . . . . . . . . . . . .  10
     4.3.  Example of Cache Behaviour  . . . . . . . . . . . . . . .  11
   5.  Origin Server Behaviour . . . . . . . . . . . . . . . . . . .  12
     5.1.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  12
       5.1.1.  Single Variant  . . . . . . . . . . . . . . . . . . .  12
       5.1.2.  Multiple Variants . . . . . . . . . . . . . . . . . .  13
       5.1.3.  Partial Coverage  . . . . . . . . . . . . . . . . . .  14
   6.  Defining Content Negotiation Using Variants . . . . . . . . .  14
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  16
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  16
     9.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .  17
   Appendix A.  Variants for Existing Content Negotiation Mechanisms  17
     A.1.  Accept  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     A.2.  Accept-Encoding . . . . . . . . . . . . . . . . . . . . .  18
     A.3.  Accept-Language . . . . . . . . . . . . . . . . . . . . .  19
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  19
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  20

Nottingham               Expires January 2, 2019                [Page 2]
Internet-Draft        HTTP Representation Variants             July 2018