HTTP Representation Variants
draft-nottingham-variants-02

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Network Working Group                                      M. Nottingham
Internet-Draft                                                    Fastly
Updates: 7234 (if approved)                            February 13, 2018
Intended status: Standards Track
Expires: August 17, 2018

                      HTTP Representation Variants
                      draft-nottingham-variants-02

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_

   The issues list for this draft can be found at
   https://github.com/mnot/I-D/labels/variants [1].

   The most recent (often, unpublished) draft is at
   https://mnot.github.io/I-D/variants/ [2].

   Recent changes are listed at https://github.com/mnot/I-D/commits/gh-
   pages/variants [3].

   See also the draft's current status in the IETF datatracker, at
   https://datatracker.ietf.org/doc/draft-nottingham-variants/ [4].

   There is a prototype implementation of the algorithms herein at
   https://github.com/mnot/variants-toy [5].

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 https://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

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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 August 17, 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 Normalised Variant-Key . . . . . . . . . . .   7
   4.  Cache Behaviour . . . . . . . . . . . . . . . . . . . . . . .   8
     4.1.  Find Available Keys . . . . . . . . . . . . . . . . . . .   9
     4.2.  Check Vary  . . . . . . . . . . . . . . . . . . . . . . .  10
     4.3.  Example of Cache Behaviour  . . . . . . . . . . . . . . .  10
   5.  Origin Server Behaviour . . . . . . . . . . . . . . . . . . .  11
     5.1.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .  12
       5.1.1.  Single Variant  . . . . . . . . . . . . . . . . . . .  12
       5.1.2.  Multiple Variants . . . . . . . . . . . . . . . . . .  13
       5.1.3.  Partial Coverage  . . . . . . . . . . . . . . . . . .  13
   6.  Defining Content Negotiation Using Variants . . . . . . . . .  14
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  15
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     10.2.  Informative References . . . . . . . . . . . . . . . . .  16
     10.3.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . .  16
   Appendix A.  Variants for Existing Content Negotiation Mechanisms  17
     A.1.  Accept  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     A.2.  Accept-Encoding . . . . . . . . . . . . . . . . . . . . .  17

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     A.3.  Accept-Language . . . . . . . . . . . . . . . . . . . . .  18
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  19