Cache Digests for HTTP/2
draft-ietf-httpbis-cache-digest-04

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HTTP Working Group                                                K. Oku
Internet-Draft                                                    Fastly
Intended status: Experimental                                   Y. Weiss
Expires: October 8, 2018                                          Akamai
                                                           April 6, 2018

                        Cache Digests for HTTP/2
                   draft-ietf-httpbis-cache-digest-04

Abstract

   This specification defines a HTTP/2 frame type to allow clients to
   inform the server of their cache's contents.  Servers can then use
   this to inform their choices of what to push to clients.

Note to Readers

   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/ .

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

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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   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 October 8, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Oku & Weiss              Expires October 8, 2018                [Page 1]
Internet-Draft          Cache Digests for HTTP/2              April 2018

   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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
   2.  The CACHE_DIGEST Frame  . . . . . . . . . . . . . . . . . . .   3
     2.1.  Client Behavior . . . . . . . . . . . . . . . . . . . . .   4
       2.1.1.  Creating a digest . . . . . . . . . . . . . . . . . .   5
       2.1.2.  Adding a URL to the Digest-Value  . . . . . . . . . .   6
       2.1.3.  Removing a URL to the Digest-Value  . . . . . . . . .   7
       2.1.4.  Computing a fingerprint value . . . . . . . . . . . .   8
       2.1.5.  Computing the key . . . . . . . . . . . . . . . . . .   9
       2.1.6.  Computing a Hash Value  . . . . . . . . . . . . . . .  10
       2.1.7.  Computing an Alternative Hash Value . . . . . . . . .  10
     2.2.  Server Behavior . . . . . . . . . . . . . . . . . . . . .  10
       2.2.1.  Querying the Digest for a Value . . . . . . . . . . .  11
   3.  The SENDING_CACHE_DIGEST SETTINGS Parameter . . . . . . . . .  12
   4.  The ACCEPT_CACHE_DIGEST SETTINGS Parameter  . . . . . . . . .  12
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Appendix A.  Encoding the CACHE_DIGEST frame as an HTTP Header  .  16
   Appendix B.  Acknowledgements . . . . . . . . . . . . . . . . . .  17
   Appendix C.  Changes  . . . . . . . . . . . . . . . . . . . . . .  17
     C.1.  Since draft-ietf-httpbis-cache-digest-03  . . . . . . . .  17
     C.2.  Since draft-ietf-httpbis-cache-digest-02  . . . . . . . .  17
     C.3.  Since draft-ietf-httpbis-cache-digest-01  . . . . . . . .  17
     C.4.  Since draft-ietf-httpbis-cache-digest-00  . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   HTTP/2 [RFC7540] allows a server to "push" synthetic request/response
   pairs into a client's cache optimistically.  While there is strong
   interest in using this facility to improve perceived Web browsing
   performance, it is sometimes counterproductive because the client