The CDN-Cache-Control HTTP Response Header Field
draft-cdn-control-header-00

Document Type Active Internet-Draft (individual)
Authors Stephen Ludin  , Mark Nottingham  , Yuchen Wu 
Last updated 2020-11-23
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HTTP                                                            S. Ludin
Internet-Draft                                                    Akamai
Intended status: Informational                             M. Nottingham
Expires: 27 May 2021                                              Fastly
                                                                   Y. Wu
                                                              Cloudflare
                                                        23 November 2020

            The CDN-Cache-Control HTTP Response Header Field
                      draft-cdn-control-header-00

Abstract

   This specification defines an HTTP header field that conveys HTTP
   cache directives to CDN caches.

Note to Readers

   _RFC EDITOR: please remove this section before publication_

   The issues list for this draft can be found at https://github.com/
   cdn-specs/control-header/issues (https://github.com/cdn-specs/
   control-header/issues).

   The most recent (often, unpublished) draft is at https://cdn-
   specs.github.io/control-header/ (https://cdn-specs.github.io/control-
   header/).

   Recent changes are listed at https://github.com/cdn-specs/control-
   header/commits/main (https://github.com/cdn-specs/control-
   header/commits/main).

   See also the draft's current status in the IETF datatracker, at
   https://datatracker.ietf.org/doc/draft-cdn-control-header/
   (https://datatracker.ietf.org/doc/draft-cdn-control-header/).

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/.

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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   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 27 May 2021.

Copyright Notice

   Copyright (c) 2020 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   3
   2.  The CDN-Cache-Control Response Header Field . . . . . . . . .   3
     2.1.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Parsing . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   4.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Appendix A.  Frequently Asked Questions . . . . . . . . . . . . .   6
     A.1.  Why not Surrogate-Control?  . . . . . . . . . . . . . . .   6
     A.2.  Why not mix with Cache-Control? . . . . . . . . . . . . .   6
     A.3.  Is this just for CDNs?  . . . . . . . . . . . . . . . . .   7
     A.4.  What if I use more than one CDN?  . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Many HTTP origin servers use Content Delivery Networks (i.e.,
   distributed HTTP gateways, usually implementing caches) to speed up
   distributing their content.

   While HTTP defines Cache-Control as a means of controlling cache
   behaviour for both private caches and shared caches, it is often
   desirable to give CDN caches separate instructions.  To meet this
   need, this specification defines a separate header field that conveys
   HTTP cache directives to CDN caches only.

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1.1.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
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