Calendar subscription upgrades
draft-douglass-subscription-upgrade-03

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Last updated 2018-05-05
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Network Working Group                                        M. Douglass
Internet-Draft                                       Spherical Cow Group
Updates: 5545 (if approved)                                  May 5, 2018
Intended status: Standards Track
Expires: November 6, 2018

                     Calendar subscription upgrades
                 draft-douglass-subscription-upgrade-03

Abstract

   This specification introduces an approach to allow subscribers to
   calendar feeds to upgrade to a more performant protocol.

   This specification updates [RFC5545] to add the value DELETED to the
   STATUS property.

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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   This Internet-Draft will expire on November 6, 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

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions Used in This Document . . . . . . . . . . . .   3
   2.  Enhanced GET  . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Deletions . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Changes to the iCalendar specifications . . . . . . . . . . .   6
     3.1.  Redefined Status property . . . . . . . . . . . . . . . .   6
   4.  Discovering alternative access methods  . . . . . . . . . . .   8
   5.  Link relation subscribe-caldav  . . . . . . . . . . . . . . .   8
   6.  Link relation subscribe-caldav-auth . . . . . . . . . . . . .   8
   7.  Link relation subscribe-webdav-sync . . . . . . . . . . . . .   8
   8.  Link relation subscribe-enhanced-get  . . . . . . . . . . . .   9
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   10. Privacy Considerations  . . . . . . . . . . . . . . . . . . .   9
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
     11.1.  Link Relation Registrations  . . . . . . . . . . . . . .   9
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   13. Normative References  . . . . . . . . . . . . . . . . . . . .  10
   Appendix A.  Open issues  . . . . . . . . . . . . . . . . . . . .  11
   Appendix B.  Change log . . . . . . . . . . . . . . . . . . . . .  11
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Currently clients subscribe to calendar feeds as an ics file which is
   often published as a resource accessible using the unofficial
   'webcal' scheme.

   The only available option for updating that resource is the usual
   HTTP polling of cached resources using Etags.

   There is the usual tension between clients wishing to see a timely
   response to changes and servers not wishing to be overloaded by
   frequent requests for possibly large amounts of data.

   This specification introduces an approach whereby clients can
   discover a more performant access method.  Given the location of the
   resource as an ics file, the client can perfom an OPTIONS request on
   the resource and inspect the returned headers which will offer a
   number of alternative access methods.

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   Given that many clients already support CalDAV this provides an easy
   upgrade path for those clients.  CalDAV and DAV subsets are specified
   here to allow lighter weight implementations.

1.1.  Conventions Used in This Document
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