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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group M. Douglass 3 Internet-Draft Spherical Cow Group 4 Updates: 5545,5546 (if approved) February 13, 2017 5 Intended status: Standards Track 6 Expires: August 17, 2017 8 Calendar subscription upgrades 9 draft-douglass-subscription-upgrade-00 11 Abstract 13 This specification introduces an approach to allow subscribers to 14 calendar feeds to upgrade to a more performant protocol. 16 Status of This Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at http://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on August 17, 2017. 33 Copyright Notice 35 Copyright (c) 2017 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 51 1.1. Conventions Used in This Document . . . . . . . . . . . . 2 52 2. Changes to the iCalendar specifications . . . . . . . . . . . 3 53 3. Link Header . . . . . . . . . . . . . . . . . . . . . . . . . 3 54 4. Link relation subscribe-caldav . . . . . . . . . . . . . . . 3 55 5. Link relation subscribe-caldav-auth . . . . . . . . . . . . . 3 56 6. Link relation subscribe-webdav-sync . . . . . . . . . . . . . 3 57 7. Link relation subscribe-something-else . . . . . . . . . . . 4 58 8. Security Considerations . . . . . . . . . . . . . . . . . . . 4 59 9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 4 60 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 61 10.1. Link Relation Registrations . . . . . . . . . . . . . . 4 62 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 63 12. Normative References . . . . . . . . . . . . . . . . . . . . 5 64 Appendix A. Open issues . . . . . . . . . . . . . . . . . . . . 6 65 Appendix B. Change log . . . . . . . . . . . . . . . . . . . . . 6 66 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 68 1. Introduction 70 Currently clients subscribe to calendar feeds as an ics file which is 71 often published as a resource accessible using the unofficial 72 'webcal' scheme. 74 The only available option for updating that resource is the usual 75 HTTP polling of cached resources using Etags. 77 There is the usual tension between clients wishing to see a timely 78 response to changes and servers not wishing to be overloaded by 79 frequent requests for possibly large amounts of data. 81 This specification introduces an approach whereby clients can 82 discover a more performant access method. Given the location of the 83 resource as an ics file, the client can download the file and inspect 84 the returned headers which will offer a number of alternative access 85 methods. 87 Given that many clients already support CalDAV this provides an easy 88 upgrade path for those clients. CalDAV and DAV subsets are specified 89 here to allow lighter weight implementations. 91 1.1. Conventions Used in This Document 93 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 94 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 95 "OPTIONAL" in this document are to be interpreted as described in 96 [RFC2119]. 98 2. Changes to the iCalendar specifications 100 This speciifcation does not require any changes to [RFC5545] or its 101 extensions. However it does introduce the use of some properties to 102 provide more information about the resource, for example the time 103 range it covers. 105 3. Link Header 107 The advertising of other access points is achieved through the use of 108 the LINK header as defined in [RFC5988]. New link relation types are 109 defined in this specification - each being associated with a protocol 110 or protocol subset. 112 4. Link relation subscribe-caldav 114 This specifies an access point which is a full implementation of 115 caldav but requires no authentication. The end point is read only 116 but allows the full range of reports as defined by the CalDAV 117 specification. 119 The client MUST follow the specification to determine exactly what 120 operations are allowed on the access point - for example to determine 121 if sync-report is supported. 123 5. Link relation subscribe-caldav-auth 125 This specifies an access point which is a full implementation of 126 caldav and requires authentication. This may allow read-write access 127 to the resource. 129 The client MUST follow the specification to determine exactly what 130 operations are allowed on the access point - for example to determine 131 if sync-report is supported. 133 6. Link relation subscribe-webdav-sync 135 This specifies an access point which supports only webdav sync. 137 This allows the client to issue a sync-report on the resource to 138 obtain updates. 140 NOTE: say something about initial startup - use ics to populate? 141 Initial token? 142 The client MUST follow that specification. 144 7. Link relation subscribe-something-else 146 This specifies an access point which supports something new. 148 The client MUST follow that specification. 150 8. Security Considerations 152 Applications using these properties need to be aware of the risks 153 entailed in using the URIs provided as values. See [RFC3986] for a 154 discussion of the security considerations relating to URIs. 156 9. Privacy Considerations 158 Properties with a "URI" value type can expose their users to privacy 159 leaks as any network access of the URI data can be tracked. Clients 160 SHOULD NOT automatically download data referenced by the URI without 161 explicit instruction from users. This specification does not 162 introduce any additional privacy concerns beyond those described in 163 [RFC5545]. 165 10. IANA Considerations 167 10.1. Link Relation Registrations 169 This document defines the following new iCalendar properties to be 170 added to the registry defined in Section 8.2.3 of [RFC5545]: 172 +--------------------------+-------------+--------------------+ 173 | Relation Name | Description | Reference | 174 +--------------------------+-------------+--------------------+ 175 | subscribe-caldav | Current | RFCXXXX, Section 4 | 176 | subscribe-caldav_auth | Current | RFCXXXX, Section 5 | 177 | subscribe-webdav-sync | Current | RFCXXXX, Section 6 | 178 | subscribe-something-else | Current | RFCXXXX, Section 7 | 179 +--------------------------+-------------+--------------------+ 181 11. Acknowledgements 183 The author would also like to thank the members of the Calendaring 184 and Scheduling Consortium Calendar Sharing technical committee and 185 the following individuals for contributing their ideas and support: 187 ... 189 The authors would also like to thank the Calendaring and Scheduling 190 Consortium for advice with this specification. 192 12. Normative References 194 [I-D.ietf-calext-extensions] 195 Daboo, C., "New Properties for iCalendar", draft-ietf- 196 calext-extensions-05 (work in progress), August 2016. 198 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 199 Requirement Levels", BCP 14, RFC 2119, 200 DOI 10.17487/RFC2119, March 1997, 201 . 203 [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an 204 IANA Considerations Section in RFCs", RFC 2434, 205 DOI 10.17487/RFC2434, October 1998, 206 . 208 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, 209 DOI 10.17487/RFC3688, January 2004, 210 . 212 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 213 Resource Identifier (URI): Generic Syntax", STD 66, 214 RFC 3986, DOI 10.17487/RFC3986, January 2005, 215 . 217 [RFC4589] Schulzrinne, H. and H. Tschofenig, "Location Types 218 Registry", RFC 4589, DOI 10.17487/RFC4589, July 2006, 219 . 221 [RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and 222 Scheduling Core Object Specification (iCalendar)", 223 RFC 5545, DOI 10.17487/RFC5545, September 2009, 224 . 226 [RFC5546] Daboo, C., Ed., "iCalendar Transport-Independent 227 Interoperability Protocol (iTIP)", RFC 5546, 228 DOI 10.17487/RFC5546, December 2009, 229 . 231 [RFC5988] Nottingham, M., "Web Linking", RFC 5988, 232 DOI 10.17487/RFC5988, October 2010, 233 . 235 [W3C.REC-xml-20060816] 236 Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and 237 F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fourth 238 Edition)", World Wide Web Consortium Recommendation REC- 239 xml-20060816, August 2006, 240 . 242 Appendix A. Open issues 244 restype values: Need to determine what if any registry of resource 245 types already exists and use that. 247 Appendix B. Change log 249 v05 2016-11-08 MD 251 o First pass 253 Author's Address 255 Michael Douglass 256 Spherical Cow Group 257 226 3rd Street 258 Troy, NY 12180 259 USA 261 Email: mdouglass@sphericalcowgroup.com 262 URI: http://sphericalcowgroup.com