draft-ietf-calext-subscription-upgrade-01.txt   draft-ietf-calext-subscription-upgrade-02.txt 
Network Working Group M. Douglass Network Working Group M. Douglass
Internet-Draft Spherical Cow Group Internet-Draft 29 July 2020
Updates: 5988,7240 (if approved) November 3, 2019 Updates: 5988 (if approved)
Intended status: Standards Track Intended status: Standards Track
Expires: May 6, 2020 Expires: 30 January 2021
Calendar subscription upgrades Calendar subscription upgrades
draft-ietf-calext-subscription-upgrade-01 draft-ietf-calext-subscription-upgrade-02
Abstract 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 This specification updates [RFC5545] to add the value DELETED to the
STATUS property. STATUS property.
This specification also updates [RFC7240] to add the subscribe- This specification also updates [RFC7240] to add the subscribe-
enhanced-get and limit preferences. enhanced-get and limit preferences.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
skipping to change at page 1, line 38 skipping to change at page 1, line 35
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 6, 2020. This Internet-Draft will expire on 30 January 2021.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terms and Definitions . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Discovering alternative access methods . . . . . . . . . . . 3 2.1. Terms and Definitions . . . . . . . . . . . . . . . . . . 3
3. Enhanced GET . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Discovering alternative access methods . . . . . . . . . . . 3
3.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Enhanced GET . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Deletions . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.3. Handling of invalid sync tokens . . . . . . . . . . . . . 5 4.2. Deletions . . . . . . . . . . . . . . . . . . . . . . . . 5
3.4. Paging the response . . . . . . . . . . . . . . . . . . . 5 4.3. Handling of invalid sync tokens . . . . . . . . . . . . . 5
3.5. Caching of responses . . . . . . . . . . . . . . . . . . 6 4.4. Paging the response . . . . . . . . . . . . . . . . . . . 5
3.6. Examples . . . . . . . . . . . . . . . . . . . . . . . . 6 4.5. Caching of responses . . . . . . . . . . . . . . . . . . 6
4. Changes to the iCalendar specifications . . . . . . . . . . . 8 4.6. Examples . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Redefined Status property . . . . . . . . . . . . . . . . 8 5. Changes to the iCalendar specifications . . . . . . . . . . . 8
5. Header Field: Sync-Token . . . . . . . . . . . . . . . . . . 10 5.1. Redefined Status property . . . . . . . . . . . . . . . . 8
6. New Prefer header field preferences . . . . . . . . . . . . . 10 6. Header Field: Sync-Token . . . . . . . . . . . . . . . . . . 10
6.1. Preference subscribe-enhanced-get . . . . . . . . . . . . 10 7. New Prefer header field preferences . . . . . . . . . . . . . 10
6.2. Preference limit . . . . . . . . . . . . . . . . . . . . 10 7.1. Preference subscribe-enhanced-get . . . . . . . . . . . . 10
7. Link relations . . . . . . . . . . . . . . . . . . . . . . . 10 7.2. Preference limit . . . . . . . . . . . . . . . . . . . . 11
7.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 10 8. Link relations . . . . . . . . . . . . . . . . . . . . . . . 11
7.2. subscribe-caldav . . . . . . . . . . . . . . . . . . . . 11 8.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.3. subscribe-caldav-auth . . . . . . . . . . . . . . . . . . 11 8.2. subscribe-caldav . . . . . . . . . . . . . . . . . . . . 11
7.4. subscribe-webdav-sync . . . . . . . . . . . . . . . . . . 11 8.3. subscribe-caldav-auth . . . . . . . . . . . . . . . . . . 11
7.5. subscribe-enhanced-get . . . . . . . . . . . . . . . . . 11 8.4. subscribe-webdav-sync . . . . . . . . . . . . . . . . . . 11
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11 8.5. subscribe-enhanced-get . . . . . . . . . . . . . . . . . 12
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12
9.1. Sync-Token HTTP Header Field Registration . . . . . . . . 12 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
9.2. Preference Registrations . . . . . . . . . . . . . . . . 12 10.1. Sync-Token HTTP Header Field Registration . . . . . . . 12
9.3. Link Relation Registrations . . . . . . . . . . . . . . . 13 10.2. Preference Registrations . . . . . . . . . . . . . . . . 12
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 10.3. Link Relation Registrations . . . . . . . . . . . . . . 13
11. Normative References . . . . . . . . . . . . . . . . . . . . 13 11. Normative References . . . . . . . . . . . . . . . . . . . . 13
Appendix A. Open issues . . . . . . . . . . . . . . . . . . . . 15 Appendix A. Open issues . . . . . . . . . . . . . . . . . . . . 14
Appendix B. Change log . . . . . . . . . . . . . . . . . . . . . 15 Appendix B. Change log . . . . . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction 1. Acknowledgements
The author would also like to thank the members of the CalConnect
Calendar Sharing technical committee and the following individuals
for contributing their ideas and support:
Marten Gajda, Ken Murchison, Garry Shutler
The authors would also like to thank CalConnect, the Calendaring and
Scheduling Consortium, for advice with this specification.
2. Introduction
Currently clients subscribe to calendar feeds as an iCalendar file Currently clients subscribe to calendar feeds as an iCalendar file
which is often published as a resource accessible using the which is often published as a resource accessible using the
unofficial 'webcal' scheme. unofficial 'webcal' scheme.
The only available option for updating that resource is the usual The only available option for updating that resource is the usual
HTTP polling of cached resources using Etags. HTTP polling of cached resources using Etags.
There is the usual tension between clients wishing to see a timely There is the usual tension between clients wishing to see a timely
response to changes and servers not wishing to be overloaded by response to changes and servers not wishing to be overloaded by
frequent requests for possibly large amounts of data. frequent requests for possibly large amounts of data.
This specification introduces an approach whereby clients can This specification introduces an approach whereby clients can
discover a more performant access method. Given the location of the discover a more performant access method. Given the location of the
resource as an iCalendar file, the client can perfom a HEAD request resource as an iCalendar file, the client can perfom a HEAD request
on the resource and inspect the returned headers which will offer a on the resource and inspect the returned headers which will offer a
number of alternative access methods. number of alternative access methods.
Given that many clients and servers already support CalDAV this Given that many clients and servers already support CalDAV this
provides an easy upgrade path for those clients. Additionally an provides an easy upgrade path for those clients. CalDAV and DAV
enhanced GEt protocol is specified here to allow a light weight subsets are specified here to allow lighter weight implementations.
implementation.
The use of subscription upgtafe may help reduce load on servers, but
perhaps more inportantly it allows mobile devices to use a more
efficient update mechanism reducing data tranferred and presumably
improving battery life.
1.1. Terms and Definitions 2.1. Terms and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
Additionally, the rule for URI is included from [RFC3986]. Additionally, the rule for URI is included from [RFC3986].
2. Discovering alternative access methods 3. Discovering alternative access methods
The advertising of other access points is achieved through the use of The advertising of other access points is achieved through the use of
the LINK header as defined in [RFC5988]. New link relation types are the LINK header as defined in [RFC5988]. New link relation types are
defined in this specification - each being associated with a protocol defined in this specification - each being associated with a protocol
or protocol subset. or protocol subset.
These LINK headers will be delivered when a client carries out a HEAD These LINK headers will be delivered when a client carries out a HEAD
request targeting the URL of the resource. request targeting the URL of the resource.
EXAMPLE
This is an example of a HEAD request and the response from a server This is an example of a HEAD request and the response from a server
that supports the enhanced GET method. that supports the enhanced GET method.
>> Request <&lt; >&gt; Request &lt;&lt;
HEAD /caldata/events.ics HTTP/1.1 HEAD /caldata/events.ics HTTP/1.1
Host: example.com Host: example.com
Accept: text/calendar Accept: text/calendar
>> Response <&lt; >&gt; Response &lt;&lt;
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Length: xxxx Content-Length: xxxx
Link: <http://example.com/subscribe/events.ics&gt;; Link: <http://example.com/subscribe/events.ics&gt;;
rel="subscribe-enhanced-get" rel="subscribe-enhanced-get"
Figure 1
Note that the target for an upgraded service may be the same as for Note that the target for an upgraded service may be the same as for
the initial resource. the initial resource.
3. Enhanced GET 4. Enhanced GET
3.1. General 4.1. General
This is a lightweight protocol which allows simple clients to This is a lightweight protocol which allows simple clients to
efficiently discover and download changes in the targeted resource. efficiently discover and download changes in the targeted resource.
It has many similarities to WebDAV sync and for a server could be It has many similarities to WebDAV sync and for a server could be
implemented as an extension of the specification. implemented as an extension of the specification.
In this protocol the client MUST include the Prefer header field In this protocol the client MUST include the Prefer header field
preference "subscribe-enhanced-get". If a sync token is available it preference "subscribe-enhanced-get". If a sync token is available it
is passed as a Sync-Token header field. is passed as a Sync-Token header field.
skipping to change at page 5, line 5 skipping to change at page 5, line 5
header field and a Sync-Token header field to indicate that it wants header field and a Sync-Token header field to indicate that it wants
a set of changes since the last fetch. a set of changes since the last fetch.
If no Sync-Token header field is supplied the server SHOULD respond If no Sync-Token header field is supplied the server SHOULD respond
with a full set of data. Otherwise, if the token is valid, it SHOULD with a full set of data. Otherwise, if the token is valid, it SHOULD
return with a set of changed entities. return with a set of changed entities.
In both cases the server should set the Preference-Applied header In both cases the server should set the Preference-Applied header
field and a new Sync-Token header field value. field and a new Sync-Token header field value.
3.2. Deletions 4.2. Deletions
When an entity (VEVENT, VTODO or other valid top-level component) is When an entity (VEVENT, VTODO or other valid top-level component) is
deleted from the source data the server needs to be able to inform a deleted from the source data the server needs to be able to inform a
client of the deletion. This specification introduces a new value client of the deletion. This specification introduces a new value
for the STATUS property of DELETED. for the STATUS property of DELETED.
On the first enhanced GET after the entity has been deleted a On the first enhanced GET after the entity has been deleted a
skeleton, but valid, entity will be returned with STATUS: DELETED. skeleton, but valid, entity will be returned with STATUS: DELETED.
The receiving client is free to remove the entity or update it's The receiving client is free to remove the entity or update it's
STATUS property. STATUS property.
On subsequent fetches the entity will not be returned. On subsequent fetches the entity will not be returned.
3.3. Handling of invalid sync tokens 4.3. Handling of invalid sync tokens
When a server receives an invalid token it MUST return a 409 status When a server receives an invalid token it MUST return a 409 status
(Conflict). The server MAY choose to return an error message in the (Conflict). The server MAY choose to return an error message in the
body. body.
The client SHOULD respond to this error by restarting the interaction The client SHOULD respond to this error by restarting the interaction
from scratch, i.e. retrieve the full set of data then poll for from scratch, i.e. retrieve the full set of data then poll for
updates. updates.
3.4. Paging the response 4.4. Paging the response
A client may explicitly request a limit on the size of the response A client may explicitly request a limit on the size of the response
by specifying the Prefer header field preference "limit=n" where n is by specifying the Prefer header field preference "limit=n" where n is
the number of components. the number of components.
When a server receives a request specifying such a limit it SHOULD When a server receives a request specifying such a limit it SHOULD
limit the response to that number of components. If the limit causes limit the response to that number of components. If the limit causes
a truncation in the response the server should respond with a a truncation in the response the server should respond with a
Preference-Applied header specifying the limit that was applied and Preference-Applied header specifying the limit that was applied and
return a sync token which may be used to retrieve the next batch of return a sync token which may be used to retrieve the next batch of
data. data.
This allows the client to immediately resubmit a request for the next This allows the client to immediately resubmit a request for the next
batch using the updated token. batch using the updated token.
A server MAY choose to limit the response size. The behavior SHOULD A server MAY choose to limit the response size. The behavior SHOULD
be as if the client had provided a preference for that size - be as if the client had provided a preference for that size -
allowing the client to retrieve the full set of data in batches. allowing the client to retrieve the full set of data in batches.
3.5. Caching of responses 4.5. Caching of responses
To enable proper caching of responses the server SHOULD provide a To enable proper caching of responses the server SHOULD provide a
VARY header field in responses that names the Prefer and Sync-Token VARY header field in responses that names the Prefer and Sync-Token
header fields along with any other that are appropriate. header fields along with any other that are appropriate.
Clients should order the preferences as following so that identical Clients should order the preferences as following so that identical
responses can be identified: responses can be identified:
o subscribe-enhanced-get * subscribe-enhanced-get
o limit * limit
3.6. Examples 4.6. Examples
EXAMPLE 1
This is an example of the initial request and response from a server This is an example of the initial request and response from a server
that supports the enhanced GET method. Note the use of the Vary that supports the enhanced GET method. Note the use of the Vary
header so a caching proxy can key off the client's Sync-Token and header so a caching proxy can key off the client's Sync-Token and
preference. preference.
>> Request <&lt; >&gt; Request &lt;&lt;
GET /events.ics HTTP/1.1 GET /events.ics HTTP/1.1
Host: example.com Host: example.com
Accept: text/calendar Accept: text/calendar
Prefer: subscribe-enhanced-get Prefer: subscribe-enhanced-get
>> Response <&lt; >&gt; Response &lt;&lt;
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Length: xxxx Content-Length: xxxx
Sync-Token: "data:,1234567" Sync-Token: "data:,1234567"
Preference-Applied: subscribe-enhanced-get Preference-Applied: subscribe-enhanced-get
Vary: Prefer, Sync-Token Vary: Prefer, Sync-Token
BEGIN:VCALENDAR: BEGIN:VCALENDAR:
? /* full feed */ ? /* full feed */
END:VCALENDAR END:VCALENDAR
Figure 2
EXAMPLE 2
This is an example of the subsequent request and response when no This is an example of the subsequent request and response when no
changes have occurred. changes have occurred.
>> Request <&lt; >&gt; Request &lt;&lt;
GET /events.ics HTTP/1.1 GET /events.ics HTTP/1.1
Host: example.com Host: example.com
Accept: text/calendar Accept: text/calendar
Prefer: subscribe-enhanced-get Prefer: subscribe-enhanced-get
Sync-Token: "data:,1234567" Sync-Token: "data:,1234567"
>> Response <&lt; >&gt; Response &lt;&lt;
HTTP/1.1 304 Not Modified HTTP/1.1 304 Not Modified
Content-Length: 0 Content-Length: 0
Sync-Token: "data:,1234567" Sync-Token: "data:,1234567"
Preference-Applied: subscribe-enhanced-get Preference-Applied: subscribe-enhanced-get
Vary: Prefer, Sync-Token Vary: Prefer, Sync-Token
Figure 3
EXAMPLE 3
This is an example of the subsequent request and response for an old This is an example of the subsequent request and response for an old
or invalid token. or invalid token.
>> Request <&lt; >&gt; Request &lt;&lt;
GET /events.ics HTTP/1.1 GET /events.ics HTTP/1.1
Host: example.com Host: example.com
Accept: text/calendar Accept: text/calendar
Sync-Token: "data:,1234567" Sync-Token: "data:,1234567"
Prefer: subscribe-enhanced-get Prefer: subscribe-enhanced-get
>> Response <&lt; >&gt; Response &lt;&lt;
HTTP/1.1 409 Conflict HTTP/1.1 409 Conflict
Content-Length: xxxx Content-Length: xxxx
Preference-Applied: subscribe-enhanced-get Preference-Applied: subscribe-enhanced-get
Figure 4
EXAMPLE 4
This is an example of the subsequent request and response when This is an example of the subsequent request and response when
changes have occurred. changes have occurred.
>> Request <&lt; >&gt; Request &lt;&lt;
GET /events.ics HTTP/1.1 GET /events.ics HTTP/1.1
Host: example.com Host: example.com
Accept: text/calendar Accept: text/calendar
Sync-Token: "data:,1234567" Sync-Token: "data:,1234567"
Prefer: subscribe-enhanced-get Prefer: subscribe-enhanced-get
>> Response <&lt; >&gt; Response &lt;&lt;
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: text/calendar Content-Type: text/calendar
Vary: Prefer, Sync-Token Vary: Prefer, Sync-Token
Sync-Token: "data:,4567890" Sync-Token: "data:,4567890"
Preference-Applied: subscribe-enhanced-get Preference-Applied: subscribe-enhanced-get
BEGIN:VCALENDAR: BEGIN:VCALENDAR:
... only new/changed events ... only new/changed events
... deleted events have STATUS:DELETED ... deleted events have STATUS:DELETED
END:VCALENDAR END:VCALENDAR
4. Changes to the iCalendar specifications Figure 5
5. Changes to the iCalendar specifications
This specification updates [RFC5545] to add the value DELETED to the This specification updates [RFC5545] to add the value DELETED to the
STATUS property. STATUS property.
4.1. Redefined Status property 5.1. Redefined Status property
Property name Property name STATUS
STATUS
Purpose Purpose This property defines the overall status or confirmation for
This property defines the overall status or confirmation for the the calendar component.
calendar component.
Value Type Value Type TEXT
TEXT
Property Parameters Property Parameters IANA and non-standard property parameters can be
IANA and non-standard property parameters can be specified on this specified on this property.
property.
Conformance Conformance This property can be specified once in "VEVENT",
This property can be specified once in "VEVENT", "VTODO", or "VTODO", or "VJOURNAL" calendar components.
"VJOURNAL" calendar components.
Description Description In a group-scheduled calendar component, the property is
In a group-scheduled calendar component, the property is used by used by the "Organizer" to provide a confirmation of the event to
the "Organizer" to provide a confirmation of the event to the the "Attendees". For example in a "VEVENT" calendar component,
"Attendees". For example in a "VEVENT" calendar component, the the "Organizer" can indicate that a meeting is tentative,
"Organizer" can indicate that a meeting is tentative, confirmed, confirmed, or cancelled. In a "VTODO" calendar component, the
or cancelled. In a "VTODO" calendar component, the "Organizer" "Organizer" can indicate that an action item needs action, is
can indicate that an action item needs action, is completed, is in completed, is in process or being worked on, or has been
process or being worked on, or has been cancelled. In a cancelled. In a "VJOURNAL" calendar component, the "Organizer"
"VJOURNAL" calendar component, the "Organizer" can indicate that a can indicate that a journal entry is draft, final, or has been
journal entry is draft, final, or has been cancelled or removed. cancelled or removed.
Format Definition Format Definition
This property is defined by the following notation: This property is defined by the following notation:
status = "STATUS" statparam ":" statvalue CRLF status = "STATUS" statparam ":" statvalue CRLF
statparam = *(";" other-param) statparam = *(";" other-param)
statvalue = (statvalue-event statvalue = (statvalue-event
skipping to change at page 9, line 47 skipping to change at page 9, line 41
/ "CANCELLED" ;Indicates to-do was cancelled. / "CANCELLED" ;Indicates to-do was cancelled.
/ "DELETED" ;Indicates to-do was deleted. / "DELETED" ;Indicates to-do was deleted.
;Status values for "VTODO". ;Status values for "VTODO".
statvalue-jour = "DRAFT" ;Indicates journal is draft. statvalue-jour = "DRAFT" ;Indicates journal is draft.
/ "FINAL" ;Indicates journal is final. / "FINAL" ;Indicates journal is final.
/ "CANCELLED" ;Indicates journal is removed. / "CANCELLED" ;Indicates journal is removed.
/ "DELETED" ;Indicates journal was deleted. / "DELETED" ;Indicates journal was deleted.
;Status values for "VJOURNAL". ;Status values for "VJOURNAL".
Figure 6
Example Example
EXAMPLE 1
The following is an example of this property for a "VEVENT" calendar The following is an example of this property for a "VEVENT" calendar
component: component:
STATUS:TENTATIVE STATUS:TENTATIVE
Figure 7
EXAMPLE 2
The following is an example of this property for a "VTODO" calendar The following is an example of this property for a "VTODO" calendar
component: component:
STATUS:NEEDS-ACTION STATUS:NEEDS-ACTION
Figure 8
EXAMPLE 3
The following is an example of this property for a "VJOURNAL" The following is an example of this property for a "VJOURNAL"
calendar component: calendar component:
STATUS:DRAFT STATUS:DRAFT
5. Header Field: Sync-Token Figure 9
6. Header Field: Sync-Token
This specification defines a new header field Sync-Token for use by This specification defines a new header field Sync-Token for use by
the enhanced GET method. the enhanced GET method.
Accept = DQUOTE URI DQUOTE Accept = DQUOTE URI DQUOTE
Figure 10
The value MUST be a URI. This will generally be a data URI The value MUST be a URI. This will generally be a data URI
representing an opaque token. Client MUST not attempt to interpret representing an opaque token. Client MUST not attempt to interpret
the data URI value. the data URI value.
EXAMPLE
This is an example of the Sync-Token header field: This is an example of the Sync-Token header field:
Sync-Token: "data:,1234567" Sync-Token: "data:,1234567"
6. New Prefer header field preferences Figure 11
6.1. Preference subscribe-enhanced-get 7. New Prefer header field preferences
7.1. Preference subscribe-enhanced-get
This indicates that the client expects the server to handle the GET This indicates that the client expects the server to handle the GET
method according to the specifications for enhanced get. method according to the specifications for enhanced get.
pref-subscribe-enhanced-get = "subscribe-enhanced-get" pref-subscribe-enhanced-get = "subscribe-enhanced-get"
6.2. Preference limit Figure 12
7.2. Preference limit
This preference parameter provides a limit on the number of This preference parameter provides a limit on the number of
components returned for enhanced get. components returned for enhanced get.
pref-limit = "limit" BWS "=" BWS 1*DIGIT pref-limit = "limit" BWS "=" BWS 1*DIGIT
7. Link relations Figure 13
7.1. General 8. Link relations
8.1. General
This clause defines a number of new link relations required to This clause defines a number of new link relations required to
facilitate subscription upgrades. facilitate subscription upgrades.
7.2. subscribe-caldav 8.2. subscribe-caldav
This specifies an access point which is a full implementation of This specifies an access point which is a full implementation of
caldav but requires no authentication. The end point allows the full caldav but requires no authentication. The end point allows the full
range of reports as defined by the CalDAV specification. range of reports as defined by the CalDAV specification.
The client MUST follow the specification to determine exactly what The client MUST follow the specification to determine exactly what
operations are allowed on the access point - for example to determine operations are allowed on the access point - for example to determine
if sync-report is supported. if sync-report is supported.
The URL MAY include some form of token to allow write access to the The URL MAY include some form of token to allow write access to the
targeted collection. The client must check it's permissions to targeted collection. The client must check it's permissions to
determine whether or not it has been granted write access. determine whether or not it has been granted write access.
7.3. subscribe-caldav-auth 8.3. subscribe-caldav-auth
This specifies an access point which is a full implementation of This specifies an access point which is a full implementation of
caldav and requires authentication. This may allow read-write access caldav and requires authentication. This may allow read-write access
to the resource. to the resource.
The client MUST follow the specification to determine exactly what The client MUST follow the specification to determine exactly what
operations are allowed on the access point -- for example to operations are allowed on the access point - for example to determine
determine if sync-report is supported. if sync-report is supported.
7.4. subscribe-webdav-sync 8.4. subscribe-webdav-sync
This specifies an access point which supports only webdav sync. This specifies an access point which supports only webdav sync.
This allows the client to issue a sync-report on the resource to This allows the client to issue a sync-report on the resource to
obtain updates. obtain updates.
The client MUST follow that specification. The client MUST follow that specification.
7.5. subscribe-enhanced-get 8.5. subscribe-enhanced-get
This specifies an access point which supports something new. This specifies an access point which supports something new.
The client MUST follow that specification. The client MUST follow that specification.
8. Security Considerations 9. Security Considerations
Applications using these properties need to be aware of the risks Applications using these properties need to be aware of the risks
entailed in using the URIs provided as values. See [RFC3986] for a entailed in using the URIs provided as values. See [RFC3986] for a
discussion of the security considerations relating to URIs. == discussion of the security considerations relating to URIs. ==
Privacy Considerations Privacy Considerations
Properties with a "URI" value type can expose their users to privacy Properties with a "URI" value type can expose their users to privacy
leaks as any network access of the URI data can be tracked. Clients leaks as any network access of the URI data can be tracked. Clients
SHOULD NOT automatically download data referenced by the URI without SHOULD NOT automatically download data referenced by the URI without
explicit instruction from users. This specification does not explicit instruction from users. This specification does not
introduce any additional privacy concerns beyond those described in introduce any additional privacy concerns beyond those described in
[RFC5545]. [RFC5545].
9. IANA Considerations 10. IANA Considerations
9.1. Sync-Token HTTP Header Field Registration 10.1. Sync-Token HTTP Header Field Registration
This specification updates the "Message Headers" registry entry for This specification updates the "Message Headers" registry entry for
"Sync-Token" in [RFC3864] to refer to this document. "Sync-Token" in [RFC3864] to refer to this document.
Header Field Name: Sync-Token Header Field Name: Sync-Token
Protocol: http Protocol: http
Status: standard Status: standard
Reference: <this-document> Reference: <this-document>
9.2. Preference Registrations Figure 14
10.2. Preference Registrations
The following preferences have been added to the HTTP Preferences The following preferences have been added to the HTTP Preferences
Registry defined in [RFC7240] Registry defined in [RFC7240]
Preference Preference subscribe-enhanced-get
subscribe-enhanced-get
Value Value None.
None.
Description Description Marks the interaction as enhanced get and provides the
Marks the interaction as enhanced get and provides the optional optional sync-token and page size.
sync-token and page size.
Reference Reference this document
this document
Preference Preference limit
limit
Value Value An integer page size.
An integer page size.
Description Description Provide a limit on the number of components in the
Provide a limit on the number of components in the response. response.
Reference Reference this document
this document
9.3. Link Relation Registrations 10.3. Link Relation Registrations
This document defines the following new iCalendar properties to be This document defines the following new iCalendar properties to be
added to the registry defined in section=8.2.3 [RFC5545]: added to the registry defined in [RFC5545]:
+------------------------+-------------+-------------+ +========================+=============+=============+
| Relation Name | Description | Reference | | Relation Name | Description | Reference |
+========================+=============+=============+
| subscribe-caldav | Current | Section 8.2 |
+------------------------+-------------+-------------+ +------------------------+-------------+-------------+
| subscribe-caldav | Current | Section 7.2 | | subscribe-caldav_auth | Current | Section 8.3 |
| subscribe-caldav_auth | Current | Section 7.3 | +------------------------+-------------+-------------+
| subscribe-webdav-sync | Current | Section 7.4 | | subscribe-webdav-sync | Current | Section 8.4 |
| subscribe-enhanced_get | Current | Section 7.5 | +------------------------+-------------+-------------+
| subscribe-enhanced_get | Current | Section 8.5 |
+------------------------+-------------+-------------+ +------------------------+-------------+-------------+
10. Acknowledgements Table 1
The author would also like to thank the members of the CalConnect
Calendar Sharing technical committee and the following individuals
for contributing their ideas and support:
Marten Gajda, Ken Murchison, Garry Shutler
The authors would also like to thank CalConnect, the Calendaring and
Scheduling Consortium, for advice with this specification.
11. Normative References 11. Normative References
[I-D.ietf-calext-extensions]
Daboo, C., "New Properties for iCalendar", draft-ietf-
calext-extensions-05 (work in progress), August 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", IETF RFC 2119, IETF RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 2434,
DOI 10.17487/RFC2434, October 1998,
<https://www.rfc-editor.org/info/rfc2434>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864, Procedures for Message Header Fields", IETF RFC 3864,
DOI 10.17487/RFC3864, September 2004, IETF RFC 3864, DOI 10.17487/RFC3864, September 2004,
<https://www.rfc-editor.org/info/rfc3864>. <https://www.rfc-editor.org/info/rfc3864>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", IETF RFC 3986,
RFC 3986, DOI 10.17487/RFC3986, January 2005, IETF RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>. <https://www.rfc-editor.org/info/rfc3986>.
[RFC4589] Schulzrinne, H. and H. Tschofenig, "Location Types
Registry", RFC 4589, DOI 10.17487/RFC4589, July 2006,
<https://www.rfc-editor.org/info/rfc4589>.
[RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and [RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and
Scheduling Core Object Specification (iCalendar)", Scheduling Core Object Specification (iCalendar)", IETF
RFC 5545, DOI 10.17487/RFC5545, September 2009, RFC 5545, IETF RFC 5545, DOI 10.17487/RFC5545, September
<https://www.rfc-editor.org/info/rfc5545>. 2009, <https://www.rfc-editor.org/info/rfc5545>.
[RFC5546] Daboo, C., Ed., "iCalendar Transport-Independent
Interoperability Protocol (iTIP)", RFC 5546,
DOI 10.17487/RFC5546, December 2009,
<https://www.rfc-editor.org/info/rfc5546>.
[RFC5988] Nottingham, M., "Web Linking", RFC 5988, [RFC5988] Nottingham, M., "Web Linking", IETF RFC 5988, IETF RFC
DOI 10.17487/RFC5988, October 2010, 5988, DOI 10.17487/RFC5988, October 2010,
<https://www.rfc-editor.org/info/rfc5988>. <https://www.rfc-editor.org/info/rfc5988>.
[RFC6578] Daboo, C. and A. Quillaud, "Collection Synchronization for [RFC7240] Snell, J., "Prefer Header for HTTP", IETF RFC 7240,
Web Distributed Authoring and Versioning (WebDAV)", IETF RFC 7240, DOI 10.17487/RFC7240, June 2014,
RFC 6578, DOI 10.17487/RFC6578, March 2012,
<https://www.rfc-editor.org/info/rfc6578>.
[RFC7240] Snell, J., "Prefer Header for HTTP", RFC 7240,
DOI 10.17487/RFC7240, June 2014,
<https://www.rfc-editor.org/info/rfc7240>. <https://www.rfc-editor.org/info/rfc7240>.
[RFC7991] Hoffman, P., "The "xml2rfc" Version 3 Vocabulary",
RFC 7991, DOI 10.17487/RFC7991, December 2016,
<https://www.rfc-editor.org/info/rfc7991>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", IETF RFC 8174, IETF RFC 8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. DOI 10.17487/RFC8174, May 2017,
<https://www.rfc-editor.org/info/rfc8174>.
[W3C.REC-xml-20060816]
Bray, T., Paoli, J., Sperberg-McQueen, M., Maler, E., and
F. Yergeau, "Extensible Markup Language (XML) 1.0 (Fourth
Edition)", World Wide Web Consortium Recommendation REC-
xml-20060816, August 2006,
<http://www.w3.org/TR/2006/REC-xml-20060816>.
Appendix A. Open issues Appendix A. Open issues
Vary Vary Ensure we get that right.
Ensure we get that right.
Appendix B. Change log Appendix B. Change log
calext00 2019-06-05 MD calext00 2019-06-05 MD
o First calext version * First calext version
o Use Sync-Token header rather than parameter * Use Sync-Token header rather than parameter
v04 2019-03-07 MD v04 2019-03-07 MD
o Reference to RFC 6538 - WebDAV sync and RFC 7240 Prefer * Reference to RFC 6538 - WebDAV sync and RFC 7240 Prefer
o Go back to HEAD * Go back to HEAD
o New Preference and parameters. * New Preference and parameters.
o Examples * Examples
o More text for extended get. Talk about deletions. * More text for extended get. Talk about deletions.
v01 2017-02-17 MD v01 2017-02-17 MD
* Add text about OPTIONS
o Add text about OPTIONS * Add text abut read/write CalDAV
o Add text abut read/write CalDAV
v00 2017-02-15 MD v00 2017-02-15 MD
o First pass * First pass
Author's Address Author's Address
Michael Douglass Michael Douglass
Spherical Cow Group
226 3rd Street
Troy 12180
United States of America
Email: mdouglass@sphericalcowgroup.com Email: mdouglass@bedework.com
URI: http://sphericalcowgroup.com
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