Internet DRAFT - draft-gondwana-caldav-scheduling-controls
draft-gondwana-caldav-scheduling-controls
calext B. Gondwana, Ed.
Internet-Draft FastMail
Updates: 6638 (if approved) March 8, 2019
Intended status: Standards Track
Expires: September 9, 2019
CalDAV Extension for scheduling controls
draft-gondwana-caldav-scheduling-controls-01
Abstract
This document adds headers to control and restrict the scheduling
behaviour of CalDAV servers when updating calendaring resources.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 9, 2019.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used In This Document . . . . . . . . . . . . . . 3
3. Extending the CalDAV OPTIONS response . . . . . . . . . . . . 3
3.1. Example: Using OPTIONS for the Discovery of Scheduling
Controls Support . . . . . . . . . . . . . . . . . . . . 3
4. New headers . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.1. Scheduling header . . . . . . . . . . . . . . . . . . . . 3
4.2. Schedule-User-Address header . . . . . . . . . . . . . . 4
5. Implementation considerations . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
9. Version History . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. v01, 2019-03-08 . . . . . . . . . . . . . . . . . . . . . 5
9.2. v00, 2019-02-08 . . . . . . . . . . . . . . . . . . . . . 5
10. Normative References . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
[RFC6638] defines automatic scheduling operations for resources
stored on [!@RFC4791] CalDAV servers.
[RFC6638] defines the "Schedule-Reply" header in Section 8.1, however
this header is not sufficient for controlling scheduling in all
cases.
Cases where it might be necessary to update the data store on a
server without causing scheduling messages to be sent include backup
after a data loss event on the server, or importing calendar events
from another system.
Calendar server operators deal with these other needs by either using
a different method than CalDAV to update their server, or by adding a
custom method to suppress scheduling. This document defines a
standard method to suppress scheduling, allowing CalDAV to be
directly used for restores and imports.
Complex sites can have users who have multiple aliases, and in the
most complex cases, a user may have multiple identities who are
present on a scheduling event as organizer and/or attendee. When an
event is updated over CalDAV, the server must calculate or guess
which of those addresses the current user is acting as. This
document defines a header which allows the client to inform the
server precisely which address they are acting as when adding,
modifying or removing a resource.
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2. Conventions Used In This Document
In examples, "C:" indicates data sent by a client that is connected
to a server. "S:" indicates data sent by the server to the client.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119] when they
appear in ALL CAPS. These words may also appear in this document in
lower case as plain English words, absent their normative meanings.
3. Extending the CalDAV OPTIONS response
A server supporting the features described in this document MUST
include "scheduling-controls" as a field in the DAV response header
from an OPTIONS request. A value of "scheduling-controls" in the DAV
response header indicates to clients that the server supports all the
requirements specified in this document.
3.1. Example: Using OPTIONS for the Discovery of Scheduling Controls
Support
Request:
OPTIONS /home/brong/calendars/ HTTP/1.1
Host: cal.example.com
Response:
HTTP/1.1 200 OK
Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE
Allow: PROPFIND, PROPPATCH, LOCK, UNLOCK, REPORT, ACL
DAV: 1, 2, 3, access-control, calendar-access,
scheduling-controls
Date: Thu, 8 Feb 2019 10:16:37 GMT
Content-Length: 0
4. New headers
This document adds two new headers for use on PUT, PROPPATCH and
DELETE:
4.1. Scheduling header
Scheduling: {all|none|internal-only|external-only|X-...}
Default: all
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Not providing this header, or providing the value of "all", instructs
the server to follow the behaviour in [RFC6638] Section 3.2.
Providing the value "none" instructs the server to perform no
scheduling at all, and to just store the event (useful for restoring
from backup)
The value "internal-only" instructs the server to update the events
in other calendars within its system where that can be done silently,
but not to send visible notifications to users (where permitted by
policy). This is useful when importing multiple related calendars
into a new system without flooding external parties with
notifications.
The value "external-only" instructs the server to import the data
without updating local calendars, but to send notifications to
external attendees so they are aware of the event. This is useful
when migrating calendar events to a new system where external parties
need to have a way to update their participation status in the new
system.
e.g.
Scheduling: none
TODO: specify error codes
4.2. Schedule-User-Address header
Schedule-User-Address: URI
Default: not present
If this header is not present, the server will calculate the address
from the authenticated user, or from the CALDAV:schedule-user-address
property on the calendar or principal.
If this header is provided, it overrides the server's internal
calculation, and informs the server to perform any scheduling as the
specified user.
TODO: specify error codes
e.g.
Schedule-User-Address: mailto:foo@example.com
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5. Implementation considerations
Any server implementing this extension MUST ensure it has a way to
validate Schedule-User-Address settings.
6. IANA Considerations
TODO: IANA request for OPTIONS item
TODO: IANA request for named headers
7. Security Considerations
The "Scheduling" header only allows reduction of the cases in which
the server will creating scheduling requests. This is generally good
for user privacy, allowing copies of events to be updated without
notifying the owner or attendees. This is particularly valuable for
cleaning up spam.
The "Schedule-User-Address" header allows the client to override the
server choice of address for the user to act as. Servers MUST ensure
that the authenticated user has permission to act as the specified
address, as well as applying any local policy limitations.
8. Acknowledgments
o Lucia Kristiansen, Google
o CalConnect
o The calext working group
9. Version History
Remove before publishing
9.1. v01, 2019-03-08
o correct name in acknowledgements
9.2. v00, 2019-02-08
o Initial draft based on discussion at CalConnect about Google and
FastMail private implementations.
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10. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC6638] Daboo, C. and B. Desruisseaux, "Scheduling Extensions to
CalDAV", RFC 6638, DOI 10.17487/RFC6638, June 2012,
<https://www.rfc-editor.org/info/rfc6638>.
Author's Address
Bron Gondwana (editor)
FastMail
Level 2, 114 William St
Melbourne VIC 3000
Australia
Email: brong@fastmailteam.com
URI: https://www.fastmail.com
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