< draft-ietf-tzdist-caldav-timezone-ref-04.txt		draft-ietf-tzdist-caldav-timezone-ref-05.txt >
	Network Working Group C. Daboo		Network Working Group C. Daboo
	Internet-Draft Apple		Internet-Draft Apple
	Updates: 4791 (if approved) August 31, 2015		Updates: 4791 (if approved) October 13, 2015
	Intended status: Standards Track		Intended status: Standards Track
	Expires: March 3, 2016		Expires: April 15, 2016
	CalDAV: Time Zones by Reference		CalDAV: Time Zones by Reference
	draft-ietf-tzdist-caldav-timezone-ref-04		draft-ietf-tzdist-caldav-timezone-ref-05
	Abstract		Abstract
	This document defines an extension to the CalDAV calendar access		This document defines an update to the CalDAV calendar access
	protocol (RFC 4791) to allow clients and servers to exchange		protocol (RFC 4791) to allow clients and servers to exchange
	iCalendar data without the need to send full time zone data.		iCalendar data without the need to send full time zone data.
	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.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	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 March 3, 2016.		This Internet-Draft will expire on April 15, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2015 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 21 ¶		skipping to change at page 2, line 21 ¶
	4. New Client Behavior . . . . . . . . . . . . . . . . . . . . . 7		4. New Client Behavior . . . . . . . . . . . . . . . . . . . . . 7
	5. New WebDAV Properties . . . . . . . . . . . . . . . . . . . . 8		5. New WebDAV Properties . . . . . . . . . . . . . . . . . . . . 8
	5.1. CALDAV:timezone-service-set . . . . . . . . . . . . . . . 8		5.1. CALDAV:timezone-service-set . . . . . . . . . . . . . . . 8
	5.2. CALDAV:calendar-timezone-id . . . . . . . . . . . . . . . 8		5.2. CALDAV:calendar-timezone-id . . . . . . . . . . . . . . . 8
	6. XML Element Definitions . . . . . . . . . . . . . . . . . . . 9		6. XML Element Definitions . . . . . . . . . . . . . . . . . . . 9
	6.1. CALDAV:calendar-query XML Element . . . . . . . . . . . . 9		6.1. CALDAV:calendar-query XML Element . . . . . . . . . . . . 9
	6.2. CALDAV:timezone-id XML Element . . . . . . . . . . . . . 9		6.2. CALDAV:timezone-id XML Element . . . . . . . . . . . . . 9
	7. Additional Message Header Fields . . . . . . . . . . . . . . 10		7. Additional Message Header Fields . . . . . . . . . . . . . . 10
	7.1. CalDAV-Timezones Request Header Field . . . . . . . . . . 10		7.1. CalDAV-Timezones Request Header Field . . . . . . . . . . 10
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 10		8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
	9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10		9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 10
	9.1. CalDAV-Timezones . . . . . . . . . . . . . . . . . . . . 10		10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
	10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11		10.1. CalDAV-Timezones . . . . . . . . . . . . . . . . . . . . 11
	11. References . . . . . . . . . . . . . . . . . . . . . . . . . 11		11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
	11.1. Normative References . . . . . . . . . . . . . . . . . . 11		12. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
	11.2. Informative References . . . . . . . . . . . . . . . . . 12		12.1. Normative References . . . . . . . . . . . . . . . . . . 11
			12.2. Informative References . . . . . . . . . . . . . . . . . 12
	Appendix A. Change History (To be removed by RFC Editor before		Appendix A. Change History (To be removed by RFC Editor before
	publication) . . . . . . . . . . . . . . . . . . . . 12		publication) . . . . . . . . . . . . . . . . . . . . 12
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13		Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14
	1. Introduction		1. Introduction
	The CalDAV [RFC4791] Calendar Access protocol allows clients to		The CalDAV [RFC4791] Calendar Access protocol allows clients to
	access calendar data stored on a server in the iCalendar [RFC5545]		access calendar data stored on a server in the iCalendar [RFC5545]
	data format. In iCalendar, calendar data that uses local time in any		data format. In iCalendar, calendar data that uses local time in any
	of its date and/or time values is specified as a date-time value in		of its date and/or time values is specified as a date-time value in
	combination with a time zone identifier ("TZID" property parameter).		combination with a time zone identifier ("TZID" property parameter).
	The time zone identifier refers to a time zone definition (a		The time zone identifier refers to a time zone definition (a
	"VTIMEZONE" component) that has all of the rules required to		"VTIMEZONE" component) that has all of the rules required to
	skipping to change at page 6, line 6 ¶		skipping to change at page 6, line 6 ¶
	standard time zone to a standard time zone definition that		standard time zone to a standard time zone definition that
	accurately matches the one supplied by the client. In doing so,		accurately matches the one supplied by the client. In doing so,
	servers will need to re-write the iCalendar data to make use of		servers will need to re-write the iCalendar data to make use of
	the new standard time zone identifier chosen by the mapping		the new standard time zone identifier chosen by the mapping
	procedure. Any subsequent request to fetch the calendar data		procedure. Any subsequent request to fetch the calendar data
	would see the new time zone identifier in the calendar data.		would see the new time zone identifier in the calendar data.
	Note there is one important situation where this re-mapping is		Note there is one important situation where this re-mapping is
	not appropriate: an attendee's copy of an event. In that case		not appropriate: an attendee's copy of an event. In that case
	the original time zone definition needs to be preserved as the		the original time zone definition needs to be preserved as the
	organizer's calendar user agent will expect to see that in any		organizer's calendar user agent will expect to see that in any
	iTIP replies sent by the attendee.		iTIP [RFC5546] replies sent by the attendee.
	3.1.5. Support Time Zone Identifiers in WebDAV Properties		3.1.5. Support of Time Zone Identifiers in WebDAV Properties
	CalDAV defines a CALDAV:calendar-timezone WebDAV property that is		CalDAV defines a CALDAV:calendar-timezone WebDAV property that is
	used by clients to set a default time zone for the server to use when		used by clients to set a default time zone for the server to use when
	doing time-based queries on calendar data (see Section 5.3.2 of		doing time-based queries on calendar data (see Section 5.3.2 of
	[RFC4791]). The content of that WebDAV property is an iCalendar		[RFC4791]). The content of that WebDAV property is an iCalendar
	"VTIMEZONE" component. This specification defines a new		"VTIMEZONE" component. This specification defines a new
	CALDAV:calendar-timezone-id WebDAV property that allows the default		CALDAV:calendar-timezone-id WebDAV property that allows the default
	time zone to be set via its time zone identifier, rather than		time zone to be set via its time zone identifier, rather than
	providing the full "VTIMEZONE" component (see Section 5.2). This		providing the full "VTIMEZONE" component (see Section 5.2). This
	WebDAV property MUST be present on all resources that also support		WebDAV property MUST be present on all resources that also support
	skipping to change at page 6, line 37 ¶		skipping to change at page 6, line 37 ¶
	return the full "VTIMEZONE" data for that time zone in the		return the full "VTIMEZONE" data for that time zone in the
	CALDAV:calendar-timezone WebDAV property.		CALDAV:calendar-timezone WebDAV property.
	If a client attempts to update the CALDAV:calendar-timezone-id with a		If a client attempts to update the CALDAV:calendar-timezone-id with a
	value that does not correspond to a time zone that is known to the		value that does not correspond to a time zone that is known to the
	server, the server MUST reject the property update using a		server, the server MUST reject the property update using a
	CALDAV:valid-timezone pre-condition error. In such cases, clients		CALDAV:valid-timezone pre-condition error. In such cases, clients
	MAY repeat the request using the CALDAV:calendar-timezone instead,		MAY repeat the request using the CALDAV:calendar-timezone instead,
	and provide the full iCalendar data for the time zone being set.		and provide the full iCalendar data for the time zone being set.
	3.1.6. Support Time Zone Identifiers in CALDAV:calendar-query REPORT		3.1.6. Support of Time Zone Identifiers in CALDAV:calendar-query REPORT
	CalDAV calendar query reports support a CALDAV:timezone XML element		CalDAV calendar query reports support a CALDAV:timezone XML element
	that is used by clients to set a specific time zone for the server to		that is used by clients to set a specific time zone for the server to
	use when doing time-based queries on calendar data (see Sections 7.3		use when doing time-based queries on calendar data (see Sections 7.3
	and 9.8 of [RFC4791]). The content of that XML element is an		and 9.8 of [RFC4791]). The content of that XML element is an
	iCalendar "VTIMEZONE" component. This specification defines a new		iCalendar "VTIMEZONE" component. This specification defines a new
	CALDAV:timezone-id XML element, that can be used as an alternative to		CALDAV:timezone-id XML element, that can be used as an alternative to
	the CALDAV:timezone XML element, that allows a specific time zone to		the CALDAV:timezone XML element, that allows a specific time zone to
	be set via its time zone identifier, rather than providing the full		be set via its time zone identifier, rather than providing the full
	"VTIMEZONE" component (see Section 6.2). Servers MUST support		"VTIMEZONE" component (see Section 6.2). Servers MUST support
	skipping to change at page 7, line 37 ¶		skipping to change at page 7, line 37 ¶
	2. Clients can include an HTTP "CalDAV-Timezones" request header		2. Clients can include an HTTP "CalDAV-Timezones" request header
	field with a value of "T" to ensure that the CalDAV server does		field with a value of "T" to ensure that the CalDAV server does
	include all "VTIMEZONE" components in any iCalendar data returned		include all "VTIMEZONE" components in any iCalendar data returned
	in a response (see Section 3.1.3).		in a response (see Section 3.1.3).
	3. Clients can expect servers not to include standard time zone		3. Clients can expect servers not to include standard time zone
	definitions in any iCalendar data they receive from the server,		definitions in any iCalendar data they receive from the server,
	if there is no "CalDAV-Timezones" request header field in the		if there is no "CalDAV-Timezones" request header field in the
	HTTP request. Clients MUST retrieve standard time zone		HTTP request. Clients MUST retrieve standard time zone
	definitions from the set of time zone distribution servers		definitions either from its own cache of standard time zones, or
	advertised by the CalDAV server (see Section 3.1.2), or a known.		from the set of time zone distribution servers advertised by the
			CalDAV server (see Section 3.1.2).
	4. Clients SHOULD remove standard time zone definitions from		4. Clients SHOULD remove standard time zone definitions from
	iCalendar data they send to the server, provided the		iCalendar data they send to the server, provided the
	corresponding time zone identifier is one available on any of the		corresponding time zone identifier is one available on any of the
	server's advertised time zone distribution servers (see		server's advertised time zone distribution servers (see
	Section 3.1.2).		Section 3.1.2).
	5. Clients MUST send time zone definitions in iCalendar data for any		5. Clients MUST send time zone definitions in iCalendar data for any
	time zone identifiers not available via any of the server's		time zone identifiers not available via any of the server's
	advertised time zone distribution servers. Clients MUST be		advertised time zone distribution servers. Clients MUST be
	skipping to change at page 10, line 35 ¶		skipping to change at page 10, line 35 ¶
	data returned, the value "F" indicates that it does not.		data returned, the value "F" indicates that it does not.
	CalDAV-Timezones = "T" / "F"		CalDAV-Timezones = "T" / "F"
	Example:		Example:
	CalDAV-Timezones: F		CalDAV-Timezones: F
	8. Security Considerations		8. Security Considerations
	This specification does not introduce any new security concerns		This specifications adds Time Zone Data Distribution Service
	beyond those addressed in CalDAV [RFC4791] and iCalendar [RFC5545].		[I-D.ietf-tzdist-service] servers into the overall calendaring and
			scheduling client/server architecture, as a critical component, and
			thus adds a new vector of attack against such systems. As such,
			administrators of CalDAV servers SHOULD ensure that any advertised
			time zone distribution servers are protected by a level of security
			commensurate with all the other components in the system.
	9. IANA Considerations		Beyond the above point, this specification does not introduce any new
			security concerns beyond those addressed in CalDAV [RFC4791],
			iCalendar [RFC5545], and the Time Zone Data Distribution Service
			[I-D.ietf-tzdist-service].
			9. Privacy Considerations
			The privacy recommendations in Section 9 of the Time Zone Data
			Distribution Service [I-D.ietf-tzdist-service] specification SHOULD
			be used to ensure that details of clients' interactions with CalDAV
			servers are not exposed to potential network observers. Note that
			since events can be delivered to a calendar user from an outside
			source (e.g., using iTIP [RFC5546]), and an attacker could create a
			calendar event with, e.g., a fake or lesser-used time zone identifier
			that could be used to monitor the calendar user's activity and
			interaction with others, this specification increases the importance
			of using the mitigations of privacy issues discussed in
			[I-D.ietf-tzdist-service].
			10. IANA Considerations
	The message header field below should be added to the Permanent		The message header field below should be added to the Permanent
	Message Header Field Registry (see [RFC3864]).		Message Header Field Registry (see [RFC3864]).
	9.1. CalDAV-Timezones		10.1. CalDAV-Timezones
	Header field name: CalDAV-Timezones		Header field name: CalDAV-Timezones
	Applicable protocol: http		Applicable protocol: http
	Status: standard		Status: standard
	Author/Change controller: IETF		Author/Change controller: IETF
	Specification document(s): this specification (Section 7.1)		Specification document(s): this specification (Section 7.1)
	Related information: none		Related information: none
	10. Acknowledgments		11. Acknowledgments
	Thanks to Mike Douglass, Andrew McMillan, and Ken Murchison. This		Thanks to Mike Douglass, Andrew McMillan, and Ken Murchison. This
	specification came about via discussions at the Calendaring and		specification came about via discussions at the Calendaring and
	Scheduling Consortium.		Scheduling Consortium.
	11. References		12. References
	11.1. Normative References		12.1. Normative References
	[I-D.ietf-tzdist-service]		[I-D.ietf-tzdist-service]
	Douglass, M. and C. Daboo, "Time Zone Data Distribution		Douglass, M. and C. Daboo, "Time Zone Data Distribution
	Service", draft-ietf-tzdist-service-11 (work in progress),		Service", draft-ietf-tzdist-service-11 (work in progress),
	July 2015.		July 2015.
	[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, DOI 10.17487/		Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
	RFC2119, March 1997,		RFC2119, March 1997,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
	skipping to change at page 12, line 5 ¶		skipping to change at page 12, line 29 ¶
	[RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and		[RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and
	Scheduling Core Object Specification (iCalendar)", RFC		Scheduling Core Object Specification (iCalendar)", RFC
	5545, DOI 10.17487/RFC5545, September 2009,		5545, DOI 10.17487/RFC5545, September 2009,
	<http://www.rfc-editor.org/info/rfc5545>.		<http://www.rfc-editor.org/info/rfc5545>.
	[RFC6638] Daboo, C. and B. Desruisseaux, "Scheduling Extensions to		[RFC6638] Daboo, C. and B. Desruisseaux, "Scheduling Extensions to
	CalDAV", RFC 6638, DOI 10.17487/RFC6638, June 2012,		CalDAV", RFC 6638, DOI 10.17487/RFC6638, June 2012,
	<http://www.rfc-editor.org/info/rfc6638>.		<http://www.rfc-editor.org/info/rfc6638>.
	11.2. Informative References		12.2. Informative References
	[RFC5546] Daboo, C., Ed., "iCalendar Transport-Independent		[RFC5546] Daboo, C., Ed., "iCalendar Transport-Independent
	Interoperability Protocol (iTIP)", RFC 5546, DOI 10.17487/		Interoperability Protocol (iTIP)", RFC 5546, DOI 10.17487/
	RFC5546, December 2009,		RFC5546, December 2009,
	<http://www.rfc-editor.org/info/rfc5546>.		<http://www.rfc-editor.org/info/rfc5546>.
	[RFC6047] Melnikov, A., Ed., "iCalendar Message-Based		[RFC6047] Melnikov, A., Ed., "iCalendar Message-Based
	Interoperability Protocol (iMIP)", RFC 6047, DOI 10.17487/		Interoperability Protocol (iMIP)", RFC 6047, DOI 10.17487/
	RFC6047, December 2010,		RFC6047, December 2010,
	<http://www.rfc-editor.org/info/rfc6047>.		<http://www.rfc-editor.org/info/rfc6047>.
	[RFC6557] Lear, E. and P. Eggert, "Procedures for Maintaining the		[RFC6557] Lear, E. and P. Eggert, "Procedures for Maintaining the
	Time Zone Database", BCP 175, RFC 6557, DOI 10.17487/		Time Zone Database", BCP 175, RFC 6557, DOI 10.17487/
	RFC6557, February 2012,		RFC6557, February 2012,
	<http://www.rfc-editor.org/info/rfc6557>.		<http://www.rfc-editor.org/info/rfc6557>.
	Appendix A. Change History (To be removed by RFC Editor before		Appendix A. Change History (To be removed by RFC Editor before
	publication)		publication)
			Changes in -05:
			1. IESG Review: abstract now says "updates" instead of "extends".
			2. IESG Review: 3.1.5, 3.1.6 section title tweaks.
			3. IESG Review: add tzdist reference in Security Considerations.
			4. IESG Review: fixed truncated sentence in bullet #3 in Section 4.
			5. IESG Review: added privacy considerations section that references
			the corresponding tzdist service section.
			6. IESG Review: added text to security considerations section to
			indicate tzdist servers need to be protected as well as the
			caldav server.
	Changes in -04:		Changes in -04:
	1. AD Review: added Updates 4791		1. AD Review: added Updates 4791
	2. AD Review: reworded first bullet of Section 4 to indicate clients		2. AD Review: reworded first bullet of Section 4 to indicate clients
	have a choice of where to locate time zones		have a choice of where to locate time zones
	3. AD Review: added text about server providing an admin config		3. AD Review: added text about server providing an admin config
	option to override new default behavior		option to override new default behavior
End of changes. 20 change blocks.
	25 lines changed or deleted		69 lines changed or added
This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/