Internet DRAFT - draft-douglass-timezone-service
draft-douglass-timezone-service
Network Working Group M. Douglass
Internet-Draft RPI
Intended status: Standards Track C. Daboo
Expires: September 16, 2014 Apple
March 15, 2014
Timezone Service Protocol
draft-douglass-timezone-service-11
Abstract
This document defines a timezone service protocol that allows
reliable, secure and fast delivery of timezone data to client systems
such as calendaring and scheduling applications or operating systems.
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 16, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Glossary of terms . . . . . . . . . . . . . . . . . . . . 4
2. Architectural Overview . . . . . . . . . . . . . . . . . . . . 5
3. General Considerations . . . . . . . . . . . . . . . . . . . . 6
3.1. Timezone Identifiers . . . . . . . . . . . . . . . . . . . 6
3.2. Timezone Aliases . . . . . . . . . . . . . . . . . . . . . 7
3.3. Timezone Localized Names . . . . . . . . . . . . . . . . . 7
3.4. Truncated Timezones . . . . . . . . . . . . . . . . . . . 7
4. Timezones Service Protocol . . . . . . . . . . . . . . . . . . 8
4.1. Server Protocol . . . . . . . . . . . . . . . . . . . . . 8
4.1.1. Timezone Queries . . . . . . . . . . . . . . . . . . . 8
4.1.2. Timezone Formats . . . . . . . . . . . . . . . . . . . 9
4.1.3. Conditional Timezone Requests . . . . . . . . . . . . 9
4.1.4. Expanded Timezone Data . . . . . . . . . . . . . . . . 9
4.1.5. Server Requirements . . . . . . . . . . . . . . . . . 10
4.1.6. Error Responses . . . . . . . . . . . . . . . . . . . 10
4.1.7. Extensions . . . . . . . . . . . . . . . . . . . . . . 10
4.2. Client Guidelines . . . . . . . . . . . . . . . . . . . . 10
4.2.1. Discovery . . . . . . . . . . . . . . . . . . . . . . 10
4.2.1.1. Timezone Service SRV Service Labels . . . . . . . 11
4.2.1.2. Timezone Service TXT records . . . . . . . . . . . 11
4.2.1.3. Timezone Service Well-Known URI . . . . . . . . . 12
4.2.1.3.1. Example: well-known URI redirects to
actual context path . . . . . . . . . . . . . 12
4.2.2. Initial Synchronization of All Timezones . . . . . . . 12
4.2.3. Subsequent Synchronization of All Timezones . . . . . 13
5. Request Parameters . . . . . . . . . . . . . . . . . . . . . . 13
5.1. "action" Parameter . . . . . . . . . . . . . . . . . . . . 13
5.2. "format" Parameter . . . . . . . . . . . . . . . . . . . . 13
5.3. "changedsince" Parameter . . . . . . . . . . . . . . . . . 14
5.4. "start" Parameter . . . . . . . . . . . . . . . . . . . . 14
5.5. "end" Parameter . . . . . . . . . . . . . . . . . . . . . 14
5.6. "lang" Parameter . . . . . . . . . . . . . . . . . . . . . 14
5.7. "tzid" Parameter . . . . . . . . . . . . . . . . . . . . . 15
5.8. "name" Parameter . . . . . . . . . . . . . . . . . . . . . 15
5.9. "truncate" Parameter . . . . . . . . . . . . . . . . . . . 15
6. Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.1. "capabilities" Action . . . . . . . . . . . . . . . . . . 16
6.1.1. Example: Get Capabilities . . . . . . . . . . . . . . 17
6.2. "list" Action . . . . . . . . . . . . . . . . . . . . . . 19
6.2.1. Example: List timezone identifiers . . . . . . . . . . 21
6.3. "get" Action . . . . . . . . . . . . . . . . . . . . . . . 21
6.3.1. Example: Get timezone . . . . . . . . . . . . . . . . 23
6.3.2. Example: Get timezone alias . . . . . . . . . . . . . 24
6.3.3. Example: Get truncated timezone . . . . . . . . . . . 24
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6.4. "expand" Action . . . . . . . . . . . . . . . . . . . . . 25
6.4.1. Example: Expanded JSON Data Format . . . . . . . . . . 27
6.5. "find" Action . . . . . . . . . . . . . . . . . . . . . . 27
6.5.1. Example: Find action . . . . . . . . . . . . . . . . . 29
7. JSON Definitions . . . . . . . . . . . . . . . . . . . . . . . 30
7.1. capabilities action response . . . . . . . . . . . . . . . 30
7.2. list action response . . . . . . . . . . . . . . . . . . . 32
7.3. expand action response . . . . . . . . . . . . . . . . . . 34
7.4. error response . . . . . . . . . . . . . . . . . . . . . . 35
8. Equivalent Timezone Identifier Property . . . . . . . . . . . 35
9. Security Considerations . . . . . . . . . . . . . . . . . . . 36
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36
10.1. Service Actions Registration . . . . . . . . . . . . . . . 37
10.1.1. Service Actions Registration Procedure . . . . . . . . 37
10.1.2. Registration Template for Actions . . . . . . . . . . 37
10.1.3. Registration Template for Action Parameters . . . . . 38
10.2. Initial Timezone Service Registries . . . . . . . . . . . 38
10.2.1. Actions Registry . . . . . . . . . . . . . . . . . . . 38
10.2.2. Action Parameters Registry . . . . . . . . . . . . . . 38
10.3. timezone Well-Known URI Registration . . . . . . . . . . . 39
10.4. Service Name Registrations . . . . . . . . . . . . . . . . 39
10.4.1. timezone Service Name Registration . . . . . . . . . . 39
10.4.2. timezones Service Name Registration . . . . . . . . . 40
10.5. iCalendar Property Registration . . . . . . . . . . . . . 40
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 40
12. Normative References . . . . . . . . . . . . . . . . . . . . . 40
Appendix A. Change History (to be removed prior to
publication as an RFC) . . . . . . . . . . . . . . . 42
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 45
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1. Introduction
Timezone data typically combines a coordinated universal time (UTC)
offset with daylight saving time (DST) rules. Timezones are
typically tied to specific geographic and geopolitical regions.
Whilst the UTC offset for particular regions changes infrequently,
DST rules can change frequently and sometimes with very little notice
(sometimes hours before a change comes into effect).
Calendaring and scheduling systems, such as those that use iCalendar
[RFC5545], as well as operating systems, critically rely on timezone
data to determine the correct local time. As such they need to be
kept up to date with changes to timezone data. To date there has
been no fast and easy way to do that. Timezone data is often
supplied in the form of a set of data files that have to be
"compiled" into a suitable database format for use by the client
application or operating system. In the case of operating systems,
often those changes only get propagated to client machines when there
is an operating system update, which can be infrequent, resulting in
inaccurate timezone data being present for significant amounts of
time.
This specification defines a timezone service protocol that allows
for fast, reliable and accurate delivery of timezone data to client
systems. This protocol is based on HTTP [RFC2616] using a REST style
API, with JSON [RFC7159] responses.
This specification does not define the source of the timezone data.
It is assumed that a reliable and accurate source is available. One
such source is the IANA hosted timezone database [RFC6557].
Discussion of this document should take place on the calsify mailing
list calsify@ietf.org
1.1. Conventions
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].
1.2. Glossary of terms
The following terms with the given meanings are used throughout this
document.
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Timezone Data: Data that defines a single timezone, including an
identifier, UTC offset values, and DST rules;
Timezone Server: A server implementing the Timezone Service Protocol
defined by this specification;
Timezone Identifier: A globally unique name which identifies
timezone data.
2. Architectural Overview
The overall process for the delivery of timezone data can be
visualized via the diagram shown below.
==================== ====================
(a) | Contributors | | Contributors |
==================== ====================
| |
==================== ====================
(b) | Publisher A | | Publisher B |
==================== ====================
|
====================
(c) | Provider |
====================
/ | \
/ | \
==================== | ====================
(d) | Provider | | | Provider |
==================== | ====================
| | | |
| | | |
========== ========== ========== ==========
(e) | Client | | Client | | Client | | Client |
========== ========== ========== ==========
Figure 1: Timezone Service Architecture
The overall service is made up of several layers:
(a) Contributors: Individuals, governments or organizations which
provide information about timezones to the publishing process.
There can be many contributors.
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(b) Publishers: Publishers aggregate information from contributors,
determine the reliability of the information and, based on that,
generate timezone data. There can be many publishers, each
getting information from many different contributors. In some
cases a publisher may choose to "re-publish" data from another
publisher.
(c) Root Providers: Servers which obtain and then provide the
timezone data from publishers and make that available to other
servers or clients. There can be many root providers. Root
providers can choose to supply timezone data from one or more
publishers.
(d) Local Providers: Servers which handle the bulk of the requests
and reduce the load on root servers. These will typically be
simple caches of the root server, located closer to clients. For
example a large Internet Service Provider (ISP) may choose to
setup their own local provider to allow clients within their
network to make requests of that server rather than making
requests of servers outside their network. Local servers will
cache and periodically refresh data from the root servers.
(e) Clients: Applications, operating systems etc., that make use of
timezone data and retrieve that from either root or local
providers.
Some of those layers may be coalesced by implementors. For example,
a vendor may choose to implement the entire service as a single
monolithic virtual server with the address embedded in distributed
systems. Others may choose to provide a service consisting of
multiple layers of providers, many local servers and a small number
of root servers.
This specification is only concerned with the protocol used to
exchange data between providers and from provider to client. This
specification does not define how contributors pass their information
to publishers, nor how those publishers vet that information to
obtain trustworthy data, nor the format of the data produced by the
publishers.
3. General Considerations
3.1. Timezone Identifiers
Timezone identifiers are unique names associated with each timezone,
as defined by publishers. The iCalendar [RFC5545] specification has
a "TZID" property and parameter whose value is set to the
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corresponding timezone identifier, and used to identify timezone data
and relate timezones to start and end dates in events, etc. This
specification does not define what format of timezone identifiers
should be used. It is possible that timezone identifiers from
different publishers overlap, and there might be a need for a
provider to distinguish those with some form of "namespace" prefix
identifying the publisher. However, development of a standard
(global) timezone identifier naming scheme is out of scope for this
specification.
3.2. Timezone Aliases
Timezone aliases map a name onto a timezone identifier. For example
"US/Eastern" is usually mapped on to "America/New_York". Timezone
aliases are typically used interchangeably with timezone identifiers
when presenting information to users.
A timezone service needs to maintain timezone alias mapping
information, and expose that data to clients as well as allow clients
to query for timezone data using aliases. When returning timezone
data to a client, the server returns the data with an identifier
matching the query, but it can include one or more equivalent
identifiers in the data to provide a hint to the client that
alternative identifiers are available. For example, a query for "US/
Eastern" could include equivalent identifiers for "America/New_York"
or "America/Montreal".
3.3. Timezone Localized Names
Localized names are names for timezones which can be presented to a
user in their own language. Each timezone may have one or more
localized names associated with it. Names would typically be unique
in their own locale as they might be presented to the user in a list.
A timezone service might need to maintain localized name information,
for one or more chosen languages, as well as allow clients to query
for timezone data using localized names.
3.4. Truncated Timezones
Timezones and daylight saving times rules have been in use for over a
century. Timezone data can thus contain a large amount of
"historical" information that may not be relevant for a particular
server's intended clients. For example, calendaring and scheduling
clients are likely most concerned with timezone data that covers a
period for one or two years in the past on into the future, as users
typically only create new events for the present and future. To
avoid having to send unnecessary data, servers are allowed to
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truncate timezone data at some appropriate date in the past, and only
provide accurate offsets and rules from that point on. The server
will need to advertise the cut-off dates it is using so that clients
that need timezone data for earlier dates can take appropriate
action. To simplify the set of data a server needs to support,
truncation always occurs at the start of a year, i.e., midnight on
1st January for the timezone's local time. A server will advertise a
set of years for truncated data it can supply, or provide an
indicator that it can truncate at any past year. In addition, the
server will advertise that it can supply untruncated data. In the
absence of any indication of truncated data available on the server,
the server will only supply untruncated data.
When truncating a "VTIMEZONE" component, the server MUST include
either a "STANDARD" or "DAYLIGHT" sub-component with a "DTSTART"
property value that matches the date-time where the truncation
occurred, and appropriate "UTC-OFFSET-FROM" and "UTC-OFFSET-TO"
properties to indicate the correct offset in effect right after the
point of truncation. This sub-component thus represents the earliest
valid date-time covered by the timezone data in the truncated
"VTIMEZONE" component.
4. Timezones Service Protocol
4.1. Server Protocol
The timezone service protocol uses HTTP [RFC2616] for query and
delivery of data. Queries are made on a single HTTP resource using
the GET method, with specific client request attributes passed in
request-URI parameters.
The "action" request-URI parameter defines the overall function being
requested, with other request parameters acting as arguments to that
function.
Most security considerations are already handled adequately by HTTP.
However, given the nature of the data being transferred and the
requirement it be correct, all interactions between client and server
SHOULD use an HTTP connection protected with TLS [RFC5246] as defined
in [RFC2818].
4.1.1. Timezone Queries
Timezone identifiers, aliases or localized names can be used to query
for timezone data. This will be more explicitly defined below for
each action. In general however, if a "tzid" request parameter is
used then the value may be an identifier or an alias. When the
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"name" parameter is used it may be an identifier, an alias or a
localized name.
4.1.2. Timezone Formats
The default format for returning timezone definitions is the
iCalendar [RFC5545] data format. In addition, the iCalendar-in-XML
[RFC6321], and iCalendar-in-JSON [I-D.ietf-jcardcal-jcal]
representations are also available. The "format" request-URI
parameter can be used to select which data format is returned.
4.1.3. Conditional Timezone Requests
Timezone data is generally slow moving, with the set of timezones
that change from even year-to-year being relatively small. However,
any changes that do occur, need to be distributed in a timely manner.
Typically it is more efficient to just provide the set of changes to
timezone data, so a client can do updates to any locally cached data.
When listing timezones, a timestamp is returned by the server, and
that can be used later by clients to determine if any "substantive"
change has occurred in the timezone data. Clients can use a
conditional "list" action (see Section 6.2), supplying a previous
timestamp value, to limit the results to timezones which have changed
in a "substantive" manner since that previous timestamp. This allows
clients to cache the last timestamp and to periodically poll the
server for possible changes.
A "substantive" change is one which affects the calculated onsets for
a timezone. Changes to properties such as a description are not
treated as a "substantive" change.
Clients SHOULD poll for such changes at least once a day. A server
acting as a local provider, caching timezone data from another
server, SHOULD poll for changes once per hour. See Section 9 on
expected client and server behavior regarding high request rates.
4.1.4. Expanded Timezone Data
Determining timezone offsets at a particular point in time is often a
complicated process, as the rules for daylight saving time can be
complex. To help with this, the timezone service provides an action
that allows clients to request the server to expand a timezone
definition into a set of "observances" over a fixed period of time
(see Section 6.4). Each of these observances describes a local onset
time and UTC offsets for the prior time and the observance time.
Together, these provide a quick way for "thin" clients to determine
an appropriate UTC offset for an arbitrary date without having to do
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full timezone expansion themselves.
4.1.5. Server Requirements
To enable a simple client implementation, servers SHOULD ensure that
they provide or cache data for all commonly used timezones, from
various publishers. That allows client implementations to configure
a single server to get all timezone data. In turn, any server can
refresh any of the data from any other server - though the root
servers may provide the most up-to-date copy of the data.
4.1.6. Error Responses
The following are examples of response codes one would expect to be
used by the server. Note, however, that unless explicitly prohibited
any 2/3/4/5xx series response code may be used in a response.
200 (OK) - The command succeeded.
400 (Bad Request) - The Sender has provided an invalid request
parameter.
404 (Not Found) - The timezone was not found.
When an error status is set the server SHOULD respond with some
descriptive text in an error object as per Section 7.4. In the case
of an invalid "action" query parameter, the following error code can
be used:
invalid-action The "action" query parameter has an incorrect value.
4.1.7. Extensions
This protocol is designed to be extensible through a standards based
registration mechanism (see Section 10). It is anticipated that
other useful timezone actions will be added in the future (e.g.,
mapping a geographical location to timezone identifiers, getting
change history for timezones), and so, servers MUST return a
description of their capabilities. This will allow clients to
determine if new features have been installed and, if not, fall back
on earlier features or disable some client capabilities.
4.2. Client Guidelines
4.2.1. Discovery
Client implementations need to either know where the timezone service
is located or discover it through some mechanism. To use a timezone
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service, a client needs a fully qualified domain name (FQDN), port
and HTTP request-URI path.
4.2.1.1. Timezone Service SRV Service Labels
[RFC2782] defines a DNS-based service discovery protocol that has
been widely adopted as a means of locating particular services within
a local area network and beyond, using SRV RR records. This can be
used to discover a service's FQDN and port.
This specification adds two service types for use with SRV records:
timezone: Identifies a Timezone server that uses HTTP without
transport layer security ([RFC2818]).
timezones: Identifies a Timezone server that uses HTTP with
transport layer security ([RFC2818]).
Clients MUST honor "TTL", "Priority" and "Weight" values in the SRV
records, as described by [RFC2782].
Example: service record for server without transport layer security
_timezone._tcp SRV 0 1 80 tz.example.com.
Example: service record for server with transport layer security
_timezones._tcp SRV 0 1 443 tz.example.com.
4.2.1.2. Timezone Service TXT records
When SRV RRs are used to advertise a timezone service, it is also
convenient to be able to specify a "context path" in the DNS to be
retrieved at the same time. To enable that, this specification uses
a TXT RR that follows the syntax defined in Section 6 of [RFC6763]
and defines a "path" key for use in that record. The value of the
key MUST be the actual "context path" to the corresponding service on
the server.
A site might provide TXT records in addition to SRV records for each
service. When present, clients MUST use the "path" value as the
"context path" for the service in HTTP requests. When not present,
clients use the ".well-known" URI approach described next.
Example: text record for service with transport layer security
_timezones._tcp TXT path=/timezones
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4.2.1.3. Timezone Service Well-Known URI
A "well-known" URI [RFC5785] is registered by this specification for
the Timezone service, "timezone" (see Section 10). This URI points
to a resource that the client can use as the initial "context path"
for the service they are trying to connect to. The server MUST
redirect HTTP requests for that resource to the actual "context path"
using one of the available mechanisms provided by HTTP (e.g., using
an appropriate 3xx status response). Clients MUST handle HTTP
redirects on the ".well-known" URI. Servers MUST NOT locate the
actual timezone service endpoint at the ".well-known" URI as per
Section 1.1 of [RFC5785].
Servers SHOULD set an appropriate Cache-Control header value (as per
Section 14.9 of [RFC2616]) in the redirect response to ensure caching
occurs as needed, or as required by the type of response generated.
For example, if it is anticipated that the location of the redirect
might change over time, then a "no-cache" value would be used.
To facilitate "context path's" that might differ from user to user,
the server MAY require authentication when a client tries to access
the ".well-known" URI (i.e., the server would return a 401 status
response to the unauthenticated request from the client, then return
the redirect response only after a successful authentication by the
client).
4.2.1.3.1. Example: well-known URI redirects to actual context path
A Timezone server has a "context path" that is "/servlet/timezone".
The client will use "/.well-known/timezone" as the path for the
service after it has first found the FQDN and port number via an SRV
lookup or via manual entry of information by the user. When the
client makes its initial HTTP request against "/.well-known/
timezone", the server would issue an HTTP 301 redirect response with
a Location response header using the path "/servlet/timezone". The
client would then "follow" this redirect to the new resource and
continue making HTTP requests there.
4.2.2. Initial Synchronization of All Timezones
When a secondary service or a client wishing to cache all timezone
data first starts, or wishes to do a full refresh, it synchronizes
with another server by first issuing a "list" action. The client
would preserve the returned datestamp for subsequent use. Each
timezone in the returned list can then be fetched and stored locally.
In addition a mapping of aliases to timezones can be built.
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4.2.3. Subsequent Synchronization of All Timezones
A secondary service or a client caching all timezone data needs to
periodically synchronize with a server. To do so it would issue a
"list" action with the "changedsince" parameter set to the value of
the datestamp returned by the last synchronization. The client would
again preserve the returned datestamp for subsequent use. Each
timezone in the returned list can then be fetched and stored locally.
Note, this process makes no provision for handling deleted timezones.
In general it is bad practice to delete timezones as they might still
be in use by consumers of timezone data.
5. Request Parameters
The "action" request-URI parameter MUST be included in all requests
to define what action is required of the server.
The following request-URI parameters are used with the various
actions.
5.1. "action" Parameter
Name: action
Description: Specify the action to be carried out.
Value: Any IANA registered action name (see Section 10.2.1).
5.2. "format" Parameter
Name: format
Description: Specify the format of the timezone data returned by the
server as a standard MIME [RFC2046] media-type. If absent, the
iCalendar [RFC5545] format will be returned with the timezones
contained within a "VCALENDAR" object (i.e., a default media-type
of "text/calendar").
Value: A MIME [RFC2046] media-type. The following values MAY be
used, with servers advertising the values they do support via the
"capabilities" action response (see Section 6.1):
text/calendar: Return data as "VTIMEZONE" components embedded in
a "VCALENDAR" object as per [RFC5545].
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application/calendar+xml: Return data using the XML
representation of iCalendar data as per iCalendar-in-XML
[RFC6321].
application/calendar+json: Return data using the JSON
representation of iCalendar data as per iCalendar-in-JSON.
5.3. "changedsince" Parameter
Name: changedsince
Description: Specify the timestamp for a conditional "list" (see
Section 6.2) or "expand" (see Section 6.4) action in order to
restrict the results to only changes since the given timestamp.
Value: An [RFC3339] UTC date-time value, typically a value returned
by a previous request.
5.4. "start" Parameter
Name: start
Description: Specify the inclusive start of a period.
Value: An integer representing a year..
5.5. "end" Parameter
Name: end
Description: Specify the exclusive end of a period.
Value: An integer representing a year.
5.6. "lang" Parameter
Name: lang
Description: Specify the language in which locale specific values
are to be returned. e.g., if a language is specified, only
localized names for that language would be returned.
Value: The value follows the specifications in [RFC5646].
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5.7. "tzid" Parameter
Name: tzid
Description: Specify a timezone to be targeted by an action.
Value: A timezone identifier or alias.
5.8. "name" Parameter
Name: name
Description: Specify a name for queries.
Value: A timezone identifier, alias or localized name. This
parameter is used when searching for matching timezones (see
Section 6.5).
5.9. "truncate" Parameter
Name: truncate
Description: Specify a year for timezone data truncation.
Value: An integer representing a year in the past. The use of this
depends on the "truncated" object returned in the server's
"capabilities" response:
If "truncated" object is not present in the "capabilities"
response, then the "truncated" parameter MUST NOT be used - the
server will always return untruncated timezone data.
If "any" is set to "true" in the "truncated" object, then any
past year is valid for truncation (though typically data prior
to 1880 is unlikely to be present).
If "any" is "false" and "years" is present with at least one
value, then any of the values in the "years" array can be used.
If "untruncated" is set to "true", then omitting the
"truncated" parameter will result in untruncated data being
returned.
If "untruncated" is set to "false", and "years" contains only
one value, and the "truncated" query parameter is omitted, then
the server will return timezone data truncated at the one value
specified in "years".
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Example: a server that can only return one set of truncated data -
client can omit the "truncate" query parameter:
truncated: {
"any": false,
"years": [1970],
"untruncated": false
}
Example: a server that can return truncated data for any past year
as well as untruncated data if client omits the "truncate" query
parameter:
truncated: {
"any": true,
"untruncated": true
}
Example: a server that can return only untruncated data - the
"truncate" query parameter would always be omitted:
truncated: {
"any": false,
"untruncated": true
}
6. Actions
Servers MUST support the following actions.
6.1. "capabilities" Action
Name: capabilities
Description: This action returns the capabilities of the server,
allowing clients to determine if a specific feature has been
deployed and/or enabled. Note that each request always includes
an "action" query parameter set to the name of the action, even
though that parameter is not listed in the "capabilities" response
for each action.
Parameters:
action REQUIRED with value "capabilities"
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Response A JSON object containing a "version" member, an "info"
member, and an "actions" member, see Section 7.1.
Possible Error Codes No specific code.
6.1.1. Example: Get Capabilities
>> Request <<
GET /?action=capabilities HTTP/1.1
Host: tz.example.com
>> Response <<
HTTP/1.1 200 OK
Date: Wed, 4 Jun 2008 09:32:12 GMT
Content-Type: application/json; charset="utf-8"
Content-Length: xxxx
{
"version": 1,
"info": {
"primary-source": "Olson:2011m",
"truncate" : {
"any": false,
"years": [1970, 2000, 2010],
"untruncated": true
},
"contacts": ["mailto:tzs@example.org"]
},
"actions": [
{
"name": "list",
"parameters": [
{
"name": "lang",
"required": false,
"multi": true
},
{
"name": "changedsince",
"required": false,
"multi": false
}
]
},
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{
"name": "get",
"parameters": [
{
"name": "format",
"required": false,
"multi": false,
"values": [
"text/calendar",
"application/calendar+xml",
"application/calendar+json"
]
},
{
"name": "lang",
"required": false,
"multi": true
},
{
"name": "tzid",
"required": true,
"multi": false
},
{
"name": "truncate",
"required": false,
"multi": false
}
]
},
{
"name": "expand",
"parameters": [
{
"name": "tzid",
"required": true,
"multi": false
},
{
"name": "start",
"required": false,
"multi": false
},
{
"name": "end",
"required": false,
"multi": false
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}
]
},
{
"name": "find",
"parameters": [
{
"name": "name",
"required": true,
"multi": false
},
{
"name": "lang",
"required": false,
"multi": true
}
]
},
{
"name":"capabilities",
"parameters": []
}
]
}
6.2. "list" Action
Name: list
Description: This action lists all timezone identifiers or the
requested timezone identifiers, in summary format, with aliases
and optional localized data. In addition, it returns a timestamp
which is the current server last modification value. If the
"changedsince" query parameter is present its value MUST
correspond to a previously returned timestamp value. When
"changedsince" timestamp is used, the server MUST return only
those timezones that have changed since the specified timestamp.
If the "tzid" parameter is present one or more times, then the
server MUST only return information for the specified timezone
identifiers.
Parameters:
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action REQUIRED with value "list"
lang=<lang-code> OPTIONAL, but MAY occur multiple times.
changedsince OPTIONAL, but MUST occur only once. MUST NOT be
present if the "tzid" parameter is present.
tzid=<identifier> OPTIONAL, and MAY occur multiple times. MUST
NOT be present if the "changedsince" parameter is present. The
value of the "dtstamp" member in the response applies to the
entire set of data, rather than the subset requested with the
"tzid" query parameter, and allows the client to determine if
it needs to refresh its full set of timezone data.
Response: A JSON object containing a "dtstamp" member and a
"timezones" member, see Section 7.2.
Possible Error Codes
invalid-changedsince The "changedsince" query parameter has an
incorrect value, or appears more than once.
invalid-tzid The "tzid" query parameter is present along with the
"changedsince", or has an incorrect value.
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6.2.1. Example: List timezone identifiers
In this example the client requests the timezone identifiers and in
addition requests that the US-English local names be returned.
>> Request <<
GET /?action=list&lang=en_US HTTP/1.1
Host: tz.example.com
>> Response <<
HTTP/1.1 200 OK
Date: Wed, 4 Jun 2008 09:32:12 GMT
Content-Type: application/json; charset="utf-8"
Content-Length: xxxx
{
"dtstamp": "2009-10-11T09:32:11Z",
"timezones": [
{
"tzid": "America/New_York",
"last-modified": "2009-09-17T01:39:34Z",
"aliases":["US/Eastern"],
"local-names": [
{
"name": "America/New_York",
"lang": "en_US"
}
]
},
...
]
}
6.3. "get" Action
Name: get
Description: This action returns a timezone. If a single timezone
is specified, the response MUST contain an ETag response header
field indicating the current value of the strong entity tag of the
timezone resource.
If the identifier is actually a timezone alias, the server will
return the matching timezone data with the alias as the identifier
in the timezone data. The server MAY include one or more
"EQUIVALENT-TZID" properties (see Section 8) in the timezone data
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to indicate equivalent identifiers for the alias.
Parameters:
action REQUIRED with value "get"
format=<media-type> OPTIONAL, but MUST occur only once.
lang=<lang-code> OPTIONAL, but MAY occur multiple times.
tzid=<identifier> REQUIRED, and MUST occur only once.
truncate=<year> OPTIONAL, and MUST occur only once. See
Section 5.9 for details.
Response: A document containing all the requested timezone data in
the format specified.
Possible Error Codes
invalid-tzid The "tzid" query parameter is not present, or
appears more than once.
tzid-not-found No timezone associated with the specified "tzid"
query parameter value was found.
invalid-format The "format" query parameter appears more than
once, or has an invalid value.
invalid-truncate The "truncate" query parameter is not present,
or appears more than once, or has an invalid year specified as
its value.
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6.3.1. Example: Get timezone
In this example the client requests the timezone with a specific
timezone identifier to be returned
>> Request <<
GET /?action=get&tzid=America/New_York
&format=text/calendar HTTP/1.1
Host: tz.example.com
>> Response <<
HTTP/1.1 200 OK
Date: Wed, 4 Jun 2008 09:32:12 GMT
Content-Type: text/calendar; charset="utf-8"
Content-Length: xxxx
ETag: "123456789-000-111"
BEGIN:VCALENDAR
...
BEGIN:VTIMEZONE
TZID:America/New_York
...
END:VTIMEZONE
END:VCALENDAR
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6.3.2. Example: Get timezone alias
In this example the client requests the timezone with an aliased
timezone identifier to be returned, and the server returns the
timezone data with that identifier, and two equivalents
>> Request <<
GET /?action=get&tzid=US/Eastern
&format=text/calendar
&truncate=2000 HTTP/1.1
Host: tz.example.com
>> Response <<
HTTP/1.1 200 OK
Date: Wed, 4 Jun 2008 09:32:12 GMT
Content-Type: text/calendar; charset="utf-8"
Content-Length: xxxx
ETag: "123456789-000-111"
BEGIN:VCALENDAR
...
BEGIN:VTIMEZONE
TZID:US/Eastern
EQUIVALENT-TZID:America/New_York
EQUIVALENT-TZID:America/Montreal
...
END:VTIMEZONE
END:VCALENDAR
6.3.3. Example: Get truncated timezone
Assume the server advertises a "truncated" object in its
"capabilities" response that appears as:
truncated: {
"any": false,
"years": [1970, 2000],
"untruncated": false
}
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In this example the client requests the timezone with a specific
timezone identifier truncated at one of the years specified as
available by the server, to be returned
>> Request <<
GET /?action=get&tzid=America/New_York
&format=text/calendar
&truncate=2000 HTTP/1.1
Host: tz.example.com
>> Response <<
HTTP/1.1 200 OK
Date: Wed, 4 Jun 2008 09:32:12 GMT
Content-Type: text/calendar; charset="utf-8"
Content-Length: xxxx
ETag: "123456789-000-111"
BEGIN:VCALENDAR
...
BEGIN:VTIMEZONE
TZID:America/New_York
...
END:VTIMEZONE
END:VCALENDAR
6.4. "expand" Action
Name: expand
Description: This action expands the specified timezone into a list
of local time onset start date/time and UTC offsets. The response
MUST contain an ETag response header field indicating the current
value of the strong entity tag for the expanded data.
Parameters:
action REQUIRED with value "expand"
tzid=<identifier> REQUIRED, but MUST only occur once.
lang=<lang-code> OPTIONAL, but MAY occur multiple times.
start=year: OPTIONAL, but MUST occur only once. If present,
specifies the start of the period of interest. The value is an
integer representing the starting year, with the start date
assumed to be January 1st of that year. If "start" is omitted,
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the value is assumed to be the current year.
end=year: OPTIONAL, but MUST occur only once. If present,
specifies the ending year of the period of interest. The value
is an integer representing the ending year, with the end date
assumed to be January 1st of that year. If "end" is omitted,
the value is the start year + 10. Note that this is the
exclusive end value - i.e., it represents the date just after
the range of interest. e.g., if a client wants the expanded
date just for the year 2014, it would use a start value of
"2014" and an end value of "2015". An error occurs if the end
year is less than or equal to the start year.
changedsince OPTIONAL, but MUST occur only once. If present, its
value MUST be taken from the "dtstamp" result of a previous
expand result. If the targeted timezone has not changed over
the expansion range queried in the request, then the server
MUST return a 304 HTTP status response.
Response: A JSON object containing a "dtstamp" member and an
"observances" member, see Section 7.3. The server MUST include an
expanded observance representing the timezone information in
effect at the start of the period (midnight local time, January
1st of the start year).
Possible Error Codes
invalid-tzid The "tzid" query parameter is not present, or
appears more than once.
tzid-not-found No timezone associated with the specified "tzid"
query parameter value was found.
invalid-start The "start" query parameter has an incorrect value,
or appears more than once.
invalid-end The "end" query parameter has an incorrect value, or
appears more than once, or is missing, or has a value less than
or equal to the "start" query parameter.
invalid-changedsince The "changedsince" query parameter has an
incorrect value, or appears more than once.
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6.4.1. Example: Expanded JSON Data Format
In this example the client requests a timezone in the expanded form.
>> Request <<
GET /?action=expand&tzid=America/New_York&start=2008&end=2009 HTTP/1.1
Host: tz.example.com
>> Response <<
HTTP/1.1 200 OK
Date: Mon, 11 Oct 2009 09:32:12 GMT
Content-Type: application/json; charset="utf-8"
Content-Length: xxxx
ETag: "123456789-000-111"
{
"dtstamp": "2009-10-11T09:32:11Z",
"observances": [
{
"name": "Standard",
"onset": "2008-01-01T00:00:00",
"utc-offset-from": -18000,
"utc-offset-to": -18000
},
{
"name": "Daylight",
"onset": "2008-03-09T02:00:00",
"utc-offset-from": -18000,
"utc-offset-to": -14400
},
{
"name": "Standard",
"onset": "2008-11-02T02:00:00",
"utc-offset-from": -14400,
"utc-offset-to": -18000
},
]
}
6.5. "find" Action
Name: find
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Description: This action allows a client to query the timezone
service for a matching identifier, alias or localized name, using
a simple "glob" style match against the names known to the server
(with an asterisk * as the wildcard character). Match strings
have the following options:
* not present An exact text match is done, e.g., "xyz"
* first character only An ends-with text match is done, e.g.,
"*xyz"
* last character only An starts-with text match is done, e.g.,
"xyz*"
* first and last characters only A sub-string text match is done,
e.g., "*xyz*"
In addition, when matching, underscore characters (0x5F) SHOULD be
mapped to a single space character (0x20) prior to string
comparison. This allows timezone identifiers such as "America/
New_York" to match a query for "*New York*". ASCII characters in
the range 0x41 ("A") through 0x5A ("Z") SHOULD be mapped to their
lowercase equivalents.
Parameters:
action REQUIRED with value "find"
name=<text> REQUIRED, but MUST only occur once.
lang=<lang-code> OPTIONAL, but MAY occur multiple times.
Response: The response has the same format as the "list" action,
with one result object per successful match, see Section 7.2.
Possible Error Codes
invalid-name The "name" query parameter is not present, or
appears more than once.
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6.5.1. Example: Find action
In this example the client asks for data about the timezone "US/
Eastern".
>> Request <<
GET /?action=find&name=US/Eastern HTTP/1.1
Host: tz.example.com
>> Response <<
HTTP/1.1 200 OK
Date: Wed, 4 Jun 2008 09:32:12 GMT
Content-Type: application/json; charset="utf-8"
Content-Length: xxxx
{
"dtstamp": "2009-10-11T09:32:11Z",
"timezones": [
{
"tzid": "America/New_York",
"last-modified": "2009-09-17T01:39:34Z",
"aliases":["US/Eastern"],
"local-names": [
{
"name": "America/New_York",
"lang": "en_US"
}
]
},
{
"tzid": "America/Detroit",
"last-modified": "2009-09-17T01:39:34Z",
"aliases":["US/Eastern"],
"local-names": [
{
"name": "America/Detroit",
"lang": "en_US"
}
]
},
...
]
}
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7. JSON Definitions
JSON members used by this specification are defined here using the
syntax in [I-D.newton-json-content-rules]. Clients MUST ignore any
JSON members they do not expect.
7.1. capabilities action response
JSON Content Rules for the JSON document returned for a
"capabilities" action request.
; root object
root {
version,
info,
actions
}
; The version number of the protocol supported - MUST be 1
version "version" : integer 1..1
; object containing service information
info "info" {
primary_source / secondary_source,
?truncated,
contacts
}
; The source of the timezone data provided by a "primary" server
primary_source "primary-source" : string
; The timezone server from which data is provided by a "secondary"
; server
secondary_source "secondary-source" : uri
; Present if the server is providing truncated timezone data. The
; value is the truncation date-time. Timezone data will not be
; valid for dates prior to this value.
; [RFC3339] UTC value
truncated "truncated" : {
any,
?years,
?untruncated
}
; Indicates whether the server can truncate timezone data at any year
; boundary in the past. When set to "true" any past year is a valid
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; value for use with the "truncated" query parameter in an action
; "get" request
any "any" : boolean
; Indicates which year boundaries the server has truncated data for.
; A value from this list may be used with the "truncated" query
; parameter in an action "get" request. Not present if "any" is set
; to "true"
years "years" : [ * : integer ]
; Indicates whether the server can can supply untruncated data. When
; set to "true" indicates that, in addition to truncated data being
; available, the server can return untruncated data if an action "get"
; request is executed without a "truncated" query parameter
untruncated "untruncated" : boolean
; Array of URIs providing contact details for the server
; administrator
contacts "contacts" [ * : uri ]
; Array of actions supported by the server
actions "actions" [ * action ]
; An action supported by the server
action {
action_name,
action_params
}
; Name of the action
action_name "name" : string
; Array of request-URI query parameters supported by the action
action_params "parameters" [ * parameter ]
; Object defining an action parameter
parameter {
param_name,
?param_required,
?param_multi,
?param_values
}
; Name of the parameter
param_name "name" : string
; If true the parameter has to be present in the request-URI
; default is false
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param_required "required" : boolean
; If true the parameter can occur more than once in the request-URI
; default is false
param_multi "multi" : boolean,
; An array that defines the allowed set of values for the parameter
; In the absence of this member, any string value is acceptable
param_values "values" [ * : string ]
7.2. list action response
JSON Content Rules for the JSON document returned for a "list" action
request.
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; root object
root {
dtstamp,
timezones
}
; Server generated timestamp used for synchronizing changes,
; [RFC3339] UTC value
dtstamp "dtstamp" : date-time
; Array of timezone objects
timezones "timezones" [ * timezone ]
; Information about a timezone available on the server
timezone {
tzid,
last_modified,
?aliases,
?local_names,
}
; Timezone identifier
tzid "tzid" : string
; Date/time when the timezone data was last modified
; [RFC3339] UTC value
last_modified "last-modified" : date-time
; An array that lists the set of timezone aliases available
; for the corresponding timezone
aliases "aliases" [ * : string ]
; An array that lists the set of localized names available
; for the corresponding timezone
local_names "local-names" [ * local_name ]
local_name [lang, lname, ?pref]
; Language tag for the language of the associated name
lang : string
; Localized name
lname : string
; Indicates whether this is the preferred name for the associated
; language default: false
pref : boolean
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7.3. expand action response
JSON Content Rules for the JSON document returned for a "expand"
action request.
; root object
root {
dtstamp,
observances
}
; Server generated timestamp used for synchronizing changes
; [RFC3339] UTC value
dtstamp "dtstamp" : date-time
; Array of timezone objects
observances "observances" [ * observance ]
; Information about a timezone available on the server
observance {
oname,
?olocal_names,
onset,
utc_offset_from,
utc_offset_to
}
; Observance name
oname "name" : string
; Array of localized observance names
olocal_names "local-names" [ * : string]
; The local time at which the observance takes effect
; [RFC3339] value modified to exclude "time-offset" part
onset "onset" : date-time
; The UTC offset in seconds before the start of this observance
utc_offset_from "utc-offset-from" : integer
; The UTC offset in seconds at and after the start of this observance
utc_offset_to "utc-offset-to" : integer
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7.4. error response
JSON Content Rules for the JSON document returned when an error
occurs.
; root object
root {
error,
?description
}
; Error code
error "error" : string
; Description of the error
description "description" : string
8. Equivalent Timezone Identifier Property
Property Name: EQUIVALENT-TZID
Purpose: This property specifies an equivalent timezone identifier
representing the same timezone data as the aliased "VTIMEZONE"
component.
Value Type: TEXT
Property Parameters: IANA and non-standard property parameters can
be specified on this property.
Conformance: This property can be specified zero or more times
within "VTIMEZONE" calendar components.
Description: This property specifies an equivalent timezone
identifier for a "VTIMEZONE" component when the "TZID" property of
the timezone is an alias identifier.
Format Definition: This property is defined by the following
notation:
equivalent-tzid = "EQUIVALENT-TZID" etzidpropparam ":"
[tzidprefix] text CRLF
etzidpropparam = *(";" other-param)
;tzidprefix defined in [RFC5545].
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Example: The following is an example of this property:
EQUIVALENT-TZID:US/Eastern
9. Security Considerations
Timezone data is critical in determining local or UTC time for
devices and in calendaring and scheduling operations. As such, it is
vital that a reliable source of timezone data is used. Servers
providing a timezone service MUST support HTTP over Transport Layer
Security (TLS) (as defined by [RFC2818]) with a valid certificate.
Clients and servers making use of a timezone service SHOULD use HTTP
over TLS and verify the authenticity of the service being used before
accepting and using any timezone data from that source.
Clients that support transport layer security as defined by [RFC2818]
SHOULD try the "_timezones" service first before trying the
"_timezone" service. Clients MUST follow the certificate
verification process specified in [RFC6125].
A malicious attacker with access to the DNS server data, or able to
get spoofed answers cached in a recursive resolver, can potentially
cause clients to connect to any server chosen by the attacker. In
the absence of a secure DNS option, clients SHOULD check that the
target FQDN returned in the SRV record matches the original service
domain that was queried. If the target FQDN is not in the queried
domain, clients SHOULD verify with the user that the SRV target FQDN
is suitable for use before executing any connections to the host.
Timezone servers SHOULD protect themselves against errant or
malicious clients by throttling high request rates or frequent
requests for large amounts of data. Clients can avoid being
throttled by using the polling capabilities outlined in Section 4.1.3
10. IANA Considerations
This specification defines a new registry of "actions" for the
timezone service protocol, defines a "well-known" URI using the
registration procedure and template from Section 5.1 of [RFC5785],
creates two new SRV service label aliases, and defines one new
iCalendar property parameter as per the registration procedure in
[RFC5545].
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10.1. Service Actions Registration
This section defines the process to register new or modified timezone
service actions with IANA.
10.1.1. Service Actions Registration Procedure
The IETF will create a mailing list, timezone-service@ietf.org, which
can be used for public discussion of timezone service actions
proposals prior to registration. Use of the mailing list is strongly
encouraged. The IESG will appoint a designated expert who will
monitor the timezone-service@ietf.org mailing list and review
registrations.
Registration of new timezone service actions MUST be reviewed by the
designated expert and published in an RFC. A Standard Tracks RFC is
REQUIRED for the registration of new timezone service actions. A
Standard Tracks RFC is also REQUIRED for changes to actions
previously documented in a Standard Tracks RFC.
The registration procedure begins when a completed registration
template, defined in the sections below, is sent to
timezone-service@ietf.org and iana@iana.org. The designated expert
is expected to tell IANA and the submitter of the registration within
two weeks whether the registration is approved, approved with minor
changes, or rejected with cause. When a registration is rejected
with cause, it can be re-submitted if the concerns listed in the
cause are addressed. Decisions made by the designated expert can be
appealed to the IESG Applications Area Director, then to the IESG.
They follow the normal appeals procedure for IESG decisions.
10.1.2. Registration Template for Actions
An action is defined by completing the following template.
Name: The name of the action. This is also the value of the
"action" parameter used in timezone service requests.
Description: A general description of the action, its purpose, etc.
Parameters: A list of allowed request parameters, indicating whether
they are "REQUIRED" or "OPTIONAL" and whether they can occur only
once or multiple times.
Response The nature of the response to the HTTP request, e.g., what
format the response data is in.
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10.1.3. Registration Template for Action Parameters
An action parameter is defined by completing the following template.
Name: The name of the parameter.
Description: A general description of the parameter, its purpose,
etc.
Value: The format of the parameter value, or an indication that the
parameter has no value.
10.2. Initial Timezone Service Registries
The IANA is requested to create and maintain the following registries
for timezone service actions with pointers to appropriate reference
documents.
10.2.1. Actions Registry
The following table is to be used to initialize the actions registry.
+--------------+---------+----------------------+
| Action Name | Status | Reference |
+--------------+---------+----------------------+
| capabilities | Current | RFCXXXX, Section 6.1 |
| list | Current | RFCXXXX, Section 6.2 |
| get | Current | RFCXXXX, Section 6.3 |
| expand | Current | RFCXXXX, Section 6.4 |
| find | Current | RFCXXXX, Section 6.5 |
+--------------+---------+----------------------+
10.2.2. Action Parameters Registry
The following table is to be used to initialize the parameters
registry.
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+--------------+---------+----------------------+
| Parameter | Status | Reference |
+--------------+---------+----------------------+
| action | Current | RFCXXXX, Section 5.1 |
| changedsince | Current | RFCXXXX, Section 5.3 |
| end | Current | RFCXXXX, Section 5.5 |
| format | Current | RFCXXXX, Section 5.2 |
| lang | Current | RFCXXXX, Section 5.6 |
| name | Current | RFCXXXX, Section 5.8 |
| start | Current | RFCXXXX, Section 5.4 |
| truncate | Current | RFCXXXX, Section 5.9 |
| tzid | Current | RFCXXXX, Section 5.7 |
+--------------+---------+----------------------+
10.3. timezone Well-Known URI Registration
URI suffix: timezone
Change controller: IETF.
Specification document(s): This RFC.
Related information:
10.4. Service Name Registrations
This document registers two new service names as per [RFC6335]. Both
are defined within this document.
10.4.1. timezone Service Name Registration
Service Name: timezone
Transport Protocol(s): TCP
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>
Description: Timezone Service Protocol - non-TLS
Reference: [draft-douglass-timezone-service]
Assignment Note: This is an extension of the http service. Defined
TXT keys: path=<context path>
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10.4.2. timezones Service Name Registration
Service Name: timezones
Transport Protocol(s): TCP
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>
Description: Timezone Service Protocol - over TLS
Reference: [draft-douglass-timezone-service]
Assignment Note: This is an extension of the https service. Defined
TXT keys: path=<context path>
10.5. iCalendar Property Registration
This document defines the following new iCalendar property to be
added to the registry defined in Section 8.2.3 of [RFC5545]:
+-----------------+---------+--------------------+
| Property | Status | Reference |
+-----------------+---------+--------------------+
| EQUIVALENT-TZID | Current | RFCXXXX, Section 8 |
+-----------------+---------+--------------------+
11. Acknowledgements
The authors would like to thank the members of the Calendaring and
Scheduling Consortium's Timezone Technical Committee and the
following individuals for contributing their ideas and support: Steve
Allen, Steve Crocker, John Haug, Ciny Joy, Bryan Keller, Andrew
McMillan, Ken Murchison, Arnaud Quillaud, and Jose Edvaldo Saraiva.
The authors would also like to thank the Calendaring and Scheduling
Consortium for advice with this specification.
12. Normative References
[I-D.ietf-jcardcal-jcal]
Kewisch, P., Daboo, C., and M. Douglass, "jCal: The JSON
format for iCalendar", draft-ietf-jcardcal-jcal-09 (work
in progress), February 2014.
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[I-D.newton-json-content-rules]
Newton, A., "A Language for Rules Describing JSON
Content", draft-newton-json-content-rules-01 (work in
progress), January 2013.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the
Internet: Timestamps", RFC 3339, July 2002.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5545] Desruisseaux, B., "Internet Calendaring and Scheduling
Core Object Specification (iCalendar)", RFC 5545,
September 2009.
[RFC5646] Phillips, A. and M. Davis, "Tags for Identifying
Languages", BCP 47, RFC 5646, September 2009.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785,
April 2010.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, March 2011.
[RFC6321] Daboo, C., Douglass, M., and S. Lees, "xCal: The XML
Format for iCalendar", RFC 6321, August 2011.
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[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, August 2011.
[RFC6557] Lear, E. and P. Eggert, "Procedures for Maintaining the
Time Zone Database", BCP 175, RFC 6557, February 2012.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, February 2013.
[RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, March 2014.
Appendix A. Change History (to be removed prior to publication as an
RFC)
Changes for -11
1. start/end query parameter values are now just year numbers, no
dates.
Changes for -10
1. Expand start/end query parameter values are now years rather than
a date/date-time.
2. Added tzid-not-found error code for get and expand actions.
Changes for -09
1. Servers are allowed to truncate timezone data but need to
advertise when they do so. Clients can select from server-
specified truncations.
2. Explicitly list suggested polling intervals.
3. Removed used of * for tzid value.
4. Removed substitute alias.
5. Added EQUIVALENT-TZID property.
6. Added more details on truncation.
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7. Various editorial issues and clarifications.
Changes for -08
1. Editorial changes.
2. Fixed JSON content rule syntax.
3. Added a "version" to capabilities.
4. Changed "error" member to a string.
5. Added error codes.
6. Updated reference.
7. Removed inactive timezone feature and returnall parameter.
Changes for -07
1. Switched to JSON instead of XML and clean-ed up schema a little
bit.
2. Added changedsince to expand action.
3. Added find into registry table.
4. Re-organized some sections.
Changes for -06
1. Refresh prior to last call
Changes for -05
1. Replaced reference to draft RFC with RFC6557 and RFC6125.
2. New XML namespace contact.
3. Templates for service name.
4. Various typos fixed.
5. More acknowledgements.
Changes for -04
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1. Replaced reference to RFC4646 with reference to RFC5646
2. New wording on polling.
Changes for -03
1. Replaced erroneous reference to ISO3036 with reference to RFC4646
2. Update reference to iCalendar in XML (RFC6321)
3. More description of ids/aliases/names
4. Add substitute-alias parameter for action=get
5. Allow tzid on list
6. Added name request parameter
7. Added find action
Changes for -02
1. Missed definitions of the inactive element
2. Restrict UtcOffsetFromType, UtcOffsetToType to a pattern - allow
seconds.
3. Use restricted XML dateTime as base for onset
4. Use restricted XML dateTime for lastmodified and dtstamp
5. Note that 0 and 1 are valid values for an XML boolean.
6. Set pref to a default value of false
7. Server will now set tzid of aliased timezones to the alias name
8. Remove returnaliases option
9. Aliases should not have lang attribute - removed
10. Add text on status codes and an error element
11. Added capabilities info element containing source | primary-
source and contacts.
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Authors' Addresses
Michael Douglass
Rensselaer Polytechnic Institute
110 8th Street
Troy, NY 12180
USA
Email: douglm@rpi.edu
URI: http://www.rpi.edu/
Cyrus Daboo
Apple Inc.
1 Infinite Loop
Cupertino, CA 95014
USA
Email: cyrus@daboo.name
URI: http://www.apple.com/
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