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Independent Submission K. Murchison
Internet-Draft FastMail
Intended status: Standards Track November 11, 2017
Expires: May 15, 2018
The Time Zone Data Distribution Service (TZDIST) Geolocate Extension
draft-murchison-tzdist-geolocate-01
Abstract
This document defines an extension to the Time Zone Data Distribution
Service (RFC 7808) to allow a client to determine the correct time
zone for a geographic point location using a 'geo' URI (RFC 5870).
Status of This Memo
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Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 2
3. "geolocate" Action . . . . . . . . . . . . . . . . . . . . . 3
3.1. Examples: geolocate
action . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6.1. Service Action Registration . . . . . . . . . . . . . . . 6
6.2. Registration of invalid-location Error URN . . . . . . . 6
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Appendix A. Change History (To be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Clients using a Time Zone Data Distribution Service (TZDIST),
particularly mobile clients, may not have prior knowledge of which
time zone is appropriate for a particular geographic region. This
specification defines a new TZDIST service action to allow a client
to query a server with a geographic point location and have that
server determine if the location lies within the boundaries of an
existing time zone and return the corresponding time zone identifier.
This specification does not define the source of the time zone
boundary data. It is assumed that a reliable and accurate source is
available. Two such sources are [TZSHAPE] and [TZBB].
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
This specification contains examples of HTTP requests and responses.
In some cases, additional line breaks have been introduced into the
request or response data to match maximum line-length limits of this
document.
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3. "geolocate" Action
Name: geolocate
Request-URI Template:
{/service-prefix,data-prefix}/zones{?location}
Description: This action allows a client to query the time zone data
distribution service for the time zone identifier corresponding to
the given geographic point location, specified as a 'geo' URI
[RFC5870].
If the 'geo' URI specifies an uncertainty value (";u=" parameter),
the server MUST return the time zone identifiers for all time
zones whose boundary passes through the radius of uncertainty. In
the absence of a client-supplied uncertainty value, the server MAY
use an implicit uncertainty to coincide with any uncertainty in
the time zone boundary data that it uses.
If the 'geo' URI specifies a coordinate reference system (";crs="
parameter) that is unsupported by the server, the server SHOULD
return a JSON "problem details" object [RFC7807] in the response
body including a "type" member with an "invalid-location" error
URN as defined below.
Parameters:
location=<geo-URI> REQUIRED, and MUST occur only once.
Response: The response has the same format as the "list" and "find"
actions (see [RFC7808] Section 6.2), with one result object for
each geolocated time zone. If for any reason the server can not
determine a time zone in which the point is located (e.g.
uninhabited location), it MUST return a "list" response containing
zero time zone objects.
Possible Error Codes
urn:ietf:params:tzdist:error:invalid-location The "location" URI
query parameter has an incorrect or unsupported value or
appears more than once.
3.1. Examples: geolocate action
The examples below presume that the timezone context path has been
discovered (see [RFC7808] Section 4.2.1) to be "/tzdist".
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In this example the client asks for the time zone corresponding to
the Royal Observatory, Greenwich [ROG].
>> Request <<
GET /tzdist/zones?location=geo:51.47778,0.001388889 HTTP/1.1
Host: tz.example.com
>> Response <<
HTTP/1.1 200 OK
Date: Thu, 09 Nov 2017 13:43:28 GMT
Content-Type: application/json; charset="utf-8"
Content-Length: xxxx
{
"synctoken": "2860088640-1510059107",
"timezones": [
{
"tzid": "Europe/London",
"etag": "873664-1510059107",
"last-modified": "2017-11-07T12:51:47Z",
"publisher": "IANA Time Zone Database",
"version": "2017c",
"aliases": [
"GB",
"GB-Eire",
"Europe/Isle_of_Man",
"Europe/Guernsey",
"Europe/Belfast",
"Europe/Jersey"
]
}
]
}
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In this example the client asks for the timezone corresponding to the
Niagara Falls [NF] with an uncertainty of 50m. Note that the
cataracts are located on the border of Ontario, Canada, and New York,
United States, and therefore straddle a time zone boundary.
>> Request <<
GET /tzdist/zones?location=geo:43.0799,-79.0747;u=50 HTTP/1.1
Host: tz.example.com
>> Response <<
HTTP/1.1 200 OK
Date: Thu, 09 Nov 2017 13:58:07 GMT
Content-Type: application/json; charset="utf-8"
Content-Length: xxxx
{
"synctoken": "2860088640-1510059107",
"timezones": [
{
"tzid": "America/New_York",
"etag": "6602582-1510059107",
"last-modified": "2017-11-07T12:51:47Z",
"publisher": "IANA Time Zone Database",
"version": "2017c",
"aliases": [
"US/Eastern"
]
},
{
"tzid": "America/Toronto",
"etag": "3297806-1510059107",
"last-modified": "2017-11-07T12:51:47Z",
"publisher": "IANA Time Zone Database",
"version": "2017c",
"aliases": [
"America/Montreal",
"Canada/Eastern"
]
}
]
}
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4. Security Considerations
This specification does not introduce any additional security
concerns beyond those described in Section 8 of [RFC7808]
5. Privacy Considerations
A client that uses this extension will leak the precise location of a
user's device. The strategies described in Section 9 of [RFC7808]
can be used to diminish the ability of an untrusted server or network
observer to track the device.
6. IANA Considerations
6.1. Service Action Registration
This document defines the following new TZDIST Service Action to be
added to the registry defined in Section 10.3.1 of [RFC7808]:
+-------------+--------------------+
| Action Name | Reference |
+-------------+--------------------+
| geolocate | RFCXXXX, Section 3 |
+-------------+--------------------+
6.2. Registration of invalid-location Error URN
This section registers the "urn:ietf:params:tzdist:error:invalid-
location" URN in the "TZDIST Identifiers" registry defined in
Section 10.4 of [RFC7808].
URN: urn:ietf:params:tzdist:error:invalid-location
Description: Error code for incorrect use of the "location" URI
query parameter.
Specification: RFCXXXX, Section 3
Contact: IESG <iesg@ietf.org>
Index value: N/A.
7. Acknowledgments
The author would like to thank the following individuals for
contributing their ideas and support for writing this specification:
Cyrus Daboo and Michael Douglass.
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8. References
8.1. 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>.
[RFC5870] Mayrhofer, A. and C. Spanring, "A Uniform Resource
Identifier for Geographic Locations ('geo' URI)",
RFC 5870, DOI 10.17487/RFC5870, June 2010,
<https://www.rfc-editor.org/info/rfc5870>.
[RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP
APIs", RFC 7807, DOI 10.17487/RFC7807, March 2016,
<https://www.rfc-editor.org/info/rfc7807>.
[RFC7808] Douglass, M. and C. Daboo, "Time Zone Data Distribution
Service", RFC 7808, DOI 10.17487/RFC7808, March 2016,
<https://www.rfc-editor.org/info/rfc7808>.
8.2. Informative References
[NF] Wikipedia, "Niagara Falls",
<https://en.wikipedia.org/wiki/Niagara_Falls>.
[ROG] Wikipedia, "Royal Observatory, Greenwich",
<https://en.wikipedia.org/wiki/
Royal_Observatory,_Greenwich>.
[TZBB] Siroky, E., "Timezone Boundary Builder",
<https://github.com/evansiroky/timezone-boundary-builder>.
[TZSHAPE] Muller, E., "A set of shapefiles for the TZ timezones",
<http://efele.net/maps/tz/>.
Appendix A. Change History (To be removed by RFC Editor before
publication)
Changes since -00:
o Updated author information.
o Changed locations used in examples.
o Closed issue "percent-encode 'geo' URI value" as unnecessary.
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o Closed issue "advertise supported coordinate reference system" as
unnecessary (only "wgs84" is defined for RFC 5870).
o Closed issue "discuss territorial and/or international waters" as
unnecessary.
o Added privacy concern.
o Minor editorial changes.
Author's Address
Kenneth Murchison
FastMail Pty Ltd
Level 2, 114 William Street
Melbourne, VIC 3000
Australia
Email: murch@fastmailteam.com
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