SIP J. Winterbottom
Internet-Draft M. Thomson
Intended status: Standards Track Andrew Corporation
Expires: January 8, 2009 H. Tschofenig
Nokia Siemens Networks
July 7, 2008
A Session Initiation Protocol (SIP) Event Package for Location
Information
draft-winterbottom-sip-location-package-00.txt
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Abstract
This document specifies a SIP event package allowing allowing a
location receiptient to subscribe for location information when
provided a location URI using the sip, sips, or pres URI schemes.
The notification that results from the subscription is either the
location of the Target or an error.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Protocol Interaction . . . . . . . . . . . . . . . . . . . . . 6
4. Overview of Operation . . . . . . . . . . . . . . . . . . . . 8
5. Event Package details . . . . . . . . . . . . . . . . . . . . 10
5.1. Event Package Name . . . . . . . . . . . . . . . . . . . . 10
5.2. Event Package Parameters . . . . . . . . . . . . . . . . . 10
5.3. Accept Header Value . . . . . . . . . . . . . . . . . . . 10
5.4. Subscription Duration . . . . . . . . . . . . . . . . . . 10
5.5. Forked SUBSCRIBE Requests . . . . . . . . . . . . . . . . 10
5.6. Subscribing for Location Information . . . . . . . . . . . 11
5.6.1. SUBSCRIBE Message Body . . . . . . . . . . . . . . . . 11
5.7. Location Notification . . . . . . . . . . . . . . . . . . 12
5.7.1. NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . 12
5.7.2. Rate of Notifications . . . . . . . . . . . . . . . . 12
5.8. State Agents . . . . . . . . . . . . . . . . . . . . . . . 13
6. Schema . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . . . 16
7.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . . 19
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
9.1. HELD Error Token Registration . . . . . . . . . . . . . . 20
9.2. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:loc-event . . . . . . . . . . . . . 20
9.3. XML Schema Registration . . . . . . . . . . . . . . . . . 21
9.4. MIME Media Type Registration for
'application/loc-event+xml' . . . . . . . . . . . . . . . 21
9.5. Event Package Registration . . . . . . . . . . . . . . . . 22
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
11.1. Normative References . . . . . . . . . . . . . . . . . . . 24
11.2. Informative References . . . . . . . . . . . . . . . . . . 24
Appendix A. Subscription Examples . . . . . . . . . . . . . . . . 27
A.1. Requesting a Quality of Position . . . . . . . . . . . . . 27
A.2. Inclusion of Mahy Loc-Filters . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31
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Intellectual Property and Copyright Statements . . . . . . . . . . 32
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1. Introduction
Location information is generally recognized as being a subset of
presence as described in [RFC4079]. It is also recognized that
location information is most readily available from the local access
network serving a specific end-device. The node in a local access
network responsible for determining and desseminating an end-point's
location is referred to as a location information server (LIS).
Where the LIS is capable of supporting SIP SUBSCRIBE and NOTIFY
messages [RFC3265] for the dissemination of location information it
becomes a limited capability presence server. To support this
limited capability a new SIP event package is defined specifically
for the subscription to, and notification of, a Target's physical
location.
This document proposes the usage of the Session Initiation Protocol
(SIP) [RFC3261] as a location dereference protocol. This is
accomplished by defining a new subscription event package as
described in RFC3265 [RFC3265].
This event package is based on the concept of a location information
server (LIS), which resides in the same access network as a Target.
the LIS is capable of accepting subscriptions, storing subscription
state, and generating notifications either periodically or when the
LIS detects changes in a Target's physical location.
The event package defines a simple but extensible XML schema which
allows a location recipient to subscribe to a LIS for a Target's
location information. A base set of subscription criteria are
defined in an XML schema. Extensions points are provided in the
schema so that additional criteria can be specified for future
application requirements.
How the location recipient learns the location URI is out of scope
for this document. The specification relies of existing SIP,
presence, and georpiv mechansisms for the authentication of location
recipients and the application of these mechanisms is deemed out of
scope for this specification. Existing presence and location
authorization policies such as those described in common policy
[RFC4745] and geolocation policy [I-D.ietf-geopriv-policy] are
assumed to be in place. Alternatively, specific constraints attached
to the location URI itself, such as those described in
[I-D.winterbottom-geopriv-held-context] are assumed to exist.
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2. Terminology
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].
The terms Location Recipient and Target are used as defined in
[RFC3693]
The term location information (LIS) is used throughout this document
as defined in [I-D.ietf-geopriv-l7-lcp-ps]. A presence server that
distributes physical location to watchers may also be regarded as a
LIS in the terms of reference for this document.
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3. Protocol Interaction
Using a location URI that provides a Target's location to a recipient
directly from the LIS is often preferable and more effient than
requiring location information originate from the LIS and traverse
the Target end-point before reaching the location recipient. This is
especially true in environments where the Target can move and change
points of network attachment without an interuption in service. The
merits and requirements of using a location URI are addressed in
detail in the location by reference requirements document
[I-D.ietf-geopriv-lbyr-requirements].
Location configuration protocols, such as HELD, provide an end-point
the ability to request a location URI that they can distribute to
external entities and applications for the purpose of later location
retrival. A scheme for dereferencing HELD URIs is described in
[I-D.winterbottom-geopriv-deref-protocol]. This specification
describes a location information event package that an application or
entity can use this to request location information directly from a
LIS or presence server using SIP.
The SIP subscription functionality is described in [RFC3265], along
with general guidelines for defining new event packages for which
subscriptions can be made. This specification defines a new event
package that allows a recipient to specifically subscribe for
location information. The event package consists of an XML schema
that is included in the body of the SIP subscribe message, and a new
subscribe event header. Both the schema and the subscribe event
header are registered with IANA in Section 9. The general context
and model for location subscription is shown in Figure 1.
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+-----------+
+------------+ | Location | +-----------+
| End Device | |Information| | Location |
| (Target) | | Server | | Recipient |
+-----+------+ +----+------+ +-----+-----+
| | |
+--+--------------------------+--+ |
| | | | |
| |===locationRequest(URI)==>0 | |
| | | | Location |
| | | | Configuration |
| 0<==locationResponse(URI)==| | Protocol |
| | | | |
+--+--------------------------+--+ |
| | |
| | |
|~~~~~~~~~~~~Location Conveyance (URI)~~~~~~~~~~~~~~~~~~>0
| | |
| +--+-----------------------------+--+
| | | | |
| Location | 0<======SUBSCRIBE(loc)========| |
| Event | | | |
| Package | |========NOTIFY(PIDF-LO)=====>0 |
| | |========NOTIFY(PIDF-LO)=====>0 |
| | |========NOTIFY(PIDF-LO)=====>0 |
| +--+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+--+
| | |
| | |
Figure 1: Context Diagram
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4. Overview of Operation
In this section, an overview of the operation of this event package
is presented. In order to provide clarity on this package the
overview describes behavior that is documented in part here, partly
in the SIP event framework [RFC3265], and in the SIP specification
[RFC3261]. However, the detailed semantics of this package require
the reader to be familiar with SIP events and the SIP specification
itself.
When an entity, the subscriber, wishes to learn about the location
from some user, it creates a SUBSCRIBE request. This request
identifies the desired Target in the Request-URI, using a SIP URI,
SIPS URI [RFC3261] or a presence (pres) URI [RFC3859]. The SUBSCRIBE
request is carried along SIP proxies as any other SIP request would
be and eventually arrives at a LIS, which will generate a response to
the request.
The LIS first authenticates the subscription, then authorizes it.
The means for authorization are outside the scope of this protocol.
If authorized, a 200 OK response is returned followed immediately by
a NOTFIY message containing the location of the target. If
authorization could not be obtained at this time, the subscription is
considered "terminated" with a reason code of "rejected" and a
$quot;403 Forbidden" response is returned. Periodicially, or as the
location of the Target changes, the LIS generates and sends NOTIFY
messages containing the location information to all subscribers with
authorized subscriptions. Changes in the state of the subscription
itself can also trigger NOTIFY messages; that state is carried in the
Subscription-State header field of the NOTIFY, and would typically
indicate whether the subscription is active or terminated. No
pending state for location information is considered.
The SUBSCRIBE message establishes a "dialog" with the LIS. A dialog
is defined in RFC 3261 [RFC3261], and it represents the SIP state
between a pair of entities to facilitate peer-to-peer message
exchanges. This state includes the sequence numbers for messages in
both directions (SUBSCRIBE from the subscriber, NOTIFY from the LIS),
in addition to a route set and remote target URI. The route set is a
list of SIP (or SIPS) URIs which identify SIP proxy servers that are
to be visited along the path of SUBSCRIBE refreshes or NOTIFY
requests. The remote target URI is the SIP or SIPS URI that
identifies the target of the message - the subscriber, in the case of
NOTIFY, or the LIS, in the case of a SUBSCRIBE refresh.
The subscription persists for a duration that is negotiated as part
of the initial SUBSCRIBE. The subscriber will need to refresh the
subscription before its expiration, if they wish to retain the
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subscription. This is accomplished by sending a SUBSCRIBE refresh
within the same dialog established by the initial SUBSCRIBE. This
SUBSCRIBE is nearly identical to the initial one, but contains a tag
in the To header field and a higher CSeq header field value.
The subscriber can terminate the subscription by sending a SUBSCRIBE,
within the dialog, with an Expires header field (which indicates
duration of the subscription) value of zero. This causes an
immediate termination of the subscription. A NOTIFY request is then
generated by the LIS with the most recent location information for
the Target.
The LIS can terminate the subscription at any time. To do so, it
sends a NOTIFY request with a Subscription-State header field with a
value of "terminated". A reason parameter is also supplied which
provides the reason for the termination.
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5. Event Package details
5.1. Event Package Name
A SIP subscription specifies precisely which event or set events
(event package) the subscriber is interested in being notified about.
This specification deals with subscription for location information
and specifies a new event package excplicitly for this purpose. The
SIP event notification specification [RFC3265] stipulates that a new
event package requires the registration of a new "Event" header token
so that a subscriber can explcitly subscribe for these events. This
specification defines the "loc-event" Event header token, and
registers it in Section 9. All subscriptions for location
information are expected to use this Event header token.
5.2. Event Package Parameters
The SIP event framework allows event packages to define additional
parameters carried in the Event header field. This package,
presence, does not define any additional parameters.
5.3. Accept Header Value
The Accept header in the SUBSCRIBE indicates to the LIS what type of
information the location recipient is expecting. This event package
requires that the Accept header bet set to "application/held+xml".
The rationale for resuing the HELD MIME type in the NOTIFY message is
provide in Section 5.7.1.
5.4. Subscription Duration
Default is 24 hours. If the URI was generated using HELD Context
management or some other policy-based mechansism then the LIS MUST
provide and expires value that is equal to or less than the expiry
time of the specified in the policy.
Very short subscription times will be treated as though they are
immediate notification requests. Assuming that the subscription is
accepted, the LIS will respond with the fastest location that it is
able to provide.
5.5. Forked SUBSCRIBE Requests
This event package does not support forked SUBSCRIBE requests.
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5.6. Subscribing for Location Information
5.6.1. SUBSCRIBE Message Body
The characteristics of the subscription are defined in the XML schema
which is conveyed from the subscriber to the LIS in the body of the
SUBSCRIBE message. A new MIME type of application/loc-event+xml is
defined for use with this schema and it is registered in Section 9.
The schema is broken into two parts, a "what" part, and a "when"
part. The "what" part defines what the subscriber requires, and the
"when" part defines when the LIS should send it. These two
components are described in more detail below.
5.6.1.1. What
The "what" part of the location subscription comprises of two basic
components. A location type element allows the subscriber to specify
the type of location information that they wish to receive, geodetic,
civic, or any. The LIS should try to provide location in the form
subscribed for. If the LIS is unable to provide location in the form
requested, then it may provide location in an alternative form. If
the subscriber is unable to process the location form returned by the
LIS, then the subscriber is expected to terminate the subscription.
An extension point is included in the schema so that additional
requirements of what is to be provided in notification responses can
be specified. Examples of how to use this this extension point are
providced in Appendix A. Thes examples should be considered
informative only.
5.6.1.2. When
The "when" part of the subscription tells the LIS when the subscriber
would like to receive location information about the Target. Two
basic components are provided. An interval, in seconds, tell the LIS
how often to send a location update to the subscriber. An trigger
for sending notifications when the Target's point of network
attachment changes is also provided. The "when" elements operate in
a logical OR manner, and a notification SHOULD be sent whenever one
of these conditions occurs.
An extension point exists in the schema so that additional
notification triggers can be specified and added as they become
required.
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5.7. Location Notification
Location information and error messages are returned to the
subscriber in the body of a SIP NOTIFY message.
5.7.1. NOTIFY Bodies
The NOTIFY body is either a HELD locationResponse, or a HELD error
message, both are defined in
[I-D.ietf-geopriv-http-location-delivery]. The rationale for reusing
the location response and error messages from HELD is twofold.
Firstly a location recipient cannot be assured ahead of time of the
location URI type that a Target will provide it; this is largely
determined by what the LIS in the local access network provides to
the Target and so is out of the control of both the Target and
recipient. So the recipient should be capable of dealing with HELD
location responses in any event. Secondly, the HELD location
response and error messages provide excellent containers for the
information that the LIS needs to provide to the location recipient
in a NOTIFY. Rules from HELD
[I-D.ietf-geopriv-http-location-delivery] apply when constructing
these messages, with the exception of the clarifications provided
later.
An error will, in some circumstances, result in a terminated
subscription, however in other cases the error condition may be
present for only one specific notification cycle in which case the
subscription will remain active. The subscriber MUST examine the
value of the Subscription-State header to determine if the
subscription has been terminated or not.
The LIS MUST send a NOTIFY with a Subscription-State header value of
"terminated" and a reason code of "noresource"when it is no longer
able to provide the Target's location though the subscribed URI.
This informs the subscriber that no further attempts to subscribe to
the resource should be attempted. The LIS MUST include a HELD error
message with a code of "locationUnknown" in the NOTFIY body when this
condition occurs.
5.7.2. Rate of Notifications
The rate at which notifications are generated is excplictly defined
in the interval element of the "when" component in the SUBSCRIBE
body. This element defines how often the subscriber wishes to
receive notifications about a Target's location. The interval value
is a positive integer respresenting seconds.
A new HELD error token of "intervalTooShort" is regsitered in
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Section 9 and MUST be used by the LIS when an inappropriately short
notification interval is requested by the subscriber. When this
error is returned the corresponding NOTIFY message MUST have a
Subscription-State header value of "termninated", reason code of
"giveup" and a value for the retry-after parameter MAY be provided.
5.8. State Agents
The LIS is responsible for keeping track of where a Target is
physically located in the access network. Stare, as it pertains to
this event package, refers to the policies associated with the URI to
which the subscription was made, and physical location of the Target.
State is therefore maintained internal to the LIS and is explcitly
resolved at the time that a notification is generated.
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6. Schema
This section defines the schema that constitutes the body of this
even package.
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Figure 2: XML Schema for Subscription Body
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7. Examples
7.1. Example 1
In this example emergency application 1, emgapp1, is subscribing for
the location information associated is xyzabc being service by the
LIS at example.com. The emergency application would like to get
geodetic location information, updated every 10 seconds or when
xyzabc changes wireless access points. The subscription is for a
duration of 30 minutes.
SUBSCRIBE sip:xyzabc@lis.example.com SIP/2.0
Via: SIP/2.0/TCP emergency.emergizone.com;branch=z9hG4bKnashds7
To:
From: ;tag=xfg9
Call-ID: 2010@emergency.emergizone.com
CSeq: 17766 SUBSCRIBE
Max-Forwards: 70
Event: loc-event
Accept: application/held+xml
Contact:
Expires: 1800
Content-Type: application/loc-event+xml
Content-Length: 330
geodetic
10
yes
Figure 3: SUBSCRIBE Message
The successful response to the subscription shown in Figure 3 is a
200 OK followed almost immediately by a NOTIFY containing the
requested location. This is shown in Figure 4.
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NOTIFY sip:emgapp1@emergizone.com SIP/2.0
Via: SIP/2.0/TCP lis.example.com;branch=z9hG4bKna998sk
From: ;tag=ffd2
To: ;tag=xfg9
Call-ID: 2010@emergency.emergizone.com
Event: loc-event
Subscription-State: active;expires=1790
Max-Forwards: 70
CSeq: 8775 NOTIFY
Contact: sip:lis.example.com
Content-Type: application/held+xml
Content-Length: 911
-34.407 150.88001
2006-01-11T03:42:28+00:00
Device-Assisted_A-GPS
2008-03-31T03:42:28+00:00
Figure 4: NOTIFY Message with Location Information
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7.2. Example 2
An error message is returned when a problem with the subscription is
encountered, for example the location URI that the subscriber
subscribed too has expired or its usage count has been exceeded.
This error message may look something like the NOTIFY shown in
Figure 5.
NOTIFY sip:emgapp1@emergizone.com SIP/2.0
Via: SIP/2.0/TCP lis.example.com;branch=z9hG4bKna998sk
From: ;tag=ffd2
To: ;tag=xfg9
Call-ID: 2010@emergency.emergizone.com
Event: loc-event
Subscription-State: terminated;reason=noresource
Max-Forwards: 70
CSeq: 8775 NOTIFY
Contact: sip:lis.example.com
Content-Type: application/held+xml
Content-Length: 159
Figure 5: NOTIFY Message with Error
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8. Security Considerations
TBD.
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9. IANA Considerations
9.1. HELD Error Token Registration
Reference: RFC-XXXX (i.e., this document) requires the following new
HELD error code to be added to the HELD error code respository
defined in [I-D.ietf-geopriv-http-location-delivery].
Error code: intervalTooShort
9.2. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:loc-event
This section registers a new XML namespace,
"urn:ietf:params:xml:ns:loc-event", as per the guidelines in
[RFC3688].
URI: urn:ietf:params:xml:ns:loc-event
Registrant Contact: IETF, SIP working group, (sip@ietf.org), James
Winterbottom (james.winterbottom@andrew.com).
XML:
BEGIN
Location Information Subscription Event Package
Namespace for the Location Information
Subscription Application Event Package
urn:ietf:params:xml:ns:loc-event
[[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX
with the RFC number for this specification.]]
See RFCXXXX.
END
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9.3. XML Schema Registration
This section registers an XML schema as per the guidelines in
[RFC3688].
URI: urn:ietf:params:xml:schema:loc-event
Registrant Contact: IETF, SIP working group, (sip@ietf.org), James
Winterbottom (james.winterbottom@andrew.com).
Schema: The XML for this schema can be found as the entirety of
Section 6 of this document.
9.4. MIME Media Type Registration for 'application/loc-event+xml'
This section registers the "application/loc-event+xml" MIME type.
To: ietf-types@iana.org
Subject: Registration of MIME media type application/loc-event+xml
MIME media type name: application
MIME subtype name: loc-event+xml
Required parameters: (none)
Optional parameters: charset
Indicates the character encoding of enclosed XML. Default is
UTF-8.
Encoding considerations: Uses XML, which can employ 8-bit
characters, depending on the character encoding used. See RFC
3023 [RFC3023], section 3.2.
Security considerations: This content type is designed to carry
protocol data related to the location of an entity, which could
include information that is considered private. Appropriate
precautions should be taken to limit disclosure of this
information.
Interoperability considerations: This content type provides a basis
for a protocol
Published specification: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please
replace XXXX with the RFC number for this specification.]]
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Applications which use this media type: Location information
consumers.
Additional Information: Magic Number(s): (none)
File extension(s): .xml
Macintosh File Type Code(s): (none)
Person & email address to contact for further information: James
Winterbottom
Intended usage: LIMITED USE
Author/Change controller: This specification is TBD
Other information: This media type is a specialization of
application/xml [RFC3023], and many of the considerations
described there also apply to application/loc-event+xml.
9.5. Event Package Registration
This specification registers an event package, based on the
registration procedures defined in RFC3265 [RFC3265]. The following
is the information required for such a registration:
Package Name: loc-event
Package or Template-Package: This is a Package
Published Document: RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please
replace XXXX with the RFC number for this specification.]]
Person or Contact: James Winterbottom, james.winterbottom@andrew.com
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10. Acknowledgements
We would like to thank Miguel Garcia and Brian Rosen for their
comments.
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11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and
J. Polk, "Geopriv Requirements", RFC 3693, February 2004.
[RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
Types", RFC 3023, January 2001.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
[RFC3859] Peterson, J., "Common Profile for Presence (CPP)",
RFC 3859, August 2004.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[I-D.ietf-geopriv-lbyr-requirements]
Marshall, R., "Requirements for a Location-by-Reference
Mechanism", draft-ietf-geopriv-lbyr-requirements-02 (work
in progress), February 2008.
[I-D.ietf-geopriv-http-location-delivery]
Barnes, M., Winterbottom, J., Thomson, M., and B. Stark,
"HTTP Enabled Location Delivery (HELD)",
draft-ietf-geopriv-http-location-delivery-07 (work in
progress), April 2008.
[I-D.ietf-geopriv-l7-lcp-ps]
Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7
Location Configuration Protocol; Problem Statement and
Requirements", draft-ietf-geopriv-l7-lcp-ps-08 (work in
progress), June 2008.
11.2. Informative References
[RFC4079] Peterson, J., "A Presence Architecture for the
Distribution of GEOPRIV Location Objects", RFC 4079,
Winterbottom, et al. Expires January 8, 2009 [Page 24]
Internet-Draft Location Event Package July 2008
July 2005.
[RFC3856] Rosenberg, J., "A Presence Event Package for the Session
Initiation Protocol (SIP)", RFC 3856, August 2004.
[I-D.ietf-geopriv-pdif-lo-profile]
Winterbottom, J., Thomson, M., and H. Tschofenig, "GEOPRIV
PIDF-LO Usage Clarification, Considerations and
Recommendations", draft-ietf-geopriv-pdif-lo-profile-11
(work in progress), February 2008.
[I-D.winterbottom-geopriv-deref-protocol]
Winterbottom, J., Tschofenig, H., Schulzrinne, H.,
Thomson, M., and M. Dawson, "An HTTPS Location
Dereferencing Protocol Using HELD",
draft-winterbottom-geopriv-deref-protocol-01 (work in
progress), July 2008.
[RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object
Format", RFC 4119, December 2005.
[RFC4745] Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J.,
Polk, J., and J. Rosenberg, "Common Policy: A Document
Format for Expressing Privacy Preferences", RFC 4745,
February 2007.
[I-D.ietf-geopriv-policy]
Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J.,
and J. Polk, "Geolocation Policy: A Document Format for
Expressing Privacy Preferences for Location Information",
draft-ietf-geopriv-policy-17 (work in progress),
June 2008.
[I-D.winterbottom-geopriv-held-context]
Winterbottom, J., Tschofenig, H., and M. Thomson, "HELD
Protocol Context Management Extensions",
draft-winterbottom-geopriv-held-context-02 (work in
progress), February 2008.
[I-D.thomson-geopriv-location-quality]
Thomson, M. and J. Winterbottom, "Specifying Location
Quality Constraints in Location Protocols",
draft-thomson-geopriv-location-quality-01 (work in
progress), May 2008.
[I-D.ietf-geopriv-loc-filters]
Mahy, R., "A Document Format for Filtering and Reporting
Location Notications in the Presence Information Document
Winterbottom, et al. Expires January 8, 2009 [Page 25]
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Format Location Object (PIDF-LO)",
draft-ietf-geopriv-loc-filters-01 (work in progress),
March 2007.
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Appendix A. Subscription Examples
The exmaples in this appendix should be regarded as non-normative,
that is that they are for informational purposes only. There intent
is to demonstrate that other geoprive location request criteria can
easily be included into the framework described in this document.
A.1. Requesting a Quality of Position
It is quite common for applications to want loation to be provided as
a set of coordinates, latitude, longitude and optionally alitutde,
and an area of uncertainty. The document
[I-D.thomson-geopriv-location-quality] describes a means by which
location information of a specific accuracy and/or confidence can be
requested. Together these characteristics are referred to as the
Quality of Position (QoP). The following example show how a location
subscription can be constructed including QoP parameters based on the
scheme provided in [I-D.thomson-geopriv-location-quality], the
location provided in the subsequent location response messages should
also comply with [I-D.thomson-geopriv-location-quality].
geodetic
150
1000
PT30S
180
true
Figure 6: Subscribing for Location with a Quality of Position
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A.2. Inclusion of Mahy Loc-Filters
Rohan Mahy produced an early specification
[I-D.ietf-geopriv-loc-filters] that described how specific location
events and triggers could be defined in an XML document. This work
is easily included into the framework.
In this example the LIS is to generate a noficiation if the Target
moves horizontally by more than 20 metres, or vertical by more than
10 metres. The LIS should provide an update every 3 minutes
regardless of the Target movements, or when the Target changes its
point of attachment to the network.
civic
180
true
20
3
Figure 7: Subscribing for Location of Location Constrained Target
In this example LIS is to generate a noficiation if the Target
exceeds a speed of 3 MPH. The LIS should provide an update every 3
minutes regardless of the Target movements, or when the Target
changes its point of attachment to the network.
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civic
60
3
Figure 8: Subscribing for Location of a Speed Limited Target
This final filters example shows how the entry or exit of a specific
polygon by the Target can be subscribed to using the framework.
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civic
60
37.41188 -121.93243
37.41142 -121.93243
37.41142 -121.93132
37.41188 -121.93132
37.41188 -121.93243
Figure 9: Subscribing for Location of Target in a Polygon
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Authors' Addresses
James Winterbottom
Andrew Corporation
PO Box U40
Wollongong University Campus, NSW 2500
AU
Phone: +61 2 4221 2938
Email: james.winterbottom@andrew.com
URI: http://www.andrew.com/
Martin Thomson
Andrew Corporation
PO Box U40
Wollongong University Campus, NSW 2500
AU
Phone: +61 2 4221 2915
Email: martin.thomson@andrew.com
URI: http://www.andrew.com/
Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo, 02600
Finland
Phone: +358 (50) 4871445
Email: Hannes.Tschofenig@nsn.com
URI: http://www.tschofenig.priv.at
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Full Copyright Statement
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Winterbottom, et al. Expires January 8, 2009 [Page 32]