Network Working Group T. Hardie
Internet-Draft Qualcomm, Inc.
Expires: December 18, 2006 A. Newton
SunRocket
H. Schulzrinne
Columbia U.
H. Tschofenig
Siemens
June 16, 2006
LoST: A Location-to-Service Translation Protocol
draft-ietf-ecrit-lost-00.txt
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
This document describes an XML-based protocol for mapping service
identifiers and geospatial or civic location information to service
contact URIs. In particular, it can be used to determine the
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location-appropriate PSAP for emergency services.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 5
3. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Server Discovery . . . . . . . . . . . . . . . . . . . . . . . 7
5. Query . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Location Information Element . . . . . . . . . . . . . . . 8
5.2. Service Identifier Element . . . . . . . . . . . . . . . . 8
5.3. Validate Attribute . . . . . . . . . . . . . . . . . . . . 8
5.4. Query Message Examples . . . . . . . . . . . . . . . . . . 8
6. Response . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.1. Uniform Resource Identifiers (URI) Element . . . . . . . . 10
6.2. Display Name Element Element . . . . . . . . . . . . . . . 10
6.3. Region Element . . . . . . . . . . . . . . . . . . . . . . 10
6.4. Dialstring Element . . . . . . . . . . . . . . . . . . . . 10
6.5. TimeToLive Attribute . . . . . . . . . . . . . . . . . . . 10
6.6. Validated Element . . . . . . . . . . . . . . . . . . . . 10
6.7. text Attribute . . . . . . . . . . . . . . . . . . . . . . 11
6.8. Response Message Examples . . . . . . . . . . . . . . . . 11
7. Miscellaneous Functionality . . . . . . . . . . . . . . . . . 13
7.1. List Service Query . . . . . . . . . . . . . . . . . . . . 13
7.2. Response to a List Service Query . . . . . . . . . . . . . 13
8. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9. Deployment Methods . . . . . . . . . . . . . . . . . . . . . . 17
10. XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 19
11. Internationalization Considerations . . . . . . . . . . . . . 24
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
13. Security Considerations . . . . . . . . . . . . . . . . . . . 26
14. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 27
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
15.1. Normative References . . . . . . . . . . . . . . . . . . . 28
15.2. Informative References . . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30
Intellectual Property and Copyright Statements . . . . . . . . . . 31
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1. Introduction
This document describes a protocol for mapping a service
identifier[6] and location information compatible with PIDF-LO [10]
to one or more service contact URIs. Example contact URI schemes
include sip, xmpp, and tel. While the initial focus is on providing
mapping functions for emergency services, it is likely that the
protocol is applicable to any service URN. For example, in the
United States, the "2-1-1" and "3-1-1" services follow a similar
location-to-service behavior as emergency services.
This document names this protocol usage "LoST" for Location-to-
Service Translation Protocol. The features of LoST are:
o Supports queries using civic as well as geospatial location
information.
o Can be used in both recursive and iterative resolution.
o Can be used for civic address validation.
o A hierarchical deployment of mapping servers is independent of
civic location labels.
o Can indicate errors in the location data to facilitate debugging
and proper user feedback while simultaneously providing best-
effort answers.
o Mapping can be based on either civic or geospatial location
information, with no performance penalty for either.
o Service regions can overlap.
o Satisfies the requirements [5] for mapping protocols.
o Minimizes round trips by caching individual mappings and by
supporting return of coverage regions ("hinting").
o Facilitates reuse of TLS.
This document focuses on the description of the protocol between the
mapping client (seeker or resolver) and the mapping server (resolver
or other servers). The relationship between other functions, such as
discovery of mapping servers, data replication and the overall
mapping server architecture in general, will be described in a
separate document. [12] is a first attempt to describe such a mapping
server architecture.
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The high-level protocol operation can be described as follows:
Location
Info +----------+
--------> | |
Service | LoST |
URN | Server |
--------> | |
+----------+
Query
URI +----------+
<------- | |
Optional | LoST |
Info (hints)| Server |
<------- | |
+----------+
Response
Figure 1: Overview
The query message carries location information and a service
identifier enconded as a Uniform Resource Name (URN) (see [6]) from
the LoST client to the LoST server. The LoST server uses its
database to map the input values to a Uniform Resource Identifiers
(URI) and returns it including optional information such as hints
about the service boundary in a response message back to the LoST
client.
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2. Requirements Notation
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 [3].
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3. Usage
The client queries a server, indicating the desired service and the
location object. If the query succeeds, the server returns a result
that includes one or more URIs for reaching the appropriate service
for the location indicated. Depending on the query, the result may
contain a region where the same mapping would apply, a reference to
another server to which the client should send a query, and error
messages indicating problems with interpretation of location
information. The combination of these components are left to the
needs and policy of the jurisdiction where the server is being
operated.
The client may perform the mapping at any time. Among the common
triggers for mapping are:
1. When the client starts up and/or attaches to a new network
location.
2. When the client detects that its location has changed
sufficiently that it is outside the bounds of the region returned
in an earlier query.
3. When cached mapping information has expired.
4. When calling for a particular service. During such calls, a
client MAY request a short response that contains only the
mapping data, omitting region information. In some operational
environments a UDP-based transport may be available and MAY be
used to confirm or update data already available.
Cached answers are expected to be used by clients only after failing
to accomplish a location-to-URI mapping at call time. Cache entries
may expire according to their time-to-live value, or they may become
invalid if the location of the caller's device moves outside the
boundary limits of the cache entry. Boundaries for cache entries may
be set in both geospatial and civic terms.
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4. Server Discovery
There are likely to be a variety of ways that clients can discover
appropriate LoST servers, including DHCP, SIP device configuration,
or DNS records for their signaling protocol domain, e.g., the AOR
domain for SIP. The appropriate server depends on, among other
considerations, who operates LoST services, including the Internet
Service Provider (ISP), Voice Service Provider (VSP), or the user's
home domain. A DNS based approach utilizing the S-NAPTR mechanism is
specified in [6].
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5. Query
LoST provides the ability to use civic or geospatial location
information in the query message message. In addition to location
information the query also contains a service identifier. An
optional parameter might furthermore request the LoST server to
validate location information.
5.1. Location Information Element
LoST supports a query using geospatial and civic location information
using the findLoSTByCivic and the findLoSTByGeo query. Geospatial
location information uses GML format [9] and civic location
information utilizes the format defined in [10]. Hence, the location
format is not defined in this document but references already
available standards.
5.2. Service Identifier Element
The type of service desired is specified by the <service> element.
The emergency identifiers listed in the registry established with [6]
will be used in this document.
5.3. Validate Attribute
The 'validate' attribute implements the validation behavior described
in [5].
5.4. Query Message Examples
This section shows an example of a query message providing geospatial
and civic location information.
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<?xml version="1.0"?>
<findLoSTByGeo
validate="false"
xmlns:p2="http://www.opengis.net/gml"
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<p2:location>
<p2:Point p2:id="point1" srsName="epsg:4326">
<p2:coordinates>37:46:30N 122:25:10W</p2:coordinates>
</p2:Point>
</p2:location>
<service>urn:service:sos</service>
</findLoSTByGeo>
Figure 2: Query Message Example using Geospatial Location Information
The example above shows a query using geospatial location information
with no validation required and asking for the 'urn:service:sos'
service.
<?xml version="1.0"?>
<findLoSTByCivic
validate="true"
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:p2="urn:ietf:params:xml:ns:pidf:geopriv10:civilLoc"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<civicLocation>
<p2:country>Germany</p2:country>
<p2:A1>Bavaria</p2:A1>
<p2:A3>Munich</p2:A3>
<p2:A6>Neu Perlach</p2:A6>
<p2:HNO>96</p2:HNO>
<p2:PC>81675</p2:PC>
</civicLocation>
<service>urn:service:sos.police</service>
</findLoSTByCivic>
Figure 3: Query Message Example using Civic Location Information
The example above shows a query using a civic location in Munich
asking for the 'urn:service:sos' service. The query also indicates
that validation is desired.
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6. Response
A response message might either be a responseGeo or a responseCivic
depending on the type of query message. If the query message was a
findLoSTByCivic then the response will be a responseCivic. If a
findLoSTByGeo message was sent as a query then the response will be a
findLoSTByGeo. The location information that is provided by the
response message depends on the query and refers to the service
boundary as described in Section 6.3.
6.1. Uniform Resource Identifiers (URI) Element
Each uri element contains an appropriate contact URI for the service
for which mapping was requested. uri elements are of type xs:anyURI.
In the emergency service context operators are strongly discouraged
from using relative URIs, even though these are permitted by the
type.
6.2. Display Name Element Element
Each displayName element contains a string that is suitable for
display. displayName elements are of type "text" as described in
Section 6.7.
6.3. Region Element
Each region element contains either one or more civic location
elements derived from the GeoPriv civic address schema or feature.xsd
expression from GML.
6.4. Dialstring Element
Each dialstring element contains from one to sixteen digits. Note
that a Tel URI may also contain the same target, expressed in a
different format; see RFC 3966 [11].
6.5. TimeToLive Attribute
Each timeToLive attribute is a positive integer, expressing the
validity period of the response in seconds.
6.6. Validated Element
Each validated element contains a string which is composed by by
concatenating the elements from the request which have been
recognized as valid by the server.
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6.7. text Attribute
This is a text type suitable for internationalized human readable
text.
6.8. Response Message Examples
This section shows an example of a query message providing geospatial
and civic location information.
<?xml version="1.0" encoding="UTF-8"?>
<responseGeo
timeToLive="10000"
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p2="http://www.opengis.net/gml">
<displayName>New York City Police Department</displayName>
<p2:Polygon srsName="urn:ogc:def::crs:EPSG::4326">
<p2:exterior>
<p2:LinearRing>
<p2:pos>37.775 -122.4194</p2:pos>
<p2:pos>37.555 -122.4194</p2:pos>
<p2:pos>37.555 -122.4264</p2:pos>
<p2:pos>37.775 -122.4264</p2:pos>
<p2:pos>37.775 -122.4194</p2:pos>
</p2:LinearRing>
</p2:exterior>
</p2:Polygon>
<uri>sip:nypd@example.com</uri>
<uri>xmpp:nypd@example.com</uri>
<dialstring>911</dialstring>
</responseGeo>
Figure 4: Response Message Example using Geospatial Location Service
Boundary Hints
This example shows a reponse with two URIs for the previously queried
service URN. Information about the service boundary is provided in
the Polyon. The <dialstring> element indicates the valid dialstring
for the expressed location and service URN.
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<?xml version="1.0" encoding="UTF-8"?>
<responseCivic
timeToLive="10000"
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p2="urn:ietf:params:xml:ns:pidf:geopriv10:civilLoc">
<displayName>Munich Police Department</displayName>
<region>
<p2:country>Germany</p2:country>
<p2:A1>Bavaria</p2:A1>
<p2:A3>Munich</p2:A3>
</region>
<validated>country A1 A3 A6 PC</validated>
<uri>sip:munich-police@example.com</uri>
<uri>xmpp:munich-police@example.com</uri>
<dialstring>110</dialstring>
</responseCivic>
Figure 5: Response Message Example providing Civic Location Service
Boundary Hints
This example shows a response that returns two URIs (one for SIP and
another one for XMPP), a distring that indicates the valid distring
for the location provided in the query, a hint about the service
boundary in the <region> element and information about the validated
civic address fields. The timeToLive indicates that the returned
information can be cached for 10000 seconds and provides a
displayName with additional, textual information about the returned
information.
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7. Miscellaneous Functionality
7.1. List Service Query
This subsection describes a query that offers the LoST client to
query for available service identifiers supported by the LoST server.
<?xml version="1.0" encoding="UTF-8"?>
<listServices
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<service>urn:service:sos</service>
</listServices>
Figure 6: Example for a List Service Query
This listService query aims to query the immediate child elements of
the 'urn:service:sos' URN.
7.2. Response to a List Service Query
This subsection describes the response message that provides the LoST
client with the list of immediate child service identifiers based on
the service identifier provided by LoST client in the query.
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<?xml version="1.0" encoding="UTF-8"?>
<returnServices
timeToLive="10000"
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<service>urn:service:sos.ambulance</service>
<service>urn:service:sos.animal-control</service>
<service>urn:service:sos.fire</service>
<service>urn:service:sos.gas</service>
<service>urn:service:sos.mountain</service>
<service>urn:service:sos.marine</service>
<service>urn:service:sos.physician</service>
<service>urn:service:sos.poison</service>
<service>urn:service:sos.police</service>
<service>urn:service:sos.suicide</service>
</returnServices>
Figure 7: Example for the Response to a List Service Query
This response corresponds to the query of Figure 6.
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8. Example
After performing link layer attachment and end host performs stateful
address autoconfiguration (in our example) using DHCP. Then, DHCP
provides the end host with civic location as described in[7].
+--------+---------------+
| CAtype | CAvalue |
+--------+---------------+
| 0 | US |
| 1 | New York |
| 3 | New York |
| 6 | Broadway |
| 22 | Suite 75 |
| 24 | 10027-0401 |
+--------+---------------+
Figure 8: DHCP Civic Information Example
Additionally, DHCP may provide information about the LoST server that
can be contacted. Alternatively, an additional step of indirection
is possible, for example by having DHCP return a domain name that has
to be resolved to one or more IP addresses hosting LoST servers.
Both at attachment time and call time, the client places a LoST
request, including its civic location and the desired service. The
request is shown below:
<?xml version="1.0"?>
<findLoSTByCivic
validate="true"
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:p2="urn:ietf:params:xml:ns:pidf:geopriv10:civilLoc"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<civicLocation>
<p2:country>US</p2:country>
<p2:A1>New York</p2:A1>
<p2:A3>New York</p2:A3>
<p2:A6>Broadway</p2:A6>
<p2:LOC>Suite 75</p2:LOC>
<p2:PC>10027-0401</p2:PC>
</civicLocation>
<service>urn:service:sos.police</service>
</findLoSTByCivic>
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Since the contacted LoST server has the requested information
available the following response is returned. The response
indicates, as a human readable display string that the 'New York City
Police Department' is responsible for the given geographical area.
The indicated URI allows the user to start communication using SIP or
XMPP. The 'validated' element indicates which parts of the civic
address were matched successfully against a database and represent a
known address. Other parts of the address, here, the suite number,
were ignored and not validated. The returned service boundary
indicates that all of New York City would result in the same
response. The dialstring element indicates that the service can be
reached via the dial string 9-1-1.
<?xml version="1.0" encoding="UTF-8"?>
<responseCivic
timeToLive="10000"
xmlns="urn:ietf:params:xml:ns:lost1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:p2="urn:ietf:params:xml:ns:pidf:geopriv10:civilLoc">
<displayName>New York City Police Department</displayName>
<region>
<p2:country>US</p2:country>
<p2:A1>New York</p2:A1>
<p2:A3>New York</p2:A3>
</region>
<validated>country A1 A3 A6 PC</validated>
<uri>sip:nypd@example.com</uri>
<uri>xmpp:nypd@example.com</uri>
<dialstring>911</dialstring>
</responseCivic>
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9. Deployment Methods
Because services for emergency contact resolution may differ
depending on local or service needs, this document only specifies the
"wire format" for LoST services and explicitly leaves open the
possibility for many different types of deployment.
For instance:
During discovery, a client may be directed to issue all queries to
an LoST service completely authoritative for a given jursidiction.
A client may be directed to issue queries to an LoST server that
acts as a reflector. In such a case, the LoST server analyzes the
query to determine the best server to wich to refer the client.
Or the client may be directed to a server that performs further
resolution on behalf of the client.
A LoST service may also be represented by multiple LoST servers,
either grouped together or at multiple network locations. Using
S-NAPTR [13], clients may be given a list of multiple servers to
which queries can be sent for a single service.
For instance, the service at emergency.example.com may advertise LoST
service at local1.emergency.example.com,
local2.emergency.example.com, and master.emergency.example.com. Each
server may given a different preference. In this case, 'local-1' and
'local-2' may be given a lower preference (more preferred) than
'master', which might be a busier server or located further away.
+-----------+ pref 10 +-----------+
| |-------------------->+ |
| client |------ | local-1 |
| |--- \ | |
+-----------+ \ \ +-----------+
\ \
\ \ +-----------+
\ \ pref 10 | |
\ --------->| local-2 |
\ | |
\ +-----------+
\
\ +-----------+
\ pref 20 | |
------------------------->| master |
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| |
+-----------+
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10. XML Schema
This section provides the XML schema used by LoST.
<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema"
targetNamespace="urn:ietf:params:xml:ns:lost1"
xmlns:lost="urn:ietf:params:xml:ns:lost1"
xmlns:civilLoc="urn:ietf:params:xml:ns:pidf:geopriv10:civilLoc"
xmlns:gml="http://www.opengis.net/gml"
xmlns:ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
elementFormDefault="qualified" attributeFormDefault="unqualified">
<annotation>
<documentation>
A schema for a Location to Service Translation Protocol
</documentation>
</annotation>
<!-- -->
<!-- Query types -->
<!-- -->
<!-- Abstract Query -->
<complexType name="queryType"/>
<element name="query" type="lost:queryType" abstract="true"/>
<!-- findLoSTByCivic -->
<element name="findLoSTByCivic" type="lost:findLoSTByCivicType"
substitutionGroup="lost:query"/>
<complexType name="findLoSTByCivicType">
<complexContent>
<extension base="lost:queryType">
<sequence>
<element name="civilAddress"
type="civilLoc:civilAddress"
minOccurs="0" maxOccurs="1"/>
<element name="service" type="anyURI"
minOccurs="1" maxOccurs="1"/>
</sequence>
<attribute name="validate"
type="boolean" default="false"/>
</extension>
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</complexContent>
</complexType>
<!-- findLoSTByGeo -->
<element name="findLoSTByGeo" type="lost:findLoSTByGeoType"
substitutionGroup="lost:query"/>
<complexType name="findLoSTByGeoType">
<complexContent>
<extension base="lost:queryType">
<sequence>
<element ref="gml:location"
minOccurs="0" maxOccurs="1"/>
<element name="service" type="anyURI"
minOccurs="1" maxOccurs="1"/>
</sequence>
<attribute name="validate"
type="boolean" default="false"/>
</extension>
</complexContent>
</complexType>
<!-- listServices -->
<element name="listServices" type="lost:listServicesType"
substitutionGroup="lost:query"/>
<complexType name="listServicesType">
<complexContent>
<extension base="lost:queryType">
<sequence>
<element name="service" type="anyURI"
minOccurs="1" maxOccurs="1"/>
</sequence>
</extension>
</complexContent>
</complexType>
<!-- -->
<!-- Responses -->
<!-- -->
<!-- Abstract Response -->
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<element name="result" type="lost:resultType" abstract="true"/>
<complexType name="resultType">
<attribute name="timeToLive" type="positiveInteger"
use="required" />
</complexType>
<!-- emergencyContact Response -->
<element name="responseCivic" type="lost:responseCivicType"
substitutionGroup="lost:result"/>
<complexType name="responseCivicType">
<complexContent>
<extension base="lost:resultType">
<sequence>
<element name="displayName"
type="normalizedString"
minOccurs="0" maxOccurs="1"/>
<element name="civilAddress"
type="civilLoc:civilAddress"
minOccurs="0" maxOccurs="1" />
<element name="uri" type="anyURI"
minOccurs="0"
maxOccurs="unbounded" />
<element name="dialstring"
type="normalizedString"
minOccurs="0" maxOccurs="1" />
</sequence>
</extension>
</complexContent>
</complexType>
<element name="responseGeo" type="lost:responseGeoType"
substitutionGroup="lost:result"/>
<complexType name="responseGeoType">
<complexContent>
<extension base="lost:resultType">
<sequence>
<element name="displayName"
type="normalizedString"
minOccurs="0" maxOccurs="1"/>
<element ref="gml:Polygon"
minOccurs="0" maxOccurs="1"/>
<element name="uri" type="anyURI"
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minOccurs="0"
maxOccurs="unbounded"/>
<element name="dialstring"
type="normalizedString"
minOccurs="0" maxOccurs="1" />
</sequence>
</extension>
</complexContent>
</complexType>
<element name="returnServices" type="lost:returnServicesType"
substitutionGroup="lost:result"/>
<complexType name="returnServicesType">
<complexContent>
<extension base="lost:resultType">
<sequence>
<element name="service" type="anyURI"
minOccurs="1" maxOccurs="unbounded"/>
</sequence>
</extension>
</complexContent>
</complexType>
<!-- -->
<!-- Error responses -->
<!-- -->
<element name="genericCode" type="lost:codeType"
abstract="true"/>
<element name="invalidCivicData" type="lost:codeType"
substitutionGroup="lost:genericCode"/>
<element name="invalidGeoData" type="lost:codeType"
substitutionGroup="lost:genericCode"/>
<element name="invalidService" type="lost:codeType"
substitutionGroup="lost:genericCode"/>
<complexType name="codeType">
<sequence minOccurs="0" maxOccurs="unbounded">
<element name="explanation">
<complexType>
<simpleContent>
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<extension base="string">
<attribute name="language"
type="language"
use="required"/>
</extension>
</simpleContent>
</complexType>
</element>
</sequence>
</complexType>
</schema>
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11. Internationalization Considerations
This mechanism is largely for passing protocol information from one
subsystem to another; as such, most of its elements are tokens not
meant for direct human consumption. If these tokens are presented to
the end user, some localization may need to occur. The content of
the displayName element may be displayed to the end user, and it is
thus a complex type designed for this purpose.
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12. IANA Considerations
TBD, such as namespace registrations.
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13. Security Considerations
There are multiple threats to the overall system of which service
mapping forms a part. An attacker that can obtain service contact
URIs can use those URIs to attempt to disrupt those services. An
attacker that can prevent the lookup of contact URIs can impair the
reachability of such services. An attacker that can eavesdrop on the
communication requesting this lookup can surmise the existence of an
emergency and possibly its nature, and may be able to use this to
launch a physical attack on the caller.
To avoid that an attacker can modify the query or its result, LoST
RECOMMENDS the use of channel security, such as TLS.
A more detailed description of threats and security requirements are
provided in [4].
[Editor's Note: A future version of this document will describe the
countermeasures based on the security requirements outlined in[4].]
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14. Open Issues
Please find open issues at: http://www.ietf-ecrit.org:8080/lost/
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15. References
15.1. Normative References
[1] World Wide Web Consortium, "XML Schema Part 2: Datatypes",
W3C XML Schema, October 2000,
<http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/>.
[2] World Wide Web Consortium, "XML Schema Part 1: Structures",
W3C XML Schema, October 2000,
<http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/>.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, BCP 14, March 1997.
[4] Taylor, T., "Security Threats and Requirements for Emergency
Call Marking and Mapping", draft-ietf-ecrit-security-threats-01
(work in progress), April 2006.
[5] Schulzrinne, H. and R. Marshall, "Requirements for Emergency
Context Resolution with Internet Technologies",
draft-ietf-ecrit-requirements-10 (work in progress), June 2006.
[6] Schulzrinne, H., "A Uniform Resource Name (URN) for Services",
draft-ietf-ecrit-service-urn-03 (work in progress), May 2006.
[7] Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4
and DHCPv6) Option for Civic Addresses Configuration
Information", draft-ietf-geopriv-dhcp-civil-09 (work in
progress), January 2006.
[8] Mealling, M., "The IETF XML Registry",
draft-mealling-iana-xmlns-registry-03 (work in progress),
November 2001.
[9] OpenGIS, "Open Geography Markup Language (GML) Implementation
Specification", OGC OGC 02-023r4, January 2003.
[10] Peterson, J., "A Presence-based GEOPRIV Location Object
Format", RFC 4119, December 2005.
15.2. Informative References
[11] Schulzrinne, H., "The tel URI for Telephone Numbers", RFC 3966,
December 2004.
[12] Schulzrinne, H., "Location-to-URL Mapping Architecture and
Framework", draft-schulzrinne-ecrit-mapping-arch-00 (work in
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progress), October 2005.
[13] Daigle, L. and A. Newton, "Domain-Based Application Service
Location Using SRV RRs and the Dynamic Delegation Discovery
Service (DDDS)", RFC 3958, January 2005.
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Authors' Addresses
Ted Hardie
Qualcomm, Inc.
Email: hardie@qualcomm.com
Andrew Newton
SunRocket
8045 Leesburg Pike, Suite 300
Vienna, VA 22182
US
Phone: +1 703 636 0852
Email: andy@hxr.us
Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Phone: +1 212 939 7004
Email: hgs+ecrit@cs.columbia.edu
URI: http://www.cs.columbia.edu
Hannes Tschofenig
Siemens
Otto-Hahn-Ring 6
Munich, Bavaria 81739
Germany
Phone: +49 89 636 40390
Email: Hannes.Tschofenig@siemens.com
URI: http://www.tschofenig.com
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