GEOPRIV WG                                                M. Barnes, Ed.
Internet-Draft                                                    Nortel
Intended status: Standards Track
Expires: March 30, 2008

                                                      September 27, 2007

                 HTTP Enabled Location Delivery (HELD)

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Copyright Notice

   Copyright (C) The IETF Trust (2007).


   A Layer 7 Location Configuration Protocol (L7 LCP) is described that
   is used for retrieving location information from a server within an
   access network.  The protocol includes options for retrieving
   location information either by-value or by-reference.  The protocol
   is an application-layer protocol that is independent of session-
   layer; an HTTP, web services binding is specified.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions & Terminology  . . . . . . . . . . . . . . . . . .  4
   3.  Overview and Scope . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Protocol Overview  . . . . . . . . . . . . . . . . . . . . . .  6
   5.  Protocol Description . . . . . . . . . . . . . . . . . . . . .  7
     5.1.  Protocol Binding . . . . . . . . . . . . . . . . . . . . .  7
     5.2.  Location Request . . . . . . . . . . . . . . . . . . . . .  8
     5.3.  Location Response  . . . . . . . . . . . . . . . . . . . .  8
     5.4.  Indicating Errors  . . . . . . . . . . . . . . . . . . . .  8
   6.  Protocol Parameters  . . . . . . . . . . . . . . . . . . . . .  8
     6.1.  "responseTime" Parameter . . . . . . . . . . . . . . . . .  9
     6.2.  "locationType" Parameter . . . . . . . . . . . . . . . . . 10
       6.2.1.  "exact" Attribute  . . . . . . . . . . . . . . . . . . 10
     6.3.  "code" Parameter . . . . . . . . . . . . . . . . . . . . . 11
     6.4.  "message" Parameter  . . . . . . . . . . . . . . . . . . . 11
     6.5.  "locationURI" Parameter  . . . . . . . . . . . . . . . . . 11
       6.5.1.  "expires" Parameter  . . . . . . . . . . . . . . . . . 12
   7.  XML Schema . . . . . . . . . . . . . . . . . . . . . . . . . . 12
   8.  HTTP Binding . . . . . . . . . . . . . . . . . . . . . . . . . 16
     8.1.  HTTP Binding WSDL  . . . . . . . . . . . . . . . . . . . . 16
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 18
     9.1.  Return Routability . . . . . . . . . . . . . . . . . . . . 18
     9.2.  Transaction Layer Security . . . . . . . . . . . . . . . . 19
   10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
     10.1. Simple HTTP Binding Example Messages . . . . . . . . . . . 19
     10.2. Simple Location Request Example  . . . . . . . . . . . . . 22
     10.3. Location Request Example for Multiple Location Types . . . 23
     10.4. Sample LIS  WSDL Document  . . . . . . . . . . . . . . . . 24
   11. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 25
     11.1. URN Sub-Namespace Registration for
           urn:ietf:params:xml:ns:geopriv:held  . . . . . . . . . . . 25
     11.2. XML Schema Registration  . . . . . . . . . . . . . . . . . 25
     11.3. URN Sub-Namespace Registration for
           urn:ietf:params:xml:ns:geopriv:held:http . . . . . . . . . 25
     11.4. MIME Media Type Registration for 'application/held+xml'  . 26
   12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 27
   13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 27
   14. Changes since last Version . . . . . . . . . . . . . . . . . . 27
   15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     15.1. Normative References . . . . . . . . . . . . . . . . . . . 29
     15.2. Informative References . . . . . . . . . . . . . . . . . . 30
   Appendix A.  HELD Compliance to IETF LCP requirements  . . . . . . 31
     A.1.  L7-1: Identifier Choice  . . . . . . . . . . . . . . . . . 31
     A.2.  L7-2: Mobility Support . . . . . . . . . . . . . . . . . . 31
     A.3.  L7-3: ASP and Access Network Provider Relationship . . . . 32
     A.4.  L7-4: Layer 2 and Layer 3 Provider Relationship  . . . . . 32

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     A.5.  L7-5: Legacy Device Considerations . . . . . . . . . . . . 32
     A.6.  L7-6: VPN Awareness  . . . . . . . . . . . . . . . . . . . 33
     A.7.  L7-7: Network Access Authentication  . . . . . . . . . . . 33
     A.8.  L7-8: Network Topology Unawareness . . . . . . . . . . . . 33
     A.9.  L7-9: Discovery Mechanism  . . . . . . . . . . . . . . . . 34
     A.10. L7-10: PIDF-LO Creation  . . . . . . . . . . . . . . . . . 34
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 34
   Intellectual Property and Copyright Statements . . . . . . . . . . 36

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1.  Introduction

   The location of a Device is information that is useful for a number
   of applications.  The L7 Location Configuration Protocol (LCP)
   problem statement and requirements document [11] provides some
   scenarios in which a Device might rely on its access network to
   provide the location information, such as fixed environments (e.g.,
   DSL/Cable), mobile networks and wireless access networks.  This
   document describes a protocol that can be used to acquire Location
   Information (LI) from a Location Information Server (LIS) within an
   access network.

   This specification identifies two methods for acquiring LI.  Location
   may be retrieved from a LIS by-value, that is, the Device may acquire
   a literal location object describing the location of the Device.
   Alternatively, the Device may request that the LIS provide a location
   reference in the form of a location URI or set of location URIs,
   allowing the Device to distribute its LI by-reference.  Both of these
   methods are compatible, and both can be provided concurrently from
   the same LIS so that application needs can be addressed individually.

   This specification defines an XML-based protocol that enables the
   retrieval of LI from a LIS by a Device.  This protocol can be bound
   to any session-layer protocol, particularly those capable of MIME
   transport; an HTTP binding is included as a minimum requirement.

2.  Conventions & Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [1].

   This document uses the terms (and their acronym forms) Access
   Provider (AP), Location Information (LI), Location Object (LO),
   Device, Target, Location Generator (LG), Location Recipient (LR),
   Rule Maker (RM) and Rule Holder (RH) as defined in RFC 3693, GEOPRIV
   Requirements [7] .  The terms Location Information Server (LIS),
   Access Network, Access Provider (AP) and Access Network Provider are
   used in the same context as defined in the L7 LCP Problem statement
   and Requirements document [11].  The usage of the terms, Civic
   Location/Address and Geodetic Location follows the usage in many of
   the referenced documents.

3.  Overview and Scope

   This document describes an interface between a Device and a Location

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   Information Server (LIS).  The LIS is present within the same
   administrative domain as the Device (the access network).  An Access
   Provider (AP) operates the LIS so that Devices (and Targets) can
   retrieve LI.  The LIS exists because not all Devices are capable of
   determining LI, and because, even if a device is able to determine
   its own LI, it may be more efficient with assistance.  This document
   does not specify how LI is derived.

   This document is based on the attribution of the LI to a Device and
   not specifically a person (end user) or Target, based on the premise
   that location determination technologies are generally designed to
   locate a device and not a person.  It is expected that, for most
   applications, LI for the device can be used as an adequate substitute
   for the end user's LI.  Since revealing the location of the device
   almost invariably reveals some information about the location of the
   user of the device, the same level of privacy protection demanded by
   a user is required for the device.  This approach may require either
   some additional assurances about the link between device and target,
   or an acceptance of the limitation that unless the device requires
   active user authentication, there is no guarantee that any particular
   individual is using the device at that instant.

   The following diagram shows the logical configuration of some of the
   functional elements identified in [7] and the LIS defined in [11] and
   where this protocol applies, with the Rule Maker and Target
   represented by the role of the Device.

                     | Access Network Provider                     |
                     |                                             |
                     |   +--------------------------------------+  |
                     |   | Location Information Server          |  |
                     |   |                                      |  |
                     |   |                                      |  |
                     |   |                                      |  |
                     |   |                                      |  |
                     |   +------|---------------------'---------+  |
                                |                     '
                                |                     '
                               HELD                  APP
                                |                     '
     Rule Maker   - _     +-----------+         +-----------+
           o          - - | Device    |         | Location  |
          <U\             |           | - - - - | Recipient |
          / \       _ - - |           |   APP   |           |
         Target - -       +-----------+         +-----------+

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                        Figure 1: Significant Roles

   The interface between the Location Recipient (LR) and the Device
   and/or LIS is application specific, as indicated by the APP
   annotation in the diagram and it is outside the scope of the
   document.  An example of an APP interface between a device and LR can
   be found in the SIP Location Conveyance document [22].

4.  Protocol Overview

   The HELD protocol facilitates retrieval of LI either by-value, as a
   PIDF-LO document, or by-reference, as a Location URI.  The policy
   that describes to whom, and how, LI is granted is outside the scope
   of this document and may be specified in separate specifications as
   required.  The Device must first discover the URI for the LIS for
   sending the HELD protocol requests as identified by the requirement
   in the L7 LCP problem statement and requirements [11].  The discovery
   methods are specified in [15].

   Where a Device requires LI directly, it can request that the LIS
   create a PIDF-LO document.  This approach fits well with a
   configuration whereby the device directly makes use of the provided
   PIDF-LO document.  With this approach, the LIS needs to uniquely
   identify the Device within the access network.  The source IP address
   of the request message is sufficient in most cases.  Once the Device
   is identified, the LIS uses network domain-specific information to
   determine the location of the Device.

   The details on the information that may be included in the PIDF-LO
   MUST follow the subset of those rules relating to the construction of
   the "location-info" element in the PIDF-LO Usage Clarification,
   Considerations and Recommendations document [10].  The LIS MUST
   follow those rules in generating the PIDF-LO in this case.  Per the
   GEOPRIV Location Object format specified in [8], the "entity" element
   MUST reflect the Target of the Location Information.  In addition,
   the default values for <retransmission-allowed> and <retention-
   expiry> as specified in [8] MUST be applied.  A default value of "no"
   SHALL be used for the <retransmission-allowed> element.  A default
   value of 24 hours SHALL be used for <retention-expiry> value of any
   generated PIDF-LO documents.  A LIS MAY provide a shorter value for
   <retention-expiry> but MUST NOT provide a value longer than 24 hours.

   Requesting location directly does not always address the requirements
   of an application.  A Device can request a location URI instead of
   literal location.  A Location URI is a URI [21] of any scheme, which
   a Location Recipient (LR) can use to retrieve LI.  A location URI
   provided by a LIS can be assumed to be globally-addressable; that is,

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   anyone in possession of the URI can access the LIS.  This does not in
   any way suggest that the LIS is bound to reveal the location
   associated with the location URI.  This issue is deemed out of scope
   for this document.  The merits and drawbacks of using a Location URI
   approach are discussed in [16].

5.  Protocol Description

   As discussed in Section 4, this protocol provides for the retrieval
   of a Location or a Location URI from a LIS.  Three messages are
   defined to support the location retrieval: locationRequest,
   locationResponse and error.  Messages are defined as XML documents.

   The Location Request (locationRequest) message is described in
   Section 5.2.  A Location Request message from a Device indicates
   whether a Location (and the specific type of location) and/or a
   Location URI should be returned.  The LIS replies with a response
   (locationResponse), including a PIDF-LO document and/or one or more
   Location URIs in case of success, or an error message in case of an

   A MIME type "application/held+xml" is registered in Section 11.4 to
   distinguish HELD messages from other XML document bodies.  This
   specification follows the recommendations and conventions described
   in [19], including the naming convention of the type ('+xml' suffix)
   and the usage of the 'charset' parameter.

   Section 6 contains a more thorough description of the protocol
   parameters, valid values, and how each should be handled.  Section 7
   contains a more specific definition of the structure of these
   messages in the form of an XML Schema [12].

5.1.  Protocol Binding

   The HELD protocol is an application-layer protocol that is defined
   independently of any lower layers.  This means that any protocol can
   be used to transport this protocol providing that it can provide a
   few basic features:
   o  The protocol must have acknowledged delivery.
   o  The protocol must be able to correlate a response with a request.
   o  The protocol must provide authentication, privacy and protection
      against modification.
   This document includes a binding that uses a combination of HTTP [3],
   TLS [2] and TCP [17] in Section 8.

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5.2.  Location Request

   A location request message is sent from the Device to the LIS when it
   requires LI.  The type of LI that a Device requests is determined by
   the type of LI that is included in the "locationType" element.

   The location request is made by sending a document formed of a
   "locationRequest" element.  The LIS uses the source IP address of the
   location request message as the primary source of identity for the
   requesting device or target.  It is anticipated that other Device
   identities MAY be provided through schema extensions.  The successful
   response to a location request message is a document formed of a
   "locationResponse" element, unless the request fails, in which case
   the LIS MUST provide an error indication document.

   The LIS MUST ignore any part of a location request message that it
   does not understand.

5.3.  Location Response

   The response to a Location request MUST contain either a PIDF-LO
   and/or Location URI(s), depending upon the requested "locationType".

   A Location URI MUST NOT contain any information that could be used to
   identify the Device or Target.  It is RECOMMENDED that a Location URI
   contain a public address for the LIS and an anonymous identifier,
   such as a local identifer or unlinked pseudonym.

5.4.  Indicating Errors

   In the event of an error, the LIS MUST respond to the Device with an
   error document.  The error response applies to all request types and
   MUST also be sent in response to any unrecognized request.

   An error indication document consists of an "error" element.  The
   "error" element MUST include a "code" attribute that indicates the
   type of error.  A set of predefined error codes are included in
   Section 6.3.

   Error responses MAY also include a "message" attribute that can
   include additional information.  This information SHOULD be for
   diagnostic purposes only, and MAY be in any language.  The language
   of the message SHOULD be indicated with an "xml:lang" attribute.

6.  Protocol Parameters

   This section describes, in detail the parameters that are used for

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   this protocol.  Table 1 lists the top-level components used within
   the protocol and where they are mandatory or optional for each of the

   | Parameter              |    Location    |     Location    | Error |
   |                        |     Request    |     Response    |       |
   | responseTime           |        o       |                 |       |
   | (Section 6.1)          |                |                 |       |
   | locationType           |        o       |                 |       |
   | (Section 6.2)          |                |                 |       |
   | exact (Section 6.2.1)  |        o       |                 |       |
   | code (Section 6.3)     |                |        m        |   m   |
   | message (Section 6.4)  |                |                 |   o   |
   | locationURI            |                |        o        |       |
   | (Section 6.5)          |                |                 |       |
   | expires                |                |        m        |       |
   | (Section 6.5.1)        |                |                 |       |

                     Table 1: Message Parameter Usage

6.1.  "responseTime" Parameter

   The "responseTime" attribute is optional and indicates to the LIS how
   long the Device is prepared to wait for a response and/or the purpose
   for which the Device needs the location.  In the case of emergency
   services, the purpose of obtaining the LI could be either for routing
   a call to the appropriate PSAP or indicating the location to which
   responders should be dispatched.  The time values defined for those
   purposes, emergencyRouting and emergencyDispatch, will likely be
   governed by jurisdictional policies, and SHOULD be configurable on
   the LIS.

   The value of the time attribute is indicative only and the LIS is
   under no obligation to strictly adhere to the time limit implied; any
   enforcement of the time limit is left to the requesting Device.  The
   time attribute is expressed with a decimal seconds value, which may
   include a decimal point.  It is RECOMMENDED that systems support
   millisecond precision for this parameter.  The LIS SHOULD provide the
   most accurate LI that can be determined within the specified interval
   for the specific service.

   The LIS MAY use the value of the "responseTime" attribute as input
   when selecting the method of location determination, where multiple
   such methods exist.  If this parameter is absent, then the LIS MUST
   return the most precise LI it is capable of determining.

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6.2.  "locationType" Parameter

   The "locationType" element MAY be included in a location request
   message.  It contains a list of LI types that are requested by the
   Device.  The following list describes the possible values:
   any:  The LIS SHOULD attempt to provide LI in all forms available to
      it.  This value MUST be assumed as the default if no
      "locationType" is specified.  The LIS SHOULD return location
      information in a form that is suited for routing and responding to
      an emergency call in its jurisdiction.  The LIS MAY alternatively
      or additionally return a location URI.
   geodetic:  The LIS SHOULD return a geodetic location for the Target.
   civic:  The LIS SHOULD return a civic address for the Target.  Any
      type of civic address may be returned.
   locationURI:  The LIS SHOULD return a location URI for the Target.

   The LIS SHOULD return the requested location type or types.  The LIS
   MAY provide additional location types, or it MAY provide alternative
   types if the request cannot be satisfied for a requested location
   type.  If the "exact" attribute is present and set to "true" in a
   location request, then a successful LIS response MUST provide the
   requested location type only, with no additional location
   information.  The "exact" attribute has no effect when this element
   is set to "any".

   The "SHOULD"-strength requirement on this parameter is included to
   allow for soft-failover.  This enables a fixed client configuration
   that prefers a specific location type without causing location
   requests to fail when that location type is unavailable.  Unless the
   "exact" attribute is set, the LIS MUST provide LI in any available
   form if it is unable to comply with the request.

   For example, a notebook computer could be configured to retrieve
   civic addresses, which is usually available from typical home or work
   situations.  However, when using a wireless modem, the LIS might be
   unable to provide a civic address and thus provides a geodetic

6.2.1.  "exact" Attribute

   When the "exact" attribute is set to "true", it indicates to the LIS
   that the contents of the "locationType" parameter MUST be strictly
   followed.  The default value of "false" allows the LIS the option of
   returning something beyond what is specified, such as a location URI
   when only a civic location was requested.

   A value of "true" indicates that the LIS MUST provide a location of
   the requested type or types or MUST provide an error.  The LIS MUST

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   provide the requested types only.  The LIS MUST handle an exact
   request that includes a "locationType" element set to "any" as if the
   "exact" attribute were set to "false".

6.3.  "code" Parameter

   All "error" responses MUST contain a response code.  All errors are
   application-level errors, and MUST only be provided in successfully
   processed transport-level responses.  For example where HTTP is used
   as the transport, HELD error messages MUST be accompanied by a 200 OK
   HTTP response.

   HELD error responses may be one of the following tokens:
   requestError:  This code indicates that the request was badly formed
      in some fashion.
   xmlError:  This code indicates that the XML content of the request
      was either badly formed or invalid.
   generalLisError:  This code indicates that an unspecified error
      occurred at the LIS.
   locationUnknown:  This code indicates that the LIS could not
      determine the location of the Device.
   unsupportedMessage:  This code indicates that the request was not
      supported or understood by the LIS.
   timeout:  This code indicates that the LIS could not satisfy the
      request within the time specified in the "responseTime" parameter.
   cannotProvideLiType:  This code indicates that the LIS was unable to
      provide LI of the type or types requested.  This code is used when
      the "exact" attribute on the "locationType" parameter is set to

6.4.  "message" Parameter

   The "error" message MAY include a "message" attribute to convey some
   additional, human-readable information about the result of the
   request.  This message MAY be included in any language, which SHOULD
   be indicated by the "xml:lang", attribute.  The default language is
   assumed to be English.

6.5.  "locationURI" Parameter

   The "locationURI" element includes a single Location URI.  Each
   Location URI that is allocated by the LIS is unique to the device
   that is requesting it.

   A "locationResponse" message MAY contain any number of "locationURI"
   elements.  It is RECOMMENDED that the LIS allocate a Location URI for
   each scheme that it supports and that each scheme is present only
   once.  URI schemes and their secure variants such as http and https

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   MUST be regarded as two separate schemes.

6.5.1.  "expires" Parameter

   The "expires" attribute indicates the time at which the Location URI
   provided by the LIS will expire.  This attribute is included in the
   "locationResponse" message only.

   Responses to Locations requests for Location URIs MUST include the
   expiry time of the Location URI.

7.  XML Schema

   This section gives the XML Schema Definition [12] of the
   "application/held+xml" format.  This is presented as a formal
   definition of the "application/held+xml" format.  Note that the XML
   Schema definition is not intended to be used with on-the-fly
   validation of the presence XML document.

  <?xml version="1.0"?>

      <xs:documentation source="">
  <!-- [[NOTE TO RFC-EDITOR: Please replace above URL with URL of
         published RFC and remove this note.]] -->
        This document defines HELD messages.

    <xs:import namespace=""
    <xs:import namespace="urn:ietf:params:xml:ns:pidf:geopriv10"

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    <xs:import namespace=""

    <!-- Return Location -->
    <xs:complexType name="returnLocationType">
        <xs:restriction base="xs:anyType">
            <xs:element name="locationURI" type="xs:anyURI"
          <xs:attribute name="expires" type="xs:dateTime"

    <!-- responseTime Type -->
    <xs:simpleType name="responseTimeType">
           <xs:restriction base="xs:token">
             <xs:enumeration value="emergencyRouting"/>
             <xs:enumeration value="emergencyDispatch"/>
           <xs:restriction base="xs:decimal">
             <xs:minInclusive value="0.0"/>

    <!-- Location Type -->
    <xs:simpleType name="locationTypeBase">
          <xs:restriction base="xs:token">
            <xs:enumeration value="any"/>
              <xs:restriction base="xs:token">
                <xs:enumeration value="civic"/>
                <xs:enumeration value="geodetic"/>

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                <xs:enumeration value="locationURI"/>

     <xs:complexType name="locationTypeType">
        <xs:extension base="held:locationTypeBase">
          <xs:attribute name="exact" type="xs:boolean"
                        use="optional" default="false"/>

    <!-- Response code -->
    <xs:simpleType name="codeType">
      <xs:restriction base="xs:token">
             <xs:enumeration value="requestError"/>
             <xs:enumeration value="xmlError"/>
             <xs:enumeration value="generalLisError"/>
             <xs:enumeration value="locationUnknown"/>
             <xs:enumeration value="unsupportedMessage"/>
             <xs:enumeration value="timeout"/>
             <xs:enumeration value="cannotProvideLiType"/>

    <!-- Message Definitions -->
    <xs:complexType name="baseRequestType">
        <xs:restriction base="xs:anyType">
          <xs:attribute name="responseTime" type="held:responseTimeType"

    <xs:complexType name="errorType">
        <xs:restriction base="xs:anyType">
          <xs:attribute name="code" type="held:codeType"

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          <xs:attribute name="message" type="xs:token"
          <xs:attribute ref="xml:lang" use="optional"/>

    <xs:element name="error" type="held:errorType"/>

  <!-- Location Response -->
    <xs:complexType name="locationResponseType">
        <xs:restriction base="xs:anyType">
            <xs:element name="locationUriSet"
            <xs:any namespace="##other" processContents="lax"
                    minOccurs="0" maxOccurs="unbounded"/>

    <xs:element name="locationResponse"

    <xs:complexType name="locationRequestType">
        <xs:extension base="held:baseRequestType">
              <xs:element name="locationType"
              <xs:any namespace="##other" processContents="lax"
                    minOccurs="0" maxOccurs="unbounded"/>

    <xs:element name="locationRequest"


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8.  HTTP Binding

   This section defines an HTTP [3] binding for this protocol, which all
   conforming implementations MUST support.  This binding takes the form
   of a Web Service (WS) that can be described by the Web Services
   Description Language (WSDL) document in Section 8.1.

   The request is carried in this binding as the body of an HTTP POST
   request.  The MIME type of both request and response bodies should be

   The LIS populates the HTTP headers so that they are consistent with
   the contents of the message.  In particular, the "expires" and cache
   control headers are used to control the caching of any PIDF-LO
   document or Location URIs.  The HTTP status code SHOULD indicate a
   2xx series response when a PIDF-LO document or Location URI is

   This binding also includes a default behaviour, which is triggered by
   a GET request, or a POST with no request body.  If either of these
   queries are received, the LIS MUST attempt to provide either a
   PIDF-LO document or a Location URI, as if the request was a location

   This binding MUST use TLS as described in [4].  TLS provides message
   integrity and privacy between Device and LIS.  The LIS MUST use the
   server authentication method described in [4]; the Device MUST fail a
   request if server authentication fails, except in the event of an

8.1.  HTTP Binding WSDL

   The following WSDL 2.0 [23] document describes the HTTP binding for
   this protocol.  Actual service instances MUST provide a "service"
   with at least one "endpoint" that implements the "heldHTTP" binding.
   A service description document MAY include this schema directly or by
   using the "import" or "include" directives.

       <?xml version="1.0"?>

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           This document describes the basic HELD sighting web service.
           Please refer to RFCXXXX for details.
       [[NOTE TO RFC-EDITOR: Please replace XXXX with the RFC number
         for this specification and remove this note.]]

           <xsd:schema xmlns:xsd="">
             <xsd:import namespace="urn:ietf:params:xml:ns:geopriv:held"
             <xsd:import namespace="urn:ietf:params:xml:ns:pidf"/>

         <wsdl:interface name="held">

           <wsdl:operation name="locationRequest" method="POST">
             <wsdl:input message="held:locationRequest"/>
             <wsdl:output message="held:locationResponse"/>
             <wsdl:fault message="held:error"/>

               name="getLocation" method="GET"
             <wsdl:output message="held:locationResponse"/>
             <wsdl:fault message="held:error"/>


         <wsdl:binding name="heldHTTP" whttp:defaultMethod="POST">
                ref="heldhttp:getLocation" whttp:method="GET"/>


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9.  Security Considerations

   The threat model for this protocol assumes that the LIS exists within
   the same administrative domain as the Device.  The LIS requires
   access to network information so that it can determine Location.
   Therefore, the LIS can use network information to protect against a
   number of the possible attacks.

   Specific requirements and security considerations for location
   acquisition protocols are provided in [11] including that the LCP
   MUST NOT assume prior network access authentication, which is
   addressed in Section 9.2

   An in-depth discussion of the security considerations applicable to
   the use of Location URIs and by-reference provision of LI is included
   in [16].

9.1.  Return Routability

   It is RECOMMENDED that Location Information Servers use return
   routability rather than requiring Device authentication.  Device
   authentication SHOULD NOT be required due to the administrative
   challenge of issuing and managing of client credentials, particularly
   when networks allow visiting users to attach devices.  However, the
   LIS MAY require any form of authentication as long as these factors
   are considered.

   Addressing information used in a request to the LIS is used to
   determine the identity of the Device, and to address a response.
   This ensures that a Device can only request its own LI.

   A temporary spoofing of IP address could mean that a device could
   request a Location URI that would result in another Device's
   location.  One or more of the follow approaches are RECOMMENDED to
   limit this exposure:
   o  Location URIs SHOULD have a limited lifetime, as reflected by the
      value for the expires element (Section 6.5.1).
   o  The network SHOULD have mechanisms that protect against IP address
   o  The LIS SHOULD ensure that requests can only originate from within
      its administrative domain.
   o  The LIS and network SHOULD be configured so that the LIS is made
      aware of Device movement within the network and addressing
      changes.  If the LIS detects a change in the network, then all
      location URIs MUST be invalidated.

   The above measures are dependent on network configuration and SHOULD
   be considered with circumstances in mind.  For instance, in a fixed

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   internet access, providers may be able to restrict the allocation of
   IP addresses to a single physical line, ensuring that spoofing is not
   possible; in such an environment, other measures may not be

9.2.  Transaction Layer Security

   All bindings for this protocol MUST ensure that messages are
   adequately protected against eavesdropping and modification.
   Bindings MUST also provide a means of authenticating the LIS.

   It is RECOMMENDED that all bindings also use TLS [2].

   For the HTTP binding, TLS MUST be used.  TLS provides protection
   against eavesdropping and modification.  The server authentication
   methods described in HTTP on TLS [4] MUST be used.

10.  Examples

10.1.  Simple HTTP Binding Example Messages

   The examples in this section show a complete HTTP message that
   includes the HELD request or response document.

   This example shows the most basic request for a LO.  This uses the
   GET feature described by the HTTP binding.  This example assumes that
   the LIS service exists at the URL "".

         GET /location HTTP/1.1
         Accept-Charset: UTF-8,*

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   The GET request is exactly identical to a minimal POST request that
   includes an empty "locationRequest" element.

         POST /location HTTP/1.1
         Accept: application/held+xml,
         Accept-Charset: UTF-8,*
         Content-Type: application/held+xml
         Content-Length: 87

         <?xml version="1.0"?>
         <locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held"/>

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   The successful response to either of these requests is a PIDF-LO
   document.  The following response shows a minimal PIDF-LO response.

         HTTP/1.x 200 OK
         Server: Example LIS
         Date: Tue, 10 Jan 2006 03:42:29 GMT
         Expires: Tue, 10 Jan 2006 03:42:29 GMT
         Cache-control: private
         Content-Type: application/held+xml
         Content-Length: 594

         <?xml version="1.0"?>
         <locationResponse xmlns="urn:ietf:params:xml:ns:geopriv:held">
         <presence xmlns="urn:ietf:params:xml:ns:pidf"
           <tuple id="3b650sf789nd">
            <geopriv xmlns="urn:ietf:params:xml:ns:pidf:geopriv10">
                <Point xmlns=""
                  <pos>-34.407 150.88001</pos>

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   The error response to either of these requests is an error document.
   The following response shows an example error response.

         HTTP/1.x 200 OK
         Server: Example LIS
         Expires: Tue, 10 Jan 2006 03:49:20 GMT
         Cache-control: private
         Content-Type: application/held+xml
         Content-Length: 135

         <?xml version="1.0"?>
         <error xmlns="urn:ietf:params:xml:ns:geopriv:held"
                message="Unable to determine location"/>

   Note:  To focus on important portions of messages, all examples
      following this note do not show HTTP headers or the XML prologue.
      In addition, sections of XML not relevant to the example are
      replaced with comments.

10.2.  Simple Location Request Example

   The location request shown below doesn't specify any location types
   or response time.

   <locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held"/>

   The response to this location request is a list of Location URIs.

      <locationResponse xmlns="urn:ietf:params:xml:ns:geopriv:held">
        <locationUriSet expires="2006-01-01T13:00:00">

   An error response to this location request is shown below:

         <error xmlns="urn:ietf:params:xml:ns:geopriv:held"
                    message="Location not available"/>

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10.3.  Location Request Example for Multiple Location Types

   The following Location Request message includes a request for
   geodetic, civic and any Location URIs.

         <locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held">
          <locationType exact="true">

   The corresponding Location Response message includes the requested
   location information, including two location URIs.

       <locationResponse xmlns="urn:ietf:params:xml:ns:geopriv:held">
          <locationUriSet expires="2006-01-01T13:00:00">
         <presence xmlns="urn:ietf:params:xml:ns:pidf:geopriv10"
         <tuple id="lisLocation">
              <gml:pos>-34.407242 150.882518</gml:pos>
              <gs:radius uom="urn:ogc:def:uom:EPSG::9001">30
              <ca:STS>Northfield Avenue</ca:STS>

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              <ca:LMK>University of Wollongong</ca:LMK>
              <ca:NAM>Andrew Corporation</ca:NAM>

10.4.  Sample LIS  WSDL Document

   The following WSDL document demonstrates how a WSDL document can be
   created for a specific service, in this case, a service at the URI

   <?xml version="1.0"?>


     <wsdl:service name="sample-held-svc" interface="heldhttp:held">
       <wsdl:endpoint name="sample-held-ep"


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11.  IANA Considerations

   This document registers an XML namespace and schema and the
   "application/held+xml" MIME type.

11.1.  URN Sub-Namespace Registration for

   This section registers a new XML namespace,
   "urn:ietf:params:xml:ns:geopriv:held", as per the guidelines in [6].
      URI: urn:ietf:params:xml:ns:geopriv:held
      Registrant Contact: IETF, GEOPRIV working group,
      (, Mary Barnes (

           <?xml version="1.0"?>
           <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
           <html xmlns="" xml:lang="en">
               <title>HELD Messages</title>
               <h1>Namespace for HELD Messages</h1>
   [[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX
       with the RFC number for this specification.]]
               <p>See <a href="[[RFC URL]]">RFCXXXX</a>.</p>

11.2.  XML Schema Registration

   This section registers an XML schema as per the guidelines in [6].
   URI:  urn:ietf:params:xml:schema:geopriv:held
   Registrant Contact:  IETF, GEOPRIV working group, (,
      Mary Barnes (
   Schema:  The XML for this schema can be found as the entirety of
      Section 7 of this document.

11.3.  URN Sub-Namespace Registration for

   This section registers a new XML namespace,
   "urn:ietf:params:xml:ns:geopriv:held:http", as per the guidelines in

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      URI: urn:ietf:params:xml:ns:geopriv:held:http
      Registrant Contact: IETF, GEOPRIV working group,
      (, Mary Barnes (

           <?xml version="1.0"?>
           <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
           <html xmlns="" xml:lang="en">
               <title>HELD HTTP Binding WS</title>
               <h1>Namespace for HELD HTTP Binding WS</h1>
   [[NOTE TO IANA/RFC-EDITOR: Please update RFC URL and replace XXXX
       with the RFC number for this specification.]]
               <p>See <a href="[[RFC URL]]">RFCXXXX</a>.</p>

11.4.  MIME Media Type Registration for 'application/held+xml'

   This section registers the "application/held+xml" MIME type.
   Subject:  Registration of MIME media type application/held+xml
   MIME media type name:  application
   MIME subtype name:  held+xml
   Required parameters:  (none)
   Optional parameters:  charset
      Indicates the character encoding of enclosed XML.  Default is
   Encoding considerations:  Uses XML, which can employ 8-bit
      characters, depending on the character encoding used.  See RFC
      3023 [19], 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
   Interoperability considerations:  This content type provides a basis
      for a protocol

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   Published specification:  RFC XXXX [[NOTE TO IANA/RFC-EDITOR: Please
      replace XXXX with the RFC number for this specification.]]
   Applications which use this media type:  Location information
      providers and 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:  Mary
      Barnes <>
   Intended usage:  LIMITED USE
   Author/Change controller:  This specification is TBD
   Other information:  This media type is a specialization of
      application/xml [19], and many of the considerations described
      there also apply to application/held+xml.

12.  Contributors

   James Winterbottom, Martin Thomson and Barbara Stark are the authors
   of the original document, from which this WG document was derived.
   Their contact information is included in the Author's address
   section.  In addition, they also contributed to the WG document, in
   particular the schema and WSDL.

13.  Acknowledgements

   The author/contributors would like to thank the following people for
   their constructive input to this document (in alphabetical order):
   Nadine Abbott, Eric Arolick, Guy Caron, Martin Dawson, Jerome
   Grenier, Neil Justusson, Tat Lam, Patti McCalmont, Perry Prozeniuk,
   Carl Reed, John Schnizlein, Shida Schubert, Henning Schulzrinne, Ed
   Shrum, and Hannes Tschofenig.

14.  Changes since last Version

   NOTE TO THE RFC-Editor: Please remove this section prior to
   publication as an RFC.

   Changes from WG 01 to 02:

   1) Updated Terminology to be consistent with WG agreements and other
   documents (e.g., LCS -> LIS and removed duplicate terms).  In the
   end, there are no new terms defined in this document.

   2) Modified definition of responseTime to reflect WG consensus.

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   3) Removed jurisdictionalCivic and postalCivic locationTypes (leaving
   just "civic").

   4) Clarified text that locationType is optional.  Fixed table 1 and
   text in section 5.2 (locationRequest description).  Text in section
   6.2 (description of locationType element) already defined the default
   to be "any".

   5) Simplified error responses.  Separated the definition of error
   response type from the locationResponse type thus no need for
   defining an error code of "success".  This simplifies the schema and

   6) Updated schema/examples for the above.

   7) Updated Appendix A based on updates to requirements document,
   specifically changes to A.1, A.3 and adding A.10.

   8) Miscellaneous editorial clarifications.

   Changes from WG 00 to 01:

   1) heldResponse renamed to locationResponse.

   2) Changed namespace references for the PIDF-LO geoShape in the
   schema to match the agreed GML PIDF-LO Geometry Shape Application

   3) Removed "options" element - leaving optionality/extensibility to
   XML mechanisms.

   4) Changed error codes to be enumerations and not redefinitions of
   HTTP response codes.

   5) Updated schema/examples for the above and removed some remnants of
   the context element.

   6) Clarified the definition of "Location Information (LI)" to include
   a reference to the location (to match the XML schema and provide
   consistency of usage throughout the document).  Added an additional
   statement in section 7.2 (locationType) to clarify that LCS MAY also
   return a Location URI.

   7) Modifed the definition of "Location Configuration Server (LCS)" to
   be consistent with the current definiton in the requirements

   8) Updated Location Response (section 6.3) to remove reference to

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   context and discuss the used of a local identifier or unlinked
   pseudonym in providing privacy/security.

   9) Clarified that the source IP address in the request is used as the
   identifier for the target/device for the HELD protocol as defined in
   this document.

   10) Miscellaneous editorial clarifications.

15.  References

15.1.  Normative References

   [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.

   [2]   Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
         RFC 2246, January 1999.

   [3]   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.

   [4]   Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [5]   Eastlake, D., Reagle, J., and D. Solo, "(Extensible Markup
         Language) XML-Signature Syntax and Processing", RFC 3275,
         March 2002.

   [6]   Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
         January 2004.

   [7]   Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J.
         Polk, "Geopriv Requirements", RFC 3693, February 2004.

   [8]   Peterson, J., "A Presence-based GEOPRIV Location Object
         Format", RFC 4119, December 2005.

   [9]   Thomson, M. and J. Winterbottom, "Revised Civic Location Format
         for PIDF-LO", draft-ietf-geopriv-revised-civic-lo-05 (work in
         progress), February 2007.

   [10]  Tschofenig, H., "GEOPRIV PIDF-LO Usage Clarification,
         Considerations and Recommendations",
         draft-ietf-geopriv-pdif-lo-profile-08 (work in progress),
         July 2007.

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   [11]  Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7 Location
         Configuration Protocol; Problem Statement and  Requirements",
         draft-ietf-geopriv-l7-lcp-ps-05 (work in progress),
         September 2007.

   [12]  Thompson, H., Mendelsohn, N., Maloney, M., and D. Beech, "XML
         Schema Part 1: Structures Second Edition", World Wide Web
         Consortium Recommendation REC-xmlschema-1-20041028,
         October 2004,

   [13]  Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes Second
         Edition", World Wide Web Consortium Recommendation REC-
         xmlschema-2-20041028, October 2004,

   [14]  Cox, S., Daisey, P., Lake, R., Portele, C., and A. Whiteside,
         "Geographic information - Geography Markup Language (GML)",
         OpenGIS 03-105r1, April 2004,

   [15]  Thomson, M. and J. Winterbottom, "Discovering the Local
         Location Information Server (LIS)",
         draft-thomson-geopriv-lis-discovery-03 (work in progress),
         September 2007.

   [16]  Marshall, R., "Requirements for a Location-by-Reference
         Mechanism", draft-ietf-geopriv-lbyr-requirements-00 (work in
         progress), September 2007.

15.2.  Informative References

   [17]  Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
         September 1981.

   [18]  Day, M., Rosenberg, J., and H. Sugano, "A Model for Presence
         and Instant Messaging", RFC 2778, February 2000.

   [19]  Murata, M., St. Laurent, S., and D. Kohn, "XML Media Types",
         RFC 3023, January 2001.

   [20]  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.

   [21]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
         Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986,
         January 2005.

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   [22]  Polk, J. and B. Rosen, "Location Conveyance for the Session
         Initiation Protocol", draft-ietf-sip-location-conveyance-08
         (work in progress), July 2007.

   [23]  Chinnici, R., Moreau, J., Ryman, A., and S. Weerawarana, "Web
         Services Description Language (WSDL) Version 2.0 Part 1: Core
         Language", W3C CR CR-wsdl20-20060106, January 2006.

Appendix A.  HELD Compliance to IETF LCP requirements

   This appendix describes HELD's compliance to the requirements
   specified in the [11].

A.1.  L7-1: Identifier Choice

   "The L7 LCP MUST be able to carry different identifiers or MUST
   define an identifier that is mandatory to implement.  Regarding the
   latter aspect, such an identifier is only appropriate if it is from
   the same realm as the one for which the location information service
   maintains identifier to location mapping."


   HELD uses the IP address of the location request message as the
   primary source of identity for the requesting device or target.  This
   identity can be used with other contextual network information to
   provide a physical location for the Target for many network
   deployments.  There may be network deployments where an IP address
   alone is insufficient to identify a Target in a network.  However,
   any necessary identity extensions for these networks is beyond the
   scope of this document.

A.2.  L7-2: Mobility Support

   "The GEOPRIV Layer 7 Location Configuration Protocol MUST support a
   broad range of mobility from devices that can only move between
   reboots, to devices that can change attachment points with the impact
   that their IP address is changed, to devices that do not change their
   IP address while roaming, to devices that continuously move by being
   attached to the same network attachment point."


   Mobility support is inherently a characteristic of the access network
   technology and HELD is designed to be access network agnostic.
   Consequently HELD complies with this requirement.  In addition HELD
   provides specific support for mobile environments by providing an

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   optional responseTime attribute in location request messages.
   Wireless networks often have several different mechanisms at their
   disposal for position determination (e.g.  Assisted GPS versus
   location based on serving base station identity), each providing
   different degrees of accuracy and taking different amounts of time to
   yield a result.  The responseTime parameter provides the LIS with a
   criterion which it can use to select a location determination

A.3.  L7-3: ASP and Access Network Provider Relationship

   "The design of the L7 LCP MUST NOT assume a business or trust
   relationship between the Application Service Provider (ASP) and the
   Access Network Provider.  Requirements for resolving a reference to
   location information are not discussed in this document."


   HELD describes a location acquisition protocol and has no
   dependencies on the business or trust relationship between the ASP
   and the Access Network Provider.  Location acquisition using HELD is
   subject to the restrictions described in Section 9.

A.4.  L7-4: Layer 2 and Layer 3 Provider Relationship

   "The design of the GEOPRIV Layer 7 Location Configuration Protocol
   MUST assume that there is a trust and business relationship between
   the L2 and the L3 provider.  The L3 provider operates the LIS and
   needs to obtain location information from the L2 provider since this
   one is closest to the end host.  If the L2 and L3 provider for the
   same host are different entities, they cooperate for the purposes
   needed to determine end system locations."


   HELD was specifically designed with this model in mind and readily
   allows itself to chaining requests between operators without a change
   in protocol being required.  HELD is a webservices protocol it can be
   bound to transports other than HTTP.  Using o offers the option of
   high request throughput over a dedicated connection between an L3
   provider and an L2 provider without incurring the serial restriction
   imposed by HTTP.  This is less easy to do with protocols that do not
   decouple themselves from the transport.

A.5.  L7-5: Legacy Device Considerations

   "The design of the GEOPRIV Layer 7 Location Configuration Protocol
   MUST consider legacy residential NAT devices and NTEs in an DSL

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   environment that cannot be upgraded to support additional protocols,
   for example to pass additional information through DHCP."


   HELD is an application protocol and operates on top of IP.  A HELD
   request from a host behind a residential NAT will traverse the NAT
   acquiring the external address of the home router.  The location
   provided to the host therefore will be the address of the home router
   in this circumstance.  No changes are required to the home router in
   order to support this function, HELD was designed specifically to
   address this deployment scenario.

A.6.  L7-6: VPN Awareness

   "The design of the GEOPRIV Layer 7 Location Configuration Protocol
   MUST assume that at least one end of a VPN is aware of the VPN
   functionality.  In an enterprise scenario, the enterprise side will
   provide the LIS used by the client and can thereby detect whether the
   LIS request was initiated through a VPN tunnel."


   HELD does not preclude a LIS on the far end of a VPN tunnel being
   aware that the client request is occurring over that tunnel.  It also
   does not preclude a client device from accessing a LIS serving the
   local physical network and subsequently using the location
   information with an application that is accessed over a VPN tunnel.

A.7.  L7-7: Network Access Authentication

   "The design of the GEOPRIV Layer 7 Location Configuration Protocol
   MUST NOT assume prior network access authentication."


   HELD makes no assumptions about prior network access authentication.
   HELD strongly recommends the use of TLS with server-side certificates
   for communication between the end-point and the LIS.  There is no
   requirement for the end-point to authenticate with the LIS.

A.8.  L7-8: Network Topology Unawareness

   "The design of the GEOPRIV Layer 7 Location Configuration Protocol
   MUST NOT assume end systems being aware of the access network
   topology.  End systems are, however, able to determine their public
   IP address(es) via mechanisms such as STUN or NSIS NATFW NSLP."

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   HELD makes no assumption about the network topology.  HELD doesn't
   require that the device know its external IP address, except where
   that is required for discovery of the LIS.

A.9.  L7-9: Discovery Mechanism

   "The L7 LCP MUST define a single mandatory to implement discovery


   HELD uses the discovery mechanism in [15].

A.10.  L7-10: PIDF-LO Creation

   "When a LIS creates a PIDF-LO per RFC 4119 then it MUST put the
   <geopriv> element into the <device> element of the presence document
   (see RFC 4479).  This ensures that the resulting PIDF-LO document,
   which is subsequently distributed to other entities, conforms to the
   rules outlined in ". [10]


   HELD protocol overview (Section 4 ) describes the requirements on the
   LIS in creating the PIDF-LO and prescribes that the PIDF-LO generated
   by the LIS MUST conform to [10].

Authors' Addresses

   Mary Barnes (editor)
   2201 Lakeside Blvd
   Richardson, TX


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   James Winterbottom
   PO Box U40
   Wollongong University Campus, NSW  2500

   Phone: +61 2 4221 2938

   Martin Thomson
   PO Box U40
   Wollongong University Campus, NSW  2500

   Phone: +61 2 4221 2915

   Barbara Stark
   Room 7A41
   725 W Peachtree St.
   Atlanta, GA  30308


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