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Versions: 00 01 02 03 04 05 draft-ietf-geopriv-deref-protocol

Geopriv                                                  J. Winterbottom
Internet-Draft                                        Andrew Corporation
Intended status: Standards Track                           H. Tschofenig
Expires: May 14, 2008                             Nokia Siemens Networks
                                                          H. Schulzrinne
                                                     Columbia University
                                                              M. Thomson
                                                               M. Dawson
                                                      Andrew Corporation
                                                       November 11, 2007


          An HTTPS Location Dereferencing Protocol Using HELD
            draft-winterbottom-geopriv-deref-protocol-00.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on May 14, 2008.

Copyright Notice

   Copyright (C) The IETF Trust (2007).








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Abstract

   This document describes how to use the Hypertext Transfer Protocol
   (HTTP) over Transport Layer Security (TLS) as a dereferencing
   protocol to resolve a reference into a Presence Information Data
   Format Location Object (PIDF-LO).  The document assumes that a
   Location Recipient possesses a secure HELD URI that can be used in
   conjunction with the HELD protocol to request the location of the
   Target.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Steps for Retrieval  . . . . . . . . . . . . . . . . . . . . .  6
   4.  Threat Models  . . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  Using HELD to Dereference a Location URI . . . . . . . . . . .  9
   6.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     10.1.  Normative References  . . . . . . . . . . . . . . . . . . 16
     10.2.  Informative references  . . . . . . . . . . . . . . . . . 16
   Appendix A.  GEOPRIV Using Protocol Compliance . . . . . . . . . . 18
   Appendix B.  HELD Compliance to IETF Location Reference
                Requirements  . . . . . . . . . . . . . . . . . . . . 23
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26
   Intellectual Property and Copyright Statements . . . . . . . . . . 28





















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1.  Introduction

   This document describes how to transport Presence Information Data
   Format Location Object (PIDF-LO) when dereferencing a location URI in
   the form of a secure HELD URI (held: URI scheme)
   [I-D.ietf-geopriv-http-location-delivery].  This held: URI indicates
   that the XML-based HELD messages are carried on top of the Hypertext
   Transfer Protocol (HTTP), which is secured using Transport Layer
   Security (TLS) ([RFC2616] and [RFC2818]).

   The document describes how HELD
   [I-D.ietf-geopriv-http-location-delivery] is used to request and to
   receive location information in a way that also satisfies the
   requirements laid out in [I-D.ietf-geopriv-lbyr-requirements].  HELD
   provides location information in the form of a PIDF-LO (see
   [RFC4119]) which, as part of its definition, complies with the
   requirements of a location object as described in [RFC3693].

   To use HELD as a dereferencing protocol has the advantage that the
   Location Recipient can indicate the type of location information it
   would like to receive.  This functionality is already available with
   the HELD base specification, described in
   [I-D.ietf-geopriv-http-location-delivery].  Furthermore, the HELD
   response from the LIS towards the Location Recipient not only
   provides the PIDF-LO but also encapsulates supplementary information,
   such as error messages, back to the Location Recipient.

   The general usage scenario envisioned by this document is shown in
   Figure 1.  While the figure shows a typical HELD location request
   being made to initially obtain the location URI.  As Figure 1
   indicates, an alternative Location Configuration Protocol (LCP) that
   can provide a HELD URI can be used.



















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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
        |                          |                             |
        |                       +--+-----------------------------+--+
        |                       |  |                             |  |
        |                       |  0<===locationRequest(Civic)===|  |
        |         Dereferencing |  |                             |  |
        |         Protocol      |  |                             |  |
        |                       |  |==locationResponse(PIDF-LO)=>0  |
        |                       |  |                             |  |
        |                       +--+-----------------------------+--+
        |                          |                             |
        |                          |                             |

          Figure 1: HTTPS Dereference Context Diagram Using HELD





















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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 key conventions and terminology used in this document are defined
   as follows:

   This document reuses the term Target, as defined in [RFC3693].

   This document uses the term Location Information Server, LIS, as the
   node in the access network providing location information to an end
   point, or to the node dereferencing a location URI.  This term is
   also used in [I-D.ietf-geopriv-l7-lcp-ps].

   The Location Recipient acts as a HELD client and the LIS as a HELD
   server in the context of this document.

































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3.  Steps for Retrieval

   1.  The Location Recipient obtains a helds: based location URI.

   2.  The HELD client establishes a TLS connection to the LIS, as
       described in [RFC2818].  The TLS ciphersuite
       TLS_NULL_WITH_NULL_NULL MUST NOT be used.

   3.  When certificate based authentication is used the client
       authenticates the server and compares the domain part of the
       location URI with the identity information in the certificate.

   4.  The server MAY require the client to be authenticated.  This is,
       however, only useful in certain deployment environments where a
       strong relationship between the LIS and the Location Recipients
       exists.

   5.  The client retrieves the PIDF-LO document encapsulated into the
       HELD locationResponse or an error message conveyed in a HELD
       error message.































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4.  Threat Models

   This document assumes that the HELD messages between the Location
   Recipient and the LIS are carried on top of HTTP and secured via TLS.
   HTTP can be used as a substrate to a number of different
   applications, and defining a set of guidelines for conveying a
   PIDF-LO for any application that might use HTTP would be difficult or
   impossible.  This document does not attempt that task.  Instead, it
   is limited in applicability to the case where a client uses a HELD
   locationRequest to retrieve a PIDF-LO object from a server.  No other
   functionality is covered.  This document does not describe how the
   Location Recipient obtains the location URI pointing to the PIDF-LO
   document.  This is subject of the Location Conveyance protocol
   [I-D.ietf-sip-location-conveyance]

   There are three security models.  They assume that the Location
   Recipient who obtains the the location URI does not act maliciously
   and does not distribute the obtained Location Object without
   inspecting the privacy policies attached with the Location Object.

   Authorization Policy Security Model:

      The assumption of this model is that the LIS has some
      authorization policies (such as those specified in [RFC4745] and
      [I-D.ietf-geopriv-policy]) that are provided by the Target and
      uploaded to the LIS.  The policies have the form of access control
      lists that indicate to which Location Recipients location
      information is disclosed.  The LIS is therefore able to control
      access to location information.  Consequently, when the reference
      is conveyed to the potential Location Recipient (e.g., via SIP
      [I-D.ietf-sip-location-conveyance]), then it does not need to be
      protected (neither hop-by-hop nor end-to-end).  Authentication by
      the Location Recipient to the LIS is necessary (e.g., TLS client
      authentication, HTTP Digest authentication) to allow the LIS to
      determine whether access to location information has to be
      granted.


   End-to-End Security Model:

      In this security model we assume that the transport of the
      location URI is encrypted end-to-end, for example using S/MIME,
      and an adversary along the signaling path is not able to
      eavesdrop, modify or replay a location URI.  The Target is able to
      control the disclosure of the PIDF-LO by making it available only
      to trusted entities.  Consequently, only the entity that is able
      to decrypt the end-to-end protected object, such as S/MIME
      encrypted object, can resolve the reference.



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   Hop-by-Hop Security Model:

      In this security model we assume that the location URI can either
      be directly communicated between the Target and the Location
      Recipient or from the Target via trusted proxies to the Location
      Recipient.  In some cases the location URI is conveyed to multiple
      Location Recipients, for example in case of location-based routing
      applications.  The entity that observes the location URI has to be
      able to resolve it into a literal location.

   The description of the security models above shows the responsibility
   of the participating entities; from a dereferencing protocol point of
   view an important responsibility can be found in the protection of
   the interaction between the Location Recipient and the LIS against
   the classical communication security threats.

   With respect to the Location Configuration and the Location
   Conveyance protocol interaction, which are outside the scope of this
   document, this document at least assumes the hop-by-hop security
   model.  Additionally, it is assumed that the requirements outlined in
   [I-D.ietf-geopriv-lbyr-requirements], such as the requirement that
   the location URI contains a random component with sufficient entropy
   and that it does not contain identity information.  When the pre-
   requisites for the end-to-end security model are met then further
   protection can be accomplished.  End-to-end security mechanisms do,
   however, not enjoy widespread deployment so in SIP so far (when SIP
   is used as the Location Conveyance protocol).  The usage of policies
   local to the LIS are possible.  Furthermore,
   [I-D.winterbottom-geopriv-held-context] allows constraints to be
   placed on the dereferencing procedure that limit the location
   information available to the Location Recipient, for example limiting
   the number of times a reference may be used.



















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5.  Using HELD to Dereference a Location URI

   This section describes how HELD protected by TLS can be used to
   qualify location requests to the LIS.  Only a subset of HELD
   functionality is required and is described in the following
   paragraphs.  The HELD based dereferencing step provides ways to tell
   the LIS what information is desired and allows the LIS to communicate
   additional information back to the client.

   The <locationType> element allows location to be requested in a
   specific form, such as civic or geodetic location information.  The
   Location Recipient SHOULD NOT request location as a locationURI.  The
   LIS MUST respond with a "requestError" if it receives a request for a
   locationURI where HELD is being used as a dereference protocol.
   Location information provided by the LIS MUST correspond to the rules
   and guidelines in [I-D.ietf-geopriv-pdif-lo-profile].  If the
   requested form of location violates any authorization policies known
   to the LIS, then the LIS MUST respond with a "cannotProvideLiType"
   error.

   The LIS will provide location information on request even if the
   location information does not fit the form requested.  This stems
   from the premise that some location is better than no location.  HELD
   provides a means for the requestor to modify this behaviour and
   instruct the LIS to return an error if location information is not
   available in the form requested.  This is done using the "exact"
   attribute.

   Location systems often have more than one location determination
   mechanism at their disposal.  Differing determination techniques
   provide different degrees of accuracy over differing periods of time.
   Generally, more accurate determination techniques require more time.
   HELD addresses this trade-off by allowing the requestor to specify
   how long they are prepared to wait for a location result.  This
   allows the LIS to select the most accurate determination technique at
   its disposal that can return a result in the specified time.  The
   HELD attribute for specifying this value is the "responseTime"
   attribute and MAY be used by a Location Recipient to specify their
   preference for the accuracy-time trade-off.

   The LIS MUST support the HELD locationRequest semantic using an HTTP
   GET as described in [I-D.ietf-geopriv-http-location-delivery].

   Where the LIS is unable to process the Location Recipient's request,
   it MUST return the appropriate error from the existing HELD error set
   defined in [I-D.ietf-geopriv-http-location-delivery].





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6.  Examples

   Figure 2 illustrates a simple dereferencing request example.


   GET /357yc6s64ceyoiuy5ax3o HTTP/1.1
   Host: lis.example.com
   Accept:application/held+xml

                  Figure 2: Minimal Dereferencing Request

   Figure 3 shows a request indicating that both civic and geodetic
   location information has to be returned.  If it cannot be provided,
   the request fails.


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

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

    Figure 3: Dereferencing Request for Civic and Geodetic Information

   Figure 4 shows the response to the previous request listing both
   civic and geodetic location information of the Target's location.


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

   <locationResponse xmlns="urn:ietf:params:xml:ns:geopriv:held">
     <presence xmlns="urn:ietf:params:xml:ns:pidf:geopriv10"
       entity="pres:ae3be8585902e2253ce2@10.102.23.9">
       <tuple id="lisLocation">
         <status>
           <geopriv>
             <location-info>



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               <gs:Circle
                 xmlns:gs="http://www.opengis.net/pidflo/1.0"
                 xmlns:gml="http://www.opengis.net/gml"
                 srsName="urn:ogc:def:crs:EPSG::4326">
                 <gml:pos>-34.407242 150.882518</gml:pos>
                 <gs:radius uom="urn:ogc:def:uom:EPSG::9001">30
                 </gs:radius>
               </gs:Circle>
               <ca:civicAddress
                 ca="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
                 xml:lang="en-au">
                 <ca:country>AU</ca:country>
                 <ca:A1>NSW</ca:A1>
                 <ca:A3>Wollongong</ca:A3>
                 <ca:A4>Gwynneville</ca:A4>
                 <ca:STS>Northfield Avenue</ca:STS>
                 <ca:LMK>University of Wollongong</ca:LMK>
                 <ca:FLR>2</ca:FLR>
                 <ca:NAM>Andrew Corporation</ca:NAM>
                 <ca:PC>2500</ca:PC>
                 <ca:BLD>39</ca:BLD>
                 <ca:SEAT>WS-183</ca:SEAT>
                 <ca:POBOX>U40</ca:POBOX>
               </ca:civicAddress>
             </location-info>
             <usage-rules>
               <retransmission-allowed>false</retransmission-allowed>
               <retention-expiry>2007-05-25T12:35:02+10:00
               </retention-expiry>
             </usage-rules>
             <method>Wiremap</method>
           </geopriv>
         </status>
         <timestamp>2007-05-24T12:35:02+10:00</timestamp>
       </tuple>
     </presence>
   </locationResponse>

      Figure 4: Response with Civic and Geodetic Location Information

   Figure 5 shows an error message returned in response to a request.










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

   <error xmlns="urn:ietf:params:xml:ns:geopriv:held"
    code="cannotProvideLiType"
   message="Authorization policies do not permit
            location information to be disclosed."/>

                          Figure 5: Error Message







































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7.  Security Considerations

   This document assumes that the use of TLS to protect HTTP is
   sufficient to protect the privacy of the PIDF-LO content while in
   flight.  When access control at the LIS is not applied, as described
   in the threat models in Section 4, then the possession of the
   location URI is equal to the possession of location information.
   When the requirements for creating a location URI, as described in
   [I-D.winterbottom-geopriv-held-context], are met, then the reference
   provides sufficiently high security guarantees for most usages.
   Furthermore, the ability of the Target to put constraints on the
   dereferencing step, as described in
   [I-D.winterbottom-geopriv-held-context], provides additional security
   guarantees.

   In the normal case, connection establishment from the Location
   Recipient to the LIS will be made on HTTP over TLS, and the location
   URI being dereferenced by the Location Recipient will contain the
   hostname of the LIS.  The Location Recipient MUST check the FQDN of
   the LIS in the reference with the identity presented in the server's
   certificate.  A discrepancy may indicate a possible man-in-the-
   middle-attack, and the Location Recipient should take appropriate
   action based on application dependent semantics.  Actions may include
   but are not limited to; proceeding anyway, flagging the result as
   suspect, or giving up.

   In some applications the Location Recipient has a pre-established
   relationship with one or several Location Information Servers and
   hence the LIS might authorize only certain Location Recipients might
   be allowed to resolve a reference.





















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8.  IANA Considerations

   There are no specific IANA considerations for this document.
















































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9.  Acknowledgements

   Thanks to Barbara Stark and Guy Caron for providing early comments.
   Thanks to Rohan Mahy for constructive comments on the scope and
   format of the document.  Thanks to Ted Hardie for his strawman
   proposal that provided assistance with the security section of this
   document.












































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10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC4119]  Peterson, J., "A Presence-based GEOPRIV Location Object
              Format", RFC 4119, December 2005.

   [RFC3693]  Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and
              J. Polk, "Geopriv Requirements", RFC 3693, February 2004.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [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-10
              (work in progress), October 2007.

   [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-02 (work in
              progress), September 2007.

   [I-D.ietf-geopriv-lbyr-requirements]
              Marshall, R., "Requirements for a Location-by-Reference
              Mechanism", draft-ietf-geopriv-lbyr-requirements-01 (work
              in progress), October 2007.

10.2.  Informative references

   [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-13 (work in progress),
              October 2007.

   [I-D.winterbottom-geopriv-held-context]
              Winterbottom, J., Tschofenig, H., and M. Thomson, "HELD
              Protocol Context Management Extensions",



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              draft-winterbottom-geopriv-held-context-01 (work in
              progress), October 2007.

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

   [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-05 (work in
              progress), September 2007.
































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Appendix A.  GEOPRIV Using Protocol Compliance

   This section compares the GEOPRIV requirements described in [RFC3693]
   with the approach outlined in this document.

   Req. 1.  (Location Object generalities):

   o  Regarding requirement 1.1, the Location Object has to be
      understood by the Location Recipient and the Location Server, the
      two communication end points.  The PIDF-LO [RFC4119] allows both
      civic and geospatial location information to be expressed.
      Combining this with [I-D.ietf-geopriv-pdif-lo-profile] ensures
      that location can be constructed and interpreted in a consistent
      manner.

   o  Regarding requirement 1.2, a number of fields in the civic
      location information format are optional.

   o  Regarding requirement 1.3, the civic location information is
      defined in an extensible way.

   o  Regarding requirement 1.4, the location information itself is not
      defined in this document.

   o  Regarding requirement 1.5, the protocol described in this document
      allows the Location Recipient to resolve a reference to a PIDF-LO
      only.

   o  Regarding requirement 1.6, the Location Object contains both
      location information and privacy rules.  Depending on the
      deployment scenario, which is outside the scope of this document,
      the privacy rules might have stronger or a weaker semantic.

   o  Regarding requirement 1.7, the Location Object is usable in a
      variety of protocols.

   o  Regarding requirement 1.8, no change regarding with respect to the
      encoding of the Location Object (see [RFC4119]) was made by this
      document.

   Req. 2.  (Location Object fields):

   o  Regarding requirement 2.1, depending on the deployment scenario an
      identifier pointing to the Target may be carried inside the
      PIDF-LO since the PIDF object provides the ability to carry this
      identifier.  In some circumstances it might be desirable not to
      carry information about the Target's identity in the PIDF-LO.




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   o  Regarding requirement 2.2, depending on the deployment scenario
      the LIS might require that the Location Recipient performs an
      authentication step.  The security mechanisms for client and
      server authentication are outside the scope of this document and
      defined already for HTTPS itself.

   o  Regarding requirement 2.3, proof of possession of the Location
      Recipient credentials is provided outside the scope of this
      document.  The security mechanisms defined for HTTPS are used by
      this document.

   o  Regarding requirement 2.5, RFC 4119 defines the basis for carrying
      location information in a PIDF document.  The ability to extend
      RFC 4119 to convey motion specific information is work in
      progress.

   o  Regarding requirement 2.6, this document as specified only allows
      the Location Recipient to resolve the reference and to indicate
      which location format has to be returned.

   o  Regarding requirement 2.7, the PIDF-LO relevant elements and
      attributes are available.

   o  Regarding requirement 2.8, provision exists for a reference to an
      external (more detailed rule set) within the PIDF-LO to be made.
      This is the <external-ruleset> element.

   o  Regarding requirement 2.9, security headers and trailers are
      provided Transport Layer Security.

   o  Regarding requirement 2.10, extensibility within the PIDF-LO is
      provided regarding the definition of namespaces.

   Req. 3.  (Location Data Types):

   o  Regarding requirement 3.1, [RFC4119] defines geospatial location
      information as the mandatory to implement location format.
      [I-D.ietf-geopriv-pdif-lo-profile] describes in more detail the
      acceptable forms of geolocation and its interaction with civic
      notations.

   o  With the support of civic and geodedic location information in
      [RFC4119] the requirement 3.2 is fulfilled.

   o  Regarding requirement 3.3, rules described in
      [I-D.ietf-geopriv-policy] apply to an absolute geodetic point.
      Geodetic information expressed in a PIDF-LO that complies with
      [I-D.ietf-geopriv-pdif-lo-profile] may express an area or volume



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      there-by "fuzzing" the location of the Target.

   o  Regarding requirement 3.4, since the PIDF-LO format is designed to
      be extensible it allows further location information types to be
      defined in the future.


   Section 7.2 of [RFC3693] details the requirements of a "Using
   Protocol".  These requirements are listed below:


   Req. 4.  The using protocol has to obey the privacy and security
            instructions coded in the Location Object regarding the
            transmission and storage of the LO.  This document carries
            the PIDF-LO as is via HTTPS from the LIS to the Location
            Recipient.  The sending and receiving parties must obey the
            instructions carried inside the object.

   Req. 5.  The using protocol will typically facilitate that the keys
            associated with the credentials are transported to the
            respective parties, that is, key establishment is the
            responsibility of the using protocol.  This document does
            not define additional security mechanisms beyond HTTPS.

   Req. 6.  (Single Message Transfer): In particular, for tracking of
            small target devices, the design should allow a single
            message / packet transmission of location as a complete
            transaction.  The encoding of the RFC 4119-defined Location
            Object format is not changed.  Because of the verbose XML
            encoding it is not tailored towards inclusion into a single
            message.


   Section 7.3 of [RFC3693] details the requirements of a "Rule based
   Location Data Transfer".  These requirements are listed below:


   Req. 7.  (LS Rules): Access to location information is controlled by
            allowing the Target (or by an entity on behalf of the
            Target) to indicate to which Location Recipients the short-
            lived location URI that contains a unguessable random
            component.  Additionally, constraints can be put on the
            dereferencing step by the Target.








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   Req. 8.  (LG Rules): In context of location URI it is not possible
            that there is no relationship between the Location Generator
            and the Location Information Server.  As such, the statement
            made in Requirement 7 applies.

   Req. 9.  (Viewer Rules): The Rule Maker might define (via mechanisms
            outside the scope of this document) which policy rules are
            disclosed to other entities.  These mechanisms are available
            with [I-D.ietf-geopriv-policy].  These rules are, however,
            best used when the location URI is not directly provided to
            Location Recipients but rather to an intermediary that
            stores these authorization policies, such as a location-
            based presence server.

   Req. 10.  (Full Rule language): Geopriv has defined a rule language
             capable of expressing a wide range of privacy rules which
             is applicable in the area of the distribution of Location
             Objects.  The format of these rules are described in
             [RFC4745] and [I-D.ietf-geopriv-policy].  These rules may
             be used in a larger context but this document does not
             define their usage.

   Req. 11.  (Limited Rule language): A limited (or basic) ruleset was
             introduced with PIDF-LO [RFC4119]).


   Section 7.4 of [RFC3693] details the requirements of "Location Object
   Privacy and Security".  These requirements are listed below:


   Req. 12.  (Identity Protection): Identity protection of the Target
             can be provided if both the following conditions are true:

             (a)  the protocol used to convey the reference does not
                  disclose the identity of the Target and

             (b)  if the PIDF-LO does not contain information about the
                  identity about the Target.


             Currently, there is no mechanism available that allows the
             Target to tell the LIS which identity information to
             include in the PIDF-LO.








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   Req. 13.  (Credential Requirements): The security mechanism specified
             in this document is Transport Layer Security.  TLS offers
             the ability to use different types of credentials,
             including symmetric, asymmetric credentials or a
             combination of them.

   Req. 14.  (Security Features): Geopriv defines a few security
             requirements for the protection of Location Objects such as
             mutual end-point authentication, data object integrity,
             data object confidentiality and replay protection.  The
             ability to use Transport Layer security fulfills these
             requirements.

   Req. 15.  Minimal Crypto: The mandatory to implement ciphersuite is
             provided in the TLS layer security specification.




































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Appendix B.  HELD Compliance to IETF Location Reference Requirements

   This section describes how HELD complies to the location reference
   requirements stipulated in [I-D.ietf-geopriv-lbyr-requirements].

   High-level requirements for a location configuration protocol.

   C1.  "Location URI support - LCP: The configuration protocol MUST
        support a location reference in URI form."


        COMPLY.  HELD only provides location references in URI form.


   C2.  "Location URI expiration: The LCP MUST support the ability to
        specify to the server, the length of time that a location URI
        will be valid."


        COMPLY. basic HELD supports the LIS informing the Target of the
        location URI expiry time.  HELD context management extension
        [I-D.winterbottom-geopriv-held-context] provides the Target the
        ability to specify exipry times for location URIs.


   C3.  "Location URI cancellation: The LCP MUST support the ability to
        request the cancellation of a specific location URI."


        COMPLY.  HELD context management extension
        [I-D.winterbottom-geopriv-held-context] provides the Target the
        ability to void location URIs when required.


   C4.  "Random Generated: The location URI MUST be hard to guess, i.e.,
        it MUST contain a cryptographically random component."


        COMPLY.  The HELD specification provides specific guidance on
        the security surrounding location URI generation.


   C5.  "Identity Protection - LCP: The location URI MUST NOT contain
        any information that identifies the user, device or address of
        record within the URI form."


        COMPLY.  The HELD specification provides specific guidance on



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        the anonymity of the Target with regards to the generation of
        location URIs.


   C6.  "Reuse flag default: The LCP MUST support the default condition
        of a requested location URI being repeatedly reused."


        COMPLY.  The default semantics of location URIs in HELD place no
        limits on the number of times that a location URI can be
        dereferenced.


   C7.  "One-time-use: The LCP MUST support the ability for the client
        to request a 'one-time-use' location URI (e.g., via a reuse flag
        setting)."


        COMPLY.  HELD context management extension
        [I-D.winterbottom-geopriv-held-context] provides the Target the
        ability to set the number of times that a location URI may yield
        the Target's location.


   High-level requirements for a location dereference protocol.

   D1.  "Location URI support - LDP: The LDP MUST support a location
        reference in URI form."


        COMPLY.  HELD only provides location references in URI form.


   D2.  "Location URI expiration status: The LDP MUST support a message
        indicating that for a location URI which is no longer valid,
        that the location URI has expired."


        COMPLY.  HELD indicates to the requestor that location for the
        URI cannot be provided by returning a locationUnknown error when
        a location URI is found to have expired.


   D3.  "Authentication: The LDP MUST support either client-side and
        server-side authentication between client and server."


        COMPLY.  Client authentication may be provided using a variety



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        of techniques.  However, this document does not mandate a
        specific procedure nor does it specify the format of
        authorization policies that may be in place to control access at
        the LIS.  The server authenticates itself using the methods
        described in HTTP on TLS [RFC2818].


   D4.  "Dereferenced Location Form: Location URI dereferencing MUST
        result in a well-formed PIDF-LO."


        COMPLY.  HELD when used as a dereference protocol MUST provide
        location information as a PIDF-LO that complies with
        [I-D.ietf-geopriv-pdif-lo-profile] as described in Section 5.


   D5.  "Repeated use: The LDP MUST support the ability for the same
        location URI to be resolved more than once, based on server
        settings and LCP parameters."


        COMPLY.  A Location Recipient may access and use a location URI
        as many times as desired until such time as the URI expires due
        to age, or is made invalid by other Target policies on the LIS.


   D6.  "Updated location: The LDP MUST support the ability for the same
        location URI to be resolved into a continuum of location values
        (e.g., location updates)."


        COMPLY.  Using base-HELD the location of the Target is
        determined each time that URI is accessed.


   D7.  "Location form: The LDP MUST support dereferenced location in
        both coordinate and civic forms."


        COMPLY.  HELD provide the locationType parameter allowing the
        Location Recipient the ability to specify the form of location
        they require.









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Authors' Addresses

   James Winterbottom
   Andrew Corporation
   PO Box U40
   University of Wollongong, NSW  2500
   AU

   Phone: +61 242 212938
   Email: james.winterbottom@andrew.com
   URI:   http://www.andrew.com/products/geometrix


   Hannes Tschofenig
   Nokia Siemens Networks
   Otto-Hahn-Ring 6
   Munich, Bavaria  81739
   Germany

   Phone: +49 89 636 40390
   Email: Hannes.Tschofenig@nsn.com
   URI:   http://www.tschofenig.com


   Henning Schulzrinne
   Columbia University
   Department of Computer Science
   450 Computer Science Building, New York, NY  10027
   US

   Phone: +1 212 939 7004
   Email: hgs@cs.columbia.edu
   URI:   http://www.cs.columbia.edu


   Martin Thomson
   Andrew Corporation
   PO Box U40
   University of Wollongong, NSW  2500
   AU

   Email: martin.thomson@andrew.com









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   Martin Dawson
   Andrew Corporation
   PO Box U40
   University of Wollongong, NSW  2500
   AU

   Email: martin.dawson@andrew.com












































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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

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   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
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