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Versions: (draft-thomson-geopriv-lis-discovery) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 RFC 5986

GEOPRIV                                                       M. Thomson
Internet-Draft                                           J. Winterbottom
Intended status: Standards Track                                  Andrew
Expires: October 3, 2009                                   April 1, 2009


        Discovering the Local Location Information Server (LIS)
                  draft-ietf-geopriv-lis-discovery-09

Status of This Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on October 3, 2009.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

Abstract

   Discovery of the correct Location Information Server (LIS) in the
   local access network is necessary for devices that wish to acquire
   location information from the network.  A method is described for the



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   discovery of a LIS.  Dynamic Host Configuration Protocol (DHCP)
   options for IP versions 4 and 6 are defined that specify a URI for a
   LIS in the local access network.  An alternative method that uses
   URI-enabled NAPTR (U-NAPTR) is described for use where the DHCP
   option is unsuccessful.

Table of Contents

   1.  Introduction and Overview  . . . . . . . . . . . . . . . . . .  3
     1.1.  DHCP Discovery . . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  U-NAPTR Discovery  . . . . . . . . . . . . . . . . . . . .  3
     1.3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  LIS Discovery Using DHCP . . . . . . . . . . . . . . . . . . .  4
     2.1.  DHCPv4 LIS URI Option  . . . . . . . . . . . . . . . . . .  4
     2.2.  DHCPv6 LIS URI Option  . . . . . . . . . . . . . . . . . .  5
   3.  U-NAPTR for LIS Discovery  . . . . . . . . . . . . . . . . . .  6
     3.1.  Determining a Domain Name  . . . . . . . . . . . . . . . .  7
   4.  Overall Discovery Procedure  . . . . . . . . . . . . . . . . .  7
     4.1.  Residential Gateways . . . . . . . . . . . . . . . . . . .  8
     4.2.  Virtual Private Networks (VPNs)  . . . . . . . . . . . . .  9
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
     6.1.  Registration of DHCPv4 and DHCPv6 LIS URI Option Codes . . 10
     6.2.  Registration of a Location Server Application Service
           Tag  . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     6.3.  Registration of a Location Server Application Protocol
           Tag for HELD . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 13




















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1.  Introduction and Overview

   The location of a device is a useful and sometimes necessary part of
   many services.  A Location Information Server (LIS) is responsible
   for providing that location information to devices with an access
   network.  The LIS uses knowledge of the access network and its
   physical topology to generate and serve location information to
   devices.

   Each access network requires specific knowledge about topology.
   Therefore, it is important to discover the LIS that has the specific
   knowledge necessary to locate a device.  That is, the LIS that serves
   the current access network.  Automatic discovery is important where
   there is any chance of movement outside a single access network.
   Reliance on static configuration can lead to unexpected errors if a
   device moves between access networks.

   This document describes DHCP options and DNS records that a device
   can use to discover a LIS.

   The product of a discovery process, such as the one described in this
   document, is the address of the service.  In this document, the
   result is an http: or https: URI, which identifies a LIS.

   The URI result from the discovery process is suitable for location
   configuration only; that is, the device MUST dereference the URI
   using the process described in HELD
   [I-D.ietf-geopriv-http-location-delivery].  URIs discovered in this
   way are not "location URIs" [I-D.ietf-geopriv-lbyr-requirements];
   dereferencing one of them provides the location of the requester
   only.  Devices MUST NOT embed these URIs in fields in other protocols
   designed to carry the location of the device.

1.1.  DHCP Discovery

   DHCP ([RFC2131], [RFC3315]) is a commonly used mechanism for
   providing bootstrap configuration information allowing a device to
   operate in a specific network environment.  The bulk of DHCP
   information is largely static; consisting of configuration
   information that does not change over the period that the device is
   attached to the network.  Physical location information might change
   over this time, however the address of the LIS does not.  Thus, DHCP
   is suitable for configuring a device with the address of a LIS.

1.2.  U-NAPTR Discovery

   Where DHCP is not available, the DNS might be able to provide a URI.
   This document describes a method that uses URI-enabled NAPTR



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   (U-NAPTR) [RFC4848], a Dynamic Delegation Discovery Service (DDDS)
   profile that supports URI results.

   For the LIS discovery DDDS application, an Application Service tag
   "LIS" and an Application Protocol tag "HELD" are created and
   registered with the IANA.  Taking a domain name, this U-NAPTR
   application uses the two tags to determine the LIS URI.

1.3.  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].

   This document also uses the term "device" to refer to an end host, or
   client consistent with its use in HELD.  In HELD and RFC3693
   [RFC3693] parlance, the Device is also the Target.

   The terms "access network" refers to the network that a device
   connects to for Internet access.  The "access network provider" is
   the entity that operates the access network.  This is consistent with
   the definition in [I-D.ietf-geopriv-l7-lcp-ps] which combines the
   Internet Access Provider (IAP) and Internet Service Provider (ISP).
   The access network provider is responsible for allocating the device
   a public IP address and for directly or indirectly providing a LIS
   service.

2.  LIS Discovery Using DHCP

   DHCP allows the access network provider to specify the address of a
   LIS as part of network configuration.  If the device is able to
   acquire a LIS URI using DHCP then this URI is used directly; the
   U-NAPTR process is not necessary if this option is provided.

   This document registers a DHCP option for a LIS URI for both IPv4 and
   IPv6.  An "https:" LIS URI that is a product of U-NAPTR MUST be
   authenticated using the domain name method described in Section 3.1
   of RFC 2818 [RFC2818].

2.1.  DHCPv4 LIS URI Option

   This section defines a DHCP for IPv4 (DHCPv4) option for the address
   of a LIS.








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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    LIS_URI    |    Length     |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   .                            LIS URI                            .
   .                              ...                              .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 1: DHCPv4 LIS URI Option

   LIS_URI:  The IANA assigned option number (TBD).  [[IANA/RFC-Editor
      Note: Please replace TBD with the assigned DHCPv4 option code.]]

   Length:  The length of the entire LIS URI option in octets.

   LIS URI:  The address of the LIS.  The URI MUST NOT be terminated by
      a zero octet.

      The DHCPv4 version of this URI SHOULD NOT exceed 255 octets in
      length, but MAY be extended by concatenating multiple option
      values if necessary, as described in [RFC3396].

2.2.  DHCPv6 LIS URI Option

   This section defines a DHCP for IPv6 (DHCPv6) option for the address
   of a LIS.  The DHCPv6 option for this parameter is similarly
   formatted to the DHCPv4 option.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       OPTION_LIS_URI          |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                            LIS URI                            .
   .                              ...                              .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 2: DHCPv6 LIS URI Option

   OPTION_LIS_URI:  The IANA assigned option number (TBD).  [[IANA/
      RFC-Editor Note: Please replace TBD with the assigned DHCPv6
      option code.]]

   Length:  The length of the LIS URI option in octets.






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      The semantics and format of the remainder of the LIS URI option
      are identical to the DHCPv4 option, except for the larger
      allowance for URI length granted by the 16 bit length field.
      DHCPv6 prohibits concatenation of option values.

3.  U-NAPTR for LIS Discovery

   U-NAPTR resolution for a LIS takes a domain name as input and
   produces a URI that identifies the LIS.  This process also requires
   an Application Service tag and an Application Protocol tag, which
   differentiate LIS-related NAPTR records from other records for that
   domain.

   Section 6.2 defines an Application Service tag of "LIS", which is
   used to identify the location service for a particular domain.  The
   Application Protocol tag "HELD", defined in Section 6.3, is used to
   identify a LIS that understands the HELD protocol
   [I-D.ietf-geopriv-http-location-delivery].

   The NAPTR records in the following example demonstrate the use of the
   Application Service and Protocol tags.  Iterative NAPTR resolution is
   used to delegate responsibility for the LIS service from
   "zonea.example.net." and "zoneb.example.net." to
   "outsource.example.com.".

      zonea.example.net.
      ;;       order pref flags
      IN NAPTR 100   10   ""  "LIS:HELD" (          ; service
          ""                                        ; regex
          outsource.example.com.                    ; replacement
          )
      zoneb.example.net.
      ;;       order pref flags
      IN NAPTR 100   10   ""  "LIS:HELD" (          ; service
          ""                                        ; regex
          outsource.example.com.                    ; replacement
          )
      outsource.example.com.
      ;;       order pref flags
      IN NAPTR 100   10   "u"  "LIS:HELD" (         ; service
          "!*.!https://lis.example.org:4802/?c=ex!" ; regex
          .                                         ; replacement
          )


              Figure 3: Sample LIS:HELD Service NAPTR Records

   Details for the "LIS" Application Service tag and the "HELD"



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   Application Protocol tag are included in Section 6.

   An "https:" LIS URI that is a product of U-NAPTR MUST be
   authenticated using the domain name method described in Section 3.1
   of RFC 2818 [RFC2818].

3.1.  Determining a Domain Name

   The U-NAPTR discovery method described requires a domain name as
   input.  This document does not specify how that domain name is
   acquired by a device.  If a device knows one or more domain names
   that might be used for discovery, it is able to attempt to use each
   domain name as input to the U-NAPTR discovery process.  Static
   configuration of a device is possible if a domain name is known to
   work for this purpose.

   A fully qualified domain name (FQDN) for the device might be provided
   by a DHCP server ([RFC4702] for DHCPv4, [RFC4704] for DHCPv6).
   DHCPv4 option 15 [RFC2131] could also be used as a source of a domain
   name suffix for the device.  If DHCP and any of these options are
   available, these values could be used as input the U-NAPTR procedure;
   however, implementers need to be aware that many DHCP servers do not
   provide a sensible value for these options.  Therefore, this method
   of discovery SHOULD be given lesser precedence than methods that are
   based on more explicit assurances.

4.  Overall Discovery Procedure

   The individual components of discovery are combined into a single
   discovery procedure.  Some networks maintain a topology analogous to
   an onion and are comprised of layers, or segments, separating devices
   from the Internet through intermediate networks.  Applying the
   individual discovery methods in an order that favours a physically
   proximate LIS over a remote LIS is preferred.

   A device MUST support DHCP discovery, where applicable.  Devices
   SHOULD support U-NAPTR discovery unless no input domain names can be
   determined.

   The following process ensures a greater likelihood of a LIS in close
   physical proximity being discovered:

   1.  Request the DHCP LIS URI Option for each network interface.

   2.  Use U-NAPTR to discover a LIS URI using all known domain names.

   3.  Use a statically configured LIS URI.




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   A device that has multiple network interfaces could potentially be
   served by a different access network on each interface, each with a
   different LIS.  The device SHOULD attempt to discover the LIS
   applicable to each network interface, stopping when a LIS is
   successfully discovered on any interface.

   A device that discovers a LIS URI MUST attempt to verify that the LIS
   is able to provide location information.  For the HELD protocol, the
   device MUST make a location request to the LIS.  If - at any time -
   the LIS responds to a request with the "notLocatable" error code (see
   Section 4.3.2 of [I-D.ietf-geopriv-http-location-delivery]), the
   device MUST continue or restart the discovery process.  A device
   SHOULD NOT make further requests to a LIS that provides a
   "notLocatable" error until its network attachment changes, or it
   discovers the LIS on an alternative network interface.

   DHCP discovery MUST be attempted before any other discovery method.
   This allows the network access provider a direct and explicit means
   of configuring a LIS address.  Alternative methods are only specified
   as a means to discover a LIS where the DHCP infrastructure does not
   support the LIS URI option.

   This document does not mandate any particular source for the domain
   name that is used as input to U-NAPTR.

   Static configuration MAY be used if all other discovery methods fail.
   Note however, that if a device has moved from its customary location,
   static configuration might indicate a LIS that is unable to provide
   accurate location information.

   The product of the LIS discovery process is an "https:" or "http:"
   URI.  Nothing distinguishes this URI from other URIs with the same
   scheme, aside from the fact that it is the product of this process.
   Only URIs produced by the discovery process can be used for location
   configuration using HELD.  URIs that are not a product of LIS
   discovery MUST NOT be used for location configuration.

4.1.  Residential Gateways

   The process described in this document is known to not work in a very
   common deployment scenario.  A fixed wireline scenario is described
   in more detail in Section 3.1 of [I-D.ietf-geopriv-l7-lcp-ps].  In
   this fixed wireline environment an intervening residential gateway
   exists between the device and the access network.  If the residential
   gateway does not provide this option to the devices it serves, those
   devices are unable to discover a LIS.

   Support of this specification by residential gateways ensures that



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   the devices they serve are able to acquire location information.  In
   most cases the residential gateway configures the devices it serves
   using DHCP.  When DHCP is used, the residential gateway MUST provide
   the devices it serves with a LIS URI option.  In order to provide a
   sensible value for this option, the residential gateway MUST either:

   1.  act as a LIS and provide location information to the devices that
       it serves, or

   2.  discover a LIS on its external interface and relay this
       information to devices.

   In either case, the residential gateway provides a LIS URI option to
   devices.

4.2.  Virtual Private Networks (VPNs)

   LIS discovery over a VPN network interface SHOULD NOT be performed.
   A LIS discovered in this way is unlikely to have the information
   necessary to determine an accurate location.

   Not all interfaces connected to a VPN can be detected by devices or
   the software running on them.  A LIS MUST NOT provide location
   information in response to requests that it can identify as
   originating from a device on the remote end of a VPN tunnel, unless
   it is able to accurately determine location.  The "notLocatable" HELD
   error code can be used to indicate to a device that discovery has
   revealed an unsuitable LIS.  This ensures that even if a device
   discovers a LIS over the VPN, it does not rely on a LIS that is
   unable to provide accurate location information.

5.  Security Considerations

   The primary attack against the methods described in this document is
   one that would lead to impersonation of a LIS.  The LIS is
   responsible for providing location information and this information
   is critical to a number of network services; furthermore, a device
   does not necessarily have a prior relationship with a LIS.  Several
   methods are described here that can limit the probablity of, or
   provide some protection against, such an attack.

   The address of a LIS is usually well-known within an access network;
   therefore, interception of messages does not introduce any specific
   concerns.

   An attacker that is able to modify or spoof messages from a DHCP
   server could provide a falsified LIS URI that a device would be able
   to use to successfully authenticate the LIS.  Preventing DHCP



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   messages from being modified or spoofed by attackers is necessary if
   this information is to be relied upon.  Physical or link layer
   security are commonplace methods that can reduce the possibility of
   such an attack within an access network; alternatively, DHCP
   authentication [RFC3118] can provide a degree of protection against
   modification or spoofing.

   An attacker could attempt to compromise the U-NAPTR resolution.  A
   more thorough description of the security considerations for U-NAPTR
   applications is included in [RFC4848].  In addition to considerations
   related to U-NAPTR, it is important to recognize that the output of
   U-NAPTR discovery is entirely dependent on its input.  An attacker
   who can control the domain name is therefore able to control the
   final URI.

   A LIS that is identified by an "http:" URI cannot be authenticated.
   Use of HTTP also does not meet requirements in HELD for
   confidentiality and integrity.  If an "http:" URI is the product of
   DHCP or U-NAPTR discovery, this leaves devices vulnerable to several
   attacks.  Lower layer protections, such as layer 2 traffic separation
   might provide some guarantees.

6.  IANA Considerations

6.1.  Registration of DHCPv4 and DHCPv6 LIS URI Option Codes

   The IANA has assigned an option code of (TBD) for the DHCPv4 option
   for a LIS URI, as described in Section 2.1 of this document.

   The IANA has assigned an option code of (TBD) for the DHCPv6 option
   for a LIS URI, as described in Section 2.2 of this document.

6.2.  Registration of a Location Server Application Service Tag

   This section registers a new S-NAPTR/U-NAPTR Application Service tag
   for a LIS, as mandated by [RFC3958].

   Application Service Tag:  LIS

   Intended usage:  Identifies a service that provides a device with its
      location information.

   Defining publication:  RFCXXXX

   Related publications:  HELD [I-D.ietf-geopriv-http-location-delivery]






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   Contact information:  The authors of this document

   Author/Change controller:  The IESG

6.3.  Registration of a Location Server Application Protocol Tag for
      HELD

   This section registers a new S-NAPTR/U-NAPTR Application Protocol tag
   for the HELD [I-D.ietf-geopriv-http-location-delivery] protocol, as
   mandated by [RFC3958].

   Application Service Tag:  HELD

   Intended Usage:  Identifies the HELD protocol.

   Applicable Service Tag(s):  LIS

   Terminal NAPTR Record Type(s):  U

   Defining Publication:  RFCXXXX

   Related Publications:  HELD [I-D.ietf-geopriv-http-location-delivery]

   Contact Information:  The authors of this document

   Author/Change Controller:  The IESG

7.  Acknowledgements

   The authors would like to thank Leslie Daigle for her work on
   U-NAPTR; Peter Koch for feedback on how not to use DNS for discovery;
   Andy Newton for constructive suggestions with regards to document
   direction; Hannes Tschofenig and Richard Barnes for input and
   reviews; Dean Willis for constructive feedback.

8.  References

8.1.  Normative References

   [RFC2131]                                  Droms, R., "Dynamic Host
                                              Configuration Protocol",
                                              RFC 2131, March 1997.

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

   [RFC3315]                                  Droms, R., Bound, J.,
                                              Volz, B., Lemon, T.,



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                                              Perkins, C., and M.
                                              Carney, "Dynamic Host
                                              Configuration Protocol for
                                              IPv6 (DHCPv6)", RFC 3315,
                                              July 2003.

   [RFC3396]                                  Lemon, T. and S. Cheshire,
                                              "Encoding Long Options in
                                              the Dynamic Host
                                              Configuration Protocol
                                              (DHCPv4)", RFC 3396,
                                              November 2002.

   [RFC4702]                                  Stapp, M., Volz, B., and
                                              Y. Rekhter, "The Dynamic
                                              Host Configuration
                                              Protocol (DHCP) Client
                                              Fully Qualified Domain
                                              Name (FQDN) Option",
                                              RFC 4702, October 2006.

   [RFC4704]                                  Volz, B., "The Dynamic
                                              Host Configuration
                                              Protocol for IPv6 (DHCPv6)
                                              Client Fully Qualified
                                              Domain Name (FQDN)
                                              Option", RFC 4704,
                                              October 2006.

   [RFC4848]                                  Daigle, L., "Domain-Based
                                              Application Service
                                              Location Using URIs and
                                              the Dynamic Delegation
                                              Discovery Service (DDDS)",
                                              RFC 4848, April 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-13 (work
                                              in progress),
                                              February 2009.

   [RFC2119]                                  Bradner, S., "Key words
                                              for use in RFCs to
                                              Indicate Requirement



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                                              Levels", BCP 14, RFC 2119,
                                              March 1997.

8.2.  Informative References

   [RFC3118]                                  Droms, R. and W. Arbaugh,
                                              "Authentication for DHCP
                                              Messages", RFC 3118,
                                              June 2001.

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

   [RFC3958]                                  Daigle, L. and A. Newton,
                                              "Domain-Based Application
                                              Service Location Using SRV
                                              RRs and the Dynamic
                                              Delegation Discovery
                                              Service (DDDS)", RFC 3958,
                                              January 2005.

   [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-09 (work
                                              in progress),
                                              February 2009.

   [I-D.ietf-geopriv-lbyr-requirements]       Marshall, R.,
                                              "Requirements for a
                                              Location-by-Reference
                                              Mechanism", draft-ietf-
                                              geopriv-lbyr-requirements-
                                              07 (work in progress),
                                              February 2009.










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Authors' Addresses

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

   Phone: +61 2 4221 2915
   EMail: martin.thomson@andrew.com
   URI:   http://www.andrew.com/


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

   Phone: +61 2 4221 2938
   EMail: james.winterbottom@andrew.com
   URI:   http://www.andrew.com/





























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