GEOPRIV                                                       M. Thomson
Internet-Draft                                           J. Winterbottom
Intended status: Standards Track                                  Andrew
Expires: October 25, November 8, 2009                                 April 23,                                    May 7, 2009

        Discovering the Local Location Information Server (LIS)
                  draft-ietf-geopriv-lis-discovery-10
                  draft-ietf-geopriv-lis-discovery-11

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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
   discovery of a LIS in the access network serving a device.  Dynamic
   Host Configuration Protocol (DHCP) options for IP versions 4 and 6
   are defined that specify a domain name.  This domain name is then
   used as input to a URI-enabled NAPTR (U-NAPTR) resolution process.

Table of Contents

   1.  Introduction and Overview  . . . . . . . . . . . . . . . . . .  3
     1.1.  Discovery Procedure Overview . . . . . . . . . . . . . . .  3
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  LIS Discovery Procedure  . . . . . . . . . . . . . . . . . . .  4
     2.1.  Residential Gateways . . . . . . . . . . . . . . . . . . .  5
     2.2.  Virtual Private Networks (VPNs)  . . . . . . . . . . . . .  6
   3.  Access Network Domain Name DHCP Option . . . . . . . . . . . .  6  7
     3.1.  Domain Name Encoding . . . . . . . . . . . . . . . . . . .  7
     3.2.  Access Network Domain Name DHCPv4 Option . . . . . . . . .  7
     3.3.  Access Network Domain Name DHCPv6 Option . . . . . . . . .  8
   4.  U-NAPTR Resolution of a LIS URI  . . . . . . . . . . . . . . .  8  9
     4.1.  Determining a Domain Name  . . . . . . . . . . . . . . . .  9 10
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 11
     6.1.  Registration of DHCPv4 and DHCPv6 Option Codes . . . . . . 11
     6.2.  Registration of a Location Server Application Service
           Tag  . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 12
     6.3.  Registration of a Location Server Application Protocol
           Tag for HELD . . . . . . . . . . . . . . . . . . . . . . . 12
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 13
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 13
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 12 13
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 14

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 a process that a device can use to discover a
   LIS.  This process uses a DHCP option and the DNS.  The product of
   this discovery process 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.  Discovery Procedure Overview

   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.

   This document defines a DHCP option that produces a domain name that
   identifies the local access network in Section 3.

   Section 4 describes a method that uses URI-enabled NAPTR (U-NAPTR)
   [RFC4848], a Dynamic Delegation Discovery Service (DDDS) profile that
   produces a URI for the LIS.  The input to this process is provided by
   the DHCP option.

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

1.2.  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].

   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 Procedure

   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.

   The LIS discovery procedure follows the following process:

   1.  Acquire the access network domain name DHCP option (Section 3).

       This process might be repeated for each of the network interfaces
       on the device.  Domain names acquired from other sources might
       also be added.

   2.  Apply U-NAPTR resolution (Section 4) to discover a LIS URI.

       The U-NAPTR process is applied using each of the domain names as
       input.

   3.  Verify that the LIS is able to provide location information.

       The first URI that results in a successful response from the LIS
       is used.

   A device MUST support discovery using the access network domain name
   DHCP option (Section 3) as input to U-NAPTR resolution (Section 4).
   Other domain names MAY be used, as described in Section 4.1.

   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 verifies the URI by making 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.

   Static configuration of a domain name or a LIS URI MAY be used if all
   other discovery methods fail.  Note 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 for HELD 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.

2.1.  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
   the devices they serve are able to acquire location information.  In
   many cases the residential gateway configures the devices it serves
   using DHCP.  When DHCP is used, the  A residential gateway MUST provide
   the is able to use DHCP to assist
   devices it serves with in gaining access to their location information.  This can be
   accomplished by providing an access network domain name DHCP option
   suitable for LIS discovery.  In order to provide discovery, or by acting as a LIS directly.  To
   actively assist devices, a useful value for
   this option, the residential gateway MUST can either:

   o  acquire an access network domain name from the access network
      provider (possibly using DHCP) and pass the resulting value to
      devices; or

   o  discover a LIS on its external interface, then provide devices
      with the domain name that was used to successfully discover the
      LIS; or

   o  explicitly include configuration that refers to a particular LIS.

   In either case, LIS;
      or

   o  act as a LIS and directly provide location information to the residential gateway provides an access network
      devices it serves, including providing a means to discover this
      service.

   As with devices, configuration of a specific domain name DHCP option or location
   information is only accurate as long as the residential gateway does
   not move.  If a residential gateway that relies on configuration
   rather than automatic discovery is moved, the devices it serves could
   be provided with inaccurate information.  Devices could be led to devices.
   discover a LIS that is unable to provide accurate location
   information, or - if location is configured on the residential
   gateway - the residential gateway could provide incorrect location
   information.

   [I-D.ietf-dhc-container-opt] might be used by an access network
   provider to convey configuration information to a residential gateway
   for use by the devices it serves.  Support and use of this option is
   RECOMMENDED for both residential gateways and devices.  Option values
   found within the container MUST be used after values that are
   directly in the DHCP response.

2.2.  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.

3.  Access Network Domain Name DHCP Option

   DHCP provides a direct means for the access network provider to
   configure a device.  The access network domain name option identifies
   a domain name that is suitable for service discovery within the
   access network.  This domain name is used as input to the U-NAPTR
   resolution process for LIS discovery.

   The domain name provided in this option is one owned by the access
   network operator.  This domain name is intended for use in
   discovering services within the access network.

   This document registers a DHCP option for the access network domain
   name for both IPv4 and IPv6.

3.1.  Domain Name Encoding

   This section describes the encoding of the domain name used in the
   DHCPv4 option defined in Section 3.2 and also used in the DHCPv6
   option defined in Section 3.3.

   The domain name is encoded according to Section 3.1 of [RFC1035].
   Each label is represented as a one-octet length field followed by
   that number of octets.  Since every domain name ends with the null
   label of the root, a domain name is terminated by a length byte of
   zero.  The high-order two bits of every length octet MUST be zero,
   and the remaining six bits of the length field limit the label to 63
   octets or less.  To simplify implementations, the total length of a
   domain name (i.e., label octets and label length octets) is
   restricted to 255 octets or less.

3.2.  Access Network Domain Name DHCPv4 Option

   This section defines a DHCP for IPv4 (DHCPv4) option for the domain
   name associated with the access network.

             Code   Len   Access Network Domain Name
            +-----+-----+-----+-----+-----+-----+-----+----
            | TBD |  n  |  s1 |  s2 |  s3 |  s4 | s5  |  ...
            +-----+-----+-----+-----+-----+-----+-----+----

            Figure 1: Access Network Domain Name DHCPv4 Option

   The values s1, s2, s3, etc. represent the domain name labels in the
   domain name encoding.  Note that the length field in the DHCPv4
   option represents the length of the entire domain name encoding,
   whereas the length fields in the domain name encoding (see Section 3)
   is the length of a single domain name label.

   Code:  OPTION_V4_ACCESS_DOMAIN (TBD).  [[IANA/RFC-Editor Note: Please
      replace TBD with the assigned DHCPv4 option code, both here and in
      Figure 1.]]

   Length:  The length of the entire access network domain name option
      in octets.

   Access Network Domain Name:  The domain name associated with the
      access network, encoded as described in Section 3.1.

   A DHCPv4 client MAY request a LoST server access network domain name option in a
   Parameter Request List option, as described in [RFC2131].

   This option contains a single domain name and, as such, MUST contain
   precisely one root label.

3.3.  Access Network Domain Name DHCPv6 Option

   This section defines a DHCP for IPv6 (DHCPv6) option for the domain
   name associated with the access network.  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_V6_ACCESS_DOMAIN    |           Length              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                  Access Network Domain Name                   .
   .                              ...                              .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 2: DHCPv6 Access Network Domain Name Option

   option-code:  OPTION_V6_ACCESS_DOMAIN (TBD).  [[IANA/RFC-Editor Note:
      Please replace TBD with the assigned DHCPv6 option code.]]

   option-length:  The length of the entire access network domain name
      option in octets.

   option-value:  The access network domain name, encoded as described
      in Section 3.1.

   A DHCPv6 client MAY request a LoST server access network domain name option in a
   Options Request Option (ORO), as described in [RFC3315].

   This option contains a single domain name and, as such, MUST contain
   precisely one root label.

4.  U-NAPTR Resolution of a LIS URI

   U-NAPTR [RFC4848] 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 given 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"
   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].  The domain name that is used in this
   authentication is the one extracted from the URI, not the input to
   the U-NAPTR resolution process.

4.1.  Determining a Domain Name

   The U-NAPTR resolution method described requires a domain name as
   input.  The access network domain name DHCP option (Section 3)
   describes one source of this domain name.

   If a device knows one or more alternative domain names that might be
   used for discovery, it MAY repeat the U-NAPTR process using those
   domain names as input.  For instance, static configuration of a
   device might be used to provide a device with a domain name.

   Alternative domain names MUST NOT be used unless the access network
   domain name option is unsuccessful or where external information
   indicates that a particular domain name is to be used.  For instance,
   domain names 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.  However, these domain names could be provided without
   considering their use for LIS discovery; therefore, many DHCP servers
   do not provide a sensible value for these options.

5.  Security Considerations

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

   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.  These methods MUST
   be applied unless similar protections are in place, or in cases -
   such as an emergency - where location information of dubious origin
   is arguably better than none at all.

   An attacker could attempt to compromise LIS discovery at any of three
   stages:

   1.  providing a falsified domain name to be used as input to U-NAPTR

   2.  altering the DNS records used in U-NAPTR resolution

   3.  impersonation of the LIS

   U-NAPTR is entirely dependent on its inputs.  In falsifying a domain
   name, an attacker avoids any later protections, bypassing them
   entirely.  To ensure that the access network domain name DHCP option
   can be relied upon, preventing DHCP messages from being modified or
   spoofed by attackers is necessary.  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.

   The domain name that is used to authenticated the LIS is the domain
   name in the URI that is the result of the U-NAPTR resolution.
   Therefore, if an attacker were able to modify or spoof any of the DNS
   records used in the DDDS resolution, this URI could be replaced by an
   invalid URI.  The application of DNS security (DNSSEC) [RFC4033]
   provides a means to limit attacks that rely on modification of the
   DNS records used in U-NAPTR resolution.  Security considerations
   specific to U-NAPTR are described in more detail in [RFC4848].

   An "https:" URI is authenticated using the method described in
   Section 3.1 of [RFC2818].  The domain name used for this
   authentication is the domain name in the URI resulting from U-NAPTR
   resolution, not the input domain name as in [RFC3958].  Using the
   domain name in the URI is more compatible with existing HTTP client
   software, which authenticate servers based on the domain name in the
   URI.

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

6.  IANA Considerations

6.1.  Registration of DHCPv4 and DHCPv6 Option Codes

   The IANA has assigned an option code of (TBD) for the DHCPv4 option
   for an access network domain name option, as described in Section 3.2
   of this document.

   The IANA has assigned an option code of (TBD) for the DHCPv6 option
   for an access network domain name option, as described in Section 3.3
   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]

   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

   This document uses a mechanism that is largely identical to that in
   [RFC5222] and [RFC5223].  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, Richard Barnes, and Joe Salowey Salowey, Barbara
   Stark, and Hannes Tschofenig for input and reviews; Dean Willis for
   constructive feedback.

8.  References

8.1.  Normative References

   [RFC1035]                                  Mockapetris, P., "Domain
                                              names - implementation and
                                              specification", STD 13,
                                              RFC 1035, November 1987.

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

   [RFC4033]                                  Arends, R., Austein, R.,
                                              Larson, M., Massey, D.,
                                              and S. Rose, "DNS Security
                                              Introduction and
                                              Requirements", RFC 4033,
                                              March 2005.

   [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.

   [I-D.ietf-dhc-container-opt]               Droms, R., "Container
                                              Option for Server
                                              Configuration", draft-
                                              ietf-dhc-container-opt-05
                                              (work in progress),
                                              March 2009.

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

   [RFC5222]                                  Hardie, T., Newton, A.,
                                              Schulzrinne, H., and H.
                                              Tschofenig, "LoST: A
                                              Location-to-Service
                                              Translation Protocol",
                                              RFC 5222, August 2008.

   [RFC5223]                                  Schulzrinne, H., Polk, J.,
                                              and H. Tschofenig,
                                              "Discovering Location-to-
                                              Service Translation (LoST)
                                              Servers Using the Dynamic
                                              Host Configuration
                                              Protocol (DHCP)",
                                              RFC 5223, August 2008.

   [I-D.ietf-geopriv-l7-lcp-ps]               Tschofenig, H. and H.
                                              Schulzrinne, "GEOPRIV
                                              Layer 7 Location
                                              Configuration Protocol;
                                              Problem Statement and
                                              Requirements", draft-ietf-
                                              geopriv-l7-lcp-ps-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.

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/