LIS Discovery: Discovering the Local Location Information Server (LIS)

Internet Engineering Task Force (IETF)                        M. Thomson
Request for Comments: 5986                               J. Winterbottom
Category: Standards Track                             Andrew Corporation
ISSN: 2070-1721                                           September 2010


        Discovering the Local Location Information Server (LIS)

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.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5986.

Copyright Notice

   Copyright (c) 2010 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
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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction and Overview  . . . . . . . . . . . . . . . . . .  2
     1.1.  Discovery Procedure Overview . . . . . . . . . . . . . . .  3
     1.2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  LIS Discovery Procedure  . . . . . . . . . . . . . . . . . . .  4
     2.1.  Residential Gateways . . . . . . . . . . . . . . . . . . .  6
     2.2.  Virtual Private Networks (VPNs)  . . . . . . . . . . . . .  7
   3.  Determining a Domain Name  . . . . . . . . . . . . . . . . . .  7
     3.1.  Domain Name Encoding . . . . . . . . . . . . . . . . . . .  7
     3.2.  Access Network Domain Name DHCPv4 Option . . . . . . . . .  8
     3.3.  Access Network Domain Name DHCPv6 Option . . . . . . . . .  8
     3.4.  Alternative Domain Names . . . . . . . . . . . . . . . . .  9
   4.  U-NAPTR Resolution of a LIS URI  . . . . . . . . . . . . . . . 10
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
     6.1.  Registration of DHCPv4 and DHCPv6 Option Codes . . . . . . 13
     6.2.  Registration of a Location Server Application Service
           Tag  . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     6.3.  Registration of a Location Server Application Protocol
           Tag for HELD . . . . . . . . . . . . . . . . . . . . . . . 13
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 15

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 attached
   access networks used to provide Internet access.  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 [RFC2616] or HTTPS [RFC2818] URI
   that 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 HTTP-Enabled Location Delivery (HELD)
   [RFC5985].  URIs discovered in this way are not "location URIs"
   [RFC5808]; dereferencing one of them provides the location of the
   requestor 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 that allows a Device to
   operate in a specific network environment.  The 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" have been 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 RFC 3693
   [RFC3693] parlance, the Device is also the Target.

   The term "access network" refers to the network to which a Device
   connects for Internet access.  The "access network provider" is the
   entity that operates the access network.  This is consistent with the
   definition in [RFC5687], 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 this process:

   1.  Acquire the access network domain name (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).
   If this option is not available, DHCPv4 option 15 [RFC2132] is used.
   Other domain names MAY be used, as described in Section 3.4.

   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.  Any
   HTTP 200 response containing a HELD response signifies success.  This
   includes HELD error responses, with the exception of the
   "notLocatable" error.

   If -- at any time -- the LIS responds to a request with the
   "notLocatable" error code (see Section 4.3.2 of [RFC5985]), 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.  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.

   The overall discovery process is summarized in Figure 1.

       -----------
      (   Start   )
       -----+-----
            |<--------------------------------------+
            |                                       |
            V                                       |
      ------^-------            ------^------       |
     /              \          /      1.     \      |
    < Next interface >-------><  Get domain   >-----+
     \              / Y  ^     \             /  N
      ------v-------     |      ------v------
            | N          |            | Y
            |            |            V
            |            |      ------^------
            |            |     /      2.     \
            |            +----<    Get URI    ><----+
            |               N  \             /      |
            |                   ------v------       |
            |                         | Y           |
            |                         V             |
            |                   ------^------       |
            |                  /      3.     \      |
            |                 <   Check URI   >-----+
            |                  \             /  N
            |                   ------v------
            |                         | Y
            V                         V
       -----------               -----------
      (  Failure  )             (  Success  )
       -----------               -----------

                     Figure 1: LIS Discovery Flowchart

2.1.  Residential Gateways

   The options available in residential gateways will affect the success
   of this algorithm in residential network scenarios.  A fixed wireline
   scenario is described in more detail in [RFC5687], Section 3.1.  In
   this fixed wireline environment, an intervening residential gateway
   exists between the Device and the access network.  If the residential
   gateway does not provide the appropriate information 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.  A residential gateway is able to use DHCP to assist
   Devices in gaining access to their location information.  This can be
   accomplished by providing an access network domain name DHCP option
   suitable for LIS discovery, or by acting as a LIS directly.  To
   actively assist Devices, a residential gateway 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;
      or

   o  act as a LIS and directly provide location information to the
      Devices it serves, including providing a means to discover this
      service.

   As with Devices, configuration of a specific domain name 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
   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.

2.2.  Virtual Private Networks (VPNs)

   A Device MUST NOT attempt LIS discovery over a VPN network interface
   until it has attempted and failed to perform discovery on all other
   non-VPN interfaces.  A Device MAY perform discovery over a VPN
   network interface if it has first attempted discovery on non-VPN
   interfaces, but 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.  In these cases, it might be that a LIS
   on the remote side of a VPN is inadvertently discovered.  A LIS
   provides a "notLocatable" error code in response to a request that it
   is unable to fulfill (see [RFC5985], Section 6.3).  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.  Determining a Domain Name

   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.

   For example, the domain "example.com." is encoded in 13 octets as:

      +---+---+---+---+---+---+---+---+---+---+---+---+---+
      | 7 | e | x | a | m | p | l | e | 3 | c | o | m | 0 |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+

   Note that the length field in either option represents the length of
   the entire domain name encoding, whereas the length fields in the
   domain name encoding is the length of a single domain name label.

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.

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Code      |   Length      |  Access Network Domain Name   .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .            Access Network Domain Name (cont.)                 .
   .                              ...                              .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

            Figure 2: Access Network Domain Name DHCPv4 Option

   option-code:  OPTION_V4_ACCESS_DOMAIN (213).

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

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

   A DHCPv4 client MAY request an 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 3: DHCPv6 Access Network Domain Name Option

   option-code:  OPTION_V6_ACCESS_DOMAIN (57).

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

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

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

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

3.4.  Alternative Domain Names

   The U-NAPTR resolution method described requires a domain name as
   input.  The access network domain name DHCP options (Sections 3.2 and
   3.3) are 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.

   DHCPv4 option 15 [RFC2132] provides an indication of the domain name
   that a host uses when resolving hostnames in DNS.  This option is
   used when the DHCPv4 access domain name is not available.

   DHCPv4 option 15 might not be suitable for some network deployments.
   For instance, a global enterprise could operate multiple sites, with
   Devices at all sites using the same value for option 15.  In this
   type of deployment, it might be desirable to discover a LIS local to
   a site.  The access domain name option can be given a different value
   at each site to enable discovery of a LIS at that site.

   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.

   Other domain names might be provided by a DHCP server (for example,
   [RFC4702] for DHCPv4, [RFC4704] for DHCPv6).  However, these domain
   names could be provided without considering their use for LIS
   discovery; therefore, it is not likely that these other domain names
   contain useful values.

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 [RFC5985].

   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 4: Sample LIS:HELD Service NAPTR Records

   Details for the "LIS" Application Service tag and the "HELD"
   Application Protocol tag are included in Section 6.

   U-NAPTR resolution might produce multiple results from each iteration
   of the algorithm.  Order and preference values in the NAPTR record
   determine which value is chosen.  A Device MAY attempt to use
   alternative choices if the first choice is not successful.  However,
   if a request to the resulting URI produces a HELD "notLocatable"
   response, or equivalent, the Device SHOULD NOT attempt to use any
   alternative choices from the same domain name.

   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 one that was input to the
   U-NAPTR resolution process.

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 probability 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.  impersonating the LIS

   The domain name that used to authenticate the LIS is the domain name
   input to the U-NAPTR process, not the output of that process
   [RFC3958], [RFC4848].  As a result, the results of DNS queries do not
   need integrity protection.

   An HTTPS URI is authenticated using the method described in Section
   3.1 of [RFC2818].  HTTP client implementations frequently do not
   provide a means to authenticate based on a domain name other than the
   one indicated in the request URI, namely the U-NAPTR output.  To
   avoid having to authenticate the LIS with a domain name that is
   different from the one used to identify it, a client MAY choose to
   reject URIs that contain a domain name that is different to the
   U-NAPTR input.  To support endpoints that enforce the above
   restriction on URIs, network administrators SHOULD ensure that the
   domain name in the DHCP option is the same as the one contained in
   the resulting URI.

   Authentication of a LIS relies on the integrity of the domain name
   acquired from DHCP.  An attacker that is able to falsify a domain
   name circumvents the protections provided.  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 commonly used to reduce the
   possibility of such an attack within an access network.  DHCP
   authentication [RFC3118] might also provide a degree of protection
   against modification or spoofing.

   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 213 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 57 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 LIS, as mandated by [RFC3958].

   Application Service Tag:  LIS

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

   Defining publication:  RFC 5986

   Related publications:  HELD [RFC5985]

   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 protocol [RFC5985], as mandated by [RFC3958].

   Application Protocol Tag:  HELD

   Intended Usage:  Identifies the HELD protocol.

   Applicable Service Tag(s):  LIS

   Terminal NAPTR Record Type(s):  U
   Defining Publication:  RFC 5986

   Related Publications:  HELD [RFC5985]

   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; Richard Barnes, Joe Salowey, Barbara
   Stark, and Hannes Tschofenig for input and reviews; and 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.

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

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

   [RFC2132]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
              Extensions", RFC 2132, 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.

   [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.

   [RFC5985]  Barnes, M., Ed., "HTTP-Enabled Location Delivery (HELD)",
              RFC 5985, September 2010.

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.

   [RFC5687]  Tschofenig, H. and H. Schulzrinne, "GEOPRIV Layer 7
              Location Configuration Protocol: Problem Statement and
              Requirements", RFC 5687, March 2010.

   [RFC5808]  Marshall, R., "Requirements for a Location-by-Reference
              Mechanism", RFC 5808, May 2010.

Authors' Addresses

   Martin Thomson
   Andrew Corporation
   Andrew Building (39)
   Wollongong University Campus
   Northfields Avenue
   Wollongong, NSW  2522
   AU

   Phone: +61 2 4221 2915
   EMail: martin.thomson@andrew.com


   James Winterbottom
   Andrew Corporation
   Andrew Building (39)
   Wollongong University Campus
   Northfields Avenue
   Wollongong, NSW  2522
   AU

   Phone: +61 2 4221 2938
   EMail: james.winterbottom@andrew.com