tech-invite   World Map     

IETF     RFCs     Groups     SIP     ABNFs    |    3GPP     Specs     Gloss.     Arch.     IMS     UICC    |    Misc.    |    search     info

RFC 5580

 
 
 

Carrying Location Objects in RADIUS and Diameter

Part 2 of 2, p. 28 to 53
Prev RFC Part

 


prevText      Top      Up      ToC       Page 28 
5.  Table of Attributes

   The following table provides a guide to which attributes may be found
   in which RADIUS messages, and in what quantity.

Top      Up      ToC       Page 29 
 Request Accept Reject Challenge Accounting  #  Attribute
                                 Request
 0-1     0-1    0      0         0+         126  Operator-Name
 0+      0      0      0         0+         127  Location-Information
 0+      0      0      0         0+         128  Location-Data
 0-1     0-1    0-1    0-1       0-1        129  Basic-Location-
                                                 Policy-Rules
 0-1     0-1    0-1    0-1       0-1        130  Extended-Location-
                                                 Policy-Rules
 0-1     0      0      0         0          131  Location-Capable
 0       0-1    0      0-1       0          132  Requested-Location-Info
 0       0      0-1    0         0          101  Error-Cause (*)

 (*) Note: The Error-Cause Attribute contains the value for the
 'Location-Info-Required' error.

 Change-of-Authorization Messages

  Request   ACK      NAK    #    Attribute
   0-1       0        0     129  Basic-Location-Policy-Rules
   0-1       0        0     130  Extended-Location-Policy-Rules
   0-1       0        0     132  Requested-Location-Info

 Legend:

    0     This attribute MUST NOT be present.
    0+    Zero or more instances of this attribute MAY be present.
    0-1   Zero or one instance of this attribute MAY be present.
    1     Exactly one instance of this attribute MUST be present.
    1+    One or more of these attributes MUST be present.

                       Figure 7: Table of Attributes

   The Error-Cause Attribute is defined in [RFC5176].

   The Location-Information and the Location-Data Attribute MAY appear
   more than once.  For example, if the server asks for civic and
   geospatial location information, two Location-Information Attributes
   need to be sent.

   The attributes defined in this document are not used in any messages
   other than the ones listed in Figure 7.

   IANA allocated a new value (509) from the Error-Cause registry with
   the semantics of 'Location-Info-Required'.

Top      Up      ToC       Page 30 
6.  Diameter RADIUS Interoperability

   When used in Diameter, the attributes defined in this specification
   can be used as Diameter attribute-value pairs (AVPs) from the code
   space 1-255 (RADIUS attribute-compatibility space).  No additional
   Diameter code values are therefore allocated.  The data types and
   flag rules, as defined in [RFC3588], for the Diameter AVPs are as
   follows:

                                     +---------------------+
                                     |    AVP Flag rules   |
                                     +----+-----+------+-----+----+
                                     |    |     |SHOULD| MUST|    |
    Attribute Name        Value Type |MUST| MAY | NOT  |  NOT|Encr|
   +---------------------------------+----+-----+------+-----+----+
   |Operator-Name         OctetString|    |  P  |      | V,M | Y  |
   |Location-Information  OctetString|    |  P  |      | V,M | Y  |
   |Location-Data         OctetString|    |  P  |      | V,M | Y  |
   |Basic-Location-                  |    |     |      |     |    |
   |   Policy-Rules       OctetString|    |  P  |      | V,M | Y  |
   |Extended-Location-               |    |     |      |     |    |
   |   Policy-Rules       OctetString|    |  P  |      | V,M | Y  |
   |Requested-                       |    |     |      |     |    |
   |   Location-Info      OctetString|    |  P  |      | V,M | Y  |
   |Location-Capable      OctetString|    |  P  |      | V,M | Y  |
   +---------------------------------+----+-----+------+-----+----+

   The RADIUS attributes in this specification have no special
   translation requirements for Diameter-to-RADIUS or RADIUS-to-Diameter
   gateways; they are copied as is, except for changes relating to
   headers, alignment, and padding.  See also Section 4.1 of [RFC3588]
   and Section 9 of [RFC4005].

   What this specification says about the applicability of the
   attributes for RADIUS Access-Request packets applies in Diameter to
   AA-Request [RFC4005] or Diameter-EAP-Request [RFC4072].  What is said
   about Access-Challenge applies in Diameter to AA-Answer [RFC4005] or
   Diameter-EAP-Answer [RFC4072] with the Result-Code AVP set to
   DIAMETER_MULTI_ROUND_AUTH.  What is said about Access-Accept applies
   in Diameter to AA-Answer or Diameter-EAP-Answer messages that
   indicate success.  Similarly, what is said about RADIUS Access-Reject
   packets applies in Diameter to AA-Answer or Diameter-EAP-Answer
   messages that indicate failure.

   What is said about CoA-Request applies in Diameter to Re-Auth-Request
   [RFC4005].

Top      Up      ToC       Page 31 
   What is said about Accounting-Request applies in Diameter to
   Accounting-Request [RFC4005] as well.

   Note that these AVPs may be used by Diameter applications other than
   RFC 4005 [RFC4005] and RFC 4072 [RFC4072].  The above-mentioned
   applications are, however, likely to be relevant in the context of
   this document.

7.  Security Considerations

   A number of security aspects are relevant for the distribution of
   location information via RADIUS.  These aspects are discussed in
   separate subsections.

7.1.  Communication Security

   Requirements for the protection of a Location Object are defined in
   [RFC3693] -- namely, mutual end-point authentication, data object
   integrity, data object confidentiality, and replay protection.

   If no authentication, integrity, and replay protection between the
   participating RADIUS entities is provided, then adversaries can spoof
   and modify transmitted attributes.  Two security mechanisms are
   proposed for RADIUS:

   o  [RFC2865] proposes the usage of a static key that raised concerns
      regarding the lack of dynamic key management.  At the time of
      writing, work is ongoing to address some shortcomings of the
      [RFC2865] attribute regarding security protection.

   o  RADIUS over IPsec [RFC3579] enables the use of standard key-
      management mechanisms, such as Kerberized Internet Negotiation of
      Keys (KINK), the Internet Key Exchange Protocol (IKE), and IKEv2
      [RFC4306], to establish IPsec security associations.
      Confidentiality protection MUST be used to prevent an eavesdropper
      from gaining access to location information.  Confidentiality
      protection is already present for other reasons in many
      environments, such as for the transport of keying material in the
      context of Extensible Authentication Protocol (EAP) authentication
      and authorization.  Hence, this requirement is, in many
      environments, already fulfilled.  Mutual authentication MUST be
      provided between neighboring RADIUS entities to prevent man-in-
      the-middle attacks.  Since mutual authentication is already
      required for key transport within RADIUS messages, it does not
      represent a deployment obstacle.  Since IPsec protection is
      already suggested as a mechanism to protect RADIUS, no additional
      considerations need to be addressed beyond those described in
      [RFC3579].

Top      Up      ToC       Page 32 
   In case IPsec protection is not available for some reason and RADIUS-
   specific security mechanisms have to be used, then the following
   considerations apply.  The Access-Request message is not integrity
   protected.  This would allow an adversary to change the contents of
   the Location Object or to insert, modify, and delete attributes or
   individual fields.  To address these problems, the Message-
   Authenticator (80) can be used to integrity protect the entire
   Access-Request packet.  The Message-Authenticator (80) is also
   required when EAP is used and, hence, is supported by many modern
   RADIUS servers.

   Access-Request packets including location attribute(s) without a
   Message-Authenticator (80) Attribute SHOULD be silently discarded by
   the RADIUS server.  A RADIUS server supporting location attributes
   MUST calculate the correct value of the Message-Authenticator (80)
   and MUST silently discard the packet if it does not match the value
   sent.

   Access-Accept messages, including location attribute(s), without a
   Message-Authenticator (80) Attribute SHOULD be silently discarded by
   the NAS.  An NAS supporting location attributes MUST calculate the
   correct value of a received Message-Authenticator (80) and MUST
   silently discard the packet if it does not match the value sent.

   RADIUS and Diameter make some assumptions about the trust between
   traversed RADIUS entities in the sense that object-level security is
   not provided by either RADIUS or Diameter.  Hence, some trust has to
   be placed on the RADIUS entities to behave according to the defined
   rules.  Furthermore, the RADIUS protocol does not involve the user in
   their protocol interaction except for tunneling authentication
   information (such as EAP messages) through their infrastructure.
   RADIUS and Diameter have even become a de facto protocol for key
   distribution for network-access authentication applications.  Hence,
   in the past there were some concerns about the trust placed into the
   infrastructure -- particularly from the security area -- when it
   comes to keying.  The EAP keying infrastructure is described in
   [RFC4282].

7.2.  Privacy Considerations

   This section discusses privacy implications for the distribution of
   location information within RADIUS.  Note also that it is possible
   for the RADIUS server to obtain some amount of location information
   from the NAS identifier.  This document, however, describes
   procedures to convey more accurate location information about the end
   host and/or the network.  In a number of deployment environments,
   location information about the network also reveals the current

Top      Up      ToC       Page 33 
   location of the user with a certain degree of precision, depending on
   the location-determination mechanism used, the update frequency, the
   size of the network, and other factors, such as movement traces.

   Three types of use cases have to be differentiated:

   o  The RADIUS server does not want to receive location information
      from the RADIUS client.

   o  In case there is an out-of-band agreement between the entity
      responsible for the NAS and the entity operating the RADIUS
      server, location information may be sent without an explicit
      request from the RADIUS server.

   o  The RADIUS server dynamically requests location information from
      the NAS.

7.2.1.  RADIUS Client

   The RADIUS client MUST behave according to the following guidelines:

   o  If neither an out-of-band agreement exists nor location
      information is requested by the RADIUS server, then location
      information is not disclosed by the RADIUS client.

   o  The RADIUS client MUST pass location information to other entities
      (e.g., when information is written to a local database or to the
      log files) only together with the policy rules.  The entity
      receiving the location information (together with the policies)
      MUST follow the guidance given with these rules.

   o  A RADIUS client MUST include Basic-Location-Policy-Rules and
      Extended-Location-Policy-Rules Attributes that are configured
      within an Access-Request packet.

   o  NAS implementations supporting this specification, which are
      configured to provide location information, MUST echo Basic-
      Location-Policy-Rules and Extended-Location-Policy-Rules
      Attributes unmodified within a subsequent Access-Request packet.
      In addition, an Access-Request packet sent with a Service-Type
      value of "Authorize Only" MUST include the Basic-Location-Policy-
      Rules or Extended-Location-Policy-Rules Attributes that were
      received in a previous Access-Accept if the FUTURE_REQUESTS flag
      was set in the Requested-Location-Info Attribute.

Top      Up      ToC       Page 34 
7.2.2.  RADIUS Server

   The RADIUS server is a natural place for storing authorization
   policies since the user typically has some sort of trust relationship
   with the entity operating the RADIUS server.  Once the infrastructure
   is deployed and location-aware applications are available, there
   might be a strong desire to use location information for other
   purposes as well.

      The Common Policy framework [RFC4745] that was extended for
      geolocation privacy [GEO-POLICY] is tailored for this purpose.
      The Extensible Markup Language (XML) Configuration Access Protocol
      (XCAP) [RFC4825] gives users the ability to change their privacy
      policies using a standardized protocol.  These policies are an
      important tool for limiting further distribution of the user's
      location to other location-based services.

   The RADIUS server MUST behave according to the following guidelines:

   o  The RADIUS server MUST attach available rules to the Access-
      Accept, Access-Reject, or Access-Challenge message when the RADIUS
      client is supposed to provide location information.

   o  When location information is made available to other entities
      (e.g., writing to stable storage for later billing processing),
      then the RADIUS server MUST attach the privacy rules to location
      information.

7.2.3.  RADIUS Proxy

   A RADIUS proxy, behaving as a combined RADIUS client and RADIUS
   server, MUST follow the rules described in Sections 7.2.1 and 7.2.2.

7.3.  Identity Information and Location Information

   For the envisioned usage scenarios, the identity of the user and his
   device is tightly coupled to the transfer of location information.
   If the identity can be determined by the visited network or RADIUS
   brokers, then it is possible to correlate location information with a
   particular user.  As such, it allows the visited network and brokers
   to learn the movement patterns of users.

   The user's identity can be "leaked" to the visited network or RADIUS
   brokers in a number of ways:

   o  The user's device may employ a fixed Media Access Control (MAC)
      address or base its IP address on such an address.  This enables
      the correlation of the particular device to its different

Top      Up      ToC       Page 35 
      locations.  Techniques exist to avoid the use of an IP address
      that is based on a MAC address [RFC4941].  Some link layers make
      it possible to avoid MAC addresses or change them dynamically.

   o  Network-access authentication procedures, such as the PPP
      Challenge Handshake Authentication Protocol (CHAP) [RFC1994] or
      EAP [RFC4187], may reveal the user's identity as a part of the
      authentication procedure.  Techniques exist to avoid this problem
      in EAP methods, for instance by employing private Network Access
      Identifiers (NAIs) [RFC4282] in the EAP Identity Response message
      and by method-specific private identity exchanges in the EAP
      method (e.g., [RFC4187], [RFC5281], [PEAP], and [RFC5106]).
      Support for identity privacy within CHAP is not available.

   o  RADIUS may return information from the home network to the visited
      one in a manner that makes it possible to either identify the user
      or at least correlate his session with other sessions, such as the
      use of static data in a Class Attribute [RFC2865] or in some
      accounting attribute usage scenarios [RFC4372].

   o  Mobility protocols may reveal some long-term identifier, such as a
      home address.

   o  Application-layer protocols may reveal other permanent
      identifiers.

   To prevent the correlation of identities with location information,
   it is necessary to prevent leakage of identity information from all
   sources, not just one.

   Unfortunately, most users are not educated about the importance of
   identity confidentiality, and some protocols lack support for
   identity-privacy mechanisms.  This problem is made worse by the fact
   that users may be unable to choose particular protocols, as the
   choice is often dictated by the type of network operator they use,
   the type of network they wish to access, the kind of equipment they
   have, or the type of authentication method they are using.

   A scenario where the user is attached to the home network is, from a
   privacy point of view, simpler than a scenario where a user roams
   into a visited network, since the NAS and the home RADIUS server are
   in the same administrative domain.  No direct relationship between
   the visited and the home network operator may be available, and some
   RADIUS brokers need to be consulted.  With subscription-based network
   access as used today, the user has a contractual relationship with
   the home network provider that could (theoretically) allow higher

Top      Up      ToC       Page 36 
   privacy considerations to be applied (including policy rules stored
   at the home network itself, for the purpose of restricting further
   distribution).

   In many cases it is necessary to secure the transport of location
   information along the RADIUS infrastructure.  Mechanisms to achieve
   this functionality are discussed in Section 7.1.

8.  IANA Considerations

   The Attribute Types and Attribute Values defined in this document
   have been registered by the Internet Assigned Numbers Authority
   (IANA) from the RADIUS namespaces as described in the "IANA
   Considerations" section of RFC 3575 [RFC3575], in accordance with BCP
   26 [RFC5226].  Additionally, the Attribute Type has been registered
   in the Diameter namespace.  For RADIUS attributes and registries
   created by this document, IANA placed them in the Radius Types
   registry.

   This document defines the following attributes:

         Operator-Name
         Location-Information
         Location-Data
         Basic-Location-Policy-Rules
         Extended-Location-Policy-Rules
         Location-Capable
         Requested-Location-Info

   Please refer to Section 5 for the registered list of numbers.

   IANA has also assigned a new value (509) for the Error-Cause
   Attribute [RFC5176] of "Location-Info-Required" according to this
   document.

   Additionally, IANA created the following new registries listed in the
   subsections below.

8.1.  New Registry: Operator Namespace Identifier

   This document also defines an Operator Namespace Identifier registry
   (used in the Namespace ID field of the Operator-Name Attribute).
   Note that this document requests IANA only to maintain a registry of
   existing namespaces for use in this identifier field, and not to
   establish any namespaces or place any values within namespaces.

Top      Up      ToC       Page 37 
   IANA added the following values to the Operator Namespace Identifier
   registry using a numerical identifier (allocated in sequence), a
   token for the operator namespace, and a contact person for the
   registry.

  +----------+--------------------+------------------------------------+
  |Identifier| Operator Namespace | Contact Person                     |
  |          | Token              |                                    |
  +----------+--------------------+------------------------------------+
  |   0x30   | TADIG              | TD.13 Coordinator                  |
  |          |                    | (td13@gsm.org)                     |
  |   0x31   | REALM              | IETF O&M Area Directors            |
  |          |                    | (ops-ads@ietf.org)                 |
  |   0x32   | E212               | ITU Director                       |
  |          |                    | (tsbdir@itu.int)                   |
  |   0x33   | ICC                | ITU Director                       |
  |          |                    | (tsbdir@itu.int)                   |
  +----------+--------------------+------------------------------------+

   Note that the above identifier values represent the ASCII value '0'
   (decimal 48 or hex 0x30), '1' (decimal 49, or hex 0x31), '2' (decimal
   50, or hex 0x32), and '3' (decimal 51, or hex 0x33).  This encoding
   was chosen to simplify parsing.

   Requests to IANA for a new value for a Namespace ID, i.e., values
   from 0x34 to 0xFE, will be approved by Expert Review.  A designated
   expert will be appointed by the IESG.

   The Expert Reviewer should ensure that a new entry is indeed required
   or could fit within an existing database, e.g., whether there is a
   real requirement to provide a token for a Namespace ID because one is
   already up and running, or whether the REALM identifier plus the name
   should be recommended to the requester.  In addition, the Expert
   Reviewer should ascertain to some reasonable degree of diligence that
   a new entry is a correct reference to an operator namespace whenever
   a new one is registered.

8.2.  New Registry: Location Profiles

   Section 4.2 defines the Location-Information Attribute and a Code
   field that contains an 8-bit integer value.  Two values, zero and
   one, are defined in this document, namely:

   Value (0): Civic location profile described in Section 4.3.1

   Value (1): Geospatial location profile described in Section 4.3.2

   The remaining values are reserved for future use.

Top      Up      ToC       Page 38 
   Following the policies outlined in [RFC3575], the available bits with
   a description of their semantics will be assigned after the Expert
   Review process.  Updates can be provided based on expert approval
   only.  Based on expert approval, it is possible to mark entries as
   "deprecated".  A designated expert will be appointed by the IESG.

   Each registration must include the value and the corresponding
   semantics of the defined location profile.

8.3.  New Registry: Location-Capable Attribute

   Section 4.6 defines the Location-Capable Attribute that contains a
   bit map. 32 bits are available, from which 4 bits are defined by this
   document.  This document creates a new IANA registry for the
   Location-Capable Attribute.  IANA added the following values to this
   registry:

    +----------+----------------------+
    |  Value   | Capability Token     |
    +----------+----------------------+
    |    1     | CIVIC_LOCATION       |
    |    2     | GEO_LOCATION         |
    |    4     | USERS_LOCATION       |
    |    8     | NAS_LOCATION         |
    +----------+----------------------+

   Following the policies outlined in [RFC3575], the available bits with
   a description of their semantics will be assigned after the Expert
   Review process.  Updates can be provided based on expert approval
   only.  Based on expert approval, it is possible to mark entries as
   "deprecated".  A designated expert will be appointed by the IESG.

   Each registration must include:

   Name:

      Capability Token (i.e., an identifier of the capability)

   Description:

      Brief description indicating the meaning of the 'info' element.

   Numerical Value:

      A numerical value that is placed into the Capability Attribute
      representing a bit in the bit-string of the Requested-Location-
      Info Attribute.

Top      Up      ToC       Page 39 
8.4.  New Registry: Entity Types

   Section 4.2 defines the Location-Information Attribute that contains
   an 8-bit Entity field.  Two values are registered by this document,
   namely:

   Value (0) describes the location of the user's client device.

   Value (1) describes the location of the RADIUS client.

   All other values are reserved for future use.

   Following the policies outlined in [RFC3575], the available bits with
   a description of their semantics will be assigned after the Expert
   Review process.  Updates can be provided based on expert approval
   only.  Based on expert approval, it is possible to mark entries as
   "deprecated".  A designated expert will be appointed by the IESG.

   Each registration must include the value and a corresponding
   description.

8.5.  New Registry: Privacy Flags

   Section 4.4 defines the Basic-Location-Policy-Rules Attribute that
   contains flags indicating privacy settings. 16 bits are available,
   from which a single bit, bit (0), indicating 'retransmission allowed'
   is defined by this document.  Bits 1-15 are reserved for future use.

   Following the policies outline in [RFC3575], the available bits with
   a description of their semantics will be assigned after the Expert
   Review process.  Updates can be provided based on expert approval
   only.  Based on expert approval, it is possible to mark entries as
   "deprecated".  A designated expert will be appointed by the IESG.

   Each registration must include the bit position and the semantics of
   the bit.

8.6.  New Registry: Requested-Location-Info Attribute

   Section 4.7 defines the Requested-Location-Info Attribute that
   contains a bit map. 32 bits are available, from which 6 bits are
   defined by this document.  This document creates a new IANA registry
   for the Requested-Location-Info Attribute.  IANA added the following
   values to this registry:

Top      Up      ToC       Page 40 
    +----------+----------------------+
    |  Value   | Capability Token     |
    +----------+----------------------+
    |    1     | CIVIC_LOCATION       |
    |    2     | GEO_LOCATION         |
    |    4     | USERS_LOCATION       |
    |    8     | NAS_LOCATION         |
    |   16     | FUTURE_REQUESTS      |
    |   32     | NONE                 |
    +----------+----------------------+

   The semantics of these values are defined in Section 4.7.

   Following the policies outlined in [RFC3575], new Capability Tokens,
   with a description of their semantics for usage with the Requested-
   Location-Info Attribute, will be assigned after the Expert Review
   process.  Updates can be provided based on expert approval only.
   Based on expert approval, it is possible to mark entries as
   "deprecated".  A designated expert will be appointed by the IESG.

   Each registration must include:

   Name:

      Capability Token (i.e., an identifier of the capability)

   Description:

      Brief description indicating the meaning of the 'info' element.

   Numerical Value:

      A numerical value that is placed into the Capability Attribute
      representing a bit in the bit-string of the Requested-Location-
      Info Attribute.

9.  Acknowledgments

   The authors would like to thank the following people for their help
   with an initial version of this document and for their input: Chuck
   Black, Paul Congdon, Jouni Korhonen, Sami Ala-luukko, Farooq Bari, Ed
   Van Horne, Mark Grayson, Jukka Tuomi, Jorge Cuellar, and Christian
   Guenther.

Top      Up      ToC       Page 41 
   Henning Schulzrinne provided the civic location information content
   found in this document.  The geospatial location-information format
   is based on work done by James Polk, John Schnizlein, and Marc
   Linsner.  The authorization policy format is based on the work done
   by Jon Peterson.

   The authors would like to thank Victor Lortz, Anthony Leibovitz, Jose
   Puthenkulam, Bernrad Aboba, Jari Arkko, Parviz Yegani, Serge Manning,
   Kuntal Chowdury, Pasi Eronen, Blair Bullock and Eugene Chang for
   their feedback to an initial version of this document.  We would like
   to thank Jari Arkko for his textual contributions.  Lionel Morand
   provided detailed feedback on numerous issues.  His comments helped
   to improve the quality of this document.  Jouni Korhonen, Victor
   Fajardo, Tolga Asveren, and John Loughney helped us with the Diameter
   RADIUS interoperability section.  Andreas Pashalidis reviewed a later
   version document and provided a number of comments.  Alan DeKok,
   Lionel Morand, Jouni Korhonen, David Nelson, and Emile van Bergen
   provided guidance on the Requested-Location-Info Attribute and
   participated in the capability-exchange discussions.  Allison Mankin,
   Jouni Korhonen, and Pasi Eronen provided text for the Operator
   Namespace Identifier registry.  Jouni Korhonen interacted with the
   GSMA to find a contact person for the TADIG operator namespace, and
   Scott Bradner consulted the ITU-T to find a contact person for the
   E212 and the ICC operator namespace.

   This document is based on the discussions within the IETF GEOPRIV
   Working Group.  Therefore, the authors thank Henning Schulzrinne,
   James Polk, John Morris, Allison Mankin, Randall Gellens, Andrew
   Newton, Ted Hardie, and Jon Peterson for their time discussing a
   number of issues with us.  We thank Stephen Hayes for aligning this
   work with 3GPP activities.

   We would like to thank members of the Wimax Forum Global Roaming
   Working Group (GRWG) for their feedback on the Operator-Name
   attribute.  Ray Jong Kiem helped us with his detailed description to
   correct the document.

   The RADEXT Working Group chairs, David Nelson and Bernard Aboba,
   provided several draft reviews and we would like to thank them for
   the help and their patience.

   Finally, we would like to thank Dan Romascanu, Glen Zorn, Russ
   Housley, Jari Arkko, Ralph Droms, Adrial Farrel, Tim Polk, and Lars
   Eggert for the IETF Last Call comments; Derek Atkins for his security
   area directorate review; and Yoshiko Chong for spotting a bug in the
   IANA Considerations section.

Top      Up      ToC       Page 42 
10.  References

10.1.  Normative References

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

   [RFC2865]     Rigney, C., Willens, S., Rubens, A., and W. Simpson,
                 "Remote Authentication Dial In User Service (RADIUS)",
                 RFC 2865, June 2000.

   [RFC3492]     Costello, A., "Punycode: A Bootstring encoding of
                 Unicode for Internationalized Domain Names in
                 Applications (IDNA)", RFC 3492, March 2003.

   [RFC3575]     Aboba, B., "IANA Considerations for RADIUS (Remote
                 Authentication Dial In User Service)", RFC 3575,
                 July 2003.

   [RFC3588]     Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and
                 J. Arkko, "Diameter Base Protocol", RFC 3588,
                 September 2003.

   [RFC3825]     Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host
                 Configuration Protocol Option for Coordinate-based
                 Location Configuration Information", RFC 3825,
                 July 2004.

   [RFC4776]     Schulzrinne, H., "Dynamic Host Configuration Protocol
                 (DHCPv4 and DHCPv6) Option for Civic Addresses
                 Configuration Information", RFC 4776, November 2006.

   [RFC5176]     Chiba, M., Dommety, G., Eklund, M., Mitton, D., and B.
                 Aboba, "Dynamic Authorization Extensions to Remote
                 Authentication Dial In User Service (RADIUS)",
                 RFC 5176, January 2008.

   [RFC5226]     Narten, T. and H. Alvestrand, "Guidelines for Writing
                 an IANA Considerations Section in RFCs", BCP 26,
                 RFC 5226, May 2008.

10.2.  Informative References

   [GEO-POLICY]  Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar,
                 J., and J. Polk, "Geolocation Policy: A Document Format
                 for Expressing Privacy Preferences for  Location
                 Information", Work in Progress, February 2009.

Top      Up      ToC       Page 43 
   [GMLv3]       "Open Geography Markup Language (GML) Implementation
                 Specification", OGC 02-023r4, January 2003,
                 <http://www.opengis.org/techno/implementation.htm>.

   [GSM]         "TADIG Naming Conventions", Version 4.1, GSM
                 Association Official Document TD.13, June 2006.

   [ISO]         "Codes for the representation of names of countries and
                 their subdivisions - Part 1: Country codes",
                 ISO 3166-1, 1997.

   [ITU1400]     "Designations for interconnections among operators'
                 networks", ITU-T Recommendation M.1400, January 2004.

   [ITU212]      "The international identification plan for mobile
                 terminals and mobile users", ITU-T
                 Recommendation E.212, May 2004.

   [PEAP]        Josefsson, S., Palekar, A., Simon, D., and G. Zorn,
                 "Protected EAP Protocol (PEAP) Version 2", Work
                 in Progress, October 2004.

   [RFC1305]     Mills, D., "Network Time Protocol (Version 3)
                 Specification, Implementation", RFC 1305, March 1992.

   [RFC1994]     Simpson, W., "PPP Challenge Handshake Authentication
                 Protocol (CHAP)", RFC 1994, August 1996.

   [RFC2866]     Rigney, C., "RADIUS Accounting", RFC 2866, June 2000.

   [RFC3579]     Aboba, B. and P. Calhoun, "RADIUS (Remote
                 Authentication Dial In User Service) Support For
                 Extensible Authentication Protocol (EAP)", RFC 3579,
                 September 2003.

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

   [RFC4005]     Calhoun, P., Zorn, G., Spence, D., and D. Mitton,
                 "Diameter Network Access Server Application", RFC 4005,
                 August 2005.

   [RFC4017]     Stanley, D., Walker, J., and B. Aboba, "Extensible
                 Authentication Protocol (EAP) Method Requirements for
                 Wireless LANs", RFC 4017, March 2005.

Top      Up      ToC       Page 44 
   [RFC4072]     Eronen, P., Hiller, T., and G. Zorn, "Diameter
                 Extensible Authentication Protocol (EAP) Application",
                 RFC 4072, August 2005.

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

   [RFC4187]     Arkko, J. and H. Haverinen, "Extensible Authentication
                 Protocol Method for 3rd Generation Authentication and
                 Key Agreement (EAP-AKA)", RFC 4187, January 2006.

   [RFC4282]     Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
                 Network Access Identifier", RFC 4282, December 2005.

   [RFC4306]     Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
                 RFC 4306, December 2005.

   [RFC4372]     Adrangi, F., Lior, A., Korhonen, J., and J. Loughney,
                 "Chargeable User Identity", RFC 4372, January 2006.

   [RFC4745]     Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar,
                 J., Polk, J., and J. Rosenberg, "Common Policy: A
                 Document Format for Expressing Privacy Preferences",
                 RFC 4745, February 2007.

   [RFC4825]     Rosenberg, J., "The Extensible Markup Language (XML)
                 Configuration Access Protocol (XCAP)", RFC 4825,
                 May 2007.

   [RFC4941]     Narten, T., Draves, R., and S. Krishnan, "Privacy
                 Extensions for Stateless Address Autoconfiguration in
                 IPv6", RFC 4941, September 2007.

   [RFC5106]     Tschofenig, H., Kroeselberg, D., Pashalidis, A., Ohba,
                 Y., and F. Bersani, "The Extensible Authentication
                 Protocol-Internet Key Exchange Protocol version 2 (EAP-
                 IKEv2) Method", RFC 5106, February 2008.

   [RFC5281]     Funk, P. and S. Blake-Wilson, "Extensible
                 Authentication Protocol Tunneled Transport Layer
                 Security Authenticated Protocol Version 0 (EAP-
                 TTLSv0)", RFC 5281, August 2008.

Top      Up      ToC       Page 45 
Appendix A.  Matching with GEOPRIV Requirements

   This section compares the requirements for a GEOPRIV using protocol,
   described in [RFC3693], against the approach of distributing Location
   Objects with RADIUS.

   In Appendices A.1 and A.2, we discuss privacy implications when
   RADIUS entities make location information available to other parties.
   In Appendix A.3, the requirements are matched against these two
   scenarios.

A.1.  Distribution of Location Information at the User's Home Network

   When location information is conveyed from the RADIUS client to the
   RADIUS server, then it might subsequently be made available for
   different purposes.  This section discusses the privacy implications
   for making location information available to other entities.

   To use a more generic scenario, we assume that the visited RADIUS and
   the home RADIUS server belong to different administrative domains.
   The Location Recipient obtains location information about a
   particular Target via protocols specified outside the scope of this
   document (e.g., SIP, HTTP, or an API).

   The subsequent figure shows the interacting entities graphically.

   visited network    |        home network
                      |
                      |        +----------+
                      |        |  Rule    |
                      |        | Holder   |
                      |        +----+-----+
                      |             |
                      |         rule|interface
    +----------+      |             V                     +----------+
    |Location  |      |        +----------+  notification |Location  |
    |Generator |      |        |Location  |<------------->|Recipient |
    +----------+  publication  |Server    |  interface    |          |
    |RADIUS    |<------------->+----------+               +----------+
    |Client    |  interface    |RADIUS    | E.g., SIP/HTTP
    +----------+      |        |Server    |
                      |        +----------+
    E.g., NAS       RADIUS
                      |
                      |

               Figure 8: Location Server at the Home Network

Top      Up      ToC       Page 46 
   The term 'Rule Holder' in Figure 8 denotes the entity that creates
   the authorization ruleset.

A.2.  Distribution of Location Information at the Visited Network

   This section describes a scenario where location information is made
   available to Location Recipients by a Location Server in the visited
   network.  Some identifier needs to be used as an index within the
   location database.  One possible identifier is the Network Access
   Identifier.  RFC 4282 [RFC4282] and RFC 4372 [RFC4372] provide
   background regarding whether entities in the visited network can
   obtain the user's NAI in cleartext.

   The visited network provides location information to a Location
   Recipient (e.g., via SIP or HTTP).  This document enables the NAS to
   obtain the user's privacy policy via the interaction with the RADIUS
   server.  Otherwise, only default policies, which are very
   restrictive, are available.  This allows the Location Server in the
   visited network to ensure they act according to the user's policies.

   The subsequent figure shows the interacting entities graphically.

Top      Up      ToC       Page 47 
    visited network    |        home network
                       |
     +----------+      |
     |Location  |      |
     |Recipient |      |
     |          |      |
     +----------+      |
          ^            |        +----------+
          |            |        |  Rule    |
      notification     |        | Holder   |
       interface       |        |          |
          |            |        +----+-----+
          |            |             |
          |            |         rule|interface
          v            |             |
     +----------+      |             |
     |Location  |      |             v
     |Server    |      |        +----------+
     +----------+ Rule Transport|RADIUS    |
     |RADIUS    |<------------->|Server    |
     |Client    |   RADIUS      +----------+
     +----------+      |
     |Location  |      |
     |Generator |
     +----------+

             Figure 9: Location Server at the Visited Network

   Location information always travels with privacy policies.  This
   document enables the RADIUS client to obtain these policies.  The
   Location Server can subsequently act according to these policies to
   provide access control using the Extended-Location-Policy-Rules and
   to adhere to the privacy statements in the Basic-Location-Policy-
   Rules.

A.3.  Requirements Matching

   Section 7.1 of [RFC3693] details the requirements of a "Location
   Object".  We discuss these requirements in the subsequent list.

   Req. 1.  (Location Object generalities):

      *  Regarding requirement 1.1, the syntax and semantics of the
         Location Object are taken from [RFC3825] and [RFC4776].  It is
         furthermore possible to convert it to the format used in the
         Geography Markup Language (GMLv3) [GMLv3], as used with PIDF-LO
         [RFC4119].

Top      Up      ToC       Page 48 
      *  Regarding requirement 1.2, a number of fields in the civic
         location-information format are optional.

      *  Regarding requirement 1.3, the inclusion of type of place item
         (CAtype 29) used in the DHCP civic format gives a further
         classification of the location.  This attribute can be seen as
         an extension.

      *  Regarding requirement 1.4, this document does not define the
         format of the location information.

      *  Regarding requirement 1.5, location information is only sent
         from the RADIUS client to the RADIUS server.

      *  Regarding requirement 1.6, the Location Object contains both
         location information and privacy rules.  Location information
         is described in Sections 4.2, 4.3.1, and 4.3.2.  The
         corresponding privacy rules are detailed in Sections 4.4 and
         4.5.

      *  Regarding requirement 1.7, the Location Object is usable in a
         variety of protocols.  The format of the object is reused from
         other documents, as detailed in Sections 4.2, 4.3.1, 4.3.2,
         4.4, and 4.5.

      *  Regarding requirement 1.8, the encoding of the Location Object
         has an emphasis on a lightweight encoding format to be used
         with RADIUS.

   Req. 2.  (Location Object fields):

      *  Regarding requirement 2.1, the target identifier is carried
         within the network-access authentication protocol (e.g., within
         the EAP-Identity Response when EAP is used and/or within the
         EAP method itself).  As described in Section 7.2 of this
         document, it has a number of advantages if this identifier is
         not carried in clear.  This is possible with certain EAP
         methods whereby the identity in the EAP-Identity Response only
         contains information relevant for routing the response to the
         user's home network.  The user identity is protected by the
         authentication and key exchange protocol.

      *  Regarding requirement 2.2, the Location Recipient is, in the
         main scenario, the home RADIUS server.  For a scenario where
         the Location Recipient is obtaining location information from
         the Location Server via HTTP or SIP, the respective mechanisms

Top      Up      ToC       Page 49 
         defined in these protocols are used to identify the recipient.
         The Location Generator cannot, a priori, know the recipients if
         they are not defined in this protocol.

      *  Regarding requirement 2.3, the credentials of the Location
         Recipient are known to the RADIUS entities based on the
         security mechanisms defined in the RADIUS protocol itself.
         Section 7 of this document describes these security mechanisms
         offered by the RADIUS protocol.  The same is true for
         requirement 2.4.

      *  Regarding requirement 2.5, Sections 4.2, 4.3.1, and 4.3.2
         describe the content of the Location fields.  Since the
         location format itself is not defined in this document, motion
         and direction vectors as listed in requirement 2.6 are not
         defined.

      *  Regarding requirement 2.6, this document provides the
         capability for the RADIUS server to indicate what type of
         location information it would like to see from the RADIUS
         client.

      *  Regarding requirement 2.7, timing information is provided with
         the 'Sighting Time' and 'Time-to-Live' fields defined in
         Section 4.2.

      *  Regarding requirement 2.8, a reference to an external (more
         detailed ruleset) is provided with the Extended-Location-
         Policy-Rules Attribute in Section 4.5.

      *  Regarding requirement 2.9, security headers and trailers are
         provided as part of the RADIUS protocol or even as part of
         IPsec.

      *  Regarding requirement 2.10, a version number in RADIUS is
         provided with the IANA registration of the attributes.  New
         attributes are assigned a new IANA number.

   Req. 3.  (Location Data Types):

      *  Regarding requirement 3.1, this document reuses civic and
         geospatial location information as described in Sections 4.3.2
         and 4.3.1.

      *  With the support of civic and geospatial location information,
         support of requirement 3.2 is fulfilled.

Top      Up      ToC       Page 50 
      *  Regarding requirement 3.3, the geospatial location information
         used by this document only refers to absolute coordinates.
         However, the granularity of the location information can be
         reduced with the help of the AltRes, LoRes, and LaRes fields
         described in [RFC3825].

      *  Regarding requirement 3.4, further Location Data Types can be
         added via new coordinate reference systems (CRSs -- see the
         Datum field in [RFC3825]) and via extensions to [RFC3825] and
         [RFC4776].

   Section 7.2 of [RFC3693] details the requirements of a "using
   protocol".  These requirements are listed below.

   Req. 4.:  The using protocol has to obey the privacy and security
      instructions coded in the Location Object (LO) regarding the
      transmission and storage of the LO.  This document requires that
      entities that aim to make location information available to third
      parties be required to obey the privacy instructions.

   Req. 5.:  The using protocol will typically facilitate that the keys
      associated with the credentials are transported to the respective
      parties, that is, key establishment is the responsibility of the
      using protocol.  Section 7 of this document specifies how security
      mechanisms are used in RADIUS and how they can be reused to
      provide security protection for the Location Object.
      Additionally, the privacy considerations (see Section 7.2) are
      also relevant for this requirement.

   Req. 6.  (Single Message Transfer):  In particular, for tracking of
      small target devices, the design should allow a single message/
      packet transmission of location as a complete transaction.  The
      encoding of the Location Object is specifically tailored towards
      the inclusion into a single message that even respects the (Path)
      MTU size.

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

   Req. 7.  (LS Rules):  With the scenario shown in Figure 8, the
      decision of a Location Server to provide a Location Recipient
      access to location information is based on Rule Maker-defined
      privacy rules that are stored at the home network.  With regard to
      the scenario shown in Figure 9, the Rule Maker-defined privacy
      rules are sent from the RADIUS server to the NAS (see Sections
      4.4, 4.5, and 7.2 for more details).

Top      Up      ToC       Page 51 
   Req. 8.  (LG Rules):  For all usage scenarios, it is possible to
      consider the privacy rule before transmitting location information
      from the NAS to the RADIUS server or even to third parties.  In
      the case of an out-of-band agreement between the owner of the NAS
      and the owner of the RADIUS server, privacy might be applied on a
      higher granularity.  For the scenario shown in Figure 8, the
      visited network is already in possession of the user's location
      information prior to the authentication and authorization of the
      user.  A correlation between the location and the user identity
      might, however, still not be possible for the visited network (as
      explained in Section 7.2).  A Location Server in the visited
      network has to evaluate available rulesets.

   Req. 9.  (Viewer Rules):  The Rule Maker might define (via mechanisms
      outside the scope of this document) which policy rules are
      disclosed to other entities.

   Req. 10.  (Full Rule language):  GEOPRIV has defined a rule language
      capable of expressing a wide range of privacy rules that is
      applicable in the area of the distribution of Location Objects.  A
      basic ruleset is provided with the Basic-Location-Policy-Rules
      Attribute (Section 4.4).  A reference to the extended ruleset is
      carried in Section 4.5.  The format of these rules is described in
      [RFC4745] and [GEO-POLICY].

   Req. 11.  (Limited Rule language):  A limited (or basic) ruleset is
      provided by the Policy-Information Attribute in Section 4.4 (and
      as introduced with PIDF-LO [RFC4119]).

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

   Req. 12 (Identity Protection):  Support for unlinkable pseudonyms is
      provided by the usage of a corresponding authentication and key-
      exchange protocol.  Such protocols are available, for example,
      with the support of EAP as network-access authentication methods.
      Some EAP methods support passive user-identity confidentiality,
      whereas others even support active user-identity confidentiality.
      This issue is further discussed in Section 7.  The importance for
      user-identity confidentiality and identity protection has already
      been recognized as an important property (see, for example, a
      document on EAP method requirements for wireless LANs [RFC4017]).

   Req. 13.  (Credential Requirements):  As described in Section 7 ,
      RADIUS signaling messages can be protected with IPsec.  This
      allows a number of authentication and key exchange protocols to be
      used as part of IKE, IKEv2, or KINK.

Top      Up      ToC       Page 52 
   Req. 14.  (Security Features):  GEOPRIV defines a few security
      requirements for the protection of Location Objects, such as
      mutual end-point authentication, data object integrity, data
      object confidentiality, and replay protection.  As described in
      Section 7, these requirements are fulfilled with the usage of
      IPsec if mutual authentication refers to the RADIUS entities
      (acting as various GEOPRIV entities) that directly communicate
      with each other.

   Req. 15.  (Minimal Crypto):  A minimum of security mechanisms are
      mandated by the usage of RADIUS.  Communication security for
      Location Objects between RADIUS infrastructure elements is
      provided by the RADIUS protocol (including IPsec and its dynamic
      key-management framework), rather than relying on object security
      via S/SIME (which is not available with RADIUS).

Top      Up      ToC       Page 53 
Authors' Addresses

   Hannes Tschofenig (editor)
   Nokia Siemens Networks
   Linnoitustie 6
   Espoo  02600
   Finland

   Phone: +358 (50) 4871445
   EMail: Hannes.Tschofenig@gmx.net
   URI:   http://www.tschofenig.priv.at


   Farid Adrangi
   Intel Corporatation
   2111 N.E. 25th Avenue
   Hillsboro OR
   USA

   EMail: farid.adrangi@intel.com


   Mark Jones
   Bridgewater Systems Corporation
   303 Terry Fox Drive
   Ottawa, Ontario  K2K 3J1
   CANADA

   EMail: mark.jones@bridgewatersystems.com


   Avi Lior
   Bridgewater Systems Corporation
   303 Terry Fox Drive
   Ottawa, Ontario  K2K 3J1
   CANADA

   EMail: avi@bridgewatersystems.com


   Bernard Aboba
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA  98052
   USA

   EMail: bernarda@microsoft.com