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RFC 5580 - Carrying Location Objects in RADIUS and Diameter


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Network Working Group                                 H. Tschofenig, Ed.
Request for Comments: 5580                        Nokia Siemens Networks
Category: Standards Track                                     F. Adrangi
                                                                   Intel
                                                                M. Jones
                                                                 A. Lior
                                                             Bridgewater
                                                                B. Aboba
                                                   Microsoft Corporation
                                                             August 2009

            Carrying Location Objects in RADIUS and Diameter

Abstract

   This document describes procedures for conveying access-network
   ownership and location information based on civic and geospatial
   location formats in Remote Authentication Dial-In User Service
   (RADIUS) and Diameter.

   The distribution of location information is a privacy-sensitive task.
   Dealing with mechanisms to preserve the user's privacy is important
   and is addressed in this document.

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

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

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

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................3
   3. Delivery Methods for Location Information .......................3
      3.1. Location Delivery Based on Out-of-Band Agreements ..........4
      3.2. Location Delivery Based on Initial Request .................5
      3.3. Location Delivery Based on Mid-Session Request .............6
      3.4. Location Delivery in Accounting Messages ..................10
   4. Attributes .....................................................11
      4.1. Operator-Name Attribute ...................................12
      4.2. Location-Information Attribute ............................14
      4.3. Location-Data Attribute ...................................16
           4.3.1. Civic Location Profile .............................17
           4.3.2. Geospatial Location Profile ........................17
      4.4. Basic-Location-Policy-Rules Attribute .....................18
      4.5. Extended-Location-Policy-Rules Attribute ..................20
      4.6. Location-Capable Attribute ................................21
      4.7. Requested-Location-Info Attribute .........................23
   5. Table of Attributes ............................................28
   6. Diameter RADIUS Interoperability ...............................30
   7. Security Considerations ........................................31
      7.1. Communication Security ....................................31
      7.2. Privacy Considerations ....................................32
           7.2.1. RADIUS Client ......................................33
           7.2.2. RADIUS Server ......................................34
           7.2.3. RADIUS Proxy .......................................34
      7.3. Identity Information and Location Information .............34
   8. IANA Considerations ............................................36
      8.1. New Registry: Operator Namespace Identifier ...............36
      8.2. New Registry: Location Profiles ...........................37
      8.3. New Registry: Location-Capable Attribute ..................38
      8.4. New Registry: Entity Types ................................39
      8.5. New Registry: Privacy Flags ...............................39
      8.6. New Registry: Requested-Location-Info Attribute ...........39
   9. Acknowledgments ................................................40
   10. References ....................................................42
      10.1. Normative References .....................................42
      10.2. Informative References ...................................42
   Appendix A.  Matching with GEOPRIV Requirements ...................45
     A.1.  Distribution of Location Information at the User's
           Home Network ..............................................45
     A.2.  Distribution of Location Information at the Visited
           Network ...................................................46
     A.3.  Requirements Matching .....................................47

1.  Introduction

   This document defines attributes within RADIUS and Diameter that can
   be used to convey location-related information within authentication
   and accounting exchanges.

   Location information may be useful in a number of scenarios.
   Wireless networks (including wireless LAN) are being deployed in
   public places such as airports, hotels, shopping malls, and coffee
   shops by a diverse set of operators such as cellular network
   operators, Wireless Internet Service Providers (WISPs), and fixed
   broadband operators.  In these situations, the home network may need
   to know the location of the user in order to enable location-aware
   billing, location-aware authorization, or other location-aware
   services.  Location information can also prove useful in other
   situations (such as wired networks) where operator-network ownership
   and location information may be needed by the home network.

   In order to preserve user privacy, location information needs to be
   protected against unauthorized access and distribution.  Requirements
   for access to location information are defined in [RFC3693].  The
   model includes a Location Generator (LG) that creates location
   information, a Location Server (LS) that authorizes access to
   location information, a Location Recipient (LR) that requests and
   receives information, and a Rule Maker (RM) that provides
   authorization policies to the LS, which enforces access-control
   policies on requests to location information.  In Appendix A, the
   requirements for a GEOPRIV using protocol [RFC3693] are compared to
   the functionality provided by this document.

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].

   RADIUS-specific terminology is borrowed from [RFC2865] and [RFC2866].

   Terminology related to privacy issues, location information, and
   authorization policy rules is taken from [RFC3693].

3.  Delivery Methods for Location Information

   The following exchanges show how location information is conveyed in
   RADIUS.  In describing the usage scenarios, we assume that privacy
   policies allow location to be conveyed in RADIUS; however, as noted
   in Section 6, similar exchanges can also take place within Diameter.
   Privacy issues are discussed in Section 7.2.

3.1.  Location Delivery Based on Out-of-Band Agreements

   Figure 1 shows an example message flow for delivering location
   information during the network-access authentication and
   authorization procedure.  Upon a network-authentication request from
   an access-network client, the Network Access Server (NAS) submits a
   RADIUS Access-Request message that contains Location-Information
   Attributes among other required attributes.  In this scenario,
   location information is attached to the Access-Request message
   without an explicit request from the RADIUS server.  Note that such
   an approach with a prior agreement between the RADIUS client and the
   RADIUS server is only applicable in certain environments, such as in
   situations where the RADIUS client and server are within the same
   administrative domain.  The Basic-Location-Policy-Rules Attribute is
   populated based on the defaults described in Section 4.4, unless it
   has been explicitly configured otherwise.

    +---------+             +---------+                   +---------+
    |         |             | Network |                   |  RADIUS |
    | User    |             | Access  |                   |  Server |
    |         |             | Server  |                   |         |
    +---------+             +---------+                   +---------+
        |                       |                              |
        | Authentication phase  |                              |
        | begin                 |                              |
        |---------------------->|                              |
        |                       |                              |
        |                       | Access-Request               |
        |                       | + Location-Information       |
        |                       | + Location-Data              |
        |                       | + Basic-Location-Policy-Rules|
        |                       | + Operator-Name              |
        |                       |----------------------------->|
        |                       |                              |
        |                       | Access-Accept                |
        |                       |<-----------------------------|
        | Authentication        |                              |
        | Success               |                              |
        |<----------------------|                              |
        |                       |                              |

        Figure 1: Location Delivery Based on Out-of-Band Agreements

3.2.  Location Delivery Based on Initial Request

   If the RADIUS client provides a Location-Capable Attribute in the
   Access-Request, then the RADIUS server MAY request location
   information from the RADIUS client if it requires that information
   for authorization and if location information was not provided in the
   Access-Request.  This exchange is shown in Figure 2.  The inclusion
   of the Location-Capable Attribute in an Access-Request message
   indicates that the NAS is capable of providing location data in
   response to an Access-Challenge.  The subsequent Access-Challenge
   message sent from the RADIUS server to the NAS provides a hint
   regarding the type of desired Location-Information Attributes.  The
   NAS treats the Basic-Location-Policy-Rules and Extended-Location-
   Policy-Rules Attributes as opaque data (e.g., it echoes these rules
   provided by the server within the Access-Challenge back in the
   Access-Request).  In the shown message flow, the location attributes
   are then provided in the subsequent Access-Request message.  When
   evaluating this Access-Request message, the authorization procedure
   at the RADIUS server might be based on a number of criteria,
   including the newly defined attributes listed in Section 4.

   +---------+             +---------+                       +---------+
   |         |             | Network |                       |  RADIUS |
   | User    |             | Access  |                       |  Server |
   |         |             | Server  |                       |         |
   +---------+             +---------+                       +---------+
       |                       |                                  |
       | Authentication phase  |                                  |
       | begin                 |                                  |
       |---------------------->|                                  |
       |                       |                                  |
       |                       | Access-Request                   |
       |                       | + Location-Capable               |
       |                       |--------------------------------->|
       |                       |                                  |
       |                       | Access-Challenge                 |
       |                       |  + Basic-Location-Policy-Rules   |
       |                       |  + Extended-Location-Policy-Rules|
       |                       |  + Requested-Location-Info       |
       |                       |<---------------------------------|
       |                       |                                  |
       |                       | Access-Request                   |
       |                       |  + Location-Information          |
       |                       |  + Location-Data                 |
       |                       |  + Basic-Location-Policy-Rules   |
       |                       |  + Extended-Location-Policy-Rules|
       |                       |--------------------------------->|
       |                       |                                  |
       :                       :                                  :
       :       Multiple Protocol Exchanges to perform             :
       :    Authentication, Key Exchange, and Authorization       :
       :                  ...continued...                         :
       :                       :                                  :
       |                       |                                  |
       |                       | Access-Accept                    |
       |                       |<---------------------------------|
       | Authentication        |                                  |
       | Success               |                                  |
       |<----------------------|                                  |
       |                       |                                  |

           Figure 2: Location Delivery Based on Initial Request

3.3.  Location Delivery Based on Mid-Session Request

   The on-demand, mid-session location-delivery method utilizes the
   Change-of-Authorization Request (CoA-Request) message and the CoA-NAK
   (CoA-Negative Acknowledgement), defined in [RFC5176].  At any time

   during the session, the Dynamic Authorization Client MAY send a CoA-
   Request containing session-identification attributes to the NAS
   (i.e., Dynamic Authorization Server).

   In order to enable the on-demand, mid-session location-delivery
   method, the RADIUS server MUST return an instance of the Requested-
   Location-Info Attribute with the 'FUTURE_REQUESTS' flag set and
   instances of the Basic-Location-Policy-Rules and Extended-Location-
   Policy-Rules Attributes in the Access-Accept message for the session.
   Upon receipt of a CoA-Request message containing a Service-Type
   Attribute with value "Authorize Only" for the same session, the NAS
   MUST include location information and echo the previously received
   Basic-Location-Policy-Rules and Extended-Location-Policy-Rules
   Attributes in the subsequent Access-Request message.

   Upon receiving the Access-Request message containing the Service-Type
   Attribute with a value of Authorize-Only from the NAS, the RADIUS
   server responds with either an Access-Accept or an Access-Reject
   message.

   The use of dynamic authorization [RFC5176] is necessary when location
   information is needed on-demand and cannot be obtained from
   accounting information in a timely fashion.

   Figure 3 shows the above-described approach graphically.

  +---------------+                        +---------------+    +------+
  | Dynamic       |                        | Dynamic       |    |RADIUS|
  | Authorization |                        | Authorization |    |Server|
  | Server/NAS    |                        | Client        |    |      |
  +---------------+                        +---------------+    +------+
      |                                             |              |
      |  Access-Request                             |              |
      |  + Location-Capable                         |              |
      |----------------------------------------------------------->|
      |                                             |              |
      |  Access-Challenge                           |              |
      |   + Basic-Location-Policy-Rules             |              |
      |   + Extended-Location-Policy-Rules          |              |
      |   + Requested-Location-Info                 |              |
      |<-----------------------------------------------------------|
      |                                             |              |
      |  Access-Request                             |              |
      |   + Location-Information                    |              |
      |   + Location-Data                           |              |
      |   + Basic-Location-Policy-Rules             |              |
      |   + Extended-Location-Policy-Rules          |              |
      |----------------------------------------------------------->|

      |                                             |              |
      |                                             |              |
      :                                             |              :
      :       Multiple Protocol Exchanges to perform               :
      :    Authentication, Key Exchange, and Authorization         :
      :                  ...continued...            |              :
      :                                             |              :
      |                                             |              |
      |                                             |              |
      |  Access-Accept                              |              |
      |      + Requested-Location-Info              |              |
               (FUTURE_REQUESTS,...)                |              |
      |      + Basic-Location-Policy-Rules          |              |
      |      + Extended-Location-Policy-Rules       |              |
      |<-----------------------------------------------------------|
      |                                             |              |
      :                                             :              :
      :                <<Some time later>>          :              :
      :                                             :              :
      |                                             |              |
      | CoA + Service-Type "Authorize Only" + State |              |
      |<--------------------------------------------|              |
      |                                             |              |
      |  CoA NAK + Service-Type "Authorize Only"    |              |
      |          + State                            |              |
      |          + Error-Cause  "Request Initiated" |              |
      |-------------------------------------------->|              |
      |                                             |              |
      |  Access-Request                             |              |
      |          + Service-Type "Authorize Only"    |              |
      |          + State                            |              |
      |          + Location-Information             |              |
      |          + Location-Data                    |              |
      |          + Basic-Location-Policy-Rules      |              |
      |          + Extended-Location-Policy-Rules   |              |
      |----------------------------------------------------------->|
      |  Access-Accept                              |              |
      |<-----------------------------------------------------------|
      |                                             |              |

               Figure 3: Location Delivery Based on CoA with
                       Service-Type 'Authorize Only'

   When the Dynamic Authorization Client wants to change the values of
   the requested location information, or set the values of the
   requested location information for the first time, it may do so
   without triggering a reauthorization.  Assuming that the NAS had
   previously sent an Access-Request containing a Location-Capable

   Attribute, the Dynamic Authorization Client (DAC) can send a CoA-
   Request to the NAS without a Service-Type Attribute, but include the
   NAS identifiers and session identifiers as per [RFC5176] and the
   Requested-Location-Info, Basic-Location-Policy-Rules, and Extended-
   Location-Policy-Rules Attributes.  The Requested-Location-Info,
   Basic-Location-Policy-Rules, and Extended-Location-Policy-Rules
   Attributes MUST NOT be used for session identification.

   Figure 4 shows this approach graphically.

  +---------------+                        +---------------+    +------+
  | Dynamic       |                        | Dynamic       |    |RADIUS|
  | Authorization |                        | Authorization |    |Server|
  | Server/NAS    |                        | Client        |    |      |
  +---------------+                        +---------------+    +------+
      |                                             |              |
      |                                             |              |
      |  Access-Request                             |              |
      |  + Location-Capable                         |              |
      |----------------------------------------------------------->|
      |                                             |              |
      |  Access-Challenge                           |              |
      |   + Basic-Location-Policy-Rules             |              |
      |   + Extended-Location-Policy-Rules          |              |
      |   + Requested-Location-Info                 |              |
      |<-----------------------------------------------------------|
      |                                             |              |
      |  Access-Request                             |              |
      |   + Location-Information                    |              |
      |   + Location-Data                           |              |
      |   + Basic-Location-Policy-Rules             |              |
      |   + Extended-Location-Policy-Rules          |              |
      |----------------------------------------------------------->|
      |                                             |              |
      |                                             |              |
      :                                             |              :
      :       Multiple Protocol Exchanges to perform               :
      :    Authentication, Key Exchange, and Authorization         :
      :                  ...continued...            |              :
      :                                             |              :
      |                                             |              |
      |                                             |              |
      |  Access-Accept                              |              |
      |      + Requested-Location-Info              |              |
      |      + Basic-Location-Policy-Rules          |              |
      |      + Extended-Location-Policy-Rules       |              |
      |<-----------------------------------------------------------|

      |                                             |              |
      :                                             :              :
      :                <<Some time later>>          :              :
      :                                             :              :
      |                                             |              |
      |  CoA                                        |              |
      |      + Requested-Location-Info              |              |
      |      + Basic-Location-Policy-Rules          |              |
      |      + Extended-Location-Policy-Rules       |              |
      |<--------------------------------------------|              |
      |                                             |              |
      |  CoA ACK                                    |              |
      |-------------------------------------------->|              |
      |                                             |              |
      :                                             :              :
      :           <<Further exchanges later>>       :              :
      :                                             :              :

                 Figure 4: Location Delivery Based on CoA

3.4.  Location Delivery in Accounting Messages

   Location information may also be reported in accounting messages.
   Accounting messages are generated when the session starts, when the
   session stops, and periodically during the lifetime of the session.
   Accounting messages may also be generated when the user roams during
   handoff.

   Accounting information may be needed by the billing system to
   calculate the user's bill.  For example, there may be different
   tariffs or tax rates applied based on the location.

   If the RADIUS server needs to obtain location information in
   accounting messages, then it needs to include a Requested-Location-
   Info Attribute with the Access-Accept message.  The Basic-Location-
   Policy-Rules and the Extended-Location-Policy-Rules Attributes are to
   be echoed in the Accounting-Request if indicated in the Access-
   Accept.

   Figure 5 shows the message exchange.

   +---------+             +---------+                       +---------+
   |         |             | Network |                       | RADIUS  |
   | User    |             | Access  |                       | Server  |
   |         |             | Server  |                       |         |
   +---------+             +---------+                       +---------+
       |                       |                                  |
       :                       :                                  :
       :          Initial Protocol Interaction                    :
       :          (details omitted)                               :
       :                       :                                  :
       |                       |                                  |
       |                       | Access-Accept                    |
       |                       |  + Requested-Location-Info       |
       |                       |  + Basic-Location-Policy-Rules   |
       |                       |  + Extended-Location-Policy-Rules|
       |                       |<---------------------------------|
       | Authentication        |                                  |
       | Success               |                                  |
       |<----------------------|                                  |
       |                       |                                  |
       |                       | Accounting-Request               |
       |                       |  + Location-Information          |
       |                       |  + Location-Data                 |
       |                       |  + Basic-Location-Policy-Rules   |
       |                       |  + Extended-Location-Policy-Rules|
       |                       |--------------------------------->|
       |                       |                                  |
       |                       | Accounting-Response              |
       |                       |<---------------------------------|
       |                       |                                  |

            Figure 5: Location Delivery in Accounting Messages

4.  Attributes

   It is important to note that the location-specific parts of the
   attributes defined below are not meant to be processed by the RADIUS
   server.  Instead, a location-server-specific component used in
   combination with the RADIUS server is responsible for receiving,
   processing, and further distributing location information (in
   combination with proper access control and privacy protection).  As
   such, from a RADIUS server point of view, location information is
   treated as opaque data.

4.1.  Operator-Name Attribute

   This attribute carries the operator namespace identifier and the
   operator name.  The operator name is combined with the namespace
   identifier to uniquely identify the owner of an access network.  The
   value of the Operator-Name is a non-NULL terminated text whose length
   MUST NOT exceed 253 bytes.

   The Operator-Name Attribute SHOULD be sent in Access-Request and
   Accounting-Request messages where the Acc-Status-Type is set to
   Start, Interim, or Stop.

   A summary of the Operator-Name Attribute is shown below.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |    Length     |            Text              ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Text (cont.)                                           ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:

      126 - Operator-Name

   Length:

      >= 4

   Text:

      The format is shown below.  The data type of this field is a text.
      All fields are transmitted from left to right:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Namespace ID  | Operator-Name                                ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Operator-Name                                                ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Namespace ID:

      The value within this field contains the operator namespace
      identifier.  The Namespace ID value is encoded in ASCII.

      Example: '1' (0x31) for REALM

   Operator-Name:

      The text field of variable length contains an Access Network
      Operator Name.  This field is a RADIUS-based data type of Text.

   The Namespace ID field provides information about the operator
   namespace.  This document defines four values for this attribute,
   which are listed below.  Additional namespace identifiers must be
   registered with IANA (see Section 8.1) and must be associated with an
   organization responsible for managing the namespace.

   TADIG ('0' (0x30)):

      This namespace can be used to indicate operator names based on
      Transferred Account Data Interchange Group (TADIG) codes, as
      defined in [GSM].  TADIG codes are assigned by the TADIG Working
      Group within the Global System for Mobile Communications (GSM)
      Association.  The TADIG code consists of two fields, with a total
      length of five ASCII characters consisting of a three-character
      country code and a two-character alphanumeric operator (or
      company) ID.

   REALM ('1' (0x31)):

      The REALM operator namespace can be used to indicate operator
      names based on any registered domain name.  Such names are
      required to be unique, and the rights to use a given realm name
      are obtained coincident with acquiring the rights to use a
      particular Fully Qualified Domain Name (FQDN).  Since this
      operator is limited to ASCII, any registered domain name that
      contains non-ASCII characters must be converted to ASCII.  The
      Punycode encoding [RFC3492] is used for this purpose.

   E212 ('2' (0x32)):

      The E212 namespace can be used to indicate operator names based on
      the Mobile Country Code (MCC) and Mobile Network Code (MNC)
      defined in [ITU212].  The MCC/MNC values are assigned by the
      Telecommunications Standardization Bureau (TSB) within the ITU-T

      and by designated administrators in different countries.  The E212
      value consists of three ASCII digits containing the MCC, followed
      by two or three ASCII digits containing the MNC.

   ICC ('3' (0x33)):

      The ICC namespace can be used to indicate operator names based on
      International Telecommunication Union (ITU) Carrier Codes (ICC)
      defined in [ITU1400].  ICC values are assigned by national
      regulatory authorities and are coordinated by the
      Telecommunication Standardization Bureau (TSB) within the ITU
      Telecommunication Standardization Sector (ITU-T).  When using the
      ICC namespace, the attribute consists of three uppercase ASCII
      characters containing a three-letter alphabetic country code, as
      defined in [ISO], followed by one to six uppercase alphanumeric
      ASCII characters containing the ICC itself.

4.2.  Location-Information Attribute

   The Location-Information Attribute MAY be sent in the Access-Request
   message, the Accounting-Request message, both of these messages, or
   no message.  For the Accounting-Request message, the Acc-Status-Type
   may be set to Start, Interim, or Stop.

   The Location-Information Attribute provides meta-data about the
   location information, such as sighting time, time-to-live, location-
   determination method, etc.

   The format is shown below.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |    Length     |            String            ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       String (cont.)                                         ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:

      127 - Location-Information

   Length:

      >= 23

   String:

      The format is shown below.  The data type of this field is a
      string.  All fields are transmitted from left to right:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Index                       | Code          |  Entity       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Sighting Time                                                 ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Sighting Time                                                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Time-to-Live                                                 ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Time-to-Live                                                  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Method                                                     ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Index (16 bits):

      The 16-bit unsigned integer value allows this attribute to provide
      information relating to the information included in the Location-
      Data Attribute to which it refers (via the Index).

   Code (8 bits):

      This field indicates the content of the location profile carried
      in the Location-Data Attribute.  Two profiles are defined in this
      document -- namely, a civic location profile (see Section 4.3.1)
      that uses value (0) and a geospatial location profile (see
      Section 4.3.2) that uses the value (1).

   Entity (8 bits):

      This field encodes which location this attribute refers to as an
      unsigned 8-bit integer value.  Location information can refer to
      different entities.  This document registers two entity values,
      namely:

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

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

      The registry used for these values is established by this
      document, see Section 8.4.

   Sighting Time (64 bits)

      This field indicates when the location information was accurate.
      The data type of this field is a string, and the content is
      expressed in the 64-bit Network Time Protocol (NTP) timestamp
      format [RFC1305].

   Time-to-Live (64 bits):

      This field gives a hint regarding for how long location
      information should be considered current.  The data type of this
      field is a string and the content is expressed in the 64-bit
      Network Time Protocol (NTP) timestamp format [RFC1305].  Note that
      the Time-to-Live field is different than the Retention Expires
      field used in the Basic-Location-Policy-Rules Attribute, see
      Section 4.4.  The Retention Expires field indicates the time the
      recipient is no longer permitted to possess the location
      information.

   Method (variable):

      Describes the way that the location information was determined.
      This field MUST contain the value of exactly one IANA-registered
      'method' token [RFC4119].

   The length of the Location-Information Attribute MUST NOT exceed 253
   octets.

4.3.  Location-Data Attribute

   The Location-Data Attribute MAY be sent in Access-Request and
   Accounting-Request messages.  For the Accounting-Request message, the
   Acc-Status-Type may be set to Start, Interim, or Stop.

   The format is shown below.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |    Length     |            String            ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       String (cont.)                                         ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:

      128 - Location-Data

   Length:

      >= 5

   String:

      The format is shown below.  The data type of this field is a
      string.  All fields are transmitted from left to right:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Index                       |  Location                    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Location                                                    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Index (16 bits):

      The 16-bit unsigned integer value allows this attribute to
      associate the Location-Data Attribute with the Location-
      Information Attributes.

   Location (variable):

      The format of the location data depends on the location profile.
      This document defines two location profiles.  Details of the
      location profiles are described below.

4.3.1.  Civic Location Profile

   Civic location is a popular way to describe the location of an
   entity.  This section defines the civic location-information profile
   corresponding to the value (0) indicated in the Code field of the
   Location-Information Attribute.  The location format is based on the
   encoding format defined in Section 3.1 of [RFC4776], whereby the
   first 3 octets are not put into the Location field of the above-
   described RADIUS Location-Data Attribute (i.e., the code for the DHCP
   option, the length of the DHCP option, and the 'what' element are not
   included).

4.3.2.  Geospatial Location Profile

   This section defines the geospatial location-information profile
   corresponding to the value (1) indicated in the Code field of the
   Location-Information Attribute.  Geospatial location information is
   encoded as an opaque object, and the format is based on the Location

   Configuration Information (LCI) format defined in Section 2 of
   [RFC3825] but starts with the third octet (i.e., the code for the
   DHCP option and the length field is not included).

4.4.  Basic-Location-Policy-Rules Attribute

   The Basic-Location-Policy-Rules Attribute MAY be sent in Access-
   Request, Access-Accept, Access-Challenge, Change-of-Authorization,
   and Accounting-Request messages.

   Policy rules control the distribution of location information.  In
   order to understand and process the Basic-Location-Policy-Rules
   Attribute, RADIUS clients are obligated to utilize a default value of
   Basic-Location-Policy-Rules, unless explicitly configured otherwise,
   and to echo the Basic-Location-Policy-Rules Attribute that they
   receive from a server.  As a default, the Note Well field does not
   carry a pointer to human-readable privacy policies, the
   retransmission-allowed is set to zero (0), i.e., further distribution
   is not allowed, and the Retention Expires field is set to 24 hours.

   With regard to authorization policies, this document reuses work done
   in [RFC4119] and encodes those policies in a non-XML format.  Two
   fields ('Sighting Time' and 'Time-to-Live') are additionally included
   in the Location-Information Attribute to conform to the GEOPRIV
   requirements [RFC3693], Section 2.7.

   The format of the Basic-Location-Policy-Rules Attribute is shown
   below.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |    Length     |            String            ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       String (cont.)                                         ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:

      129 - Basic-Location-Policy-Rules

   Length:

      >= 12

   String:

      The format is shown below.  The data type of this field is a
      string.  All fields are transmitted from left to right:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Flags                        | Retention Expires            ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Retention Expires                                            ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Retention Expires             | Note Well                    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Note Well                                                    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This document reuses fields from the RFC 4119 [RFC4119] 'usage-rules'
   element.  These fields have the following meaning:

   Flags (16 bits):

      The Flags field is a bit mask.  Only the first bit (R) is defined
      in this document, and it corresponds to the Retransmission Allowed
      field:

        0                   1
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |R|o o o o o o o o o o o o o o o|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       R = Retransmission Allowed
       o = reserved.

   All reserved bits MUST be zero.  When the value of the Retransmission
   Allowed field is set to zero (0), then the recipient of this Location
   Object is not permitted to share the enclosed location information,
   or the object as a whole, with other parties.  The value of '1'
   allows this attribute to share the location information with other
   parties by considering the extended policy rules.

   Retention Expires (64 bits):

      This field specifies an absolute date at which time the Recipient
      is no longer permitted to possess the location information.  The
      data type of this field is a string and the format is a 64-bit NTP
      timestamp [RFC1305].

   Note Well (variable):

      This field contains a URI that points to human-readable privacy
      instructions.  The data type of this field is a string.  This
      field is useful when location information is distributed to third-
      party entities, which can include humans in a location-based
      service.  RADIUS entities are not supposed to process this field.

      Whenever a Location Object leaves the RADIUS ecosystem, the URI in
      the Note Well Attribute MUST be expanded to the human-readable
      text.  For example, when the Location Object is transferred to a
      SIP-based environment, then the human-readable text is placed into
      the 'note-well' element of the 'usage-rules' element contained in
      the PIDF-LO (Presence Information Data Format - Location Object)
      document (see [RFC4119]).  The Note Well field may be empty.

4.5.  Extended-Location-Policy-Rules Attribute

   The Extended-Location-Policy-Rules Attribute MAY be sent in Access-
   Request, Access-Accept, Access-Challenge, Access-Reject, Change-of-
   Authorization, and Accounting-Request messages.

   The Ruleset Reference field of this attribute is of variable length.
   It contains a URI that indicates where the richer ruleset can be
   found.  This URI SHOULD use the HTTPS URI scheme.  As a deviation
   from [RFC4119], this field only contains a reference and does not
   carry an attached, extended ruleset.  This modification is motivated
   by the size limitations imposed by RADIUS.

   In order to understand and process the Extended-Location-Policy-Rules
   Attribute, RADIUS clients are obligated to attach the URI to the
   Extended-Location-Policy-Rules Attribute when they are explicitly
   configured to do so, and to echo the Extended-Location-Policy-Rules
   Attribute that they receive from a server.  There is no expectation
   that RADIUS clients will need to retrieve data at the URL specified
   in the attribute or to parse the XML policies.

   The format of the Extended-Location-Policy-Rules Attribute is shown
   below.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |    Length     |            String            ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       String (cont.)                                         ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:

      130 - Extended-Location-Policy-Rules

   Length:

      >= 3

   String:

      This field is at least two octets in length, and the format is
      shown below.  The data type of this field is a string.  The fields
      are transmitted from left to right:

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Ruleset Reference                                         ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Ruleset Reference:

      This field contains a URI that points to the policy rules.

4.6.  Location-Capable Attribute

   The Location-Capable Attribute allows an NAS (or client function of a
   proxy server) to indicate support for the functionality specified in
   this document.  The Location-Capable Attribute with the value for
   'Location Capable' MUST be sent with the Access-Request messages, if
   the NAS supports the functionality described in this document and is
   capable of sending location information.  A RADIUS server MUST NOT
   challenge for location information unless the Location-Capable
   Attribute has been sent to it.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Type          | Length        | Integer                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Integer (cont.)         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:

      131 - Location-Capable Attribute

   Length:

      6

   Integer:

      The content of the Integer field encodes the requested
      capabilities.  Each capability value represents a bit position.

   This document specifies the following capabilities.

   Name:

      CIVIC_LOCATION

   Description:

      The RADIUS client uses the CIVIC_LOCATION to indicate that it is
      able to return civic location based on the location profile
      defined in Section 4.3.1.

   Numerical Value:

      A numerical value of this token is '1'.

   Name:

      GEO_LOCATION

   Description:

      The RADIUS client uses the GEO_LOCATION to indicate that it is
      able to return geodetic location based on the location profile
      defined in Section 4.3.2.

   Numerical Value:

      A numerical value of this token is '2'.

   Name:

      USERS_LOCATION

   Description:

      The numerical value representing USERS_LOCATION indicates that the
      RADIUS client is able to provide a Location-Information Attribute
      with the Entity Attribute expressing the value of zero (0), i.e.,
      the RADIUS client is capable of returning the location information
      of the user's client device.

   Numerical Value:

      A numerical value of this token is '4'.

   Name:

      NAS_LOCATION

   Description:

      The numerical value representing NAS_LOCATION indicates that the
      RADIUS client is able to provide a Location-Information Attribute
      that contains location information with the Entity Attribute
      expressing the value of one (1), i.e., the RADIUS client is
      capable of returning the location information of the NAS.

   Numerical Value:

      A numerical value of this token is '8'.

4.7.  Requested-Location-Info Attribute

   The Requested-Location-Info Attribute allows the RADIUS server to
   indicate which location information about which entity it wants to
   receive.  The latter aspect refers to the entities that are indicated
   in the Entity field of the Location-Information Attribute.

   The Requested-Location-Info Attribute MAY be sent in an Access-
   Accept, Access-Challenge, or Change-of-Authorization packet.

   If the RADIUS server wants to dynamically decide on a per-request
   basis to ask for location information from the RADIUS client, then
   the following cases need to be differentiated.  If the RADIUS client
   and the RADIUS server have agreed out-of-band to mandate the transfer
   of location information for every network-access authentication
   request, then the processing listed below is not applicable.

   o  If the RADIUS server requires location information for computing
      the authorization decision and the RADIUS client does not provide
      it with the Access-Request message, then the Requested-Location-
      Info Attribute is attached to the Access-Challenge with a hint
      about what is required.

   o  If the RADIUS server does not receive the requested information in
      response to the Access-Challenge (including the Requested-
      Location-Info Attribute), then the RADIUS server may respond with
      an Access-Reject message with an Error-Cause Attribute (including
      the "Location-Info-Required" value).

   o  If the RADIUS server would like location information in the
      Accounting-Request message but does not require it for computing
      an authorization decision, then the Access-Accept message MUST
      include a Required-Info Attribute.  This is typically the case
      when location information is used only for billing.  The RADIUS
      client SHOULD attach location information, if available, to the
      Accounting-Request (unless authorization policies dictate
      something different).

   If the RADIUS server does not send a Requested-Location-Info
   Attribute, then the RADIUS client MUST NOT attach location
   information to messages towards the RADIUS server.  The user's
   authorization policies, if available, MUST be consulted by the RADIUS
   server before requesting location information delivery from the
   RADIUS client.

   Figure 6 shows a simple protocol exchange where the RADIUS server
   indicates the desire to obtain location information, namely civic
   location information of the user, to grant access.  Since the
   Requested-Location-Info Attribute is attached to the Access-
   Challenge, the RADIUS server indicates that location information is
   required for computing an authorization decision.

    +---------+                        +---------+
    | RADIUS  |                        | RADIUS  |
    | Client  |                        | Server  |
    +---------+                        +---------+
         |                                  |
         |                                  |
         | Access-Request                   |
         | + Location-Capable               |
         |   ('CIVIC_LOCATION',             |
         |    'GEO_LOCATION',               |
         |    'NAS_LOCATION',               |
         |    'USERS_LOCATION')             |
         |--------------------------------->|
         |                                  |
         | Access-Challenge                 |
         | + Requested-Location-Info        |
         |   ('CIVIC_LOCATION',             |
         |    'USERS_LOCATION')             |
         | + Basic-Location-Policy-Rules    |
         | + Extended-Location-Policy-Rules |
         |<---------------------------------|
         |                                  |
         | Access-Request                   |
         | + Location-Information           |
         | + Location-Data                  |
         | + Basic-Location-Policy-Rules    |
         | + Extended-Location-Policy-Rules |
         |--------------------------------->|
         |                                  |
         |        ....                      |

          Figure 6: RADIUS Server Requesting Location Information

   The Requested-Location-Info Attribute MUST be sent by the RADIUS
   server, in the absence of an out-of-band agreement, if it wants the
   RADIUS client to return location information and if authorization
   policies permit it.  This Requested-Location-Info Attribute MAY
   appear in the Access-Accept or in the Access-Challenge message.

   A summary of the attribute is shown below.

      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |    Length     |            Integer           ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Integer (cont.)         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:

      132 - Requested-Location-Info Attribute

   Length:

      6

   Integer:

      The content of the Integer field encodes the requested information
      attributes.  Each capability value represents a bit position.

   This document specifies the following capabilities:

   Name:

      CIVIC_LOCATION

   Description:

      The RADIUS server uses the Requested-Location-Info Attribute with
      the value set to CIVIC_LOCATION to request specific location
      information from the RADIUS client.  The numerical value
      representing CIVIC_LOCATION requires the RADIUS client to attach
      civic location attributes.  CIVIC_LOCATION refers to the location
      profile defined in Section 4.3.1.

   Numerical Value:

      A numerical value of this token is '1'.

   Name:

      GEO_LOCATION

   Description:

      The RADIUS server uses the Requested-Location-Info Attribute with
      the value set to GEO_LOCATION to request specific location
      information from the RADIUS client.  The numerical value
      representing GEO_LOCATION requires the RADIUS client to attach
      geospatial location attributes.  GEO_LOCATION refers to the
      location profile described in Section 4.3.2.

   Numerical Value:

      A numerical value of this token is '2'.

   Name:

      USERS_LOCATION

   Description:

      The numerical value representing USERS_LOCATION indicates that the
      RADIUS client MUST send a Location-Information Attribute with the
      Entity Attribute expressing the value of zero (0).  Hence, there
      is a one-to-one relationship between the USERS_LOCATION token and
      the value of zero (0) of the Entity Attribute inside the Location-
      Information Attribute.  A value of zero indicates that the
      location information in the Location-Information Attribute refers
      to the user's client device.

   Numerical Value:

      A numerical value of this token is '4'.

   Name:

      NAS_LOCATION

   Description:

      The numerical value representing NAS_LOCATION indicates that the
      RADIUS client MUST send a Location-Information Attribute that
      contains location information with the Entity Attribute expressing
      the value of one (1).  Hence, there is a one-to-one relationship
      between the NAS_LOCATION token and the value of one (1) of the
      Entity Attribute inside the Location-Information Attribute.  A
      value of one indicates that the location information in the
      Location-Information Attribute refers to the RADIUS client.

   Numerical Value:

      A numerical value of this token is '8'.

   Name:

      FUTURE_REQUESTS

   Description:

      The numerical value representing FUTURE_REQUESTS indicates that
      the RADIUS client MUST provide future Access-Requests for the same
      session with the same type of information as returned in the
      initial Access-Request message.

   Numerical Value:

      A numerical value of this token is '16'.

   Name:

      NONE

   Description:

      The RADIUS server uses this token to request that the RADIUS
      client stop sending location information.

   Numerical Value:

      A numerical value of this token is '32'.

   If neither the NAS_LOCATION nor the USERS_LOCATION bit is set, then
   per-default the location of the user's client device is returned (if
   authorization policies allow it).  If both the NAS_LOCATION and the
   USERS_LOCATION bits are set, then the returned location information
   has to be put into separate attributes.  If neither the
   CIVIC_LOCATION nor the GEO_LOCATION bit is set in the Requested-
   Location-Info Attribute, then no location information is returned.
   If both the CIVIC_LOCATION and the GEO_LOCATION bits are set, then
   the location information has to be put into separate attributes.  The
   value of NAS_LOCATION and USERS_LOCATION refers to the location
   information requested via CIVIC_LOCATION and GEO_LOCATION.

   As an example, if the bits for NAS_LOCATION, USERS_LOCATION, and
   GEO_LOCATION are set, then the location information of the RADIUS
   client and the users' client device are returned in a geospatial-
   location format.

5.  Table of Attributes

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

 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'.

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].

   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].

   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

   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.

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

      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

   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.

   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.

   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.

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:

    +----------+----------------------+
    |  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.

   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.

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.

   [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.

   [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.

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

   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.

    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].

      *  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

         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.

      *  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).

   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.

   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).

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

 

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