Geopriv                                                    H. Tschofenig
Internet-Draft                                                   Siemens
Expires: April 5, 21, 2005                                       F. Adrangi
                                                                   Intel
                                                                 A. Lior
                                                                M. Jones
                                                             Bridgewater
                                                        October 5, 21, 2004

                  Carrying Location Objects in RADIUS
                  draft-ietf-geopriv-radius-lo-00.txt
                  draft-ietf-geopriv-radius-lo-01.txt

Status of this Memo

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   of section 3 of RFC 3667.  By submitting this Internet-Draft, each
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Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   This document describes RADIUS attributes for conveying the Access
   Network's operational ownership and location information based on a
   civil and geospatial location location format.

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

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5  4
   3.  Delivery Methods for Location Information  . . . . . . . . . .  6  5
     3.1   Authentication/Authorization Phase Delivery  . . . . . . .  6  5
     3.2   Mid-session Delivery . . . . . . . . . . . . . . . . . . .  7  6
   4.  Scenarios  . . . . . . . . . . . . . . . . . . . . . . . . . .  9  8
     4.1   Use Case   Scenario 1 - Use of Location Information in AAA  . . . . .  9  8
     4.2   Scenario 2 - Use of Location Information for other
           Services . . . . . . . . . . . . . . . . . . . . . . . . .  9  8
   5.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 10
     5.1   Operator-Name Attribute  . . . . . . . . . . . . . . . . . 11 10
     5.2   Location-Information Attribute . . . . . . . . . . . . . . 11 10
       5.2.1   Civil Location Information . . . . . . . . . . . . . . 12 11
       5.2.2   Geospatial Location Information  . . . . . . . . . . . 14 12
   6.  Basic- and Extended-Policy-Rule Attributes . . . . . . . . . . 15 14
   7.  Location-Type Attribute  . . . . . . . . . . . . . . . . . . . 16 15
   8.  Billing-Description Attribute  . . . . . . . . . . . . . . . . 17
   9.  Diameter RADIUS Interoperability . . . . . . . . . . . . . . . 18
   10. 16
   9.  Attributes . . . . . . . . . . . . . . . . . . . . . . . . . 19
     10.1 . 17
     9.1   Operator-Name Attribute  . . . . . . . . . . . . . . . . . 19
     10.2 17
     9.2   Location-Information Attribute . . . . . . . . . . . . . . 19
     10.3 17
     9.3   Basic Policy Rules Attribute . . . . . . . . . . . . . . . 23
     10.4 21
     9.4   Extended Policy Rules Attribute  . . . . . . . . . . . . . 24
     10.5 22
     9.5   Location-Type Attribute  . . . . . . . . . . . . . . . . . 25
     10.6  Billing-Description Attribute  . . . . . . . . . . . . . . 25
   11. 23
   10.   Table of Attributes  . . . . . . . . . . . . . . . . . . . . 26
   12. 24
   11.   IANA Considerations  . . . . . . . . . . . . . . . . . . . . 27
   13. 25
   12.   Matching with Geopriv Requirements . . . . . . . . . . . . . 28
     13.1 26
     12.1  Distribution of Location Information at the User's
           Home Network . . . . . . . . . . . . . . . . . . . . . . . 28
     13.2 26
     12.2  Distribution of Location Information at the Visited
           Network  . . . . . . . . . . . . . . . . . . . . . . . . . 29
     13.3 27
     12.3  Requirements matching  . . . . . . . . . . . . . . . . . . 30
   14. 28
   13.   Example  . . . . . . . . . . . . . . . . . . . . . . . . . . 35
   15. 33
   14.   Privacy Considerations . . . . . . . . . . . . . . . . . . . 36
     15.1 34
     14.1  Entity in the visited network  . . . . . . . . . . . . . . 36
     15.2 34
     14.2  Entity in the home network . . . . . . . . . . . . . . . . 37
   16. 35
   15.   Security Considerations  . . . . . . . . . . . . . . . . . . 40
   17. 38
   16.   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . 43
   18. 41
   17.   References . . . . . . . . . . . . . . . . . . . . . . . . . 44
   18.1 42
   17.1  Normative References . . . . . . . . . . . . . . . . . . . . 44
   18.2 42
   17.2  Informative References . . . . . . . . . . . . . . . . . . . 44 42
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 46 44
       Intellectual Property and Copyright Statements . . . . . . . . 47 45

1.  Introduction

   Wireless LAN (WLAN) Access Networks (AN) are being deployed in public
   places such as airports, hotels, shopping malls, and coffee shops by
   a diverse set of incumbent operators such as cellular carriers (GSM and CDMA),
   Wireless Internet Service Providers (WISP), and fixed broadband
   operators.

   When a user executes the network access authentication procedure to
   such a network, information about the location and operational
   ownership of this network needs to be conveyed to the users's user's home
   network to which the user has a contractal relationship.  The main
   intent of this document is to enable location aware billing (e.g.,
   determine the appropriate tariff and taxation), taxation in dependence of the
   location of the access network/user), location aware subscriber
   authentication and authorization for roaming environments and to
   enable location aware services.

   This document describes AAA attributes that are used by a AAA client
   or a local AAA server in an access network for conveying
   location-related information to the user's home AAA server.  This
   document defines attributes for RADIUS [1].

   Although the proposed attributes in this draft are intended for
   wireless LAN deployments, they can also be used in other wireless and
   wired networks where location-aware services are required.

   Location information needs to be protected against unauthorized
   access and distribution to preserve privacy of the owner of the user's privacy with regard to
   location information.  With [8] requirements for a
   protocol-independent model for the access to geographic location
   information was defined.  The model includes a Location Generator
   (LG) that creates Location Information, location information, a Location Server (LS) that
   authorizes access to Location Information, location information, a Location Recipient (LR)
   that requests and receives information, and a Rule Maker (RM) that
   provides authorization policies to the LS which enforce enforces access
   control policies on access requests to location information of a target.

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 [2].

   RADIUS specific terminology is reused from [1] and [3].

   Terminology related to privacy issues, location information and
   authorization policy rules are taken from [8].

3.  Delivery Methods for Location Information

   Location Infomation Objects defined in this document Objects, which consist of location information and privacy
   rules, are transported over the RADIUS protocol from visited access
   network to the home AAA server.
   The information  To embedd a Location Object into
   RADIUS a number of AVPs are used, such as Location-Information AVP,
   Basic-Policy-Rules AVP, Extended-Policy-Rules AVP, Location-Type AVP
   and Operator-Name AVP.  These AVPs can be delivered to the RADIUS
   server during the authentication/authorization phase described in
   Section 3.1, or in the mid-session using the dynamic authorization
   protocol framework described in Section 3.2.  This section describes
   messages flow for both delivery methods.

3.1  Authentication/Authorization Phase Delivery

   Figure 1 shows an example message flow for delivering Location
   Information location
   information during the network access authentication/authorization
   procedure.  Upon a network authentication request from an access
   network client, the NAS submits a RADIUS Access-Request message which
   contains location information attributes among other required
   attributes.  The authentication and/or authorization procedure is
   completed based on a number of criteria, including the newly defined
   Location-Information, Operator-Name, Location-Type,
   Policy-Information attributes.  A RADIUS Accounting Request message
   is again also allowed to carry location specific attributes.

    +---------+             +---------+                   +---------+
    | Access  |             | Network |                   |   AAA   |
    | Network |             | Access  |                   |  Server |
    | Client  |             | Server  |                   |         |
    +---------+             +---------+                   +---------+
        |                       |                              |
        | Authentication phase  |                              |
        | begin                 |                              |
        |---------------------->|                              |
        |                       |                              |
        |                       |                              |
        |                       | RADIUS                       |
        |                       | Access-Request               |
        |                       | + Location-Information       |
        |                       |   attributes                 |
        |                       |----------------------------->|
        |                       |                              |
        :                       :                              :
        :       Multiple Protocol Exchanges to perform         :
        :    Authentication, Key Exchange and Authorization    :
        :                  ...continued...                     :

        :                       :                  ...continued...                     :                              :
        |                       |
        |                       | RADIUS                       |
        |                       | Access-Accept                |
        |                       |  + Rule set Information      |
        |                       |<-----------------------------|
        | Authentication        |                              |
        | Accept                |                              |
        |<----------------------|                              |
        |                       |                              |
        |                       | RADIUS                       |
        |                       | Accounting Request           |
        |                       | + Location-Information       |
        |                       |   attributes                 |
        |                       |----------------------------->|
        |                       |                              |

  Figure 1: Message Flow: Authentication/Authorization Phase Delivery

3.2  Mid-session Delivery

   Mid-session delivery method uses the Change of Authorization (COA)
   message as defined in [4].  In accordance to [4], at  At anytime during the session the AAA
   server may send the access network a COA message containing session
   identification attributes (see [4] for the
   possible options). attributes.  The COA message may instruct the access
   network to generate an Authorize-Only Access-Request (Access-Request
   with Service-Type set to "Authorize-Only") in which case it is
   instructing the access network to send the location information
   attributes.

   Figure 2 shows the approach graphically.

            Access network                                    AAA server
                |                                               |
                |  COA  + Service-Type "Authorize Only"         |
                |<----------------------------------------------|
                |                                               |
                |  COA NAK + Service-Type "Authorize Only"      |
                |          + Error-Cause  "Request Initiated"   |
                |---------------------------------------------->|
                |                                               |
                | Access-Request + Service-Type "Authorize Only"|
                |             + Location Information attributes |
                |             + Location Information policy     |
                |---------------------------------------------->|
                |                                               |
                | Access-Accept                                 |
                |<----------------------------------------------|
                |                                               |

              Figure 2: Message Flow: Mid-session Delivery

   Upon receiving the Authorize-Only message from the Access access network,
   the AAA server MUST respond with either an Access-Accept message or
   an Access-Reject message.

4.  Scenarios

   In the following subsections we describe two scenarios for use of
   location information.  The location infomration may refer to network
   or user location information which in some cases may be identical.
   How the network obtains the user's location information is out of
   scope of this document.  There are two consumers of the location
   information: the AAA servers and other location-based services.  The
   privacy implications of these scenarios are described in Section 15. 14.

4.1  Use Case  Scenario 1 - Use of Location Information in AAA

   An Operator

   The home network operator requires Location Informaion location informaion for Authorization
   authorization and
   Billing billing purposes.  The operator may deny service if Location
   Information
   location information is not available.  Or it may offer limited
   service.  The NAS delivers Location Information location information to the Home home AAA
   server.

   The user's location is transferred from the NAS to the RADIUS server
   and the server.
   The NAS and intermediaries (if any) are not allowed to use that
   information other then to forward it to the home network.

   The RADIUS server authenticates and authorizes the session.  If the
   user's location policies are available to the RADIUS server, the
   RADIUS server may must deliver those policies in an Access Accept. Accept to the
   RADIUS client.  This information may be needed if intermediaries or
   other elements want to act as Location Servers (see Section 4.2).  In
   the absence of receiving the policies intermediaries MUST NOT divulge
   the location information.

   Location Information may also be reported in accouning messages.
   Accounting messages are generated when the session starts, stops and
   periodically.  Accounting messages may also be generated when the
   user roams during handoff.  This information may be needed by the
   billing system to calculate the users user's bill.  For example, there may
   be different tarrif a rates applied based on the location and their
   maybe there may be
   different tax rates applied based on the location.  Unless otherwise specified,
   specified by authorization rules, location information in the
   accounting stream may not be transmitted to third parties.

   The location information in the accounting stream MUST only be sent
   in the proxy chain to the home network (unless specified otherwise).

4.2  Scenario 2 - Use of Location Information for other Services

   Location Servers are entities that receive the user's location
   information and transmit it to other entities.  For the purpose of  In this scenario second
   scenario, Location servers are Servers comprise also the NAS, NAS and RADIUS servers. server
   roles.  The RADIUS servers are in the home network, in the visited
   network, or in broker networks.

   Unless otherwise specified, excluding

   The Location Server MUST NOT transmit location information to parties
   other than members of the proxy chain from the NAS to the Home RADIUS, the Location Server may not transmit the location
   information to other parties. home RADIUS
   server.

   Upon authentication and authorization, the Home home RADIUS may server must
   transmit the Rule set ruleset (if available) in an Access-Accept to the other Location Server
   allowing them to transmit Location Information.  Then and only then
   they Access-Accept.  The RADIUS
   client, intermediate proxies are allowed to share the information. location
   information if they received ruleset indicates that it is allowed.

   Note that the NAS is the source of all Location Information location information that is
   disseminated by RADIUS, the NAS could tag the Location Information location information
   with the policy rules or a reference for the policy rules received in
   an Access-Accept.  All Location Information location information in the accounting stream
   will now be tagged.

5.  Overview

   Location Information information and operational ownership of the access network is conveyed
   in the following RADIUS attributes: Operator-Name,
   Location-Information, Location-Type
   Location-Information and Billing-Description. Location-Type.  Furthermore, the
   Basic-Policy-Rules and the Extended-Policy-Rules attributes are
   attached to the Location-Information attribute turning
   Location Information location
   information into a Location Object as defined in [8].

5.1  Operator-Name Attribute

   This attribute contains an operator name which uniquely identifies
   the ownership of an access network.  The Attribute attribute value is a
   non-NULL terminated string whose Length MUST NOT exceed 253 bytes.
   The attribute value is comprised of the a prefix and the an identity,
   separated by a colon.  The prefix identifies the operator type;
   example: GSM, CDMA, and REALM.  The identity uniquely identifies the
   operator name within the scope of the operator type.

   As an example consider the string 'GSM:TADIG' where GSM is a prefix
   indicating an operator type and TADIC is a unique globally known GSM
   operator ID.

   This document defines three operator type prefixes which are: GSM,
   CDMA, and REALM.  The GSM prefix can be used to indicate operator
   names based on GSMA TADIG codes.  REALM can be used by any domain
   name acquired from IANA.  Possible forthcoming operator types MUST be
   associated with an ogranization organization responsible for assigning/managing
   operator names.

5.2  Location-Information Attribute

   This document describes two formats for conveying location
   information: civil and geospatial location information.  Section
   5.2.1 defines the civil location information format.  Section 5.2.2
   defines the geospatial location information format.

   Additionally, a few additional the following fields provide more details about the
   transmitted Location Information. location information.
      The 'Precision' field provides information about of the accuracy about
      the provided Location Information.  When the user's home
      network receives a Location Object within RADIUS then this field
      gives further indication about the accuracy. location information.  Location information can refer
      to the Access Point, the user, the or the RADIUS server or the
      network itself.  With large networks the Location
      Information location information of
      each of these entities might be different.  The 'Precision' field
      allows to give a hint about the precision of the provided location
      information.
      The 'Method' field describes the way that the location information
      was derived or discovered.  Possible values for this field
      include, as an example GPS or manual configuration.  The inclusion
      of this field should help the user's home network deduce further
      information about the accuracy and to provide an easier
      translation into a Geopriv Location Object for transmission to third party entities.
      entities (e.g., using SIP).  Note that the values for this field
      are reused from [9].

5.2.1  Civil Location Information

   Civil location is a popular way to describe the location of an
   entity.  Using an unstructured (as a text string) or a custom format
   for civil location format is dangerous since the automatic processing
   capabilities are limited.

   For this document document, we reuse the civil location format defined in [5].

   The civil location format includes a number of fields, including the
   country (expressed as a two-letter ISO 3166 code) and the
   administrative units of [5] A1 through A6. A6 of [5] .  This designation offers
   street-level precision.

   For completeness we include more detailed information from [5] with
   regard to the defined civil location elements (A1 through A6): elements:

   +----------------------+----------------------+---------------------+
   | Label                | Description          | Example             |
   +----------------------+----------------------+---------------------+
   | country              | The country is       | US                  |
   |                      | identified by the    |                     |
   |                      | two-letter ISO 3166  |                     |
   |                      | code.                |                     |
   |                      |                      |                     |
   | A1                   | national             | New York            |
   |                      | subdivisions (state, |                     |
   |                      | region, province,    |                     |
   |                      | prefecture)          |                     |
   |                      |                      |                     |
   | A2                   | county, parish, gun  | King's County       |
   |                      | (JP), district (IN)  |                     |
   |                      |                      |                     |
   | A3                   | city, township, shi  | New York            |
   |                      | (JP)                 |                     |
   |                      |                      |                     |
   | A4                   | city division,       | Manhattan           |
   |                      | borough, city        |                     |
   |                      | district, ward, chou |                     |
   |                      | (JP)                 |                     |
   |                      |                      |                     |
   | A5                   | neighborhood, block  | Morningside Heights |
   |                      |                      |                     |
   | A6                   | street               | Broadway            |
   |                      |                      |                     |
   | PRD                  | Leading street       | N, W                |
   |                      | direction            |                     |
   |                      |                      |                     |
   | POD                  | Trailing street      | SW                  |
   |                      | suffix               |                     |
   |                      |                      |                     |
   | STS                  | Street suffix        | Avenue, Platz,      |
   |                      |                      | Street              |
   |                      |                      |                     |
   | HNO                  | House number,        | 123                 |
   |                      | numeric part only.   |                     |
   |                      |                      |                     |
   | HNS                  | House number suffix  | A, 1/2              |
   |                      |                      |                     |
   | LMK                  | Landmark or vanity   | Low Library         |
   |                      | address              |                     |
   |                      |                      |                     |
   | LOC                  | Additional location  | Room 543            |
   |                      | information          |                     |
   |                      |                      |                     |
   | FLR                  | Floor                | 5                   |
   |                      |                      |                     |
   | NAM                  | Name (residence,     | Joe's Barbershop    |
   |                      | business or office   |                     |
   |                      | occupant)            |                     |
   |                      |                      |                     |
   | PC                   | Postal code          | 10027-0401          |
   +----------------------+----------------------+---------------------+

                                Table 1

   Additional CA types are defined

   More description of these civil location elements can be found in
   Section 3.4 of [5].  These types
   are useful elements can be used to express further
   information about the location, language specific settings via the
   'language' item and encoding information via the 'script' item.
   Section 14 13 shows usage examples of this attribute.

   All attributes are optional and can appear in any order.  The values
   are encoded using UTF-8 [6].

5.2.2  Geospatial Location Information

   This document reusing reuses geospatial location information from [7] which
   defines latitude, longitude, and altitude, with resolution indicators
   for each.  The value in the Altitude field either indicates meters or
   floors (via the Altitude Type field).  As a coordinate reference
   system Section 2.1 of [7] defines (via extensible mechanism using
   IANA registration) three values in the Datum field: WGS 84, NAD 83
   (with the associated vertical datum for the North American Vertical
   Datum of 1988), NAD 83 (with the associated vertical datum for the
   Mean Lower Low Water (MLLW).  WGS 84 is used by the GPS system.

   During a protocol run it is possible to return Location-Information
   attributes which provide both location information elements.  If only
   one location information element is provided then civil location MUST
   be included in the request.  Additionally, geospatial location MAY be
   provided.

6.  Basic- and Extended-Policy-Rule Attributes

   In some environments it is possible for the user to attach
   information about its privacy preferences.  These preferences allow
   the visited network, intermediate RADIUS proxies and the home network
   to authorize the distribution of the user's location information.

   Without the user providing authorization information two approaches
   are possible:

   o  The user hides its location information from the access network
      and from intermediate networks using the appropriate network
      access authentication mechanism.  Section 15 14 discusses these
      issues in more details.
   o  The access network attaches default authorization policies which
      prevents intermediate networks and the home network to distribute
      the location information to other entities.  Additionally, the
      home network might have authorization policies which control
      distribution of location information.  Users can dynamically
      change their policies using the authroization framework defined in
      [10] and [11].

   With regard to authorization policies this document reuses work done
   in [9] and encodes it in an 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
   [8], Section 2.7.  Two RADIUS attributes are used for this purpose:
   Basic-Policy-Rule and Extended-Policy-Rule attribute; attribute.  The
   Basic-Policy-Rule attribute contains a fixed set of privacy relevant
   fields whereas the Extended-Policy-Rule attribute contains a
   reference to a more extensive authorization rule set.

7.  Location-Type Attribute

   This document defines a separate attribute for the type of the
   location.  Instead of the values of the 'type-of-place' attribute
   defined in Section 4.6 of [12] which is reused by [5] we define our
   own list of values for the Location-Type attribute.  The reason for
   this is given by the size constraints of the attribute, dependence to
   other documents and to the location names required for the RADIUS
   context.  Consequently, CA type '25' which equals the placetype is
   not used in the Location-Information attribute as described in
   Section 5.2.

       0 Reserved
       1 Coffee Shop
       2 Hotel
       3 Airport
       4 Mall
       5 Restaurant
       6 Bus
       7 Library
       8 Convention Center
       9 School
      10 Office
      11 Airplane
      12 Train
      13 Ship
      14 Educational Institute
      15 Public Place
      16 Other

   Using these attribute types it is possible to describe the area in
   more detail.

8.  Billing-Description Attribute

   The Billing-Description Attribute contains unstructured text to be
   printed on the users bill.

9.  Diameter RADIUS Interoperability

   In deployments where both RADIUS clients talking talk with Diameter
   Servers DIAMETER servers or Diameter Client talking
   DIAMETER clients talk with RADIUS server servers then a translation agent
   will be deployed and operate in accordance to the NASREQ
   specification [13].

10.

9.  Attributes

   This section defines attributes for access network operational
   ownership, Location Name, Location Information the Operator-Name AVP, Location-Information AVP,
   Basic Policy Rules AVP, Extended Policy Rules AVP and Billing
   Description.

10.1 the
   Location-Type AVP.

9.1  Operator-Name Attribute

   Operator-Name Attribute SHOULD be sent in Access-Request, and
   Accounting-Request records 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        | Operator-Name                ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Type:
       To Be Assigned by IANA - Operator-Name

     Length:
       >= 3 Bytes

     Operator-Name:
       The text field contains an Access Network Operator Name in
       prefix-based format as describe above. format.
       Example: REALM:anyisp.com

10.2

9.2  Location-Information Attribute

   Location-Information attribute SHOULD be sent in Access-Request, and
   Accounting-Request records where the Acc-Status-Type is set to Start,
   Interim or Stop if available.

   The Location-Information Attribute has two variations depending on
   civil or geospatial location information.  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       | Code          |  Precision    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Sighting Time                                                 ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Sighting Time                                                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Time-to-Live                                                  ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Time-to-Live                                                  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Method      |    Location-Info                             ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Type (8 bits):
       To Be Assigned by IANA  - Location-Information

     Length (8 bits):
       >= 3 Bytes

     Code (8 bits):
       Describes which location format is carried in this attribute:
       (0) describes civil location information
       (1) describes geospatial location information
       All other bites of the Code field is reserved
       and required for alignment.

     Precision (8 bits):
       Describes which location this attribute refers to:
       (0) describes the location of the NAS
       (1) describes the location of the AAA server
       (2) describes the location of the end host (user)
       (3) describes the location of the network

     Sighting Time (64 bits):
       NTP timestamp for the 'sighting time' field.

     Time-to-Live (64 bits):
       NTP timestamp for the 'time-to-live' field.

     Method (8 bits):
       Describes the way that the location information was
       derived or discovered. The following values are currently
       defined:
       (0) Global Positioning System (GPS)
       (1) GPS with assistance (A-GPS)
       (2) Manual configured information
       (3) Provided by DHCP
       (4) Triangulation: triangulated from time-of-arrival,
           signal strength or similar measurements
       (5) Cell: location of the cellular radio antenna
       (6) IEEE 802.11 WLAN access point

     Location-Info (variable):
       Contains either civil civic or
       geospatial location information attributes.

   The following two fields need some explanation:
   sighting time: This field indicates when the Location Information was
      accurate.  The data type of this field is a string and the format
      is a 64 bit NTP timestamp [14].
   time-to-live: This field gives a hint until when it should be
      considered current.  Note that the time-to-live field is different
      than the 'retention-expires' rule.  The data type of this field is
      a string and the format is a 64 bit NTP timestamp [14].

   For civil location information the Location-Info field in the above
   structure is defined as followed:

       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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Countrycode          |  Civic address elements      ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Countrycode (16 bits):
       Two-letter ISO 3166 country code in capital ASCII leters. letters.

     Civic address elements (variable):
       The text field contains location information element.

   The format of the civic address elements is described in Section 3.3
   of [5] with a TLV pair (whereby the Type and Length fields are
   one-octed
   one-octet long).  An example is given in Section 14. 13.

   For geospatial location information the Location-Info field is
   defined as follows:

        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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   LaRes   |     Latitude                                      +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Latitude      |    LoRes  |  Longitude                        +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Longitude                 |  AT   |  AltRes   | Altitude  +
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   Altitude                    |    Datum      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     LaRes (6 bits):
       Latitude resolution

     Latitude (34 bits)

     LoRes (6 bits):
       Longitude resolution.

     Longitude (34 bits)

     Altitude (30 bits)

     AltRes (6 bits):
       Altitude resolution

     AT (4 bits):
       Altitude Type for altitude. The following codes are defined:

       (1) Meters
       (2) Floors

    Datum (8 bits):
      Coordinate reference system
      The following codes for the this field are defined:

      (1) WGS 84
      (2) NAD 83 (with the associated vertical datum for
                  the North American Vertical Datum of 1988)
      (3) NAD 83 (with the associated vertical datum for
                  the Mean Lower Low Water (MLLW))

   The length of the Location-Information Attribute MUST NOT exceed 253
   octets.  The length of the geospatial location information format is
   fixed with 16 bytes plus a four byte header.

   The Datum field contains an identifier for the coordinate system used
   to interpret the values of Latitude, Longitude and Altitude.  The
   field with value (2) and the value (3) both represent the NAD 83
   coordinate reference system but they differ from each other with
   regard to their vertical datum representation as briefly noted in
   Section 5.2.2 and described in more detail in [7].

10.3

9.3  Basic Policy Rules Attribute

   The Basic-Policy-Rules attribute MUST be sent in Access-Accept,
   Access-Challenge, Access-and Access-Reject messages if Location
   Information location
   information is transmitted with this exchange.  If authorization
   policy rules are available to the RADIUS client then the
   Access-Request MUST carry the Basic-Policy-Rules attribute to to the
   RADIUS server.

   A summary of the Basic-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        |R|  Flags                      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Retention Expires                                            ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Retention Expires                                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Note Well                                                    ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Type :
       To Be Assigned by IANA  - Basic-Policy-Rules

     Length:
       > 3 Bytes

     Flag (16 bits) bits):
       Only the first bit (R) is defined an corresponds to the
       retransmission-allowed field. All other bits are reserved.

     Retention Expires (64 bits) bits):
       NTP timestamp for the 'retention-expires' field.

     Note Well (variable)
       Contains (variable):
       This field contains a text URI with human readable
       privacy instructions.
       Its length MUST NOT exceed 64 octets.

   For this

   This document we reuse the following reuses fields of the 'usage-rules' element, described
   in [9]: [9].  These fields have the following meaning:

   retransmission-allowed: When the value of this element is '0', then
      the recipient of this Location Object is not permitted to share
      the enclosed Location Information, location information, or the object as a whole, with
      other parties.  The value of '1' allows to share the Location
      Information location
      information with other parties by considering the extended policy
      rules.
   retention-expires: 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 [14].
   note-well: This field contains a block of text URI with generic human readable privacy
      directives which are human-readable only.
      instructions.  This field is useful when Location Information 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.

10.4

9.4  Extended Policy Rules Attribute

   The Extended-Policy-Rules attribute SHOULD be sent in Access-Accept,
   Access-Challenge, Access-and Access-Reject messages if Location
   Information location
   information is transmitted with this exchange.  If authorization
   policy rules are available to the RADIUS client then the
   Access-Request MUST carry the Basic-Policy-Rules attribute to to the
   RADIUS server.

   This

   Ruleset reference field of this attribute contains a is of variable length ruleset reference.  This
   attribute length.  It
   contains a URI that indicates where a fuller richer ruleset of
   policies related to this object can be found. is available.
   The full ruleset SHOULD be fetched using Transport Layer Security
   (TLS).  As a deviation from [9] this field only contains a reference
   and does not carry an attached rule set.  This modification is
   motivated by the size limitations imposed by RADIUS.

   A summary of the Extended-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        | Ruleset reference            ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Type :
       To Be Assigned by IANA  - Extended-Policy-Rules

     Length:
       > 3 Bytes

     Ruleset reference:
       The text field contains a reference to the policy rules
       (see 'usage-rules' field description).
       Its length MUST NOT exceed 64 octets.

10.5 rules.

9.5  Location-Type Attribute

   Location-Type Attribute SHOULD be sent in Access-Request, and
   Accounting-Request records where the Acc-Status-Type is set to Start,
   Interim, or Stop if available.

   A summary of the Location-Type 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        | Loc-Type                      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Type (8 bits):
       To Be Assigned by IANA - Location-Name

     Length (8 bits):
       4 Bytes

     Loc-Type (16 bits):
       The content of this field corresponds to the integer codes for
       access network location type.

10.6  Billing-Description Attribute

   The Billing-Description attribute contains unstructured text to be
   printed on the users bill.

       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        | Billing-Text                 ...
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

     Type (8 bits):
       To Be Assigned by IANA - Billing-Description

     Length (8 bits):
       >= 3 Bytes

     Billing-Text (variable):
       The content of this field contains text

   These integer codes for billing purpose.

   The length of the Billing-Description attribute MUST NOT exceed 32
   octets.

11. location type can be found in Section 7.

10.  Table of Attributes

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

      Request Accept Reject Challenge Accounting  #  Attribute
                                      Request
      0-1     0      0      0         0-1     TBD  Operator-Name
      0+      0      0      0         0+      TBD  Location-Information
      0-1     0-1    0-1    0-1       0-1     TBD  Basic-Policy-Rules
      0-1     0-1    0-1    0-1       0-1     TBD  Extended-Policy-Rules
      0-1     0      0      0         0-1     TBD  Location-Type
      0-1     0      0      0         0-1     TBD  Billing-Description

   The Location-Information attribute may appear more than once.  This
   is useful if the size of one Location-Information attribute exceeds
   the maximum size of an AVP.  This might happen in case of civil
   location information which has a variable number of fields.  The
   fields used for the civil location information format of the
   Location-Information AVP (see Section 5.2.1 MUST NOT appear more than
   once.

12.

11.  IANA Considerations

   This document requires the assignment of four new RADIUS attribute
   numbers for the following attributes:

         Operator-Name
         Location-Information
         Basic-Policy-Rules
         Extended-Policy-Rules
         Location-Name
         Billing-Description

   Please refer to Section 11 10 for the registered list of numbers.

13.

12.  Matching with Geopriv Requirements

   This section compares the Geopriv requirements described in [8] and
   the approach of distributing Location Objects Objects with RADIUS.

   The main usage scenario aimed for Location Object transport in RADIUS
   assumes that the Location Server and the Location Recipient are
   co-located at a single entity with RADIUS.

   First, we differentiate between the two scenarios in regard to location based network
   access authorization, taxation and billing.  In Section 13.1 12.1 and
   Section 13.2.  These two scenarios focus on the 12.2 we discuss privacy related
   aspects descrbed in Section 4. implications when RADIUS is not used
   according to these usage scenario.

   In Section 13.3 then matches the 12.3 Geopriv requirements are matched against these two
   scenarios.

13.1

12.1  Distribution of Location Information at the User's Home Network

   This paragraph section focuses on a scenario whereby the RADIUS protocol
   transport iocation location information transport from the Location Generator (e.g., local
   AAA server) to server (acting as the Location Server (e.g., Generator) to the home AAA server). server
   (acting as the Location Server).  To use a more generic scenario we
   assume that the visited AAA and the home AAA server belong to
   different administrative domains.  The Location Recipient obtains
   location information about a particular Target via protocols
   specified outside the scope this document (e.g., SIP, HTTP or an
   API).

   Please note that the main usage scenario defined in this document
   assumes that the Location Server and the Location Recipient are
   co-located into a single entity with regard to location based network
   access authorization, taxation and billing.

   The usage of SIP or HTTP
   to distribute location information to third party entities is not the
   main envised use case.  However, the authors are aware of the fact
   that the user's location information might be used in a non-intended
   way.  To reflect the users privacy even in these cases it is
   necessary to offer appropriate mechanisms also for this environments.
   The Target is the user requesting network access.

   The subsequent figure shows the interacting entities graphically.

    visited network    |        home network
                       |
                       |        +----------+
                       |        |  Rule    |
                       |        | Holder   |
                       |        |          |
                       |        +----+-----+
                       |             |
                       |         rule|interface
                       |             V
     +----------+      |        +----------+               +----------+
     |Location  |  publication  | Location |  notification |Location  |
     |Generator |<------------->| Server   |<------------->|Recipient |
     |          |  interface    |          |  interface    |          |
     +----------+      |        +----------+               +----------+
                       |
     Local AAA      RADIUS       Home AAA     SIP/HTTP/API/etc.
     Server            |         Server
                       |

             Figure 15: 14: Location Server at the Home Network

13.2

   The term 'Rule Holder' in Figure 14 denotes the entity which creates
   the authorization ruleset.

12.2  Distribution of Location Information at the Visited Network

   This paragraph section describes a scenario which might happen during the
   deployment but where Location Information is not within
   distributed by the focus of this document. visited network.

   In order for this scenario to be applicable a few assumptions must
   hold:
   o  The visited network deploys a Location Server and wants to
      distribute Location Objects of a user
   o  The visited network is able to learn the user identity of the user

   The visited network provides location information to a Location
   Recipient (e.g., via SIP or HTTP).  During the network access
   authentication procedure the visited network is able to retrieve
   authorization policies of the user via RADIUS from the home AAA
   server.

   The subsequent figure shows the interacting entities graphically.
   The transport of the Location Object is not shown in this figure
   since this aspect is already covered in the previous paragraph.

    visited network    |        home network
                       |
     +----------+      |
     |Location  |      |
     |Recipient |      |
     |          |      |
     +----------+      |
          ^            |        +----------+
          |            |        |  Rule    |
          |            |        | Holder   |
      notification     |        |          |
       interface       |        +----+-----+
          |            |             |
          |            |         rule|interface
          v            |             V
     +----------+      |        +----------+
     |Location  | Rule Transport| Home AAA |
     |Generator |<------------->| Server   |
     |& Server  |   RADIUS      |          |
     +----------+      |        +----------+
                       |

           Figure 16: 15: Location Server at the Visited Network

13.3

12.3  Requirements matching

   Section 7.1 of [8] details the requirements of a "Location Object".

   There are:

   Req. 1.  (Location Object generalities):
      *  Regarding requirement 1.1, the Location Object has to be
         understood by the RADIUS server (and possibly a Diameter server
         in case of interworking between the two) as defined in this
         document.  Due to the encoding of the Location Object it is
         possible to convert it to the format used in GMLv3.  The same
         civil location information format is used in PIDF-LO and this
         document.
      *  Regarding requirement 1.2, some fields of the Location Object
         defined in this document are optional.  See Section 5.2.1 as an
         example.
      *  Regarding requirement 1.3, the inclusion of the Location-Type
         attribute which gives a further classification of the location.
         This attribute can be seen as an extension.
      *  Regarding requirement 1.4, the Location Object is extensible in
         the same fashion as RADIUS is extensible.

      *  Regarding requirement 1.5, the Location Object is useful for
         both receiving and sending location information as described in
         this document.
      *  Regarding requirement 1.6, the Location Object contains both,
         location information and privacy rules.  Location information
         is described in Section 5.2 and the corresponding privacy rules
         are detailed in Section 10.3 9.3 and in Section 10.4. 9.4.
      *  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 the respective sections (see
         Section 5.2, Section 10.3 9.3 and in Section 10.4). 9.4).
      *  Regarding requirement 1.8, the encoding of the Location Object
         has an emphasis on a lighweight lightweight encoding format.  As such it
         is useable on constrained devices.

   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 15 14 it has a number
         of advantages if this identifier is not carried in clear text.
         This is possible with cetain certain EAP methods whereby the identity
         in the EAP-Identity Response only contains information relevant
         for routing the response to the users home network.  The true
         user identity is protected by the authentication and key
         exchange protocol.
      *  Regarding requirement 2.2, the Location Recipient Identity is,
         in the main scenario the home AAA server.  This entity is
         located using the structure of the Network Access Identifier.
         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 16 15 describes these security mechanisms offered by the
         RADIUS protocol.  The same is true for requirement 2.4.
      *  Regarding requirement 2.5, Section 5.2 describes the content of
         the Location Field.  Motion and direction vectors as listed in
         requirement 2.6 are not provided as attributes.  It is,
         however, possible to deduce the motion and direction of an
         entity via the Mid-session Delivery mechanism as shown in
         Figure 2.
      *  Regarding requirement 2.6, this document only describes one
         Location Data Type for civil and for geospatial location
         information, respectively.  No negotiation needs to take place.
      *  Regarding requirement 2.7, timing information is provided with
         'sighting time' and 'time-to-live' field defined in Section
         10.3.
         9.3.
      *  Regarding requirement 2.8, a reference to an external (more
         detailed ruleset) is provided with the Section 10.4 9.4 attribute.
      *  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 defines two Location
         Data Types as described in Section 5.2.
      *  With the support of civil and geospatial location information
         support requirement 3.2 is fullfilled. fulfilled.
      *  Regarding requirement 3.3, geospatial location information only
         supports absolute coordinates rather than a delta.  However,
         the granuality granularity of the location information can be reduced with
         the help of the AltRes, LoRes, LaRes fields described in the
         Location-Information attribute (see Section 10.2). 9.2).
      *  Regarding requirement 3.4, further Location Data Types can be
         added via new coordinate reference systems (CRSs) (see Datum
         field in the Location-Information attribut attribute of Section 5.2),
         extensions to existing fields (e.g., new location types as
         shown in Section 7) or via additional attributes.

   Section 7.2 of [8] details the requirements of a "Using Protocol".

   There are:

   Req.  4.: The using protocol has to obey the privacy and security
      instructions coded in the Location Object and in the corresponding
      Rules regarding the transmission and storage of the LO.  This
      document requires, that RADIUS entities sending or receiving
      location MUST obey such 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 16 15 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 15) 14) are also applicable for this
      discussion.

   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.  The concept of a transaction is not immediately
      applicable to RADIUS.

   Section 7.3 of [8] details the requirements of a "Rule based Location
   Data Transfer".

   There are:

   Req.  7.  (LS Rules): With the scenario shown in Figure 15 14 the
      decision of a Location Server to provide a Location Recipient
      access to location information is based on Rule Maker-defined
      Privacy Rules which are stored at the home network or are
      accessible for the home network.  With regard to the scenario
      shown in Figure 16 15 the Rule Maker-defined Privacy Rules are sent
      from the home network to the visited network as part of the
      Policy-Information attribute (see Section 10.3, 9.3, Section 10.4 9.4 and
      Section 15 14 for more details).

   Req.  8.  (LG Rules): It is possible for the non-initial transmission
      (i.e., mid-session delivery) of a Location Object to enforce the
      users privacy rules.  For the initial transmission of a Location
      Object the user would have to use network access authentication
      methods which provide user identity confidentiality which would
      render the Location Object completely useless for the visited
      network.  For the scenario shown in Figure 15 14 the visited network
      is already in possession of the users location information prior
      to the authentication and authorization of the user (which might
      require several roundtrips).  A correlation between the location
      and the user identity might, however, still not be possible for
      the visited network (as explained in Section 15). 14).  The visited
      network MUST evaluate ruleset provided by the home AAA server as
      soon as possible.

   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 which is
      applicable in this area concerning the distribution of Location
      Objects.  A basic ruleset is provided with the Basic-Policy-Rules
      attribute Section 10.3. 9.3.  A reference to the extended ruleset is
      carried in Section 10.4. 9.4.  The format of these rules are described
      in [10] and [11].

   Req.  11.  (Limited Rule language): A limited (or basic) ruleset is
      provided by the Policy-Information attribute Section 10.3 9.3 (and as
      introduced with PIDF-LO [9]).

   Section 7.4 of [8] details the requirements of a "Location Object
   Privacy and Security".

   There are:

   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 identitiy identity confidentiality
      whereas others even support active user identity confidentiality.
      This issue is further discussed in Section 16. 15.  The importance for
      user identity confidentiality and identity protection has already
      been recognized (see for example a document on 'EAP Method
      Requirements for Wireless LANs' [15]).

   Req.  13.  (Credential Requirements): As described in Section 16 15
      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 16 15
      these requirements are fullfilled fulfilled with the usage of IPsec if the
      mutual authentication refers to the RADIUS entities (acting as
      various Geopriv entities) which directly communicate with each
      other.

   Req.  15.  (Minimal Crypto): A minimum of security mechanisms are
      mandated by the usage of RADIUS.  Security for Location Objects is
      provided by the RADIUS protocol (including IPsec and its dynamic
      key management framework) rather than on relying on object
      security via S/SIME (which is not available with RADIUS).  The
      handling of emergency calls is not specified as part of the RADIUS
      protocol and subject for an architectural investigation.  As such
      it might not even be applicable to RADIUS itself.

14.

13.  Example

   This section provides an example for a civil location information
   format within the Location-Information attribute.  The size of the
   geo-spatial location information object is fixed and well-described
   examples can be found in the Appendix of [7].

   Due to the size limitations of the RADIUS attributes we give a more
   detailed example borrowed from Section 4 of [5].

                +-------------+-----------+-------------------+
                | Type        | Length    | Value             |
                +-------------+-----------+-------------------+
                | Type        | 8 bits    | TBD               |
                | Length      | 8 bits    | 43                |
                | Code        | 16 bits   | 1                 |
                | Precision   | 8 bits    | 2                 |
                | Countrycode | 16 bits   | DE                |
                | CAtype      | 8 bits    | 1                 |
                | CAlength    | 8 bits    | 7                 |
                | CAvalue     | 7 bytes   | Bavaria           |
                | CAtype      | 8 bits    | 3                 |
                | CAlength    | 8 bits    | 6                 |
                | CAvalue     | 6 byte    | Munich            |
                | CAtype      | 8 bits    | 6                 |
                | CAlength    | 8 bits    | 11                |
                | CAvalue     | 11 bytes  | Marienplatz       |
                | CAtype      | 8 bits    | 19                |
                | CAlength    | 8 bits    | 1                 |
                | CAvalue     | 1 byte    | 8                 |
                | CAtype      | 8 bits    | 24                |
                | CAlength    | 8 bits    | 5                 |
                | CAvalue     | 5 bytes   | 80331             |
                +-------------+-----------+-------------------+

   The Length element provides the length of the entire payload minus
   the length of the initial 'Type', the 'Length' and the 'Code'
   attribute.  The Precision field has a value of '2' which refers to
   the location of the end host (user).  The CountryCode is set to 'DE'.
   Note that the subsequent attributes are in Type-Length-Value format.
   Type '1' indicates the region of 'Bavaria', '3' refers to the city
   'Munich', '6' to the street 'Marienplatz', the house number '8' is
   indicated by the type '19' and the zip code of '80331' is of type
   '24'.

   The total sum of these attributes is 46 bytes.

15.

14.  Privacy Considerations

   This section discusses privacy implications for the distribution of
   location lnformation information within RADIUS.

   In many cases the location information of the network also reveals
   the current location of the user with a certain degree of precision
   depending on the mechanism used, the positioning system, update
   frequence,
   frequency, where the location was generated, size of the network and
   other mechanisms (such as movement traces or interpolation).

   Two entities might act as Location Servers as shown in Section 4,
   Figure 15 14 or in Figure 16:

15.1 15:

14.1  Entity in the visited network

   In this scenario it is be difficult to obtain authorization policies
   from the end host (or user) immediately when the user attaches to the
   network.  In this case we have to assume that the visited network
   does not allow unrestricted distribution of location information
   other than the intended recipients (e.g, (e.g., to third party entities)
   immediately.

   The visited network MUST behave according to the following
   guidelines:
   o  Per default only the home network is allowed to receive location
      information.  The visited network MUST NOT distribute location
      information to third parties without seeing the user's privacy
      rule se.
   o  If the home network provides the Basic-Policy-Rules attribute
      either as part of the Access-Accept, the Access-Reject or the
      Access-Challenge message then the visited network MUST follow the
      guidance given with these rules.
   o  If the home network provides the Extended-Policy-Rules attributes
      either as part of the Access-Accept, the Access-Reject or the
      Access-Challenge message then the visited network MUST fetch the
      full ruleset at the indicated URL and MUST follow the guidance
      given with these rules.
   o  If the RADIUS client in the visited network learns the basic rule
      set or a reference to the extended rule set by means outside the
      RADIUS protocol (e.g., provided by the end host) then it MUST
      include the Basic-Policy-Rules and the Extended-Policy-Rules
      attribute in the Access-Request message towards the home AAA
      server.  Furthermore, the visited network MUST evaluate these
      rules prior to the transmission of Location Information location information either to
      the home network or a third party.  The visited network MUST
      follow the guidance given with these rules.

   o  If the RADIUS client in the visited network received receives the
      Basic-Policy-Rules attribute with Access-Accept or the
      Access-Challenge message then the Basic-Policy-Rules MUST be
      attach in subsequent RADIUS messages which contain the
      Location-Information attribute (such as interim accounting
      messages).
   o  If the RADIUS client in the visited network received receives the
      Extended-Policy-Rules attribute with Access-Accept or the
      Access-Challenge message then the Basic-Policy-Rules attribute
      MUST be attach in subsequent RADIUS messages which contain the
      Location-Information attribute (such as interim accounting
      messages).

15.2

14.2  Entity in the home network

   The AAA server in the home network might be an ideal place for
   storing authorization policies.  The user typically has a contractual
   relationship to his home network and hence the trust relationship
   between them are higher.  Once the infrastructure is deployed and
   useful applications are available there might be a strong desire to
   use location information for other purposes as well (such as location
   aware applications).  Authorization policy rules described in [11]
   and in [10] are tailored for this environment.  These policies might
   be useful for preventing further distribution of the user's location
   to other location based services.  The home AAA server (or a similar
   entity) thereby acts as a location server for access to location
   services.

   The home network MUST behave according to the following guidelines:
   o  As a default policy the home network MUST NOT distribute the
      user's location information to third party entities.
   o  If a user provided provides basic authorization policies then these rules
      MUST be returned to the visited network in the Access-Accept, the
      Access-Reject or the Access-Challenge message.
   o  If a user provided provides basic authorization policies then these rules
      MUST be returned to the visited network in the Access-Accept, the
      Access-Reject or the Access-Challenge message.
   o  If a user provided provides extended authorization policies then they MUST
      be accessible for the visited networking using a reference to
      these rule set.  The Extended-Policy-Rules attribute MUST include
      the reference and they MUST be sent to the visited network in the
      Access-Accept, the Access-Reject or the Access-Challenge message.
   o  The home network MUST follow the user provided rule set for both
      local storage and for further distribution.  With regard to the
      usage of these rules the home network MUST ensure that the users
      preferences are taken care of within the given boundaries (such as
      legal regulations or operational considerations).  For example, a
      user might not want the home network to store information about
      its Location Information location information beyond a indicated time frame.  However,
      a user might on the other hand want to ensure that disputes
      concerning the billed amount can be resolved.  Location
      Information  location
      information might help to resolve the dispute.  The user might,
      for example, be able to show that he has never been at the
      indicated place.
   o  If the policy rules provided by the user indicate that location
      information must not be distributed at all then the home network
      MUST provide the Basic-Policy-Rules to the RADIUS entity in the
      visited network via an Access-Accept, the Access-Reject or the
      Access-Challenge message.  The RADIUS server in the user's home
      network would set the 'Retention-Expires' and the
      'Retransmission-allowed' field to the user indicated value.  and
      the Extended-Policy-Rules to particular recipients

   For the envisioned usage scenarios the network access authentication
   procedure is tighly tightly coupled to the transfer of location information.
   If the authentication mechanism allows the visited network or AAA
   brokers to learn the user's identity then it is possible to
   correleate correlate
   location information with a particular user.  As such, it allows the
   visited network and brokers to learn movement patterns of users.

   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 AAA are in the same
   administrative domain.  No direct relationship between the visited
   and the home network operator may be available available and some AAA brokers
   need to be consulted.  With subscription-based network access as used
   today the user has a contractual relationship with the home network
   provider which could 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.  Mechanism to achieve
   this functionality are discussed in Section 16. 15.

   One way to ensure that the visited network and intermediate networks
   are incapable to learn the user identity is to use EAP methods that
   hide the user's identity either actively or passively.  Some EAP
   methods (such as [16]) protect the user's identity against passive
   adversaries by utilizing temporal identities.  In some cases the
   visited network is still able to retrieve the plaintext identity of
   the user and user identity confidentiality is only provided against
   eavesdroppers at the wireless link.  Depending on the movement
   patters of the user, the network topology and available roaming
   agreements it is possible that a AAA broker is able to see both the
   plaintext user identity and subsequent temporal identities.
   Associating location information and the user identity is possible in
   these cases.

   It is assumed that the true username is not carried within the
   initial EAP-Identity Request/Response message exchange.  Support for
   username privacy is supported with [17].

   For stronger security and privacy protection active user identity
   confidentiality is highly suggested.  EAP methods such as [18] or
   [19] provide such a protection.

   Unfortunately, most users are not educated about the importance of
   user identity confidentiality and many EAP methods do not provide
   active user identity confidentiality.  User identity confidentiality
   is often treated as an exotic features feature which mainly aims to prevent
   eavesdroppers on the wireless link to learn the user identity of the
   attached users.  Awareness for this threat type does often not exist.
   In many cases it is even not possible for users to freely select
   their favorite authentication and key exchange protocol (based on
   their security requirements).  Instead the choice is often
   predetermined by a given architecture.

   It was noted that different granularity of location information can
   be provided to the home network.  From a privacy point of view lower
   granularity is preferrable. preferable.  The user, however, has no control over
   the granularity and cannot lie about its location.

16.

15.  Security Considerations

   Requirements for the security protection of a Location Object is
   defined in [8]: Mutual end-point authentication, data object
   integrity, data object confidentiality and replay protection.  The
   distribution of location information can be restricted with the help
   of authorization policies.  Basic authorization policies are attached
   to the location information itself, in the same fashion as described
   in [9].  It is possible that the user was already able to transfer
   some authorization policies to the access network to restrict the
   distribution of location information.  This is, however, rather
   unlikely in case of roaming users.  Hence, it will be primarily the
   NAS creating the Location Object which also sets the authorization
   policies.  If no authorization information is provided by the user
   then the visited network MUST set the authorization policies to only
   allow the home AAA server to use the provided location information.
   Other entities, such as the visited network and possibly AAA brokers
   MUST NOT use the location information for a purpose other than
   described in this document.  More extensible authorization policies
   can be stored at the user's home network.  These policies are useful
   when location information is distributed to other entities in a
   location-based service.  This scenario is, however, outside the scope
   of this document.

   It is necessary to use authorization policies to prevent the
   unauthorized distribution of location information.  The security
   requirements which are created based on [8] are inline with threats
   which appear in the relationship with disclosure of location
   information as described in [20].  [9] proposes S/MIME to protect the
   Location Object against modifications and against eavesdropping.  To
   provide mutual authentication confidentiality protection and a
   digital signature is necessary.  Furthermore, to offer replay
   protection a gurantee guarantee of freshness is necessary (for example, based
   on timestamps).

   The security of S/SIME is based on public key cryptography which
   raises performance, deployment and size considerations.  Encryption
   requires that the local AAA server or the NAS knows the recipient's
   public key (e.g., the public key of the home AAA server).  Knowing
   the final recipient of the location information is in fact impossible
   for RADIUS entities.  Some sort of public key infrastructure would be
   required to obtain the public key and to verify the digital signature
   (at the home network).  Providing per-object cryptographic protection
   is, both at the home and at the visited network, computationally
   expensive.

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

   o  [1] proposes the usage of a static key which might raise some
      concerns about the lack dynamic key management.
   o  RADIUS over IPsec [21] allows to run standard key management
      mechanisms, such as KINK [22], IKE and IKEv2 [23], to establish
      IPsec security associations.  Confidentiality protection MUST be
      used to prevent eavesdropper gaining access to location
      information.  Confidentiality protection is not only a property
      required by this document, it is also required for the transport
      of keying material in the context of EAP authentication and
      authorization.  Hence, this requirement is, in many environments,
      already fulfilled.  Mutual authentication must be provided between
      the local AAA server and the home AAA server to prevent
      man-in-the-middle attacks.  This is another requirement raised in
      the area of key transport with RADIUS and does not represent a
      deployment obstacle.  The performance advantages a superior
      compared to the usage of S/MIME and object security since the
      expensive authentication and key exchange protocol run needs to be
      provided only once (at for a long time).  Symmetric channel
      security with IPsec is highly efficient.  Since IPsec protection
      is suggested as a mechanism to protect RAIDUS already no
      additional considerations need to be addressed beyond those
      described in [21].  Where an untrusted AAA intermediary is
      present, the Location Object MUST NOT be provided to the
      intermediary.

   In case that 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 and modify attributes
   and fields or to delete attributes.  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 the 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, including Location attribute(s) without a
   Message-Authenticator(80) attribute SHOULD be silently discarded by
   the NAS.  A NAS supporting the Location attribute 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 AAA entities in sense that object level security is not
   provided by neither RADIUS nor DIAMETER.  Hence, some trust has to be
   placed on the AAA entities to behave according to the defined rules.
   Furthermore, the AAA protocols do 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.
   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.  [24] documents this keying infrastructure and the
   security implications.  The uniqueness of the AAA infrastructure
   therefore raises some concerns about the interpretation of the
   retention and redistribution restrictions.  The privacy guidelines
   listed in Section 15 14 are applicable in this context.

17.

16.  Acknowledgments

   The authors would like to thank the following people for their help
   with a previous version of this draft and for their input:

      Chuck Black
      Paul Congdon
      Jouni Korhonen
      Sami Ala-luukko
      Farooq Bari
      Ed Van Horne
      Mark Grayson
      Jukkat Tuomi
      Jorge Cuellar
      Christian Guenther

   Henning Schulzrinne provided the civil location information content
   found in this draft.  The geospatial location information format is
   based on work done by J.  Polk, J.  Schnizlein and M.  Linsner.  The
   authorization policy format is based on the work done by Jon
   Peterson.

   The authors would like to thank Victor Lortz, 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 draft.

   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, Jon Peterson for their time to discuss a number
   of issues with us.  We think Stephen Hayes for aligning this work
   with 3GPP activities.

18.

17.  References

18.1

17.1  Normative References

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

   [2]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", March 1997.

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

   [4]  Chiba, M., Dommety, G., Eklund, M., Mitton, D. and B. Aboba,
        "Dynamic Authorization Extensions to Remote Authentication Dial
        In User Service (RADIUS)", RFC 3576, July 2003.

   [5]  Schulzrinne, H., "Dynamic Host Configuration Protocol (DHCPv4
        and DHCPv6) Option for Civic  Addresses",
        draft-ietf-geopriv-dhcp-civil-03  Addresses Configuration
        Information", draft-ietf-geopriv-dhcp-civil-04 (work in
        progress), July October 2004.

   [6]  Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD
        63, RFC 3629, November 2003.

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

18.2

17.2  Informative References

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

   [9]   Peterson, J., "A Presence-based GEOPRIV Location Object
         Format", draft-ietf-geopriv-pidf-lo-03 (work in progress),
         September 2004.

   [10]  Schulzrinne, H., "A Document Format for Expressing Privacy
         Preferences", draft-ietf-geopriv-common-policy-01 draft-ietf-geopriv-common-policy-02 (work in
         progress), July October 2004.

   [11]  Schulzrinne, H., "A Document Format for Expressing Privacy
         Preferences for Location  Information",
         draft-ietf-geopriv-policy-02
         draft-ietf-geopriv-policy-03 (work in progress), July October 2004.

   [12]  Schulzrinne, H., Gurbani, V., Kyzivat, P. and J. Rosenberg,
         "RPID: Rich Presence: Extensions to the Presence Information
         Data Format  (PIDF)", draft-ietf-simple-rpid-03 (work in
         progress), March 2004.

   [13]  Calhoun, P., Zorn, G., Spence, D. and D. Mitton, "Diameter
         Network Access Server Application",
         draft-ietf-aaa-diameter-nasreq-17 (work in progress), July
         2004.

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

   [15]  Stanley, D., Walker, J. and B. Aboba, "EAP Method Requirements
         for Wireless LANs", draft-walker-ieee802-req-04 (work in
         progress), August 2004.

   [16]  Arkko, J. and H. Haverinen, "EAP AKA Authentication",
         draft-arkko-pppext-eap-aka-12 (work in progress), April 2004.

   [17]  Aboba, B., "The Network Access Identifier",
         draft-arkko-roamops-rfc2486bis-02 (work in progress), July
         2004.

   [18]  Josefsson, S., Palekar, A., Simon, D. and G. Zorn, "Protected
         EAP Protocol (PEAP) Version 2",
         draft-josefsson-pppext-eap-tls-eap-08
         draft-josefsson-pppext-eap-tls-eap-09 (work in progress), July
         October 2004.

   [19]  Tschofenig, H. and D. Kroeselberg, "EAP IKEv2 Method
         (EAP-IKEv2)", draft-tschofenig-eap-ikev2-04 (work in progress),
         July 2004.

   [20]  Danley, M., "Threat Analysis of the Geopriv Protocol", RFC
         3694, September 2003, <reference.RFC3694.xml>.

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

   [22]  Thomas, M. and J. Vilhuber, "Kerberized Internet Negotiation of
         Keys (KINK)", draft-ietf-kink-kink-06 (work in progress), July
         2004.

   [23]  Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
         draft-ietf-ipsec-ikev2-17 (work in progress), October 2004.

   [24]  Aboba, B., "Extensible Authentication Protocol (EAP) Key
         Management Framework", draft-ietf-eap-keying-03 (work in
         progress), July 2004.

   [25]  Adrangi, F., "Access Network Bandwidth Capability",
         draft-adrangi-radius-bandwidth-capability-01 (work in
         progress), July 2004.

Authors' Addresses

   Hannes Tschofenig
   Siemens
   Otto-Hahn-Ring 6
   Munich, Bayern  81739
   Germany

   EMail: Hannes.Tschofenig@siemens.com

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

   EMail: farid.adrangi@intel.com

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

   EMail: avi@bridgewatersystems.com

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

   EMail: mark.jones@bridgewatersystems.com

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