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Versions: (draft-chowdhury-mip6-radius) 00 01 02 03 04 05 06

Network Working Group                                       K. Chowdhury
Internet-Draft                                          Starent Networks
Expires: April 8, 2007                                           A. Lior
                                                     Bridgewater Systems
                                                           H. Tschofenig
                                                                 Siemens
                                                         October 5, 2006


                       RADIUS Mobile IPv6 Support
                     draft-ietf-mip6-radius-00.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
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   This Internet-Draft will expire on April 8, 2007.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   A Mobile IPv6 node requires a home agent address, a home address, and
   IPsec security association with its home agent before it can start
   utilizing Mobile IPv6 service.  RFC 3775 requires that some or all of
   these parameters are statically configured.  Ongoing work aims to
   make this information dynamically available to the mobile node.  An



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   important aspect of the Mobile IPv6 bootstrapping solution is to
   support interworking with existing authentication, authorization and
   accounting infrastructure.  This document defines the new attributes
   to facilitate Mobile IPv6 bootstrapping via a RADIUS infrastructure.
   This information exchange may take place as part of the initial
   network access authentication procedure or as part of a separate
   protocol exchange between the mobile node, the home agent and the AAA
   infrastructure.











































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Solution Overview  . . . . . . . . . . . . . . . . . . . . . .  6
     3.1   Integrated Scenario  . . . . . . . . . . . . . . . . . . .  6
     3.2   Split Scenario . . . . . . . . . . . . . . . . . . . . . .  7
   4.  RADIUS Attribute Overview  . . . . . . . . . . . . . . . . . .  9
     4.1   Home Agent Address Attribute . . . . . . . . . . . . . . .  9
     4.2   Home Agent FQDN Attribute  . . . . . . . . . . . . . . . .  9
     4.3   Home Link Prefix Attribute . . . . . . . . . . . . . . . .  9
     4.4   Home Address Attribute . . . . . . . . . . . . . . . . . .  9
     4.5   DNS Update Mobility Option Attribute . . . . . . . . . . .  9
   5.  RADIUS attributes  . . . . . . . . . . . . . . . . . . . . . . 10
     5.1   Home Agent Address Attribute . . . . . . . . . . . . . . . 10
     5.2   Home Agent FQDN Attribute  . . . . . . . . . . . . . . . . 11
     5.3   Home Link Prefix Attribute . . . . . . . . . . . . . . . . 11
     5.4   Home Address Attribute . . . . . . . . . . . . . . . . . . 12
     5.5   DNS Update Mobility Option Attribute . . . . . . . . . . . 13
   6.  Message Flows  . . . . . . . . . . . . . . . . . . . . . . . . 15
     6.1   Integrated Scenario (MSA=ASA)  . . . . . . . . . . . . . . 15
       6.1.1   Home Agent allocation in the MSP . . . . . . . . . . . 15
       6.1.2   Home Agent allocation in the ASP (visited network) . . 16
     6.2   Split Scenario (MSA!=ASA)  . . . . . . . . . . . . . . . . 17
       6.2.1   Mobile Service Provider and Mobile Service
               Authorizer are the same entity.  . . . . . . . . . . . 17
       6.2.2   Mobile Service Provider and Mobile Service
               Authorizer are different entities. . . . . . . . . . . 19
   7.  Goals for the HA-AAA Interface . . . . . . . . . . . . . . . . 20
     7.1   General Goals  . . . . . . . . . . . . . . . . . . . . . . 20
     7.2   Service Authorization  . . . . . . . . . . . . . . . . . . 20
     7.3   Accounting . . . . . . . . . . . . . . . . . . . . . . . . 21
     7.4   Mobile Node Authentication . . . . . . . . . . . . . . . . 21
     7.5   Provisioning of Configuration Parameters . . . . . . . . . 21
   8.  Table of Attributes  . . . . . . . . . . . . . . . . . . . . . 22
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 23
   10.   IANA Considerations  . . . . . . . . . . . . . . . . . . . . 24
   11.   Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25
   12.   References . . . . . . . . . . . . . . . . . . . . . . . . . 26
     12.1  Normative References . . . . . . . . . . . . . . . . . . . 26
     12.2  Informative References . . . . . . . . . . . . . . . . . . 26
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 27
       Intellectual Property and Copyright Statements . . . . . . . . 28








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1.  Introduction

   Mobile IPv6 specification [5] requires a Mobile Node (MN) to perform
   registration with a Home Agent with information about its current
   point of attachment (Care-of Address).  The Home Agent creates and
   maintains binding between the MN's Home Address and the MN's Care-of
   Address.

   In order to register with a Home Agent, the MN needs to know some
   information such as, the Home Link prefix, the Home Agent Address,
   the Home Address, the Home Link prefix Length and security related
   information in order to secure the Binding Update.

   The aforementioned set of information may be statically provisioned
   in the MN.  However, static provisioning of this information has its
   drawbacks.  It increases provisioning and network maintenance burden
   for the operator.  Moreover, static provisioning does not allow load
   balancing, failover, opportunistic home link assignment etc.  For
   example, the user may be accessing the network from a location that
   may be geographically far away from the preconfigured home link; the
   administrative burden to configure the MN's with the respective
   addresses is large and the ability to react on environmental changes
   is minimal.  In these situations static provisioning may not be
   desirable.

   Dynamic assignment of Mobile IPv6 home registration information is a
   desirable feature for ease of deployment and network maintenance.
   For this purpose, the RADIUS infrastructure, which is used for access
   authentication, can be leveraged to assign some or all of the
   necessary parameters.  The RADIUS server in the Access Service
   Provider (ASP) or in the Mobility Service Provider's (MSP) network
   may return these parameters to the AAA client.  The AAA client might
   either be the NAS, in case of the integrated scenario, or the home
   agent, in case of the split scenario.  The terms integrated and split
   are described in the terminology section and were introduced in [6].
















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2.  Terminology

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [1].

   General mobility terminology can be found in [7].  The following
   additional terms, as defined in [6], are used in this document:

   Access Service Authorizer (ASA):

      A network operator that authenticates a mobile node and
      establishes the mobile node's authorization to receive Internet
      service.

   Access Service Provider (ASP):

      A network operator that provides direct IP packet forwarding to
      and from the mobile node.

   Mobility Service Authorizer (MSA):

      A service provider that authorizes Mobile IPv6 service.

   Mobility Service Provider (MSP):

      A service provider that provides Mobile IPv6 service.  In order to
      obtain such service, the mobile node must be authenticated and
      authorized to obtain the Mobile IPv6 service.

   Split Scenario:

      A scenario where the mobility service and the network access
      service are authorized by different entities.

   Integrated Scenario:

      A scenario where the mobility service and the network access
      service are authorized by the same entity.












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3.  Solution Overview

   This document addresses the authentication, authorization and
   accounting functionality required by for the MIPv6 bootstrapping as
   outlined in the MIPv6 bootstrapping problem statement document (see
   [6]).  As such, the AAA functionality for the integrated and the
   split scenario needs to be defined.  This requires the ability to
   offer support for the home agent to AAA server and the network access
   server to AAA server communication.

   To highlight the main use cases, we briefly describe the integrated
   and the split scenarios in Section 3.1 and Section 3.2, respectively.

3.1  Integrated Scenario

   In the integrated scenario MIPv6 bootstrapping is provided as part of
   the network access authentication procedure.  Figure 1 shows the
   participating entity.

                      +---------------------------+  +-----------------+
                      |Access Service Provider    |  |ASA/MSA/(/MSP)   |
                      |(Mobility Service Provider)|  |                 |
                      |                           |  |    +-------+    |
                      | +-------+                 |  |    |Remote |    |
                      | |Local  |          RADIUS |  |    |RADIUS |    |
                      | |RADIUS |-------------------------|Server |    |
                      | |Proxy  |                 |  |    +-------+    |
                      | +-------+                 |  |        ^        |
                      |     ^  ^                  |  |        |RADIUS  |
                      |     |  |                  |  |        |        |
                      |     |  |                  |  |        v        |
                      |     |RADIUS               |  |    +-------+    |
                      |     |  |        +-------+ |  |    |Local  |    |
                      |     |  | RADIUS |Home   | |  |    |Home   |    |
                      |     |  +------->|Agent  | |  |    |Agent  |    |
                      |     |           |in ASP | |  |    +-------+    |
                      |     v           +-------+ |  +-----------------+
   +-------+ IEEE     | +-----------+   +-------+ |
   |Mobile | 802.1X   | |NAS / Relay|   |DHCPv6 | |
   |Node   |----------+-|RADIUS     |---|Server | |
   |       | PANA,... | |Client     |   |       | |
   +-------+ DHCP     | +-----------+   +-------+ |
                      +---------------------------+

      Figure 1: Mobile IPv6 Service Access in the Integrated Scenario

   In the typical Mobile IPv6 access scenario as shown above, the MN
   attaches in a Access Service Provider's network.  During this network



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   attachment procedure, the NAS/RADIUS client interacts with the mobile
   node.  As shown in Figure 1, the authentication and authorization
   happens via a RADIUS infrastructure.

   At the time of authorizing the user for IPv6 access, the RADIUS
   server in the MSA detects that the user is authorized for Mobile IPv6
   access.  Based on the MSA's policy, the RADIUS server may allocate
   several parameters to the MN for use during the subsequent Mobile
   IPv6 protocol interaction with the home agent.

   Depending on the details of the solution interaction with the DHCPv6
   server may be required, as described in [2].

3.2  Split Scenario

   In the split scenario, Mobile IPv6 bootstrapping is not provided as
   part of the network access authentication procedure.  The Mobile IPv6
   bootstrapping procedure is executed with the Mobility Service
   Provider when desired by the mobile node.  Two variations can be
   considered:

   1.  the MSA and the MSP are the same entity.

   2.  the MSA and the MSP are different entities.

   Since scenario (1) is the more generic scenario we show it in
   Figure 2.
























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                                         +----------------------+
                                         |                      |
                                         |Mobility   +-------+  |
                                         |Service    |Remote |  |
                                         |Authorizer |RADIUS |  |
                                         |(MSA)      |Server |  |
                                         |           +-------+  |
                                         +---------------^------+
                                                         |
                                                         |RADIUS
                                                         |
                                                         |
                       +---------------------------------|------+
                       |Mobility Service Provider (MSP)  v      |
   +-------+           | +-----------+               +-------+  |
   |Mobile |  MIPv6 /  | |Home Agent/|     RADIUS    |Local  |  |
   |Node   |-------------|RADIUS     |-------------- |RADIUS |  |
   |       |  IKEv2    | |Client     |               |Proxy  |  |
   +-------+           | +-----------+               +-------+  |
                       +----------------------------------------+

    Figure 2: Mobile IPv6 service access in the split scenario (MSA !=
                                   MSP)

   As shown in Figure 2 the interaction between the RADIUS client and
   the RADIUS server is triggered by the protocol interaction between
   the mobile node and the home agent/RADIUS client using IKEv2 (see [3]
   and [8]).  The home agent / RADIUS Client interacts with the RADIUS
   infrastructure to perform authentication, authorization, accounting
   and parameter bootstrapping.  The exchange is triggered by the home
   agent and an interaction with the RADIUS infrastructure is initiated.
   When the protocol exchange is completed then the home agent needs to
   possess the Mobile IPv6 specific parameters (see [6]).

   Additionally, the mobile node might instruct the RADIUS server (via
   the home agent) to perform a dynamic DNS update.















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4.  RADIUS Attribute Overview

4.1  Home Agent Address Attribute

   The RADIUS server may decide to assign a Home Agent to the MN that is
   in close proximity to the point of attachment (e.g., determined by
   the NAS-ID).  There may be other reasons for dynamically assigning
   Home Agents to the MN, for example to share the traffic load.  The
   attribute also contains the prefix length so that the MN can easily
   infer the Home Link prefix from the Home Agent address.

4.2  Home Agent FQDN Attribute

   The RADIUS server may assign an FQDN of the home address to the MN.
   The mobile node can perform DNS query with the FQDN to derive the
   home agent address.

4.3  Home Link Prefix Attribute

   For the same reason as the HA assignment, the RADIUS server may
   assign a Home Link that is in close proximity to the point of
   attachment (NAS-ID).  The MN can perform [5] specific procedures to
   discover other information for Mobile IPv6 registration.

4.4  Home Address Attribute

   The RADIUS server may assign a Home Address to the MN.  This allows
   the network operator to support mobile devices that are not
   configured with static addresses.  The attribute also contains the
   prefix length so that the MN can easily infer the Home Link prefix
   from the Home Agent address.

4.5  DNS Update Mobility Option Attribute

   By using this payload the RADIUS client instructs the RADIUS server
   to perform a dynamic DNS update.  When this payload is included in
   the reverse direction, i.e., from the RADIUS server to the RADIUS
   client, it informs about the status of the dynamic DNS update.  When
   the payload is sent from the RADIUS client to the RADIUS server then
   the response MUST include the DNS Update Mobility Option attribute.











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5.  RADIUS attributes

   This section defines format and syntax for the attribute that carries
   the Mobile IPv6 parameters that are described in the previous
   section.

   The attributes MAY be present in Access-Accept, Accounting-Request.

5.1  Home Agent Address Attribute

   This attribute is sent by the RADIUS server to the NAS in an Access-
   Accept message.  The attribute carries the assigned Home Agent
   address.

       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      |    Reserved   | Prefix-Length |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                                                               |
      |              IPv6 address of assigned Home Agent              |
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type:

         ASSIGNED-HA-ADDR-TYPE to be defined by IANA.

      Length:

         = 20 octets

      Reserved:

         Reserved for future use.  All bits set to 0.

      Prefix-Length:

         This field indicates the prefix length of the Home Link.

      IPv6 address of assigned Home Agent:

         128-bit IPv6 address of the assigned Home Agent.






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5.2  Home Agent FQDN Attribute

   This attribute is sent by the RADIUS server to the NAS in an Access-
   Accept message.  The attribute carries the FQDN of the assigned home
   agent.

       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      |            Reserved           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             FQDN of the assigned home agent                 ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type:

         ASSIGNED-HA-FQDN-TYPE to be defined by IANA.

      Length:

         Variable length.

      Reserved:

         Reserved for future use.  All bits set to 0.

      FQDN of the assigned home agent:

         The data field MUST contain a FQDN as described in [9].


5.3  Home Link Prefix Attribute

   This attribute is sent by the RADIUS-MIP server to the NAS in an
   Access-Accept message.  The attribute carries the assigned Home Link
   prefix.

       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      |            Reserved           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                                                               |
      |                       Home Link Prefix                        |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




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      Type:

         ASSIGNED-HL-TYPE to be defined by IANA.

      Length:

         >= 4 octets + the minimum length of a prefix.

      Reserved:

         Reserved for future use.  All bits set to 0.

      Home Link Prefix:

         Home Link prefix (upper order bits) of the assigned Home Link
         where the MN should send binding update.


5.4  Home Address Attribute

   This attribute is sent by the RADIUS server to the NAS in an Access-
   Accept message.  The attribute carries the assigned Home IPv6 Address
   for the MN.

       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      |   Reserved    | Prefix-Length |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                                                               |
      |                   Assigned IPv6 Home Address                  |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type:

         ASSIGNED-HOA-TYPE to be defined by IANA.

      Length:

         = 20 octets.

      Reserved:

         Reserved for future use.  All bits set to 0.





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      Prefix-Length:

         This field indicates the prefix length of the Home Link.

      Assigned IPv6 Home Address:

         IPv6 Home Address that is assigned to the MN.


5.5  DNS Update Mobility Option Attribute

   The DNS Update Mobility Option attribute is used for triggering a DNS
   update by the RADIUS server and to return the result to the RADIUS
   client.  The request MUST carry the mobile node's FQDN but the
   attribute carried in response to the request MAY not carry a FQDN
   value.

       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      |   Reserved-1  |     Status    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |R| Reserved-2  |   FQDN                                       ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Type:

         DNS-UPDATE-TYPE to be defined by IANA.

      Length:

         Variable length.

      Reserved-1:

         Reserved for future use.  All bits set to 0.

      Status:

         This 8 bit unsigned integer field indicates the result of the
         dynamic DNS update procedure.  This field MUST be set to 0 and
         ignored by the RADIUS server when the DNS Update Mobility
         Option is sent from the RADIUS client to the RADIUS server.
         When the DNS Update Mobility Option is provided in the
         response, values of the Status field less than 128 indicate
         that the dynamic DNS update was performed successfully by the
         RADIUS server.  Values greater than or equal to 128 indicate
         that the dynamic DNS update was not successfully completed.



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         The following values for the Status field are currently
         defined:

         0 DNS update performed

         128 Reason unspecified

         129 Administratively prohibited

         130 DNS Update Failed

      R flag:

         If this bit for the R flag is set then the RADIUS client
         requests the RADIUS server to remove the DNS entry identified
         by the FQDN included in this attribute.  If not set, the RADIUS
         client is requesting the RADIUS server to create or update a
         DNS entry with the FQDN specified in this attribute and the
         Home Address carried in another attribute specified in this
         document.

      Reserved-2:

         Reserved for future use.  All bits set to 0.

      FQDN of the mobile node:

         The data field MUST contain a FQDN as described in [9].























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6.  Message Flows

6.1  Integrated Scenario (MSA=ASA)

   This section is based on [2] and uses the previously defined RADIUS
   attributes.

6.1.1  Home Agent allocation in the MSP

   RADIUS is used to authenticate the mobile node, to authorize it for
   the mobility service and to send information about the assigned home
   agent to the NAS.


                                            |
                    --------------ASP------>|<--ASA+MSA--
                                            |
      +----+        +------+      +-------+   +-------+
      |    |        |RADIUS|      |       |   |       |
      |    |        |Client|      |       |   |       |
      | MN |        |NAS/  |      | DHCP  |   |Home   |
      |    |        |DHCP  |      | Server|   |RADIUS |
      |    |        |Relay |      |       |   |Server |
      +----+        +------+      +-------+   +-------+
        |               |             |          |
        |     1         |          1  |          |
        |<------------->|<---------------------->|
        |               |             |          |
        |               |             |          |
        |     2         |             |          |
        |-------------->|             |          |
        |               |             |          |
        |               |       3     |          |
        |               |------------>|          |
        |               |             |          |
        |               |       4     |          |
        |               |<------------|          |
        |               |             |          |
        |     5         |             |          |
        |<--------------|             |          |
        |               |             |          |

   In step (1), the MN executes the normal network access authentication
   procedure (e.g., IEEE 802.11i/802.1x, PANA) with the NAS.  The NAS
   acts as an authenticator in "pass-through" mode, i.e., the endpoint
   of the authentication dialogue is the MN's home RADIUS server.  This
   is the typical scenario in case the messages involved in the
   authentication protocol are transported in EAP.



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   The NAS encapsulates/decapsulates EAP packets into/from RADIUS
   messages until an Access-Response (either an Access-Accept or an
   Access/Reject packet is received by the NAS).  This concludes the
   network access authentication phase.

   Depending on the RADIUS server configuration, the Home Agent Address
   attribute or the the Home Agent FQDN attribute may be appended to the
   Access-Accept message.  In the latter case the MN needs to perform a
   DNS query in order to discover the Home Agent address.

   The Home Agent Address or Home Agent FQDN attribute is appended to
   the access accept in case the home RADIUS server knows or has
   allocated a HA to the access request (this is assumed in this
   scenario).

   In step (2) the MN sends a DHCPv6 Information Request message to
   all_DHCP_Relay_Agents_and_Servers.  In the OPTION_ORO, Option Code
   for the Home Network Identifier Option shall be included in that
   message.  The Home Network Identifier Option should have id-type of
   1, the message is a request to discover home network information that
   pertains to the given realm, i.e., the user's home domain (identified
   by the NAI of the MN).  The OPTION_CLIENTID is set by the MN to
   identify itself to the DHCP server.

   In step (3) the DHCP relay agent forwards this request to the DHCP
   server.  The OPTION_MIP6-RELAY-Option is included in this forwarded
   message.  This option carries the RADIUS Home Agent Address Attribute
   from the access accept message.

   In step (4), the DHCP server identifies the client (by DUID) and
   finds out that it requests home agent information in the MSP (by the
   Home Network Identifier Option = 1).  The DHCP server extracts the
   home agent address from OPTION_MIP6-RELAY-Option and places it into
   Home Network Information Option in the Reply message.

   In step (5), the Relay Agent forwards the Reply Message to the Mobile
   Node.  On reception of this message, the home agent address or the
   FQDN of the home agent is available at the MN.

6.1.2  Home Agent allocation in the ASP (visited network)

   This scenario is similar to the one described in Section 6.1.1.  The
   difference is in step (2), where the type-id field in the Home
   Network Identifier Option is set to zero, indicating that a Home
   Agent is requested in the ASP instead of in the MSP.  Thus, the
   information received by the home RADIUS server, via the DHCP relay,
   in the OPTION_MIP6-RELAY-Option (Information Request) is ignored.
   The DHCP server allocates a home agent from its list of possible home



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   agents and returns it in the Reply message (Home Network Information
   Option).

6.2  Split Scenario (MSA!=ASA)

6.2.1  Mobile Service Provider and Mobile Service Authorizer are the
       same entity.

   The assumption in this scenario is that the MN has the domain name of
   the MSP preconfigured.

   In this scenario there is no relationship between the network access
   authentication procedure and the MIPv6 bootstrapping procedure.

   In order to learn the IP address of the home agent, the MN either
   performs a DNS lookup of the Home Agent Name or a DNS lookup by
   service name.  In the first case, the MN is preconfigured with the
   FQDN of the HA, and thus sends a DNS request, where QNAME = name of
   HA, QTYPE='AAAA' (request for IPv6 address of HA).  A DNS reply
   message is returned by the DNS server with the HA address.

   The MN then runs IKEv2 with the HA in order to set up IPsec SAs
   (MN-HA).  As part of this,the MN authenticates itself to the RADIUS
   server in the MSA domain, and obtains authorization for mobility
   service (including the Home Address).

   The MN shares credentials with the RADIUS server in the MSA domain.
   The RADIUS communication between the HA and the this RADIUS server is
   also secured by RADIUS-specific mechanisms (e.g., IPsec).  Using EAP
   within IKEv2, the MN is authenticated and authorized for the IPv6
   mobility service and is also assigned a home address.

   The setup of SAs and mutual authentication between MN and AAAH using
   RADIUS (and EAP) is similar to the one described for Diameter
   protocol in [10].  The described mechanism ensureas that common
   keying material will be available at the MN and HA after successful
   completion.














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        ----------------------------ASP--------->|<-----MSA/MSP

     +----+      IKEv2  +----+    RADIUS (EAP)      +--------------------+
     | MN |<----------->| HA |<-------------------->|Remote RADIUS Server|
     +----+             +----+                      +--------------------+

      MN                             HA                Remote RADIUS server
      --                             --                --------------------
               IKE_SA_INIT
      <------------------------------>

       HDR, SK{IDi,[CERTREQ,] [IDr,]
               SAi2, TSi, TSr}
      ------------------------------->
                                      RADIUS Access Request(EAP-Response)
                                      ---------------------------------->
                                      RADIUS Access Challenge(EAP-Request)
                                      <-----------------------------------
       HDR, SK {IDr, [CERT,] AUTH,
                EAP }
      <-------------------------------
       HDR, SK {EAP}
      -------------------------------->
                                      RADIUS Access Request(EAP-Response)
                                       ---------------------------------->
                                      RADIUS Access Challenge(EAP-Request)
                                      <-----------------------------------
       HDR, SK{EAP-Request}
      <-------------------------------
       HDR, SK{EAP-Response}
      -------------------------------->
                                       RADIUS Access Request(EAP-Response)
                                       ---------------------------------->
                ...                           ...


                                       RADIUS Access Accept(EAP-Success)
                                       <------------------------

           HDR, SK{EAP-Success}
      <-------------------------------
       HDR, SK{AUTH}
      ------------------------------->
       HDR, SK {AUTH, SAr2, TSi, TSr }
      <-------------------------------

   MN and HA start with an IKE_SA_INIT to setup the IKE SA (messages
   defined in the IKEv2 specification, negotiating crypto algorithms and



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   running DH key exchange).  IKEv2 supports integration with EAP.  The
   MN indicates its desire to use EAP by not including the AUTH payload
   in the third message.  However, it indicates its identity (NAI) by
   using the IDi field.  If the HA supports EAP for authentication, it
   forwards the identity to the Remote RADIUS server by sending a RADIUS
   Access-Request message containing the identity in the EAP-Payload AVP
   and in the RADIUS User-Name attribute.  Based on this identity, the
   Remote RADIUS server chooses authentication method and sends the
   first EAP-Request in the RADIUS Access-Challenge message.  During the
   EAP authentication phase, the HA relays EAP packets between the MN
   and the Remote RADIUS server.  If the authentication succeeds and if
   the MN is authorized to use Mobile IPv6 service, the Remote RADIUS
   server sends a RADIUS Access Accept message containing the EAP-
   Success and the AAA-Key derived from the EAP authentication method.
   EAP authentication methods that do not derive keys are not
   recommended.  This key is used by both MN and HA to generate the AUTH
   payload.  In subsequent messages, MN and HA setup IPsec SAs for
   Mobile IPv6.

6.2.2  Mobile Service Provider and Mobile Service Authorizer are
       different entities.

   The HA address discovery is performed as described in Section 6.2.1.


   -----------ASP--------->|<-----MSP------------------->|<-----MSA--------

     +----+      IKEv2  +----+ RADIUS (EAP)+------+ RADIUS(EAP)+------+
     | MN |<----------> | HA |<----------->|Local |<---------->|Remote|
     +----+             +----+             |RADIUS|            |RADIUS|
                                           |Proxy |            |Server|
                                           +------+            +------+

   The scenario is similar to previously described scenarios with the
   difference of utilizing AAA roaming agreements between the MSP and
   the MSA.















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7.  Goals for the HA-AAA Interface

   Here, we follow the classification and labels listed in the MIPv6-
   AAA-Goals document [11].

7.1  General Goals

   G1.1-G1.4 Security

   These are standard requirements for a AAA protocol - mutual
   authentication, integrity, replay protection, confidentiality.  IPsec
   can be used to achieve the goals.  Goal G1.5 regarding inactive peer
   detection needs further investigations since heartbeat messages do
   not exist (like in the Diameter case, Watch-Dog-Request/Answer).

7.2  Service Authorization

   G2.1.  The AAA-HA interface should allow the use of Network Access
   Identifier (NAI) to identify the mobile node.  The User-Name
   attribute can be used for the purpose to carry the NAI.

   G2.2 The HA should be able to query the AAAH server to verify Mobile
   IPv6 service authorization for the mobile node.  Any node
   implementing RADIUS functionality can possibly initiate a request
   message.  In combination with the ability of the RADIUS protocol to
   carry EAP messages, our solution will enable an HA to query a RADIUS
   server and verify MIPv6 authorization for the MN.

   G2.3 The AAAH server should be able to enforce explicit operational
   limitations and authorization restrictions on the HA (e.g., packet
   filters, QoS parameters).  Work in progress in the area, including
   NAS-Filter-Rule, RADIUS quality of service support, prepaid
   extensions etc. is performed.  The relevant attributes may be reused
   for providing required functionality over the AAAH-HA interface.

   G2.4 - G2.6.  Issues addressing the maintenance of a Mobile IPv6
   session by the AAAH server, e.g., authorization lifetime, extension
   of the authorization lifetime and explicit session termination by the
   AAAH server side.

   The attribute Session-Timeout may be sent in Access Challenge or
   Access Accept message by the RADIUS server, thus limiting the
   authorization session duration.  In order to reauthenticate/
   reauthorize the user, the Termination-Action attribute can be
   included, with value 1, meaning the NAS should send a new RADIUS-
   Request packet.  Additional AVPs for dealing with pre-paid sessions
   (e.g,. volume, resource used--VolumeQuota AVP, ResourceQuota AVP) are
   specified in RADIUS prepaid extension.  Exchanging of application



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   specific authorization request/answer messages provides extension of
   the authorization session (e.g., Authorize Only Access Request sent
   by the HA (NAS) to the RADIUS server).  Initiation of the re-
   authorization by both sides could be supported.  Both sides could
   initiate session termination - the RADIUS server by sending
   Disconnect message.

7.3  Accounting

   G3.1 The AAA-HA interface must support the transfer of accounting
   records needed for service control and charging.  These include (but
   may not be limited to): time of binding cache entry creation and
   deletion, octets sent and received by the mobile node in bi-
   directional tunneling, etc.

   The requirements for accounting over the AAAH-HA interface does not
   require enhancements to the existing accounting functionality.

7.4  Mobile Node Authentication

   G4.1 The AAA-HA interface MUST support pass-through EAP
   authentication with the HA working as EAP authenticator operating in
   pass-through mode and the AAAH server working as back-end
   authentication server.

   These issues require the functionality of AAAH server working as a
   back-end authentication server and HA working as NAS and EAP
   authenticator in pass-through mode for providing a mobile node
   authentication.  This document suggests this mode of operation in the
   context of the relevant scenarios.

7.5  Provisioning of Configuration Parameters

   G5.1 The HA should be able to communicate to the AAAH server the Home
   Address allocated to the MN (e.g. for allowing the AAAH server to
   perform DNS update on behalf of the MN).

   This document describes needed AVPs for this purpose, see section
   "DNS Update Mobility Option Attribute"












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8.  Table of Attributes

   The following table provides a guide to which attributes may be found
   in RADIUS message and in what number.


   Request  Accept  Reject  Challenge    Attribute

   0-1        0-1     0       0          Home Agent Address Attribute
   0-1        0-1     0       0          Home Agent FQDN Attribute
   0-1        0-1     0       0          Home Link Prefix Attribute
   0-1        0-1     0       0          Home Address Attribute
   0-1        0-1     0       0          DNS Update Mobility Option
                                         Attribute


   The following table defines the meaning of the above table entries.

      0     This attribute MUST NOT be present.
      0-1   Zero or one instance of this attribute MAY be present.































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9.  Security Considerations

   Assignment of these values to a user should be based on successful
   authentication of the user at the NAS and/or at the home agent.  The
   RADIUS server should only assign these values to a user who is
   authorized for Mobile IPv6 service (this check could be performed
   with the user's subscription profile in the Home Network).

   The NAS and the home agent to the RADIUS server transactions must be
   adequately secured.  Otherwise there is a possibility that the user
   may receive fraudulent values from a rogue RADIUS server potentially
   hijacking the user's Mobile IPv6 session.

   These new attributes do not introduce additional security
   considerations besides the ones identified in [4].




































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10.  IANA Considerations

   The following RADIUS attribute Type values MUST be assigned by IANA.

   ASSIGNED-HA-ADDR-TYPE

   ASSIGNED-HA-FQDN-TYPE

   ASSIGNED-HL-TYPE

   ASSIGNED-HOA-TYPE

   DNS-UPDATE-TYPE






































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11.  Acknowledgements

   We would like to thank the following individuals for their review and
   constructive comments during the development of this document:

   Florian Kohlmayer, Mark Watson, Jayshree Bharatia, Dimiter Milushev,
   Andreas Pashalidis, Rafa Marin Lopez.












































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12.  References

12.1  Normative References

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

   [2]  Chowdhury, K. and A. Yegin, "MIP6-bootstrapping via DHCPv6 for
        the Integrated Scenario",
        draft-ietf-mip6-bootstrapping-integrated-dhc-01 (work in
        progress), June 2006.

   [3]  Giaretta, G., "Mobile IPv6 bootstrapping in split scenario",
        draft-ietf-mip6-bootstrapping-split-02 (work in progress),
        March 2006.

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

12.2  Informative References

   [5]   Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
         IPv6", RFC 3775, June 2004.

   [6]   Giaretta, G. and A. Patel, "Problem Statement for bootstrapping
         Mobile IPv6", draft-ietf-mip6-bootstrap-ps-05 (work in
         progress), May 2006.

   [7]   Manner, J. and M. Kojo, "Mobility Related Terminology",
         RFC 3753, June 2004.

   [8]   Dupont, F. and V. Devarapalli, "Mobile IPv6 Operation with
         IKEv2 and the revised IPsec Architecture",
         draft-ietf-mip6-ikev2-ipsec-06 (work in progress), April 2006.

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

   [10]  Tschofenig, H., "Mobile IPv6 Bootstrapping using Diameter",
         draft-tschofenig-mip6-aaa-ha-diameter-01 (work in progress),
         October 2005.

   [11]  Giaretta, G., "AAA Goals for Mobile IPv6",
         draft-ietf-mip6-aaa-ha-goals-03 (work in progress),
         September 2006.

   [12]  Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,



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         "DNS Security Introduction and Requirements", RFC 4033,
         March 2005.

   [13]  Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec to
         Protect Mobile IPv6 Signaling Between Mobile Nodes and Home
         Agents", RFC 3776, June 2004.

   [14]  Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, "Dynamic
         Updates in the Domain Name System (DNS UPDATE)", RFC 2136,
         April 1997.


Authors' Addresses

   Kuntal Chowdhury
   Starent Networks
   30 International Place
   Tewksbury, MA  01876
   US

   Phone: +1 214-550-1416
   Email: kchowdhury@starentnetworks.com


   Avi Lior
   Bridgewater Systems
   303 Terry Fox Drive, Suite 100
   Ottawa, Ontario
   Canada K2K 3J1

   Phone: +1 613-591-6655
   Email: avi@bridgewatersystems.com


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

   Email: Hannes.Tschofenig@siemens.com










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