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Versions: 00 01                                                         
Network Working Group                                       K. Chowdhury
Internet-Draft                                           Nortel Networks
Expires: January 10, 2005                                        A. Lior
                                                     Bridgewater Systems
                                                           July 12, 2004


            RADIUS Attributes for Mobile IPv6 bootstrapping
              draft-chowdhury-mip6-bootstrap-radius-00.txt

Status of this Memo

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   and any of which I become aware will be disclosed, in accordance with
   RFC 3668.

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   This Internet-Draft will expire on January 10, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.

Abstract

   This document defines new attributes to facilitate Mobile IPv6
   bootstrapping via a RADIUS infrastructure.  In an access network
   where the user attaches to get IPv6 access, there may be a Network
   Access Server (NAS) or an Access Gateway that will require
   authentication and authorization.  In some cases, this type of access
   authentication takes place via RADIUS infrastructure.  As part of the
   authentication setup the NAS may receive useful configuration
   information from the home RADIUS server of the user.  In case of



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   Mobile IPv6 access, the Home RADIUS server may assign various
   information relevant to the user's device for bootstrapping.

Table of Contents

   1.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1   Home Agent or a List of Home Agents  . . . . . . . . . . .  4
     2.2   Home Link Prefix or a list of Home Link prefixes . . . . .  5
     2.3   Home Address . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  RADIUS attributes to carry Mobile IPv6 parameters  . . . . . .  7
     4.1   Home Agent Attribute . . . . . . . . . . . . . . . . . . .  7
     4.2   Home Link Prefix Attribute . . . . . . . . . . . . . . . .  7
     4.3   Home Address . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  Table of Attributes  . . . . . . . . . . . . . . . . . . . . . 10
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
   9.  Normative References . . . . . . . . . . . . . . . . . . . . . 13
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 13
       Intellectual Property and Copyright Statements . . . . . . . . 14





























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1.  Motivation

   Mobile IPv6 specification [RFC3775] 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
   information such as, the Home Link prefix, the Home Agent Address,
   the Home Address, the Home Link prefix Length etc.  Moreover during
   normal operation of the Mobile IPv6 session, the MN needs to know the
   lifetime of the Home Address.

   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; or
   the cost of the link between the NAS and the Home Link is too great.
   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 Home RADIUS server, which is used for access
   authentication, can be leveraged to assign some or all of the
   necessary parameters.  The Home RADIUS server may return these
   parameters to the NAS.

   The NAS may convey the received information to the MN using various
   techniques.  One such technique may utilize the role of the NAS as a
   relay agent for Dynamic Host Configuration Protocol.  In this case,
   upon receiving the information from the Home RADIUS server, the NAS
   forwards the set of parameters to the DHCP server.  The DHCP server
   attaches the information in new DHCP options while responding to an
   information-request from the MN.  The part where the NAS acts as a
   DHCP relay agent and forwards the received information to the DHCP
   server is outside the scope of this document.











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2.  Overview


                                                  |
                  Visited Network        |        Home Network
                                         |
                      +-------+          |        +-------+
                      |       |          |        |       |
                      |Visited|----------|--------| Home  |
                      |RADIUS |          |        |RADIUS |
                      |       |          |        |       |
                      +-------+          |        +-------+
                          |              |
                          |              |
                          |     +------+ |
                          | +---| DHCP | |
                          | |   |Server| |
                          | |   +------+ |
                          | |            |
                       +-----+           |         +-----+
   +----+              |     |           |         | Home|
   | MN |--------------| NAS/|           |         |Agent|
   +----+              |Relay|           |         |     |
                       +-----+           |         +-----+



   In the typical Mobile IPv6 access scenario as shown above, the MN
   attaches in a visited network.  During this attach procedure, the NAS
   authenticates and authorizes the MN for IPv6 access service.  In the
   scenario shown, the authentication and authorization happens via
   RADIUS infrastructure.

   At the time of authorizing the user for IPv6 access, the Home RADIUS
   server detects that the user is authorized for Mobile IPv6 access.
   Based on Home network policy, the Home RADIUS server may allocate
   several parameters to the MN for use during the subsequent Mobile
   IPv6 Binding Update.  A list of such parameters is described in the
   following sub sections.

2.1  Home Agent or a List of Home Agents

   The Home network provider 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 assigning
   Home Agents to the MN, e.g.  load sharing in the network.  The Home
   network may also assign a list of Home Agents for the MN to choose
   from.



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2.2  Home Link Prefix or a list of Home Link prefixes

   For the same reason as HA assignment, the Home network may assign a
   Home Link that is in close proximity to the point of attachment
   (NAS-ID).  The Home RADIUS server may also assign a list of Home Link
   prefixes to the MN and allow the MN to choose one.  The MN can
   perform [RFC3775] specific procedures to discover other information
   for Mobile IPv6 registration.  The length of the assigned prefix(es)
   can be included as well.

2.3  Home Address

   The Home 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 lifetime of the Home Address
   can be indicated along with the address.



































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3.  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 RFC 2119.














































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4.  RADIUS attributes to carry Mobile IPv6 parameters

   This section defines format and syntax for the attribute that carries
   the Mobile IPv6 parameters described in section 2.

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

4.1  Home Agent Attribute

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



       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                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |               IPv6 address of assigned HA-1                   |
      |                              ...                              |
      |               IPv6 address of assigned HA-n                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Type:

         ASSIGNED-HA-TYPE to be defined by IANA.

      Length:

         >= 20 octets

      Reserved:

         Reserved for future use.  All bits set to 0.

      IPv6 address of assigned HA-1 to HA-n:

         128-bit IPv6 address of one or more assigned Home Agents.  The
         addresses appear in the order of preference.

4.2  Home Link Prefix Attribute

   This attribute is sent by the RADIUS server to the NAS in an
   Access-Accept message.  The attribute carries the assigned Home Link
   prefix or a list of assigned Home Link Prefixes.  to the NAS.



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       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      |  HL Length    |  Reserved     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |               IPv6 address of assigned HL-1                   |
      |                              ...                              |
      |               IPv6 address of assigned HL-n ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Type:

         ASSIGNED-HL-TYPE to be defined by IANA.

      Length:

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

      HL Length:

         8-bit unsigned integer, representing the length in octets of
         the Home Link Prefix(es).

      Reserved:

         Reserved for future use.  All bits set to 0.

      IPv6 address of assigned HL-1 to HL-n:

         Home Link prefixes (upper order bits) of the assigned Home
         Links where the MN should send binding update.  The Home Link
         prefixes appear in the order of preference.

4.3  Home Address

   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      |           Lifetime            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |



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      |                                                               |
      |                   Assigned IPv6 Home Address                  |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      Type:

         ASSIGNED-HOA-TYPE to be defined by IANA.

      Length:

         >= 20 octets.

      Lifetime:

         16-bit unsigned integer.  The number of time units remaining
         before the IPv6 Home Address MUST be considered expired.  A
         value of zero indicates that the IPv6 Home Address has expired.
         One time unit is 4 seconds.

      Assigned IPv6 Home Address:

         IPv6 Home Address that is assigned to the MN.



























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Internet-Draft                                                 July 2004


5.  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        0-1     0       0            TBD   Home Agent
   0        0-1     0       0            TBD   Home Link Prefix
   0        0-1     0       0            TBD   Home Address


   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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6.  Security Considerations

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

   The NAS to the Home 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 threats
   besides the one identified in [RFC2865].




































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Internet-Draft                                                 July 2004


7.  IANA Considerations

   The RADIUS attribute types: ASSIGNED-HA-TYPE, ASSIGNED-HL-TYPE,
   ASSIGNED-HOA-TYPE Must be assigned by IANA.















































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8.  Acknowledgements

   Thanks to the following individuals for their review and constructive
   comments during the development of this document:

   Mark Watson, Jayshree Bharatia.

9  Normative References

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

   [RFC3775]  Johnson, D., Perkins, C. and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.


Authors' Addresses

   Kuntal Chowdhury
   Nortel Networks
   2221 Lakeside Blvd.
   Richardson, TX  75082
   US

   Phone: +1 972-685-7788
   EMail: chowdury@nortelnetworks.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














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Internet-Draft                                                 July 2004


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   Internet Society.




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