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Errata Exist
Network Working Group                                           A. Patel
Request for Comments: 4283                                      K. Leung
Category: Standards Track                                  Cisco Systems
                                                               M. Khalil
                                                               H. Akhtar
                                                         Nortel Networks
                                                            K. Chowdhury
                                                        Starent Networks
                                                           November 2005

         Mobile Node Identifier Option for Mobile IPv6 (MIPv6)

Status of This Memo

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

Copyright Notice

   Copyright (C) The Internet Society (2005).


   Mobile IPv6 (MIPv6) defines a new Mobility header that is used by
   mobile nodes, correspondent nodes, and home agents in all messaging
   related to the creation and management of bindings.  Mobile IPv6
   nodes need the capability to identify themselves using an identity
   other than the default home IP address.  Some examples of identifiers
   include Network Access Identifier (NAI), Fully Qualified Domain Name
   (FQDN), International Mobile Station Identifier (IMSI), and Mobile
   Subscriber Number (MSISDN).  This document defines a new mobility
   option that can be used by Mobile IPv6 entities to identify
   themselves in messages containing a mobility header.

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RFC 4283        Mobile Node Identifier Option for MIPv6    November 2005

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................3
   3. Mobile Node Identifier Option ...................................3
      3.1. MN-NAI Mobility Option .....................................4
      3.2. Processing Considerations ..................................4
   4. Security Considerations .........................................4
      4.1. General Considerations .....................................4
      4.2. MN-NAI Considerations ......................................4
   5. IANA Considerations .............................................5
   6. Acknowledgements ................................................5
   7. Normative References ............................................5
   8. Informative Reference ...........................................6

1.  Introduction

   The base specification of Mobile IPv6 [RFC3775] identifies mobility
   entities using an IPv6 address.  It is essential to have a mechanism
   wherein mobility entities can be identified using other identifiers
   (for example, a Network Access Identifier (NAI) [RFC4282],
   International Mobile Station Identifier (IMSI), or an application/
   deployment specific opaque identifier).

   The capability to identify a mobility entity via identifiers other
   than the IPv6 address can be leveraged for performing various
   functions, for example,

   o  authentication and authorization using an existing AAA
      (Authentication, Authorization, and Accounting) infrastructure or
      via an HLR/AuC (Home Location Register/Authentication Center)

   o  dynamic allocation of a mobility anchor point

   o  dynamic allocation of a home address

   This document defines an option with a subtype number that denotes a
   specific type of identifier.  One instance of subtype, the NAI, is
   defined in Section 3.1.  It is anticipated that other identifiers
   will be defined for use in the mobility header in the future.

   This option SHOULD be used when Internet Key Exchange (IKE)/IPsec is
   not used for protecting binding updates or binding acknowledgements
   as specified in [RFC3775].  It is typically used with the
   authentication option [RFC4285].  But this option may be used
   independently.  For example, the identifier can provide accounting
   and billing services.

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RFC 4283        Mobile Node Identifier Option for MIPv6    November 2005

2.  Terminology

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

3.  Mobile Node Identifier Option

   The Mobile Node Identifier option is a new optional data field that
   is carried in the Mobile IPv6-defined messages that includes the
   Mobility header.  Various forms of identifiers can be used to
   identify a Mobile Node (MN).  Two examples are a Network Access
   Identifier (NAI) [RFC4282] and an opaque identifier applicable to a
   particular application.  The Subtype field in the option defines the
   specific type of identifier.

   This option can be used in mobility messages containing a mobility
   header.  The subtype field in the option is used to interpret the
   specific type of identifier.

       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
                                       |  Option Type  | Option Length |
       |  Subtype      |          Identifier ...

      Option Type:

         MN-ID-OPTION-TYPE has been assigned value 8 by the IANA.  It is
         an  8-bit identifier of the type mobility option.

      Option Length:

         8-bit unsigned integer, representing the length in octets of
         the Subtype and Identifier fields.


         Subtype field defines the specific type of identifier included
         in the Identifier field.


         A variable length identifier of type, as specified by the
         Subtype field of this option.

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RFC 4283        Mobile Node Identifier Option for MIPv6    November 2005

   This option does not have any alignment requirements.

3.1.  MN-NAI Mobility Option

   The MN-NAI mobility option uses the general format of the Mobile Node
   Identifier option as defined in Section 3.  This option uses the
   subtype value of 1.  The MN-NAI mobility option is used to identify
   the mobile node.

   The MN-NAI mobility option uses an identifier of the form user@realm
   [RFC4282].  This option MUST be implemented by the entities
   implementing this specification.

3.2.  Processing Considerations

   The location of the MN Identifier option is as follows: When present,
   this option MUST appear before any authentication-related option in a
   message containing a Mobility header.

4.  Security Considerations

4.1.  General Considerations

   Mobile IPv6 already contains one mechanism for identifying mobile
   nodes, the Home Address option [RFC3775].  As a result, the
   vulnerabilities of the new option defined in this document are
   similar to those that already exist for Mobile IPv6.  In particular,
   the use of a permanent, stable identifier may compromise the privacy
   of the user, making it possible to track a particular device or user
   as it moves through different locations.

4.2.  MN-NAI Considerations

   Since the Mobile Node Identifier option described in Section 3
   reveals the home affiliation of a user, it may assist an attacker in
   determining the identity of the user, help the attacker in targeting
   specific victims, or assist in further probing of the username space.

   These vulnerabilities can be addressed through various mechanisms,
   such as those discussed below:

   o  Encrypting traffic at the link layer, such that other users on the
      same link do not see the identifiers.  This mechanism does not
      help against attackers on the rest of the path between the mobile
      node and its home agent.

   o  Encrypting the whole packet, such as when using IPsec to protect
      the communications with the home agent [RFC3776].

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RFC 4283        Mobile Node Identifier Option for MIPv6    November 2005

   o  Using an authentication mechanism that enables the use of privacy
      NAIs [RFC4282] or temporary, changing "pseudonyms" as identifiers.

   In any case, it should be noted that as the identifier option is only
   needed on the first registration at the home agent and subsequent
   registrations can use the home address, the window of privacy
   vulnerability in this document is reduced as compared to [RFC3775].
   In addition, this document is a part of a solution to allow dynamic
   home addresses to be used.  This is an improvement to privacy as
   well, and it affects both communications with the home agent and the
   correspondent nodes, both of which have to be told the home address.

5.  IANA Considerations

   The values for new mobility options must be assigned from the Mobile
   IPv6 [RFC3775] numbering space.

   The IANA has assigned the value 8 for the MN-ID-OPTION-TYPE.

   In addition, IANA has created a new namespace for the subtype field
   of the Mobile Node Identifier option.  The currently allocated values
   are as follows:

   NAI (defined in [RFC4282]).

   New values for this namespace can be allocated using Standards Action

6.  Acknowledgements

   The authors would like to thank Basavaraj Patil for his review and
   suggestions on this document.  Thanks to Jari Arkko for review and
   suggestions regarding security considerations and various other
   aspects of the document.

7.  Normative References

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

   [RFC2434]    Narten, T. and H. Alvestrand, "Guidelines for Writing an
                IANA Considerations Section in RFCs", BCP 26, RFC 2434,
                October 1998.

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

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RFC 4283        Mobile Node Identifier Option for MIPv6    November 2005

   [RFC3776]    Arkko, J., Devarapalli, V., and F. Dupont, "Using IPsec
                to Protect Mobile IPv6 Signaling Between Mobile Nodes
                and Home Agents", RFC 3776, June 2004.

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

8.  Informative Reference

   [RFC4285]    Patel, A., Leung, K., Khalil, M., Akhtar, H., and K.
                Chowdhury, "Authentication Protocol for Mobile IPv6",
                RFC 4285, November 2005.

Authors' Addresses

   Alpesh Patel
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134

   Phone: +1 408-853-9580
   EMail: alpesh@cisco.com

   Kent Leung
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134

   Phone: +1 408-526-5030
   EMail: kleung@cisco.com

   Mohamed Khalil
   Nortel Networks
   2221 Lakeside Blvd.
   Richardson, TX  75082

   Phone: +1 972-685-0574
   EMail: mkhalil@nortel.com

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RFC 4283        Mobile Node Identifier Option for MIPv6    November 2005

   Haseeb Akhtar
   Nortel Networks
   2221 Lakeside Blvd.
   Richardson, TX  75082

   Phone: +1 972-684-4732
   EMail: haseebak@nortel.com

   Kuntal Chowdhury
   Starent Networks
   30 International Place
   Tewksbury, MA  01876

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

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RFC 4283        Mobile Node Identifier Option for MIPv6    November 2005

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