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Versions: 00                                                            
IETF Mobile IPv6 Working Group
Internet Draft                                               H. Ohnishi
Expires: August 2004                                         M.Yanagiya
                                                                    NTT
                                                                 Y.Ohba
                                                                Toshiba
                                                          February 2004


                    Mobile IPv6 AAA Problem Statement
             <draft-ohnishi-mip6-aaa-problem-statement-00.txt>


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
        http://www.ietf.org/ietf/1id-abstracts.txt
   The list of Internet-Draft Shadow Directories can be accessed at
        http://www.ietf.org/shadow.html.


Abstract

   Mobile IP achieves that Mobile Node(MN) moves from one subnet to
   another. If MN moves across different administrative domains in a
   commercial network, Mobile IPv6 requires AAA's support. This document
   describes the problem statement to use AAA functions in Mobile IPv6.


Conventions used in this document

   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 RFC-2119 [i].






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              MIPv6 AAA problem statement       February 2004

Table of Contents

   1. Introduction...................................................2
   2. AAA usage scenario for Mobile IPv6.............................3
      2.1 Roaming to foreign domain..................................3
      2.2 Dynamic home address prefix assignment via AAA.............3
      2.3 Dynamic HA address assignment via AAA......................3
      2.4 Bootstrapping Mobile IPv6 SA from AAA......................3
   3. Problem Statement..............................................4
   4. Mobile IPv4 AAA solution (informative).........................4
   5. Security Consideration.........................................5
   Reference.........................................................6
   Acknowledgments...................................................6
   Author's Addresses................................................7


1. Introduction

   Mobile IP(v4/v6) [RFC3344][I-D.ietf-mobileip-ipv6] achieves that
   Mobile Node (MN) moves from one subnet to another.  If MN moves
   across different administrative domains where authentication,
   authorization and accounting (AAA) is always an issue especially in
   commercial-based deployments.  Mobile IPv4 already defines an
   interface to AAA functionality [I-D.ietf-mip4-rfc3012bis]
   [I-D.ietf-aaa-diameter-mobileip] [I-D.ietf-mip4-aaa-nai].  Mobile
   IPv6 requires an interface to AAA as well.  However such an interface
   has been a missing piece that needs to be filled with an appropriate
   solution.

   This document describes several usage cases that deemed necessary to
   support when Mobile IPv6 is used in an environment where the users
   subscribe to commercial Mobile IPv6 services with credentials
   (username, password, certificate, etc.) that are used by the
   operators as the basis to perform the task of AAA for the Mobile IPv6
   services.
   The usage cases are described in terms of service bootstrapping and
   security, both are important in large-scale deployments.  This
   document then addresses the fundamental issue that needs to be taken
   into account when designing an interface between AAA and Mobile IPv6.
   This document also contains informative description on the approach
   which is taken by Mobile IPv4 to support AAA, however, it should be
   noted that the informative description is not advocating or
   recommending the same approach adopted to Mobile IPv4 to be used for
   Mobile IPv6.

   For more information related to IPv6 address assignment in
   3GPP, it is recommended to read [RFC3314].





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              MIPv6 AAA problem statement       February 2004

2. AAA usage scenario for Mobile IPv6

   In this section, we show some application that we are going to solve
   by using AAA function. 2.1 shows the application to authenticate an
   MN when the MN accesses to the visiting network. From 2.2 to 2.4
   shows service bootstrapping scenarios. Operators may choose a
   combination of scenarios from these for their services.


2.1 Roaming to foreign domain

   Mobile IPv6 supports MN's mobility. But if MN moves to a foreign
   domain, the foreign domain requires the way of Authentication,
   Authorization and Accounting. RFC2977 shows requirements for this
   scheme.  RFC2977 shows  the applications of AAA to the Mobile IP, e.g.
   the basic model, the local payment model, the local home agent model
   and so on.


2.2 Dynamic home address prefix assignment via AAA

   In some cases, operators want to assign home address prefix to mobile
   node dynamically for the purpose of reducing management cost, etc.
   Mobile IPv6 prescribes Mobile Prefix Solicitation(MPS) and Mobile
   Prefix Advertisement(MPA). But in this method, MN needs to know HA
   address previously. A solution for dynamically and securely assigning
   home address prefix to mobile node with involving an appropriate
   authentication and authorization protocol is demanded.


2.3 Dynamic HA address assignment via AAA

   In some cases, operators want to assign HA to the MN dynamically from
   the perspective of load balancing.  Mobile IPv6 prescribes dynamic HA
   allocation mechanism in which it sends anycast address to find HA and
   the HA sends back HAs' list to the MN.  HA sends this list without
   authenticating the MN.   A solution for dynamically and securely
   assigning HA's address to mobile node with involving an appropriate
   authentication and authorization protocol is demanded.


2.4 Bootstrapping Mobile IPv6 SA from AAA

   Mobile IPv6 [I-D.ietf-mobileip-ipv6] requires an IPsec SA (Security
   Association) established between mobile node and its home agent to
   protect Binding Updates to the home agent.  This SA is referred to as
   Mobile IPv6 SA(MSA).  When a home agent is dynamically allocated, it
   is difficult to assume pre-established security association (such as
   an IKE [RFC2409] pre-shared secret) between the mobile node and every
   potential home agent, unless a trusted third-party is involved in the


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              MIPv6 AAA problem statement       February 2004

   authentication procedure between a mobile node and its home agent.
   Among several alternative models (e.g., Kerberos) that rely on a
   trusted third-party, there is demand for AAA-based solutions possibly
   with leveraging the EAP keying framework [I-D.ietf-eap-keying] which
   allows the key material generated by an EAP authentication algorithm
   to turn into a credential needed for mutually authenticating mobile
   node and home agent in the IPsec key management protocol.


3. Problem Statement

   In Mobile IPv4, AAA for network access service and AAA for Mobile
   IPv4 service are integrated for optimization purpose.  These two
   types of AAA are different in functionality
   [I-D.ietf-pana-usage-scenarios], and such an integration is possible
   in the architecture where an agent that acts as an AAA attendant for
   both types of AAA is placed in the visiting network.  In the case of
   Mobile IPv4, mobility agent itself (i.e., FA) is such an integrated
   agent.

   In Mobile IPv6 architecture, there is no FA unlike Mobile IPv4. The
   fundamental problem that needs to be solved is to support the usage
   cases described in Section 2 without introducing FA in Mobile IPv6.
   This would lead to a need to define a MIPv6 Service Aware AAA
   Attendant (MSAAA), which is an AAA attendant to provide AAA for
   Mobile IPv6 service for MN.  The MSAAA may be integrated with an AAA
   attendant of other protocol or service, or may be integrated with
   MIPv6 home agent, depending on Mobile IPv6 service models.  The
   protocol to transfer information between HA and AAA server is needed
   in every above MSAAA deployment scenarios.


4. Mobile IPv4 AAA solution (informative)

   Mobile IPv4 defines two different registration procedures, one via
   foreign agent that relays the registration to mobile node's home
   agent, and the other directly with the mobile node's home agent. Both
   registration procedures involve the exchange of Registration Request
   and Registration Reply messages. In order to prevent spoofing, Mobile
   IPv4 defines authentication extension in Registration Request and
   Reply message [RFC3344]. MN sends Registration Request with
   authentication extension which includes authenticator to FA or HA. FA
   or HA evaluates the authenticator by using shared key or
   public/private key pair. In a large scale roaming service network
   such as public wireless LAN access service network, it is difficult
   to distribute all key material to FA and/or HA. Thus, AAA
   architecture is used to manage key materials of MNs or/and verify
   credential. Fig 1 shows an example of sequence using RADIUS. It is
   assumed that MN does not have a security association with FA. MN
   sends Registration Request which includes challenge value and Network


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              MIPv6 AAA problem statement       February 2004

   Access Identifier (NAI). According to NAI, FA makes a decision on AAA
   message routing, and passes the authenticator to AAA server. AAA
   server verifies the authenticator and sends authentication reply. If
   an authentication is success, FA sends Agent Reply to MN.

   MN                         FA                    AAA
    |Agent Advertisement   |                         |
    |[Challenge ext.]      |                         |
    |<---------------------|                         |
    |Registration Request  |                         |
    |[MN-FA Challenge Ext.,|                         |
    | MN-HA Auth. ext.,    |                         |
    | MN-AAA Auth. ext.,   |                         |
    | NAI. ext.]           |                         |
    |--------------------->|                         |
    |                      |Authentication Request   |
    |                      |--------------------->   |
    |                      |                         |
    |                      |Authentication Reply     |
    |                      |<---------------------   |
    |Registration Reply    |                         |
    |(registration accept) |                         |
    |<-------------------- |                         |
    |                      |                         |

   Figure 1: MN-FA authentication with AAA in Mobile IPv4

   In [I-D.ietf-aaa-diameter-mobileip], a similar method is specified by
   using Diameter application. MN sends Registration Request to FA. FA
   invokes the local AAA infrastructure (AAAF) to request that a mobile
   node be authenticated. If AAAF is not aware of the identity of MN,
   AAAF will forward authentication data to home AAA server (AAAH).


5. Security Consideration

   This draft identifies a need for bootstrapping Mobile IPv6 by
   leveraging the AAA infrastructure.  Although any solution is not
   specified in this document, a AAA-based solution for dynamically
   assigning Mobile IPv6 home agent address is expected to improve
   Mobile IPv6 security by not relying on the anycast-based scheme built
   in Mobile IPv6 but relying on the AAA infrastructure instead.  More
   security analysis on bootstrapping MSA should be made when designing
   a solution.  Although security consideration section of
   [I-D.ietf-eap-keying] covers general security issues for EAP-based
   service bootstrapping, there may be Mobile IPv6 specific security
   issues in bootstrapping MSA.





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              MIPv6 AAA problem statement       February 2004

Reference


   [RFC3344] C. Perkins, "IP Mobility Support", RFC 3344, August 2002.

   [I-D.ietf-mobileip-ipv6] Johnson, D., "Mobility Support in IPv6",
   draft-ietf-mobileip-ipv6-24.txt, (work in progress), June 30 2003.

   [I-D.ietf-mip4-rfc3012bis] C. Perkins, et al., "Mobile IPv4
   Challenge/Response Extensions (revised)",
   draft-ietf-mip4-rfc3012bis-00.txt (work in progress), 7 October 2003.

   [I-D.ietf-aaa-diameter-mobileip] P. Calhoun, et al., "Diameter Mobile
   IP Application", draft-ietf-aaa-diameter-mobileip-15.txt (work in
   progress), November 2003.

   [I-D.ietf-mip4-aaa-nai] F. Johansson and T. Johansson, "Mobile IPv4
   Extension for carrying Network Access Identifiers",
   draft-ietf-mip4-aaa-nai-02.txt (work in progress), December 12, 2003

   [RFC3314] M. Wasserman, "Recommendations for IPv6 in Third Generation
   Partnership Project (3GPP) Standards", RFC 3314, September 2002.

   [I-D.ietf-pana-usage-scenarios] Y. Ohba, et al., "Problem Statement
   and Usage Scenarios for PANA", draft-ietf-pana-usage-scenarios-06.txt
   (work in progress), April 28, 2003.

   [RFC2977] S. Glass, et al.,"Mobile IP Authentication, Authorization,
      and Accounting Requirements", RFC 2977, October 2000

   [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
   (IKE)", RFC 2409, November 1998.

   [I-D.ietf-eap-keying] Aboba, B., "EAP Key Management Framework",
   draft-ietf-eap-keying-01 (work in progress), October 2003.

   [I-D.ietf-ipsec-ikev2] Kaufman, C., "Internet Key Exchange (IKEv2)
   Protocol", draft-ietf-ipsec-ikev2-12 (work in progress), January 2004.


Acknowledgments

   We would like to thank Alper Yegin and Rafa Marin Lopez for their
   valuable contributions to the discussions and preparation of this
   document.

   We also would like to thank Basavaraj Patil and Gopal Dommety for
   their encouraging us to submit this document.




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              MIPv6 AAA problem statement       February 2004


Author's Addresses

   Hiroyuki Ohnishi
   NTT Network service systems laboratories, NTT Corporation
   9-11, Midori-Cho, 3-Chome
   Musashino-Shi, Tokyo 180-8585
   Japan
   Phone: +81 422 59 4132
   Email: ohnishi.hiroyuki@lab.ntt.co.jp


   Mayumi Yanagiya
   NTT Network service systems laboratories, NTT Corporation
   9-11, Midori-Cho, 3-Chome
   Musashino-Shi, Tokyo 180-8585
   Japan
   Phone: +81 422 59 6783
   Email: yanagiya.mayumi @lab.ntt.co.jp


   Yoshihiro Ohba
   Toshiba America Information Systems, Inc.
   9740 Irvine Blvd.
   Irvine, CA  92619-1697
   USA
   Phone: +1 973 829 5174
   EMail: yohba@tari.toshiba.com
























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