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Versions: 00 01 02 03 04 05 06 07 08 09                                 
INTERNET DRAFT                                             Pat R. Calhoun
Category: Standards Track                              Gabriel Montenegro
Title: draft-ietf-mobileip-reg-tunnel-00.txt           Charles E. Perkins
Date: November 1998                                Sun Laboratories, Inc.



                Mobile IP Regionalized Tunnel Management



Status of this Memo

   This document is a submission by the Mobile IP Working Group of the
   Internet Engineering Task Force (IETF).  Comments should be submitted
   to the mobile-ip@smallworks.com mailing list.

   Distribution of this memo is unlimited.

   This document is an Internet-Draft.  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.''

   To view the entire list of current Internet-Drafts, please check the
   ``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow
   Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern
   Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific
   Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast).


Abstract

   RFC2002 defines a method for a Mobile Node to be assigned a Home
   Agent dynamically through the use of a limited broadcast message.
   However, most corporate networks do not allow such packets to
   traverse through their firewall, which renders this feature difficult
   to use. This draft introduces new entity named the Home Domain
   Allocation Agency (HDAA) that can dynamically assign a Home Address
   to the Mobile Node. This draft also proposes a method for the HDAA to
   assign a dynamic Home Agent to the Mobile Node.





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Table of Contents

      1.0  Introduction
      2.0  Router Discovery Extensions
            2.1  PFA IP Address
      3.0  Mobile IP Registration Extensions
            3.1  Hierarchical Mobility Agent Extension
      4.0  Security Considerations
      5.0  References
      6.0  Acknowledgements
      7.0  Chairs' Addresses
      8.0  Author's Address


1.0 Introduction

   RFC2002 [2] assumes that the Foreign Agent and the Home Agent
   interact directly during the registration process. This assumption
   creates two problems; first the Mobility Agents can not exist on a
   private networks and this does not allow for efficient smooth hand-
   off of the Mobile Node between Foreign Agents.

                   +------------------------------------+
                   |      Private Foreign Network       |
                   | +------+   +------+      +-------+ |
                   | |  MN  |---|  FA  |------|  PFA  | |
                   | +------+   +------+      +---+---+ |
                   |                              |     |
                   +------------------------------|-----+
                                          +-------|--------+
                                          |       |        |
                                          | Public Network |
                                          |       |        |
                                          +-------|--------+
                                                  |
                   +------------------------------|-----+
                   |       Private Home Network   |     |
                   |            +------+      +---+---+ |
                   |            |  HA  |------|  PHA  | |
                   |            +------+      +-------+ |
                   |                                    |
                   +------------------------------------+

                      Figure 1: Proxy Mobility Agents

   The figure above depicts the Foreign Agent and the Home Agent on a
   private network. The Proxy Foreign Agent (PFA) and the Proxy Home
   Agent (PHA) each have one routable address that is accessible from



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   the public network and one address that resides on the private
   network. In order to reach either the FA or the HA from the public
   network, the request must be sent through the appropriate Proxy Agent
   (PA). In this figure the PHA can be viewed as the HDAA as described
   in [4] and [5].

   Note that although the figure only shows one level of hierarchy, this
   document does not limit the number. It is possible for a complex
   network to contain many levels before reaching the Proxy Agent.

   The Mobile IP Challenge Draft [5] describes smooth hand-off and how
   the short-lived session keys are transferred from one Foreign Agent
   to another within a given Administrative Domain. When using
   regionalized tunnels, the Foreign Agent's session key generated by
   the HDAA belongs to the PFA since this is the only known Mobility
   Agent to the HDAA. Since the session key is owned by the PFA, the
   Mobility Agent can move from one Foreign Agent to another within the
   same foreign network without having to redistribute the session keys.
   This of course assumes that all of the foreign agents share some form
   of security association.

   We will describe the message flow of the Mobile Node's registration
   as shown in figure 1. The Foreign Agent announces his presences via
   the Router Advertisement message, which includes the PFA's publicly
   routable address in the PFA IP Address extension as describe in
   section 2.1. Upon receipt of this message the Mobile Node must
   determine whether to use the FA or the PFA address. The Router
   Advertisement also MUST include the FA's NAI [5], which is used by
   the Mobile Node to determine if it is on its home or a foreign
   network. If the Mobile Network determines that it is visiting a
   foreign network, it MUST use the PFA's IP Address in the care-of-
   address field of the Registration Request.

   The Mobile Node must then register with the Home Domain, and since it
   had determined that it was visiting it MUST use its configured PHA
   address in the Registration Request's Home Agent field. The message
   is then forwarded to the Foreign Agent, which adds a Hierarchical
   Mobility Agent Extension to the message and forwads the request to
   the PFA. The PFA must authenticate the message in the Mobile-Foreign
   Authentication extension (if present). If the Hierarchical Mobility
   Agent extension is present, the PFA must retain the Mobile Node's
   current point of attachment and remove the extension from the
   request. The PFA then adds the Foreign-Home Authentication extension
   to the request and forwards the request to the PHA.

   The PHA must authenticate the request from the PFA and determine the
   Mobile Node's true Home Agent within the private network. This can be
   statically configured on the PHA, or this can be retrieved from an



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   Authentication, Authorization and Accounting protocol such as [6].
   The PHA then adds the Hierarchical Mobility Agent extension to the
   Registration Request and forward the request to the Home Agent. The
   Home Agent uses the Hierarchical Mobility Agent extension to find the
   next Mobility Agent to use in order to contact the Mobile Node. The
   Registration Request is processed by the Home Agent as desribed in
   [2] and the Registration Reply is forwarded to the PHA. The PHA adds
   the necessary Foreign-Home Authentication extension and forwards the
   request to the PFA.

   The PFA then authenticates the packet and must find the Foreign Agent
   within its network to use in order that is serving the Mobile Node.
   It uses the information that was in the Hierarchical Mobility Agent
   extension of the Registration Request, which it had cached. The PFA
   removes the Foreign-Home Authentication extension and forwards the
   reply to the Foreign Agent, which hands it off to the Mobile Node.

   In the event that the Mobile Node moves to another Foreign Agent
   within the same foreign domain, the Mobile Node issues another
   Registration Request (similar to the one previously described). The
   Foreign Agent will forward this request to the PFA, which will update
   the Mobile Node's current point of attachment through the
   Hierarchical Mobility Agent extension. The PFA can then issue a
   Registration Reply directly to the Mobile Node through the Foreign
   Agent.


2.0  Router Discovery Extensions

   This section will define the extensions necessary to the Router
   Discovery Protocol [7]. The Mobile Node can assume that the Foreign
   Agent supports this specification if the extensions in this section
   are part of the Router Advertisements.


2.1  PFA IP Address

   The PFA IP Address Extension is present in the Router Advertisements
   by the Foreign Agent in order to provide the Mobile Node with the
   publicly routable address for the Proxy Foreign Agent. The Mobile
   Node MUST use this address as the care-of-address in the Registration
   Request if the Foreign Agent does not belong to the same
   administrative domain. This is known by comparing the domain in the
   Foreign Agent's NAI [5] with the Mobile Node's NAI.

   The PFA IP Address Extension is defined as follows:





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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |     Length    |        PFA IP Address ....
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               PFA IP Address         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      TDB

   Length

      4

   PFA IP Address

      The PFA IP Address field contains the Foreign Domains' Proxy
      Foreign Agent's publicly routable address.


3.0  Mobile IP Registration Extensions

   This section will define new Mobile IP Registration Extensions that
   must be used in order to use the functionality described in this
   document.


3.1  Hierarchical Mobility Agent Extension

   One or more Hierarchical Mobility Agent Extension MAY be present  in
   a Registration  Request  or Reply. If more than one Hierarchical
   Mobility Agent Extension is present, the order  of  these  extensions
   MUST  be maintained through the hierarchy.

   When replying with a Registration Reply, the Home  Agent  MUST
   ensure that  the  order  of  the  Hierarchical Mobility Agent
   extensions are reversed from the order found in the Registration
   Request.

   If the Hierarchical Mobility Agent Extension is present in the
   Request, Each  foreign  agent  MUST  check  to  make  sure  that its
   address is Included in the list of tunnel agents. If not, it rejects
   the  Request with a status code of 70.

   Otherwise, the foreign agent makes note of the  address  of  the
   next lower-level  tunnel  agent,  for  future  association  with the
   mobile node's network address.




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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    |       MA IP Address ....
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              MA IP Address ....      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type

      TDB

   Length

      4

   MA IP Address

      The IP Address of the Mobility Agent in the hierarchy.


4.0 Security Considerations

   This document proposes methods for Mobility Agents on private
   networks to communicate with other agents on public or private
   networks. It assumes that any security authentication extensions used
   are defined either in [2] or [5].


5.0 References

   [1] P. Calhoun, G. Montenegro, C. Perkins, "Tunnel Establishment
       Protocol", draft-ietf-mobileip-calhoun-tep-01.txt,
       Work in Progress, March 1998.

   [2] C. Perkins, Editor.  IP Mobility Support.  RFC 2002, October
       1996.

   [3] B. Aboba. "The Network Access Identifier." Internet-Draft,
       Work in Progress, August 1997.

   [4] P. Calhoun, C. Perkins, "DIAMETER Dynamic Home Address
   Allocation",
       draft-ietf-mobileip-home-addr-alloc-00.txt, Work in Progress,
       November 1998.

   [5] P. Calhoun, C. Perkins, "DIAMETER Challenge Extension",
       draft-ietf-mobileip-challenge-00.txt, Work in Progress,



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       November 1998.

   [6] P. Calhoun, C. Perkins, "DIAMETER Mobile IP Extension",
       draft-calhoun-diameter-mobileip-00.txt, July 1998.

   [7] Deering, S., Editor, "ICMP Router Discovery Messages",
       RFC 1256, September 1991.


6.0  Acknowledgements

The author would like to thank Vipul Gupta for useful discussions.


7.0  Chairs' Addresses

   The working group can be contacted via the current chairs:

      Jim Solomon
      RedBack Networks
      1389 Moffett Park Drive
      Sunnyvale, CA  94089-1134
      USA

      Phone:  +1 408 548-3583
      Fax:    +1 408 548-3599
      E-mail: solomon@rback.com

      Erik Nordmark
      Sun Microsystems, Inc.
      901 San Antonio Road
      Mailstop UMPK17-202
      Mountain View, California 94303

       Phone:  +1 650 786-5166
         Fax:  +1 650 786-5896
       E-Mail:  erik.nordmark@eng.sun.com


8.0 Author's Address

   Questions about this memo can be directed to:

      Pat R. Calhoun
      Network and Security Center
      Sun Microsystems Laboratories, Inc.
      15 Network Circle
      Menlo Park, California, 94025



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      USA

       Phone:  1-650-786-7733
         Fax:  1-650-786-6445
      E-mail:  pat.calhoun@eng.sun.com

      Gabriel E. Montenegro
      Network and Security Center
      Sun Microsystems Laboratories, Inc.
      15 Network Circle
      Menlo Park, California, 94025
      USA

       Phone:  1-650-786-6288
         Fax:  1-650-786-6445
      E-mail:  gabriel.montenegro@Eng.Sun.Com


      Charles E. Perkins
      Network and Security Center
      Sun Microsystems Laboratories, Inc.
      15 Network Circle
      Menlo Park, California, 94025
      USA

       Phone:  1-650-786-6464
         Fax:  1-650-786-6445
      E-mail:  charles.perkins@eng.sun.com























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