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Versions: 00                                                            
Internet Engineering Task Force                        Lachu Aravamudhan
INTERNET-DRAFT                                           Mark R. O`Brien
<draft-ietf-mobileip-nai-wn-00.txt>                      Basavaraj Patil
Date:    February 1999                                   Nortel Networks
Expires: July 1999


                  NAI Resolution for Wireless Networks




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

     RFC 2468 [1] defines the need of a standardized format for
     identifying ISP subscribers for dial-up roaming operations. It
     introduced the Network Access Identifier (NAI) to fulfill this
     need. The NAI is provided by the mobile node to the dialed ISP
     during PPP authentication.

     The ability to resolve an NAI for second and third generation
     cellular mobile nodes allow traditional cellular service providers
     to evolve their home cellular networks to provide cellular
     services, IP packet data services and so on with a single
     subscription using NAIs. Additionally, this allows cellular
     provider to evolve their networks to be IP based.

     Second and third generation cellular mobile nodes must perform a
     registration and authentication process with their wireless service
     provider before the mobile node user may initiate other operations
     (See [1] for examples). These mobile nodes do not support the
     programming of an NAI nor does the cellular registration message
     support the transfer of an NAI to the wireless access network. For
     example, North American cellular networks (e.g. AMPS, TDMA, CDMA)
     service mobile nodes that register with a Mobile Identification
     Number (MIN). The MIN is then associated with a cellular
     subscriber. For the same reasons stated in [1], it would be
     convenient if an option was available to provide the wireless
     subscriber identification in the form of an NAI during the wireless
     registration and authentication process. This draft proposes a
     solution to resolve NAIs from traditional mobile node identifiers.

1.  Introduction

     RFC 2468 [1] defines the need of a standardized format for
     identifying ISP subscribers for dial-up roaming operations. It
     introduced the Network Access Identifier (NAI) to fulfill this
     need. The NAI is provided by the mobile node to the dialed ISP
     during PPP authentication.

     The ability to resolve an NAI for second and third generation
     cellular mobile nodes allow traditional cellular service providers
     to evolve their home cellular networks to provide cellular
     services, IP packet data services and so on with a single
     subscription using NAIs. Additionally, this allows cellular
     provider to evolve their networks to be IP based.

     Second and third generation cellular mobile nodes must perform a
     registration and authentication process with their wireless service
     provider before the mobile node user may initiate other operations
     (See [1] for examples). These mobile nodes do not support the
     programming of an NAI nor does the cellular registration message
     support the transfer of an NAI to the wireless access network. For
     example, North American cellular networks (e.g. AMPS, TDMA, CDMA)
     service mobile nodes that register with a Mobile Identification
     Number (MIN). The MIN is then associated with a cellular
     subscriber. For the same reasons stated in [1], it would be
     convenient if an option was available to provide the wireless
     subscriber identification in the form of an NAI during the wireless
     registration and authentication process. This draft proposes a
     solution to resolve NAIs from traditional mobile node identifiers.




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Internet-Draft    NAI Resolution for Wireless Networks     February 1999


     Consider the following scenario to illustrate the NAI resolution
     required to register and authenticate wireless mobile nodes with
     their wireless service provider:

     NAI enabled Wireless Service Provider owns the cellular service for
     Subscriber A (SUB A).


     ------------  ------------  ----------------
     |   SUB A  |  |          |  |              |
     | Cellular |  | Wireless |  | NAI Enabled  |
     |  Mobile  |  | Access   |  | Wireless Home|
     |   Node   |  | Network  |  |   Network    |
     ------------  ------------  ----------------

         |              |               |        event
         |)))))))))))))>|               |          a
         |              |-------------->|          b
         |              |<--------------|          c
         |<(((((((((((((|               |          d
         |              |               |


     a    SUB A powers-on his second or third generation cellular mobile
          node. The act of powering on causes the cellular mobile mode
          to attempt a wireless registration. The registration message
          identifies the mobile node by its MIN.

     b    The wireless access network receives the wireless registration
          message and resolves an NAI based on the MIN sent by the
          cellular mobile node. The wireless access network sends an
          appropriate registration message to its NAI enabled home
          network.

     c    The NAI enabled home network registers and authenticates
          wireless SUB A and sends an appropriate registration response
          back to the wireless access network.

     d    The wireless access network receives the registration response
          from its home network and sends an appropriate wireless
          registration return result to SUB A`s cellular mobile node.




2.  Terminology

     This document uses the following terminology:



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     MIN       Mobile Identification Number: A 10-digit number assigned
               to the mobile station.


3.  Specification Language

     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 [2].


4.  NAI Resolution

     There are many alternatives to resolve an NAI. The intent of
     defining this draft is to stimulate discussion on the merits of
     resolving NAIs from second and third generation wireless mobile
     nodes. One method is presented herein.

     The NAI is of the form user@realm. At the wireless access provider,
     using the wireless registration information, a temporary NAI may be
     constructed of the form <MIN>@realm. The IP address corresponding
     to the realm may then be resolved through DNS or other appropriate
     mechanisms. That resolution should return the IP address of the
     realm (i.e. the Service Provider owning the subscriber's wireless
     service). The temporary NAI, <MIN>@realm, should then be supplied
     in the registration message to the wireless service provider
     identified by that IP address. The wireless service provider should
     receive the registration message and may decode the "user"
     component of the temporary NAI to lookup the subscriber's NAI if it
     is, in fact, different from the temporary NAI.

     For example, suppose a cellular mobile node sends a registration
     message to the wireless access network with a MIN of 9726841000. A
     table resident at wireless access network may be populated with a
     range of MINs covered by each entry. In this example, each range
     specifies only the most significant 6 digits and implicitly
     includes all subscriber numbers (last 4 digits) within the range:

        MIN RANGE            REALM
     214790 - 214799    abc_company.net
     972680 - 972689    def_company.net
     972700 - 972730    hij_company.net


     In this case "def_company.net" is the ISP for the 9726841000 MIN.
     The resulting temporary NAI to use for IP address resolution and
     for routing of registration messages over the Internet would be:
     9726841000@def_company.net.



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Internet-Draft    NAI Resolution for Wireless Networks     February 1999


     Table lookups such as these have been widely used in cellular
     networks since the subscriber/terminal identifiers are: numeric, a
     maximum of 15 digits, and the leading digits typically defined a
     geographical region to facilitate routing. Further, ranges of
     subscriber/terminal identifications were assigned in blocks to
     service providers in each regions. As shown in the table,
     def_company.net is assigned all of the subscriber numbers from
     exchanges 680 though 689 inclusive. This facilitated scalability by
     alleviating access providers from a requirement of enumerating each
     MIN in their tables.

     NOTE:     The interface from the wireless access network to the
               wireless service provider network should use protocols
               produced by the IETF and is outside of the scope of this
               document. With the exception of the derivation of an NAI
               from a MIN, the means by which a cellular registration or
               authentication message is converted by the wireless
               access network to the relevant IETF protocol message(s)
               is outside the scope of this document.
































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Internet-Draft    NAI Resolution for Wireless Networks     February 1999


5.  References


     [1]  Aboba B., Beadles M., "Network Access Identifier" RFC 2486,
          January 1999.

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



6.  Acknowledgments

     The authors would like to thank Emad Qaddoura, Scott Skraboly, Russ
     Coffin and Rambabu Tummala of Nortel Networks for their review and
     valuable input.



7.  Authors' Addresses

     Lachu Aravamudhan
     Nortel Networks Inc.
     2201 Lakeside Blvd.
     Richardson, TX.  75082-4399

     Phone: 972-684-4855
     email: lachu@nortelnetworks.com


     Mark O'Brien
     Nortel Networks Inc.
     2201 Lakeside Blvd.
     Richardson, TX.  75082-4399

     Phone: 972-684-5164
     email: markob@nortelnetworks.com














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