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Versions: 00 01 02 03 04 05 06                                          
Internet-Draft                                            Yoshihiro Ohba
Expires: July, 2002                                            Subir Das
                                                         Henry Haverinen
                                                         Basavaraj Patil
                                                            Phil Roberts
                                                          Hesham Soliman
                                                          Barani Subbiah


                                                        January 28, 2002


                          PANA Usage Scenarios

                <draft-ietf-pana-usage-scenarios-00.txt>


Status of This Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC 2026.

   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

   Many commercial networks today require users to provide their
   authentication information before being allowed access to network
   resources.  Resources could include basic access to the network or
   could be more specific services in the network or a certain grade of
   service, etc.  Currently, the authentication process depends upon the
   type of network that a user is attaching to and in most cases it is
   specific to an access technology.  Therefore, a common protocol for
   performing user authentication (which is independent of access
   technologies) at the network layer (IP) or above is deemed necessary.
   This document attempts to capture various such scenarios where a
   higher layer protocol, such as, PANA (Protocol for carrying
   Authentication for Network Access) would be appropriate.  The purpose
   of this draft is to help in understanding the problem space clearly,
   issues involved for different usage scenarios, and finally to
   facilitate the discussion for PANA requirements and framework.




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Table of Contents

   1         Introduction ............................................ 2
   1.1.      Requirements Language ................................... 2
   1.2.      Acronyms ................................................ 3
   1.3.      Terminology ............................................. 3
   2.        Current Mechanisms ...................................... 4
   3.        Scenarios Where PANA is Applicable ...................... 5
   3.1.      NAS ..................................................... 5
   3.1.1.    Layer Two Specific Network Access Mechanisms ............ 5
   3.1.2.    Multiple Access Routers ................................. 6
   3.1.3.    Multiple Interfaces on a Single Device .................. 8
   3.1.3.1.  Interface Switching ..................................... 8
   3.1.3.2.  Multi-homing ............................................ 9
   3.1.3.3.  Interface Sharing ....................................... 9
   3.2.      WLAN ................................................... 10
   3.3.      GPRS ................................................... 11
   3.4.      Intra-domain, Inter-technology Handoff ................. 11
   4.        LSA Usages ............................................. 12
   4.1.      Using LSA for Re-authentication ........................ 12
   4.2.      Using LSA for IKE ...................................... 12
   5.        Conclusion ............................................. 13
   6.        Acknowledgments ........................................ 13
   7.        References ............................................. 13
   8.        Authors' Information ................................... 14




1  Introduction

   Many commercial networks today require users to provide their
   authentication information before being allowed access to network
   resources. Resources could include basic access to the network or
   could be more specific services in the network or a certain grade of
   service (e.g., free vs. paid services), etc.  Although authentication
   process varies from network to network, current best practices are to
   perform the authentication at the link layer.  Since existing
   solutions are specific to access technologies, network providers need
   either a new transport mechanism or an extension to existing
   mechanism to authenticate users each time a new access technology is
   being standardized.  A common protocol designed at the network layer
   (IP) or above could solve this problem.

   This document attempts to capture various scenarios where a higher
   layer protocol, such as, PANA (Protocol for carrying Authentication
   for Network Access) would be appropriate.  The purpose of this draft
   is to help in understanding the problem space clearly, issues
   involved for different usage scenarios, and finally to facilitate the
   discussion for PANA requirements and framework.


1.1.  Requirements Language

   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 [Keywords].



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1.2.  Acronyms


   AAA: Authentication, Authorization and Accounting

   AP: Access Point

   AR: Access Router

   DSL: Digital Subscriber Line

   GPRS: General Packet Radio Service

   ISP: Internet Service Provider

   NAS: Network Access Server

   PPP: Point-to-Point Protocol

   RADIUS: Remote Authentication Dial In User Service

   SA: Security Association

   WISP: Wireless ISP

   WLAN: Wireless Local Area Network


1.3.  Terminology

   Following terminologies are defined for this document.

     Device

       A user's equipment (namely notebook computers, PDAs, etc.) that
       requires access to a provider's network.

     Local Network

       The immediate network(s) that is available to the device/user for
       Connecting. The network that the device is connecting to may be
       operated by anyone (not necessarily the users home network
       operator).


     PAA (PANA Authentication Agent)

       The functional element in the access network that a user device
       communicates with and provides it with the credentials used for
       authentication.  PAA MAY also have an interface to AAA backend
       infrastructures for authenticating the device/user or may use any
       other authentication mechanism.


     PANA (Protocol for carrying Authentication for Network Access)

       A protocol which is used for carrying authentication information



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       between a device (acting on behalf of a user) and a PAA in order
       for the device to be allowed to access the network.


     Credentials

       Information that is transferred or presented to establish either
       a claimed identity or the authorizations of a system entity
       [RFC2828].  Credentials include things such as, private keys,
       trusted roots, tickets, or the private part of a Personal
       Security Environment (PSE) [RFC3157,RFC2510].


     Initial Authentication

       Authentication performed by PAA when a device needs to be
       authenticated and authorized for network access.


     Re-authentication

       Authentication performed after successful initial authentication
       when a device needs to be authenticated again in order to extend
       the authorization lifetime for the network access.


     LSA (Local Security Association)

       A temporary security association between a device and a PAA,
       which is derived from a credential that is provided by the device
       on behalf of a user during initial authentication.


2.  Current Mechanisms


   Today's technologies mostly rely on access specific mechanisms.  For
   example, dial-up networks have relied on PPP's [RFC1661] capability
   to do user authentication in conjunction with AAA (RADIUS) [RFC2865]
   as a means to initial authentication.  However, PPP may not be
   appropriate for most new type of networks.  Moreover, node
   configuration through PPP is not always necessary.  Today's wireless
   networks, especially cellular networks, also have relied on specific
   layer 2 identifiers and layer 3 messaging (NOT IP) to accomplish user
   authentication.  Access control in most current technologies is
   performed on layer 2 based on device identification combined with
   layer 2 security.  As new type of networks (including wireless LANs)
   are deployed in hotspot areas the legacy mechanisms may not be
   appropriate in such scenarios.  Different kinds of service models are
   also emerging in today's Internet.  For example, while basic
   connectivity may be user-agnostic, enhanced services will be
   available only to authorized users (since charging is involved for
   such services).


   The following scenarios are described in the next section:




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         - NAS
         - WLAN
         - GPRS
         - Intra-domain, inter-technology handoff

3.  Scenarios Where PANA is Applicable


3.1.  NAS


   Basic NAS functionality includes authentication of users with an
   authentication server.  It has also hooks for access control.
   Although PPP offers these functionalities, it assumes few network
   characteristics:

   i) PPP always assumes a link layer disconnect indication.

      -- This feature is not available in networks such as Wireless LANs
         and others.  So there has to be some mechanism to detect when
         the client disconnects.  This might mean that there is also a
         need to re-authenticate client X to appear just after client A
         left, spoof the MAC and IP addresses of the client A, and
         basically continue to use client A's authenticated access.

   ii) Since PPP works in scenarios where dedicated links exist, it
       normally assumes a single access router in that link.


      -- However, this is not true in multi-access links, such as WLANs.
         Multiple ARs are required for efficient control and robustness.
         The multi-AR scenario is discussed in section 3.3.

   iii) PPP does address configuration to the client.

      -- Address configuration should be decoupled from AAA
         functionalities since in many cases devices may use other
         address configuration mechanisms such as DHCP, stateless
         address autoconfiguration, etc.



   In view of the above, we need a flexible NAS type of functionality.
   There are definitely architectural tradeoffs relating to the
   relationship between the PAA and the access control enforcement point
   in terms of their relative location (same box, or different box) as
   well as how close or far away from the client.  Also there may be a
   need for defining some rules or policies on how this will interwork
   with L2 authentication and access control mechanisms, such as 802.1X
   and cellular systems.


3.1.1.  Layer Two Specific Network Access Mechanisms

   WISPs are becoming prevalent and they are also starting Internet
   access services in public areas such as airports and hotel lobbies.
   The access control technologies they are currently considering would



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   be (i) web-based access control or (ii) L2 access control such as
   802.1X.  The web-based access control is performed at a higher layer
   after obtaining an IP address, whereas the L2 access control is
   performed before obtaining an IP address.  There are pros and cons as
   to which layer access control is performed.  However, a higher layer
   access control would be suitable for realizing user-agnostic network
   access services in which a user can access local information such as
   local-area map and flight information for free of charge, while
   access to specific external web-sites is subject to charge.

   The web-based access control could provide such a service, but there
   is no standard protocol or method which could help WISPs to support
   roaming users.  While web-based access control can support devices
   with web browsers, there are number of other applications such as
   FTP, VoIP require a standard client application or protocol at the
   client. The client will use this protocol to initiate the network
   access for any non browser based applications.  In addition to charge
   a user for external web access, a local WISP can also provide charge-
   based information delivery services such as music download, VoIP,
   etc.  These services are provided by the local network and external
   connectivity is supported by gateways.  It is also envisioned that
   NAS can be triggered either by the device or PAA, based on provider
   business model. PANA could provide a standardized way of
   L2-independent user-agnostic network access with roaming enabled.


3.1.2.  Multiple Access Routers


   In multi-access environments such as Ethernet and 802.11a/b, it is
   possible for multiple ARs to exist on the same subnet. This is a
   fundamental difference from PPP in which a single AR is always
   associated with a PPP tunnel and the association never changes
   throughout the lifetime of the PPP connection.

   It would be desirable to use multiple ARs in such a way that traffic
   coming from and going to a specific device always goes through a
   single AR for ease of access control, but traffic among different
   devices diverges for the purpose of load balancing and redundancy.

   Although many NAS-based networks support multiple ARs for inbound
   traffic, however, for outbound traffic (originated from user devices
   connected via PPP tunnels to a single NAS) a single AR is always
   used.  In an 802.11a/b network, it is possible to support multiple
   ARs if all first hop routers reside behind the layer-2 access points.
   On the other hand, if WLAN access points act as first hop access
   routers then it boils down to the same NAS type of model as described
   earlier.

   Thus in order to achieve load balancing and redundancy in a more
   flexible way we may need a different type of solution and in which
   case PANA seems to be appropriate.  Consider the following scenario
   (see Fig.1 for IPv4 example):


   o  Unlike the existing PPP-based NAS model, the device randomly (or
      by using some other criteria) selects one of the ARs as the



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      default router and always uses the selected AR as the next hop for
      the outgoing traffic.  The network is also configured in such a
      way that ICMP Redirect would not occur in the edge subnet to avoid
      divergence of traffic coming from the user terminal.

   o  Like the existing PPP-based NAS model, each AR has at least two
      interfaces, one (Ie) is attached to the edge subnet and the other
      (Ic) is attached to the core network.  The subnet prefix assigned
      to Interface Ic covers that is assigned to Interface Ie.  When an
      AR receives an address resolution request (ARP REQUEST or Neighbor
      Solicitation) from R (who is searching for the device on Interface
      Ic) the AR that is selected by the device replies to the address
      resolution request on behalf of the device and thereby guarantees
      that all incoming traffic going to the device passes through the
      AR.  This part is the same as the existing PPP-based NAS scenario.


   For example, assume that devices D1 and D3 perform initial
   authentication with AR1 and that devices D2 and D4 perform initial
   authentication with AR2.  If initial authentication is successful,
   AR1 and AR2 will open firewall and create proxy ARP (or ND) entries
   for D1/D3 and D2/D4, respectively.  Packets originated from D1 or D3
   are forwarded to AR1.  Packets originated from D2 or D4 are forwarded
   to AR2.  On the other hand, in terms of the reverse direction, when
   core router R receives a packet destined for either D1 or D2, it is
   delivered to the final destination through AR1 in the following way.
   If R does not yet have an ARP/Neighbor cache of the destination, it
   performs address resolution since it thinks that the destination is
   on-link according to the prefix assignment.  Only AR1 makes a
   response to the address resolution request with specifying the MAC
   address of Ic1.  Then, R forwards the packet to AR1 which delivers it
   to the final destination device.  In the same way, when R receives a
   packet destined for either D3 or D4, it is delivered to the final
   destination through AR2.


























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                   [D1] ----+
                            | Ie1    Ic1
                   [D2] ----+---[AR1]---+
                            | Ie2    Ic2|
                   [D3] ----+---[AR2]---+
                            |           |
                   [D4] ----+           |
                                        +---[R]----
                   [D5] ----+           |
                            | Ie3    Ic3|
                   [D6] ----+---[AR3]---+
                            | Ie4    Ic4|
                   [D7] ----+---[AR4]---+
                            |
                   [D8] ----+

                   D1..D8: Devices
                   AR1..AR4: Access Routers
                   R: Core Router

                   Ie1 = x.y.1.1/24, Ic1 = x.y.0.1/16
                   Ie2 = x.y.1.2/24, Ic2 = x.y.0.2/16
                   Ie3 = x.y.2.1/24, Ic3 = x.y.0.3/16
                   Ie4 = x.y.2.2/24, Ic4 = x.y.0.4/16

             Fig.1:  A possible multi-AR environment

   In the above case, since both the incoming and outgoing traffic with
   regard to a specific device are controlled to pass though a single
   AR, it would be easier to perform authentication via the same AR.
   However, this would change if the topology is different or if traffic
   coming from and going to a specific device diverges among different
   ARs as a result of ICMP Redirect or the use of "Default Router
   Preferences and More-Specific Routes" [Draves] in IPv6.  Detailed
   architecture tradeoffs will be discussed in framework document.


3.1.3.  Multiple Interfaces on a Single Device

   PANA would be useful when a host has multiple interfaces of
   homogeneous or heterogeneous technologies.  A typical example is a
   device with a Bluetooth interface and and an 802.11 interface or with
   multiple Bluetooth interfaces.  There are three possible scenarios:
   interface switching, multi-homing, and interface sharing.


3.1.3.1.  Interface Switching

   If multiple interfaces are connectable to the same local network,
   only one of those interfaces may be activated at a time for the
   purpose of battery saving, and perform interface switching when other
   interface is to be activated, with or without changing IP address. In
   such an environment, the device may have to perform initial
   authentication each time interface switching occurs, as well as
   periodical re-authentication for the activated interface.  This would
   not be desired if initial authentication or re-authentication
   involves communication with the AAA infrastructure which would



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   increase AAA signaling traffic in the core network unless the user's
   credential is stored in the L2 network access point.

   The LSA established by using PANA as a result of successful initial
   authentication with an interface can be used for local re-
   authentication which would be performed periodically or at every
   interface switching event.  See section "Using LSA for details.

   Note that this kind of optimization by PANA would not be possible if
   (i) multiple interfaces are connected to different local networks
   each managed by an independent PAA and (ii) re-authentication is not
   required.


3.1.3.2.  Multi-homing

   If multiple interfaces are connectable to the same local network,
   those interfaces may be activated at the same time for the purpose of
   bandwidth increase and/or load balancing.

   In such an environment, the device may have to perform initial
   authentication multiple times, one for each interface, and periodical
   re-authentication for each interface.  This would not be desired for
   the same reason described in section "Interface Switching".

   The LSA established by using PANA as a result of successful initial
   authentication with an interface can be can be shared among all the
   interfaces and used for local re-authentication which would be
   performed periodically or when an additional interface comes up.  See
   section "Using LSA for Re-authentication" for details.

   Note that this kind of optimization by PANA would not be possible if
   (i) multiple interfaces are connected to different local networks
   each managed by an independent PAA and (ii) re-authentication is not
   required.


3.1.3.3.  Interface Sharing


   There may be cases in which a device (i.e., a gateway device) has one
   provider interface and multiple private interfaces, where only the
   provider interface is connected to the ISP's local network and other
   interfaces are connected to other devices (child devices) under
   administration of the user (i.e., both the gateway device and child
   devices are owned by the same user).  Traffic coming from the private
   interfaces would be bridged or routed to the provider interface and
   vice versa.  Such a scenario would be more realistic in IPv6 where a
   /64 prefix could be allocated to the user, enabling a distinct IP
   address within the allocated prefix to be assigned to each of the
   devices of the same user.  In terms of both access control overhead
   and AAA signaling overhead, it would be desirable to perform access
   control per prefix rather than per child device.  PANA would be very
   suitable for such a prefix-based access control, especially in DSL or
   cable modem environment (see Fig.2).





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            [D1a] ----+        /64 prefix +--------+
                      |           <--     |        |
            [D1b] ----+---[GD1]--(DSL)-+  |        |
                      |                |  |        |
            [D1c] ----+                |  |        |
                                   .   +--+   AR   +----
            [D2a] ----+            .   |  |        |
                      |                |  |        |
            [D2b] ----+---[GD2]--(DSL)-+  |        |
                      |                   |        |
            [D2c] ----+                   +--------+


               GD1: Gateway Device of User 1
               GD2: Gateway Device of User 2
               D1a,D1b,D1c: Other Devices of User 1
               D2a,D2b,D2c: Other Devices of User 2
               AR: Access Router

                    Fig.2:  PANA usage in DSL


   In this usage scenario, it would be required to prevent other users
   from using the advertised prefix especially when the AR uses a single
   Ethernet interface for multiple gateway devices (i.e., multiple
   gateway devices of different users are on the same shared media, as
   shown in Fig.2).  Details will be discussed in framework document.

   Note that if the gateway device and child devices are owned by
   different users, access control would be performed per-device instead
   of per-prefix.  Then it boils down to one of the models as described
   earlier in which each device performs PANA with PAA.


3.2.  WLAN


   WLAN is a one of the many scenarios where PANA could be useful. While
   802.1X specification is being deployed by WISPs today, it would not
   meet the future needs such as inter-technology hand-offs,
   differentiation between free and paid access and others.

   While interworking with 802.1X needs to be taken into consideration,
   a solution at the higher layer is clearly another option, especially
   where only legacy 802.11a/b interface cards and APs are available.
   An alternative is that L2 authentication could be used to get free
   local access, and PANA could then later be used to access specific
   paid services or access to global Internet.

   PANA and 802.1X-based authentication together may not be required for
   all situations rather it would be preferable to use them in different
   places - 802.1X authentication is preferred in public operator
   networks where there are no free local services (or if all services
   are charged at a flat rate), and PANA is preferred in hotels and
   other places with free intranets.  However, both mechanisms can
   coexist in a service provider's network since they belong to two
   different layers.



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3.3.  GPRS

   In GPRS there are only two methods of authenticating/acquiring an
   address from networks other than the GPRS access network (corporate
   or ISP).  In one mode PPP is terminated by the GGSN which then
   authenticates the user (using the RADIUS client) to the "other"
   network, being the ISP the user connects to or the "home" corporate
   network depending on the requested APN.  In the second mode, PPP is
   terminated in the MT, ONLY the Challenge Response is piggybacked on
   PDP context requests. The RADIUS client in the GGSN then relays this
   info to the RADIUS server wherever that maybe (Based on the APN).

   As yet another example, there is no  mechanism for exchanging a
   second level of authentication and addressing information, only the
   interaction with the cellular systems' authentication and address
   assignment mechanism is possible (although Mobile IP could be used).

   A protocol that decouples the authentication and addressing from PPP
   (and Mobile IP) could allow an operator to provide remote
   authentication and authorization of home network services and address
   assignment within such a domain using one of the available IP layer
   tunneling mechanisms to deliver packets.


3.4.  Intra-domain, Inter-technology Handoff

   Although the PANA WG will not directly work on solutions relating to
   mobility of the device.  However, it is noted in the PANA WG charter
   that the ability to re-authenticate locally with the PAA, can be an
   important element in allowing efficient handling of mobile devices.
   This section describe possible situations where an LSA established by
   using PANA would be useful for mobile nodes.

   Different radio technologies will have different characteristics in
   terms of BW, cost, resilience and speed. Different applications may
   prefer to use access technologies that are most suited to their
   needs. It is foreseen that network operators will overlay different
   access technologies on top of their existing IP backbones to satisfy
   users' needs, hot spot coverages, etc.  For an operator to have
   control over the access to their networks some mechanism for user
   authentication and access control is required.  Currently these
   mechanisms are access dependent (e.g.,. HLR in GPRS and 802.1X
   specific mechanisms). Such access dependence requires an access
   dependent identity for the user. Hence while connected to a Cellular
   network, a user is identified by an IMSI, on a WLAN or Bluetooth
   network a user will have a different identity.

   For users to be able to roam seamlessly within an operator's domain
   between different access technologies they need to avoid re-
   authentication all the way back to their home AAA servers each time
   the move.  Context Transfer (CT) may help, however if the identity of
   a user is different in each access technology, CT will not help and
   re-authentication will become necessary.  Hence an access independent
   mechanism that uses a standard access independent identity is need to
   identify the user regardless of which access technology he/she is
   connected to.  The LSA established by using PANA can be used for
   minimize the re-authentication overhead so that re-authentication is



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   performed only locally in a similar way that is described in section
   "Interface Switching".  CT and MIP can solve the rest of the problem
   for seamless mobility.

   Another possible scenario in Mobile IPv6 is described in [Soliman].


4.  LSA Usages


   Establishing an LSA between a device and a PAA is equivalent to
   having a shared secret between them.  The shared secret for the LSA
   can be derived from credentials of a user.  The credentials could be
   a symmetric cryptographic key (i.e., shared key) or an asymmetric
   cryptographic key (i.e., public key).  A typical example of symmetric
   cryptographic key is a password stored in the database of the user's
   home ISP.  A typical example of asymmetric cryptographic key is a PKI
   digital certificate issued by a trusted 3rd party.


4.1.  Using LSA for Re-authentication

   Once initial authentication is successful, re-authentication would be
   necessary in the following situations:

   o  When there is a change in attributes of either the device or PAA.
      For example, re-authentication would be necessary when the
      device's IP address changes due to e.g., interface switching or
      handoff.

   o  If the underlying access network does not have a capability to
      detect physical disconnection of devices, periodical re-
      authentication is necessary for (i) preventing connection
      hijacking from malicious users which would possibly occur when the
      device is shutdown or the user leaves the local network with the
      device without performing explicit log-off from the local network
      or (ii) improve the accuracy of accounting.

   On the other hand, it is desired that periodical re-authentication is
   performed locally between the device and PAA in order to minimize the
   signaling traffic.

   Once the LSA is established, re-authentication could be performed
   locally based on the shared secret for the established LSA.


4.2.  Using LSA for IKE

   The shared key for the LSA or other shared key derived from the LSA
   can also be used as an IKE credential with which an IPsec SA between
   the device and PAA is established via IKE[RFC2409].  This would be
   useful especially in roaming environment where it is difficult to
   share the IKE credential a priori between the device and an IPsec
   entity in the local network.

   The established IPsec SA can be used for protecting PANA message
   exchange, which would be useful for quick re-authentication and/or



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   secure explicit log-off.

   It is also possible to utilize the LSA to establish an IPsec tunnel
   between a device and an IPsec gateway.  The established IPsec tunnel
   can be used for protecting user data packets in the access network at
   the IP layer.  This would provide access network security without
   relying on L2 security mechanisms, which is important considering the
   recent exposure of WEP vulnerabilities.


5.  Conclusion

   The scenarios described above show a clear need for a common edge
   protocol that would provide network or service providers a vehicle
   for user authentication irrespective of what access technology they
   are using.  It is anticipated that a higher layer solution like PANA
   can support future flexible service models.  However, there are
   several issues that need to be resolved before we deploy this
   solution.  We hope this draft will help the WG to understand
   different usage scenarios either existing or upcoming and the
   rationale behind this approach.


6.  Acknowledgments

   The authors would like to thank James Kempf, David Spence, and the
   rest of the PANA Working Group for the ideas and support they have
   given to this document.


7.  References

   [DIAMETER] P. Calhoun, et al., "Diameter Base Protocol", Work in
       progress, November 2001.

   [Draves] R. Draves, "Default Router Preferences and More-Specific
       Routes", Work in Progress, May 2001.


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

   [RFC1661] W. Simpson, "The Point-to-Point Protocol (PPP)", RFC 1661
       (STD 51), July 1994.


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

   [RFC2510] C. Adams, et al., "Internet X.509 Public Key Infrastructure
       Certificate Management Protocols", RFC 2510, March 1999.


   [RFC2828] R. Shirey, "Internet Security Glossary", RFC 2828, May 2000.

   [RFC2865] C. Rigney, "Remote Authentication Dial In User Service
       (RADIUS)", RFC 2865, June 2000.



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   [RFC3157] A. Arsenault, et. al, "Securely Available Credentials -
       Requirements", RFC 3157, August 2001.

   [Soliman] H. Soliman, et al., "Security Association establishment for
       Mobile IPv6 Route Optimisation using AAA", Internet-Draft, Work in
       progress, July 2001.


8.  Authors' Information

   Yoshihiro Ohba
   Toshiba America Research, Inc.
   P.O. Box 136
   Convent Station, NJ 07961-0136
   USA
   Phone: +1 973 829 5174
   Fax:   +1 973 829 5601
   Email: yohba@tari.toshiba.com

   Subir Das
   MCC 1D210R, Telcordia Technologies
   445 South Street, Morristown, NJ 07960
   Phone: +1 973 829 4959
   email: subir@research.telcordia.com

   Henry Haverinen
   Nokia Mobile Phones
   P.O. Box 88
   FIN-33721 Tampere
   Finland
   E-mail: henry.haverinen@nokia.com
   Phone: +358 50 594 4899
   Fax:   +358 3 318 3690


   Basavaraj Patil
   Nokia
   6000 Connection Dr.
   Irving, TX. 75039
   USA
   Phone:  +1 972-894-6709
   Email:  Basavaraj.Patil@nokia.com

   Phil Roberts
   Megisto Corp.
   Suite 120
   20251 Century Blvd
   Germantown MD 20874
   USA
   Phone:  +1 847-202-9314
   Email:  PRoberts@MEGISTO.com

   Hesham Soliman
   Ericsson Radio Systems AB
   Torshamnsgatan 29,
   Kista, Stockholm 16480
   Sweden



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   Phone:  +46 8 7578162
   Fax:    +46 8 4043630
   E-mail: Hesham.Soliman@era.ericsson.se

   Barani Subbiah
   3Com Corporation
   5400 Bayfront Plaza
   Santa Clara CA 95052
   Email: barani_subbiah@3com.com



















































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