Internet Draft                                 J. Kempf, Editor
  Document: draft-ietf-netlmm-nohost-ps-05.txt   September, 2006
  Expires: March, 2007
      Problem Statement for Network-based Localized Mobility Management
  Status of this Memo
     By submitting this Internet-Draft, each author represents that any
     applicable patent or other IPR claims of which he or she is aware
     have been or will be disclosed, and any of which he or she becomes
     aware will be disclosed, in accordance with Section 6 of BCP 79.
     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-
     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
     The  list  of  current  Internet-Drafts  can  be  accessed  at
     The list of Internet-Draft Shadow Directories can be accessed at
     Localized mobility management is a well understood concept in the
     IETF with a number of solutions already available. This document
     looks at the principal shortcomings of the existing solutions, all
     of which involve the host in mobility management, and makes a case
     for network-based local mobility management.
     Gerardo Giaretta, Kent Leung, Katsutoshi Nishida, Phil Roberts, and
     Marco Liebsch all contributed major effort to this document. Their
     names are not included in the authors' section due to the RFC
     Editor's limit of 5 names.
  Table of Contents
     1.0  Introduction............................................2
     2.0  The Local Mobility Problem..............................4
     3.0  Scenarios for Localized Mobility Management.............6
     4.0  Problems with Existing Solutions........................7
     5.0  Advantages of Network-based Localized Mobility
     J. Kempf, editor       Expires March, 2007                [Page 1]

     Internet Draft       NETLMM Problem Statement      September, 2006
     6.0  IANA Considerations.....................................9
     7.0  Security Considerations.................................9
     8.0  References..............................................9
     9.0  Acknowledgements.......................................10
     10.0 Author's Addresses.....................................10
     11.0 IPR Statements.........................................11
     12.0 Disclaimer of Validity.................................12
     13.0 Copyright Notice.......................................12
  1.0  Introduction
     Localized mobility management has been the topic of much work in
     the IETF. The experimental protocols developed from previous work,
     namely FMIPv6 [13] and HMIPv6 [18], involve host-based solutions
     that require host involvement at the IP layer similar to or in
     addition to that required by Mobile IPv6 [10] for global mobility
     management. However, recent developments in the IETF and the WLAN
     infrastructure market suggest that it may be time to take a fresh
     look at localized mobility management.
     Firstly, new IETF work on global mobility management protocols that
     are not Mobile IPv6, such as HIP [16] and MOBIKE [4], suggests that
     future wireless IP nodes may support a more diverse set of global
     mobility protocols. While it is possible that existing localized
     mobility management protocols could be used with HIP and MOBIKE,
     some would require additional effort to implement, deploy, or in
     some cases even to specify in a non-Mobile IPv6 mobile environment.
     Secondly, the success in the WLAN infrastructure market of WLAN
     switches, which perform localized management without any host stack
     involvement, suggests a possible paradigm that could be used to
     accommodate other global mobility options on the mobile node while
     reducing host stack software complexity expanding the range of
     mobile nodes that could be accommodated.
     This document briefly describes the general local mobility problem
     and  scenarios  where  localized  mobility  management  would  be
     desirable. Then problems with existing or proposed IETF localized
     mobility management protocols are briefly discussed. The network-
     based mobility management architecture and a short description of
     how  it  solves  these  problems  is  presented.  A  more  detailed
     discussion  of  goals  for  a  network-based,  localized  mobility
     management protocol and gap analysis for existing protocols can be
     found in [11]. Note that IPv6 and wireless links are considered to
     be  the  initial  scope  for  a  network-based  localized  mobility
     management, so the language in this document reflects that scope.
     However, the conclusions of this document apply equally to IPv4 and
     wired links where nodes are disconnecting and reconnecting.
  1.1 Terminology
     J. Kempf, editor          Expires March, 2007             [Page 2]

     Internet Draft       NETLMM Problem Statement      September, 2006
        Mobility terminology in this draft follows that in RFC 3753
        [7], with the addition of some new and revised terminology
        given here:
          WLAN Switch
            A Wireless LAN (WLAN) switch is an Ethernet [8]switch - that
            is a multiport bridge that connects network segments but
            allows a physical and logical star topology - which also
            runs a protocol to control a collection of 802.11 [6] access
            points. The access point control protocol allows the switch
            to perform radio resource management functions such as power
            control and terminal load balancing between the access
            points.  Most  WLAN  switches  also  support  a  proprietary
            protocol for inter-subnet IP mobility, usually involving
            some kind of inter-switch IP tunnel, which provides session
            continuity when a terminal moves between subnets.
          Access Network
            An access network is a collection of fixed and mobile
            network components allowing access to the Internet all
            belonging to a single operational domain.  It may consist of
            multiple air interface technologies (for example 802.16e
            [5], UMTS [1], etc.) interconnected with multiple types of
            backhaul interconnections (such as SONET [9], metro Ethernet
            [15] [8], etc.).
          Local Mobility (revised)
            Local Mobility is mobility over an access network. Note
            that, although the area of network topology over which the
            mobile node moves may be restricted, the actual geographic
            area could be quite large, depending on the mapping between
            the network topology and the wireless coverage area.
          Localized Mobility Management
            Localized Mobility Management is a generic term for any
            protocol that maintains the IP connectivity and reachability
            of  a  mobile  node  for  purposes  of  maintaining  session
            continuitity when the mobile node moves, and whose signaling
            is confined to an access network.
          Localized Mobility Management Protocol
            A protocol that supports localized mobility management.
          Global Mobility Management Protocol
            A Global Mobility Management Protocol is a mobility protocol
            used by the mobile node to change the global, end-to-end
            routing of packets for purposes of maintaining session
     J. Kempf, editor          Expires March, 2007             [Page 3]

     Internet Draft       NETLMM Problem Statement      September, 2006
            continuity when movement causes a topology change and thus
            invalidates a global unicast address of the mobile node.
            This protocol could be Mobile IP [10][17] but it could also
            be HIP [14] or MOBIKE [4].
          Global Mobility Anchor Point
            A node in the network where the mobile node maintains a
            permanent  address  and  a  mapping  between  the  permanent
            address and the local temporary address where the mobile
            node happens to be currently located. The Global Mobility
            Anchor Point may be used for purposes of rendezvous and
            possibly traffic forwarding.
          Intra-Link Mobility
            Intra-Link Mobility is mobility between wireless access
            points within a link. Typically, this kind of mobility only
            involves Layer 2 mechanisms, so Intra-Link Mobility is often
            called Layer 2 mobility. No IP subnet configuration is
            required upon movement since the link does not change, but
            some IP signaling may be required for the mobile node to
            confirm whether or not the change of wireless access point
            also  resulted  in  the  previous  access  routers  becoming
            unreachable. If the link is served by a single access
            point/router combination,  then  this  type  of  mobility
            is typically absent. See Figure 1.
  2.0  The Local Mobility Problem
     The local mobility problem is restricted to providing IP mobility
     management for mobile nodes within an access network. The access
     network gateways function as aggregation routers. In this case,
     there is no specialized routing protocol (e.g. GTP, Cellular IP,
     Hawaii, etc.) and the routers form a standard IP routed network
     (e.g. OSPF, IS-IS, RIP, etc.). This is illustrated in Figure 1,
     where the access network gateway routers are designated as "ANG".
     Transitions  between  service  providers  in  separate  autonomous
     systems or across broader topological "boundaries" within the same
     service provider are excluded.
     Figure 1 depicts the scope of local mobility in comparison to
     global mobility. The Access Network Gateways (ANGs) GA1 and GB1 are
     gateways to their access networks. The Access Routers (ARs) RA1 and
     RA2 are in access network A, RB1 is in access network B. Note that
     it is possible to have additional aggregation routers between ANG
     GA1 and ANG GB1 and the access routers if the access network is
     large. Access Points (APs) PA1 through PA3 are in access network A,
     PB1 and PB2 are in access network B. Other ANGs, ARs, and APs are
     also possible, and other routers can separate the ARs from the
     ANGs. The figure implies a star topology for the access network
     deployment, and the star topology is the primary one of interest
     since it is quite common, but the problems discussed here are
     J. Kempf, editor          Expires March, 2007             [Page 4]

     Internet Draft       NETLMM Problem Statement      September, 2006
     equally relevant to ring or mesh topologies in which ARs are
     directly connected through some part of the network.
               Access Network A         Access Network B
                  +-------+                  +-------+
                  |ANG GA1| (other ANGs)     |ANG GB1| (other ANGs)
                  +-------+                  +-------+
                   @    @                       @
                  @      @                      @
                 @        @                     @   (other routers)
                @          @                    @
               @            @                   @
              @              @                  @
           +------+       +------+            +------+
           |AR RA1|       |AR RA2|(other ARs) |AR RB1|  (other ARs)
           +------+       +------+            +------+
              *             *                    *
             * *            *                   * *
            *   *           *                  *   *
           *     *          *                 *     *
          *       *         *                *       *
         *         *        * (other APs)   *         * (other APs)
        /\         /\       /\             /\         /\
       /AP\       /AP\     /AP\           /AP\       /AP\
      /PA1 \     /PA2 \   /PA3 \         /PB1 \     /PB2 \
      ------     ------   ------         ------     ------
         +--+      +--+      +--+         +--+
         +--+      +--+      +--+         +--+
       Intra-link      Local        Global
       (Layer 2)      Mobility     Mobility
          Figure 1. Scope of Local and Global Mobility Management
     As shown in the figure, a global mobility protocol may be necessary
     when a mobile node (MN) moves between two access networks. Exactly
     what the scope of the access networks is depends on deployment
     considerations.  Mobility  between  two  APs  under  the  same  AR
     constitutes intra-link, or Layer 2, mobility, and is typically
     handled by Layer 2 mobility protocols (if there is only one AP/cell
     per AR, then intra-link mobility may be lacking). Between these two
     lies local mobility. Local mobility occurs when a mobile node moves
     between two APs connected to two different ARs.
     Global  mobility  protocols  allow  a  mobile  node  to  maintain
     reachability when the MN's globally routable IP address changes. It
     does this by updating the address mapping between the permanent
     address and temporary local address at the global mobility anchor
     point, or even end to end by changing the temporary local address
     directly at the node with which the mobile node is corresponding. A
     global mobility management protocol can therefore be used between
     J. Kempf, editor          Expires March, 2007             [Page 5]

     Internet Draft       NETLMM Problem Statement      September, 2006
     ARs for handling local mobility. However, there are three well-
     known problems involved in using a global mobility protocol for
     every movement between ARs. Briefly, they are:
     1) Update latency. If the global mobility anchor point and/or
         correspondent node (for route optimized traffic) is at some
         distance from the mobile node's access network, the global
         mobility update may require a considerable amount of time.
         During this time, packets continue to be routed to the old
         temporary local address and are essentially dropped.
     2) Signaling overhead. The amount of signaling required when a
         mobile node moves from one last hop link to another can be
         quite  extensive,  including  all  the  signaling  required  to
         configure an IP address on the new link and global mobility
         protocol signaling back into the network for changing the
         permanent to temporary local address mapping. The signaling
         volume may negatively impact wireless bandwidth usage and real
         time service performance.
      3) Location privacy. The change in temporary local address as the
         mobile  node  moves  exposes  the  mobile  node's  topological
         location to correspondents and potentially to eavesdroppers. An
         attacker that can assemble a mapping between subnet prefixes in
         the mobile node's access network and geographical locations can
         determine exactly where the mobile node is located. This can
         expose the mobile node's user to threats on their location
         privacy. A more detailed discussion of location privacy for
         Mobile IPv6 can be found in [12].
     These problems suggest that a protocol to localize the management
     of topologically small movements is preferable to using a global
     mobility management protocol on each movement to a new link. In
     addition to these problems, localized mobility management can
     provide a measure of local control, so mobility management can be
     tuned for specialized local conditions. Note also that if localized
     mobility management is provided, it is not strictly required for a
     mobile node to support a global mobility management protocol since
     movement  within  a  restricted  IP  access  network  can  still
     be accommodated. Without such support, however, a mobile node
     experiences a disruption in its traffic when it moves beyond the
     border of the localized mobility management domain.
  3.0  Scenarios for Localized Mobility Management
     There are a variety of scenarios in which localized mobility
     management is useful.
  3.1 Large Campus
     One  scenario  where  localized  mobility  management  would  be
     attractive is a campus wireless LAN deployment, in which the
     geographical  span  of  the  campus,  distribution  of  buildings,
     availability of wiring in buildings, etc. preclude deploying all
     WLAN access points as part of the same IP subnet. WLAN Layer 2
     mobility could not be used across the entire campus.
     J. Kempf, editor          Expires March, 2007             [Page 6]

     Internet Draft       NETLMM Problem Statement      September, 2006
     In this case, the campus is divided into separate last hop links
     each served by one or more access routers. This kind of deployment
     is served today by wireless LAN switches that co-ordinate IP
     mobility between them, effectively providing localized mobility
     management at the link layer. Since the protocols are proprietary
     and not interoperable, any deployments that require IP mobility
     necessarily require switches from the same vendor.
  3.2 Advanced Cellular Network
     Next generation cellular protocols such as 802.16e [5] and Super
     3G/3.9G [2] have the potential to run IP deeper into the access
     network than the current 3G cellular protocols, similar to today's
     WLAN networks. This means that the access network can become a
     routed IP network. Interoperable localized mobility management can
     unify local mobility across a diverse set of wireless protocols all
     served by IP, including advanced cellular, WLAN, and personal area
     wireless  technologies  such  as  UltraWide  Band  (UWB)  [5]  and
     Bluetooth [3]. Localized mobility management at the IP layer does
     not  replace  Layer  2  mobility  (where  available)  but  rather
     complements it. A standardized, interoperable localized mobility
     management protocol for IP can remove the dependence on IP layer
     localized mobility protocols that are specialized to specific link
     technologies or proprietary, which is the situation with today's 3G
     protocols. The expected benefit is a reduction in maintenance cost
     and deployment complexity. See [11] for a more detailed discussion
     of the goals for a network-based localized mobility management
  3.3 Picocellular Network with Small But Node-Dense Last Hop Links
     Future radio link protocols at very high frequencies may be
     constrained to very short, line of sight operation. Even some
     existing protocols, such as UWB [5] and Bluetooth [3], are designed
     for low transmit power, short range operation. For such protocols,
     extremely small picocells become more practical. Although picocells
     do not necessarily imply "pico subnets", wireless sensors and other
     advanced applications may end up making such picocellular type
     networks   node-dense,   requiring   subnets   that   cover   small
     geographical areas, such as a single room. The ability to aggregate
     many subnets under a localized mobility management scheme can help
     reduce the amount of IP signaling required on link movement.
  4.0  Problems with Existing Solutions
     Existing solutions for localized mobility management fall into
     three classes:
     1) Interoperable IP level protocols that require changes to the
        mobile node's IP stack and handle localized mobility management
        as a service provided to the mobile node by the access network,
     J. Kempf, editor          Expires March, 2007             [Page 7]

     Internet Draft       NETLMM Problem Statement      September, 2006
     2) Link specific or proprietary protocols that handle localized
        mobility for any mobile node but only for a specific type of
        link layer, for example, 802.11 [6].
     The dedicated localized mobility management IETF protocols for
     Solution 1 are not yet widely deployed, but work continues on
     standardization.  Some  Mobile  IPv4  deployments  use  localized
     mobility management. For Solution 1, the following are specific
     1) The host stack software requirement limits broad usage even if
        the modifications are small. The success of WLAN switches
        indicates that network operators and users prefer no host stack
        software modifications. This preference is independent of the
        lack of widespread Mobile IPv4 deployment, since it is much
        easier to deploy and use the network.
     2) Future mobile nodes may choose other global mobility management
        protocols, such as HIP or MOBIKE. The existing localized
        mobility management solutions all depend on Mobile IP or
     3) Existing localized mobility management solutions do not support
        both IPv4 and IPv6.
     4) Existing host-based localized mobility management solutions
        require setting up additional security associations with network
        elements in the access domain.
     Market acceptance of WLAN switches has been very large, so Solution
     2 is widely deployed and continuing to grow. Solution 2 has the
     following problems:
     1) Existing solutions only support WLAN networks with Ethernet
        backhaul and therefore are not available for advanced cellular
        networks or picocellular protocols, or other types of wired
     2) Each WLAN switch vendor has its own proprietary protocol that
        does not interoperate with other vendor's equipment.
     3) Because the solutions are based on layer 2 routing, they may not
        scale up to a metropolitan area, or local province particularly
        when multiple kinds of link technologies are used in the
  5.0  Advantages of Network-based Localized Mobility Management
     Having an interoperable, standardized localized mobility management
     protocol that is scalable to topologically large networks, but
     requires no host stack involvement for localized mobility
     management is a highly desirable solution. The advantages that this
     solution has over the Solutions 1 and 2 above are as follows:
     1) Compared with Solution 1, a network-based solution requires no
        localized mobility management support on the mobile node and is
        independent of global mobility management protocol, so it can
        be used with any or none of the existing global mobility
        management protocols. The result is a more modular mobility
     J. Kempf, editor          Expires March, 2007             [Page 8]

     Internet Draft       NETLMM Problem Statement      September, 2006
        management architecture that better accommodates changing
        technology and market requirements.
     2) Compared with Solution 2, an IP level network-based localized
        mobility management solution works for link protocols other
        than Ethernet, and for wide area networks.
     Reference [11] discusses a reference architecture for a network-
     based, localized mobility protocol and goals the protocol design.
  6.0  IANA Considerations
     There are no IANA considerations in this document.
  7.0  Security Considerations
     Localized mobility management has certain security considerations,
     one of which - need for access network to mobile node security -
     was touched on in this document. Host-based localized mobility
     management protocols have all the security problems involved with
     providing a service to a host. Network-based localized mobility
     management requires security among network elements equivalent to
     what is needed for routing information security, and security
     between the host and network equivalent to what is needed for
     network access, but no more. A more complete discussion of the
     security goals for network-based localized mobility management can
     be found in [11].
  8.0  References
  8.1 Informative References
      [1] 3GPP, "UTRAN Iu interface: General aspects and principles",
          3GPP TS 25.410, 2002.
      [2] 3GPP, "3GPP System Architecture Evolution: Report on Technical
          Options     and     Conclusions",     TR     23.882,     2005,

      [3] Bluetooth  SIG,  "Specification  of  the  Bluetooth  System",
          November, 2004, available at
      [4] Eronen, P., editor, "IKEv2 Mobility and Multihoming Protocol
          (MOBIKE)", RFC 4555, June, 2006.
      [6] IEEE, "Wireless LAN Medium Access Control (MAC)and Physical
          Layer (PHY) specifications", IEEE Std. 802.11, 1999.
      [7] IEEE, "Amendment to IEEE Standard for Local and Metropolitan
          Area Networks - Part 16: Air Interface for Fixed Broadband
          Wireless Access Systems- Physical and Medium Access Control
          Layers for Combined Fixed and Mobile Operation in Licensed
          Bands", IEEE Std. 802.16e-2005, 2005.
      [8] IEEE, "Carrier sense multiple access with collision detection
          (CSMA/CD) access method and physical layer specifications",
          IEEE Std. 802.3-2005, 2005.
     J. Kempf, editor          Expires March, 2007             [Page 9]

     Internet Draft       NETLMM Problem Statement      September, 2006
      [9] ITU-T,  "Architecture  of  Transport  Networks  Based  on  the
          Synchronous Digital Hierarchy (SDH)", ITU-T G.803, March,
     [10] Johnson, D., Perkins, C., and Arkko, J., "Mobility Support in
          IPv6," RFC 3775.
     [11] Kempf, J., editor, "Goals for Network-based Localized Mobility
          Management", Internet Draft, work in progress.
     [12] Koodli, R., "IP Address Location Privacy and Mobile IPv6:
          Problem Statement", Internet Draft, work in progress.
     [13] Koodli, R., editor, "Fast Handovers for Mobile IPv6," RFC
          4068, July, 2005.
     [14] Manner, J., and Kojo, M., "Mobility Related Terminology", RFC
          3753, June, 2004.
     [15] Metro Ethernet Forum, " Metro Ethernet Network Architecture
          Framework - Part 1: Generic Framework", MEF 4, May, 2004.
     [16] Moskowitz, R., and Nikander, P., "Host Identity Protocol (HIP)
          Architecture", RFC 4423, May, 2006.
     [17] Perkins, C., editor, "IP Mobility Support for IPv4", RFC 3220,
          August, 2002.
     [18] Soliman, H., Castelluccia, C., El Malki, K., and Bellier. L.,
          "Hierarchical Mobile IPv6 Mobility Management," RFC 4140,
          August, 2005.
  9.0  Acknowledgements
     The  authors  would  like  to  acknowledge  the  following  for
     particularly diligent reviewing: Vijay Devarapalli, Peter McCann,
     Gabriel  Montenegro,  Vidya  Narayanan,  Pekka  Savola,  and  Fred
  10.0     Author's Addresses
        James Kempf
        DoCoMo USA Labs
        181 Metro Drive, Suite 300
        San Jose, CA 95110
        Phone: +1 408 451 4711
        Kent Leung
        Cisco Systems, Inc.
        170 West Tasman Drive
        San Jose, CA 95134
        Phil Roberts
        Motorola Labs
     J. Kempf, editor          Expires March, 2007             [Page 10]

     Internet Draft       NETLMM Problem Statement      September, 2006
        Schaumberg, IL
        Katsutoshi Nishida
        NTT DoCoMo Inc.
        3-5 Hikarino-oka, Yokosuka-shi
        Phone: +81 46 840 3545
        Gerardo Giaretta
        Telecom Italia Lab
        via G. Reiss Romoli, 274
        10148 Torino
        Phone: +39 011 2286904
        Marco Liebsch
        NEC Network Laboratories
        Kurfuersten-Anlage 36
        69115 Heidelberg
        Phone: +49 6221-90511-46
  11.0     IPR Statements
     The IETF takes no position regarding the validity or scope of any
     Intellectual Property Rights or other rights that might be claimed
     to pertain to the implementation or use of the technology described
     in this document or the extent to which any license under such
     rights might or might not be available; nor does it represent that
     it has made any independent effort to identify any such rights.
     Information on the procedures with respect to rights in RFC
     documents can be found in BCP 78 and BCP 79.
     Copies of IPR disclosures made to the IETF Secretariat and any
     assurances of licenses to be made available, or the result of an
     attempt made to obtain a general license or permission for the use
     of such proprietary rights by implementers or users of this
     specification can be obtained from the IETF on-line IPR repository
     The IETF invites any interested party to bring to its attention any
     copyrights, patents or patent applications, or other proprietary
     rights that may cover technology that may be required to implement
     this standard.  Please address the information to the IETF at ietf-
     J. Kempf, editor          Expires March, 2007             [Page 11]

     Internet Draft       NETLMM Problem Statement      September, 2006
  12.0     Disclaimer of Validity
     This document and the information contained herein are provided on
  13.0    Copyright Notice
     Copyright (C) The Internet Society (2006).  This document is
     subject to the rights, licenses and restrictions contained in BCP
     78, and except as set forth therein, the authors retain all their
     J. Kempf, editor          Expires March, 2007             [Page 12]