Network Working Group                                      H. Chan (Ed.)
Internet-Draft                                       Huawei Technologies
Intended status: Informational                              July 7, 2012
Expires: January 8, 2013

            Requirements of distributed mobility management


   The traditional hierarchical structure of cellular networks has led
   to deployment models which are heavily centralized.  Mobility
   management with centralized mobility anchoring in existing
   hierarchical mobile networks is quite prone to suboptimal routing and
   issues related to scalability.  Centralized functions present a
   single point of failure, and inevitably introduce longer delays and
   higher signaling loads for network operations related to mobility
   management.  This document defines the requirements for distributed
   mobility management for IPv6 deployment.  The objectives are to match
   the mobility deployment with the current trend in network evolution,
   to improve scalability, to avoid single point of failure, to enable
   transparency to upper layers only when needed, etc.  The distributed
   mobility management also needs to be compatible with existing network
   deployments and end hosts, and be secured.

Status of this Memo

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   This Internet-Draft will expire on January 8, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions used in this document  . . . . . . . . . . . . . .  5
   3.  Centralized versus distributed mobility management . . . . . .  5
     3.1.  Centralized mobility management  . . . . . . . . . . . . .  5
     3.2.  Distributed mobility management  . . . . . . . . . . . . .  6
   4.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Distributed deployment . . . . . . . . . . . . . . . . . .  8
     4.2.  Transparency to Upper Layers when needed . . . . . . . . .  9
     4.3.  IPv6 deployment  . . . . . . . . . . . . . . . . . . . . . 10
     4.4.  Compatibility  . . . . . . . . . . . . . . . . . . . . . . 10
     4.5.  Existing mobility protocols  . . . . . . . . . . . . . . . 11
     4.6.  Security considerations  . . . . . . . . . . . . . . . . . 11
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   7.  Co-authors and Contributors  . . . . . . . . . . . . . . . . . 12
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 13
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 15

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1.  Introduction

   In the past decade a fair number of mobility protocols have been
   standardized.  Although the protocols differ in terms of functions
   and associated message format, we can identify a few key common

      presence of a centralized mobility anchor providing global
      reachability and an always-on experience;

      extensions to optimize handover performance while users roam
      across wireless cells;

      extensions to enable the use of heterogeneous wireless interfaces
      for multi-mode terminals (e.g. cellular phones).

   The presence of the centralized mobility anchor allows a mobile
   device to be reachable when it is not connected to its home domain.
   The anchor point, among other tasks, ensures reachability of
   forwarding of packets destined to or sent from the mobile device.
   Most of the deployed architectures today have a small number of
   centralized anchors managing the traffic of millions of mobile
   subscribers.  Compared with a distributed approach, a centralized
   approach is likely to have several issues or limitations affecting
   performance and scalability, which require costly network
   dimensioning and engineering to resolve.

   To optimize handovers from the perspective of mobile nodes, the base
   protocols have been extended to efficiently handle packet forwarding
   between the previous and new points of attachment.  These extensions
   are necessary when applications impose stringent requirements in
   terms of delay.  Notions of localization and distribution of local
   agents have been introduced to reduce signaling overhead.
   Unfortunately today we witness difficulties in getting such protocols
   deployed, often leading to sub-optimal choices.

   Moreover, the availability of multi-mode devices and the possibility
   of using several network interfaces simultaneously have motivated the
   development of more new protocol extensions.  Deployment is further
   complicated with so many extensions.

   Mobile users are, more than ever, consuming Internet content; such
   traffic imposes new requirements on mobile core networks for data
   traffic delivery.  When the traffic demand exceeds available
   capacity, service providers need to implement new strategies such as
   selective traffic offload (e.g. 3GPP work items LIPA/SIPTO) through
   alternative access networks (e.g.  WLAN).  Moreover, the localization
   of content providers closer to the Mobile/Fixed Internet Service

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   Providers network requires taking into account local Content Delivery
   Networks (CDNs) while providing mobility services.

   When demand exceeds capacity, both offloading and CDN techniques
   could benefit from the development of mobile architectures with fewer
   levels of routing hierarchy introduced into the data path by the
   mobility management system.  This trend in network flattening is
   reinforced by a shift in users traffic behavior, aimed at increasing
   direct communications among peers in the same geographical area.
   Distributed mobility management in a truly flat mobile architecture
   would anchor the traffic closer to the point of attachment of the
   user and overcome the suboptimal routing issues of a centralized
   mobility scheme.

   While deploying [Paper-Locating.User] today's mobile networks,
   service providers face new challenges.  More often than not, mobile
   devices remain attached to the same point of attachment.  Specific IP
   mobility management support is not required for applications that
   launch and complete while the mobile device is connected to the same
   point of attachment.  However, the mobility support has been designed
   to be always on and to maintain the context for each mobile
   subscriber as long as they are connected to the network.  This can
   result in a waste of resources and ever-increasing costs for the
   service provider.  Infrequent mobility and intelligence of many
   applications suggest that mobility can be provided dynamically, thus
   simplifying the context maintained in the different nodes of the
   mobile network.

   The proposed charter will address two complementary aspects of
   mobility management procedures: the distribution of mobility anchors
   to achieve a more flat design and the dynamic activation/deactivation
   of mobility protocol support as an enabler to distributed mobility
   management.  The former has the goal of positioning mobility anchors
   (HA, LMA) closer to the user; ideally, these mobility agents could be
   collocated with the first hop router.  The latter, facilitated by the
   distribution of mobility anchors, aims at identifying when mobility
   must be activated and identifying sessions that do not impose
   mobility management -- thus reducing the amount of state information
   to be maintained in the various mobility agents of the mobile
   network.  The key idea is that dynamic mobility management relaxes
   some constraints while also repositioning mobility anchors; it avoids
   the establishment of non optimal tunnels between two topologically
   distant anchors.

   This document describes the motivations of distributed mobility
   management in Section 1.  Section 3 compares distributed mobility
   management with centralized mobility management.  The requirements to
   address these problems are given in Section 4.

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   The problem statement and the use cases [I-D.yokota-dmm-scenario] can
   be found in the following review paper: [Paper-

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT",
   document are to be interpreted as described in [RFC2119].

3.  Centralized versus distributed mobility management

   Mobility management functions may be implemented at different layers
   of the network protocol stack.  At the IP (network) layer, they may
   reside in the network or in the mobile node.  In particular, a
   network-based solution resides in the network only.  It therefore
   enables mobility for existing hosts and network applications which
   are already in deployment but lack mobility support.

   At the IP layer, a mobility management protocol to achieve session
   continuity is typically based on the principle of distinguishing
   between identifier and routing address and maintaining a mapping
   between them.  With Mobile IP, the home address serves as an
   identifier of the device whereas the care-of-address takes the role
   of routing address, and the binding between them is maintained at the
   mobility anchor, i.e., the home agent.  If packets can be
   continuously delivered to a mobile device at its home address, then
   all sessions using that home address can be preserved even though the
   routing or care-of address changes.

   The next two subsections explain centralized and distributed mobility
   management functions in the network.

3.1.  Centralized mobility management

   With centralized mobility management, the mapping information between
   the stable node identifier and the changing IP address of a mobile
   node (MN) is kept at a centralized mobility anchor.  Packets destined
   to an MN are routed via this anchor.  In other words, such mobility
   management systems are centralized in both the control plane and the
   data plane.

   Many existing mobility management deployments make use of centralized
   mobility anchoring in a hierarchical network architecture, as shown
   in Figure 1.  Examples of such centralized mobility anchors are the
   home agent (HA) and local mobility anchor (LMA) in Mobile IPv6

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   [RFC6275] and Proxy Mobile IPv6 [RFC5213], respectively.  Current
   mobile networks such as the Third Generation Partnership Project
   (3GPP) UMTS networks, CDMA networks, and 3GPP Evolved Packet System
   (EPS) networks also employ centralized mobility management, with
   Gateway GPRS Support Node (GGSN) and Serving GPRS Support Node (SGSN)
   in the 3GPP UMTS hierarchical network and with Packet data network
   Gateway (P-GW) and Serving Gateway (S-GW) in the 3GPP EPS network.

          UMTS                3GPP SAE              MIP/PMIP
        +------+              +------+              +------+
        | GGSN |              | P-GW |              |HA/LMA|
        +------+              +------+              +------+
           /\                    /\                    /\
          /  \                  /  \                  /  \
         /    \                /    \                /    \
        /      \              /      \              /      \
       /        \            /        \            /        \
   +------+  +------+    +------+  +------+    +------+  +------+
   | SGSN |  | SGSN |    | S-GW |  | S-GW |    |FA/MAG|  |FA/MAG|
   +------+  +------+    +------+  +------+    +------+  +------+

   Figure 1.  Centralized mobility management.

3.2.  Distributed mobility management

   Mobility management functions may also be distributed to multiple
   locations in different networks as shown in Figure 2, so that a
   mobile node in any of these networks may be served by a closeby
   mobility function (MF).

   +------+  +------+  +------+  +------+
   |  MF  |  |  MF  |  |  MF  |  |  MF  |
   +------+  +------+  +------+  +------+
                       | MN |

   Figure 2.  Distributed mobility management.

   Mobility management may be partially distributed, i.e., only the data
   plane is distributed, or fully distributed where both the data plane
   and control plane are distributed.  These different approaches are
   described in detail in [I-D.yokota-dmm-scenario].

   [Paper-New.Perspective] discusses some initial steps towards a clear

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   definition of what mobility management may be, to assist in better
   developing distributed architecture.  [Paper-
   Characterization.Mobility.Management] analyses current mobility
   solutions and proposes an initial decoupling of mobility management
   into well-defined functional blocks, identifying their interactions,
   as well as a potential grouping, which later can assist in deriving
   more flexible mobility management architectures.  According to the
   split functional blocks, this paper proposes three ways into which
   mobility management functional blocks can be groups, as an initial
   way to consider a better distribution: location and handover
   management, control and data plane, user and access perspective.

   A distributed mobility management scheme is proposed in [Paper-
   Distributed.Dynamic.Mobility] for future flat IP architecture
   consisting of access nodes.  The benefits of this design over
   centralized mobility management are also verified through simulations
   in [Paper-Distributed.Centralized.Mobility].

   Before designing new mobility management protocols for a future flat
   IP architecture, one should first ask whether the existing mobility
   management protocols that have already been deployed for the
   hierarchical mobile networks can be extended to serve the flat IP
   architecture.  MIPv4 has already been deployed in 3GPP2 networks, and
   PMIPv6 has already been adopted in WiMAX Forum and in 3GPP standards.
   Using MIP or PMIP for both centralized and distributed architectures
   would ease the migration of the current mobile networks towards a
   flat architecture.  It has therefore been proposed to adapt MIP or
   PMIPv6 to achieve distributed mobility management by using a
   distributed mobility anchor architecture.

   In [Paper-Migrating.Home.Agents], the HA functionality is copied to
   many locations.  The HoA of all MNs are anycast addresses, so that a
   packet destined to the HoA from any corresponding node (CN) from any
   network can be routed via the nearest copy of the HA.  In addition,
   distributing the function of HA using a distributed hash table
   structure is proposed in [Paper-Distributed.Mobility.SAE].  A lookup
   query to the hash table will retrieve the location information of an
   MN is stored.

   In [Paper-Distributed.Mobility.PMIP], only the mobility routing (MR)
   function is duplicated and distributed in many locations.  The
   location information for any MN that has moved to a visited network
   is still centralized and kept at a location management (LM) function
   in the home network of the MN.  The LM function at different networks
   constitutes a distributed database system of all the MNs that belong
   to any of these networks and have moved to a visited network.  The
   location information is maintained in the form of a hierarchy: the LM
   at the home network, the CoA of the MR of the visited network, and

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   then the CoA to reach the MN in the visited network.  The LM in the
   home network keeps a binding of the HoA of the MN to the CoA of the
   MR of the visited network.  The MR keeps the binding of the HoA of
   the MN to the CoA of the MN in the case of MIP, or the proxy-CoA of
   the Mobile Access Gateway (MAG) serving the MN in the case of PMIP.

   [I-D.jikim-dmm-pmip] discusses two distributed mobility control
   schemes using the PMIP protocol: Signal-driven PMIP (S-PMIP) and
   Signal-driven Distributed PMIP (SD-PMIP).  S-PMIP is a partially
   distributed scheme, in which the control plane (using a Proxy Binding
   Query to get the Proxy-CoA of the MN) is separate from the data
   plane, and the optimized data path is directly between the CN and the
   MN.  SD-PMIP is a fully distributed scheme, in which the Proxy
   Binding Update is not performed, and instead each MAG will multicast
   a Proxy Binding Query message to all of the MAGs in its local PMIP
   domain to retrieve the Proxy-CoA of the MN.

4.  Requirements

   After reviewing the problems and limitations of centralized
   deployment in Section 4, this section states the requirements as

4.1.  Distributed deployment

   REQ1:  Distributed deployment

          IP mobility, network access and routing solutions provided by
          DMM MUST enable a distributed deployment of mobility
          management of IP sessions so that the traffic can be routed in
          an optimal manner without traversing centrally deployed
          mobility anchors.

          Motivation: The motivations of this requirement are to match
          mobility deployment with current trend in network evolution:
          more cost and resource effective to cache and distribute
          contents when combining distributed anchors with caching
          systems (e.g., CDN); improve scalability; avoid single point
          of failure; mitigate threats being focused on a centrally
          deployed anchor, e.g., home agent and local mobility anchor.

   This requirement addresses the following problems PS1, PS2, PS3, and

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   PS1:  Non-optimal routes

         Routing via a centralized anchor often results in a longer
         route, and the problem is especially manifested when accessing
         a local or cache server of a Content Delivery Network (CDN).

   PS2:  Non-optimality in Evolved Network Architecture

         The centralized mobility management can become non-optimal as a
         network architecture evolves and becomes more flattened.

   PS3:  Low scalability of centralized route and mobility context

         Setting up such special routes and maintaining the mobility
         context for each MN is more difficult to scale in a centralized
         design with a large number of MNs.  Distributing the route
         maintenance function and the mobility context maintenance
         function among different networks can be more scalable.

   PS4:  Single point of failure and attack

         Centralized anchoring may be more vulnerable to single point of
         failure and attack than a distributed system.

4.2.  Transparency to Upper Layers when needed

   REQ2:  Transparency to Upper Layers when needed

          The DMM solutions MUST provide transparency above the IP layer
          when needed.  Such transparency is needed, when the mobile
          hosts or entire mobile networks [RFC3963] change their point
          of attachment to the Internet, for the application flows that
          cannot cope with a change of IP address.  Otherwise the
          support to maintain a stable home IP address or prefix during
          handover may be declined.

          Motivation: The motivation of this requirement is to enable
          more efficient use of network resources and more efficient
          routing by not maintaining a stable IP home IP address when
          there is no such need.

   This requirement addresses the problems PS5 as well as the other
   related problem O-PS1.

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   PS5:  Wasting resources to support mobile nodes not needing mobility

         IP mobility support is not always required.  For example, some
         applications do not need a stable IP address during handover,
         i.e., IP session continuity.  Sometimes, the entire application
         session runs while the terminal does not change the point of
         attachment.  In these situations that do not require IP
         mobility support, network resources are wasted when mobility
         context is set up.

   O-PS1:  Mobility signaling overhead with peer-to-peer communication

           Wasting resources when mobility signaling (e.g., maintenance
           of the tunnel, keep alive, etc.) is not turned off for peer-
           to-peer communication.

4.3.  IPv6 deployment

   REQ3:  IPv6 deployment

          The DMM solutions SHOULD target IPv6 as primary deployment and
          SHOULD NOT be tailored specifically to support IPv4, in
          particular in situations where private IPv4 addresses and/or
          NATs are used.

          Motivation: The motivation for this requirement is to be
          inline with the general orientation of IETF.  Moreover, DMM
          deployment is foreseen in mid-term/long-term, hopefully in an
          IPv6 world.  It is also unnecessarily complex to solve this
          problem for IPv4, as we will not be able to use some of the
          IPv6-specific features/tools.

4.4.  Compatibility

   REQ4:  Compatibility

          The DMM solution SHOULD be able to work between trusted
          administrative domains when allowed by the security measures
          deployed between these domains.  Furthermore, the DMM solution
          MUST be able to co-exist with existing network deployment and
          end hosts so that the existing deployment can continue to be
          supported.  For example, depending on the environment in which
          dmm is deployed, the dmm solutions may need to be compatible
          with other existing mobility protocols that are deployed in
          that environment or may need to be interoperable with the
          network or the mobile hosts/routers that do not support the
          dmm enabling protocol.

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          Motivation: The motivation of this requirement is to allow
          inter-domain operation if desired and to preserve backwards
          compatibility so that the existing networks and hosts are not
          affected and do not break.

   This requirement addresses the following other related problem O-PS2.

   O-PS2:  Complicated deployment with too many variants and extensions
           of MIP Deployment is complicated with many variants and
           extensions of MIP.  When introducing new functions which may
           add to the complicity, existing solutions are more vulnerable
           to break.

4.5.  Existing mobility protocols

   REQ5:  Existing mobility protocols

          A DMM solution SHOULD first consider reusing and extending the
          existing mobility protocols before specifying new protocols.

          Motivation: The purpose is to reuse the existing protocols
          first before considering new protocols.

4.6.  Security considerations

   REQ6:  Security considerations

          The protocol solutions for DMM MUST consider security, for
          example authentication and authorization mechanisms that allow
          a legitimate mobile host/router to access to the DMM service,
          protection of signaling messages of the protocol solutions in
          terms of authentication, data integrity, and data
          confidentiality, opti-in or opt-out data confidentiality to
          signaling messages depending on network environments or user

          Motivation and problem statement: Mutual authentication and
          authorization between a mobile host/router and an access
          router providing the DMM service to the mobile host/router are
          required to prevent potential attacks in the access network of
          the DMM service.  Otherwise, various attacks such as
          impersonation, denial of service, man-in-the-middle attacks,
          etc. are present to obtain illegitimate access or to collapse
          the DMM service.

          Signaling messages are subject to various attacks since these
          messages carry context of a mobile host/router.  For instance,
          a malicious node can forge and send a number of signaling

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          messages to redirect traffic to a specific node.
          Consequently, the specific node is under a denial of service
          attack, whereas other nodes are not receiving their traffic.
          As signaling messages travel over the Internet, the end-to-end
          security is required.

5.  Security Considerations

   Distributed mobility management (DMM) requires two kinds of security
   considerations: 1) access network security that only allows a
   legitimate mobile host/router to access the DMM service; 2) end-to-
   end security that protects signaling messages for the DMM service.
   Access network security is required between the mobile host/router
   and the access network providing the DMM service.  End-to-end
   security is required between nodes that participate in the DMM

   It is necessary to provide sufficient defense against possible
   security attacks, or to adopt existing security mechanisms and
   protocols to provide sufficient security protections.  For instance,
   EAP based authentication can be used for access network security,
   while IPsec can be used for end-to-end security.

6.  IANA Considerations


7.  Co-authors and Contributors

   This problem statement document is a joint effort among the following
   participants.  Each individual has made significant contributions to
   this work.

   Dapeng Liu:

   Pierrick Seite:

   Hidetoshi Yokota:

   Charles E. Perkins:

   Melia Telemaco:

   Elena Demaria:

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   Peter McCann:

   Tricci So:

   Jong-Hyouk Lee:

   Jouni Korhonen:

   Wen Luo:

   Carlos J. Bernardos:

   Marco Liebsch:

   Georgios Karagian:

   Julien Laganier:

   Wassim Michel Haddad:

   Seok Joo Koh:

8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

8.2.  Informative References

              Zhou, X., Korhonen, J., Williams, C., Gundavelli, S., and
              C. Bernardos, "Prefix Delegation for Proxy Mobile IPv6",
              draft-ietf-netext-pd-pmip-02 (work in progress),
              March 2012.

              Kim, J., Koh, S., Jung, H., and Y. Han, "Use of Proxy
              Mobile IPv6 for  Distributed Mobility Control",
              draft-jikim-dmm-pmip-00 (work in progress), March 2012.

              Yokota, H., Seite, P., Demaria, E., and Z. Cao, "Use case
              scenarios  for Distributed Mobility Management",
              draft-yokota-dmm-scenario-00 (work in progress),
              October 2010.

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              Bertin, P., Bonjour, S., and J-M. Bonnin, "A Distributed
              or Centralized Mobility",  Proceedings of Global
              Communications Conference  (GlobeCom), December 2009.

              Bertin, P., Bonjour, S., and J-M. Bonnin, "A Distributed
              Dynamic Mobility Management Scheme  Designed for Flat IP
              Architectures",  Proceedings of 3rd International
              Conference  on New Technologies, Mobility and Security
              (NTMS), 2008.

              Chan, H., "Proxy Mobile IP  with Distributed Mobility
              Anchors",  Proceedings of GlobeCom Workshop  on Seamless
              Wireless Mobility, December 2010.

              Chan, H., Yokota, H., Xie, J., Seite, P., and D. Liu,
              "Distributed and Dynamic Mobility Management  in Mobile
              Internet: Current Approaches and Issues, Journal of
              Communications, vol. 6, no. 1, pp. 4-15, Feb 2011.",
               Proceedings of GlobeCom Workshop  on Seamless Wireless
              Mobility, February 2011.

              Fisher, M., Anderson, F., Kopsel, A., Schafer, G., and M.
              Schlager, "A Distributed IP Mobility Approach for 3G SAE",
               Proceedings of the 19th International Symposium  on
              Personal, Indoor and Mobile Radio Communications (PIMRC),

              Kirby, G., "Locating the User",  Communication
              International, 1995.

              Wakikawa, R., Valadon, G., and J. Murai, "Migrating Home
              Agents  Towards Internet-scale Mobility Deployments",
               Proceedings of the ACM 2nd CoNEXT Conference  on Future
              Networking Technologies, December 2006.

   [RFC3963]  Devarapalli, V., Wakikawa, R., Petrescu, A., and P.
              Thubert, "Network Mobility (NEMO) Basic Support Protocol",
              RFC 3963, January 2005.

   [RFC5213]  Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
              and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.

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   [RFC6275]  Perkins, C., Johnson, D., and J. Arkko, "Mobility Support
              in IPv6", RFC 6275, July 2011.

Author's Address

   H Anthony Chan (editor)
   Huawei Technologies
   5340 Legacy Dr. Building 3, Plano, TX 75024, USA
   Dapeng Liu
   China Mobile
   Unit2, 28 Xuanwumenxi Ave, Xuanwu District,  Beijing 100053, China
   Pierrick Seite
   France Telecom - Orange
   4, rue du Clos Courtel, BP 91226,  Cesson-Sevigne 35512, France
   Hidetoshi Yokota
   KDDI Lab
   2-1-15 Ohara, Fujimino, Saitama, 356-8502 Japan
   Charles E. Perkins
   Huawei Technologies
   Jouni Korhonen
   Nokia Siemens Networks
   Melia Telemaco
   Alcatel-Lucent Bell Labs
   Elena Demaria
   Telecom Italia
   via G. Reiss Romoli, 274, TORINO, 10148, Italy
   Jong-Hyouk Lee
   RSM Department, Telecom Bretagne
   Cesson-Sevigne, 35512, France

Chan (Ed.)               Expires January 8, 2013               [Page 15]

Internet-Draft                  DMM-Reqs                       July 2012

   Tricci So
   Carlos J. Bernardos
   Universidad Carlos III de Madrid
   Av. Universidad, 30, Leganes, Madrid 28911, Spain
   Peter McCann
   Huawei Technologies
   Seok Joo Koh
   Kyungpook National University, Korea
   Wen Luo
   No.68, Zijinhua RD,Yuhuatai District, Nanjing, Jiangsu 210012, China
   Marco Liebsch
   NEC Laboratories Europe

Chan (Ed.)               Expires January 8, 2013               [Page 16]