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Network Working Group                                      H. Chan (Ed.)
Internet-Draft                                       Huawei Technologies
Intended status: Informational                            March 30, 2011
Expires: October 1, 2011

   Problem statement for distributed and dynamic mobility management


   Cellular networks have been hierarchical so that mobility management
   have primarily been deployed in a centralized architecture.  Mobility
   solutions deployed with centralized mobility anchoring in existing
   hierarchical mobile networks are more prone to the following problems
   or limitations compared with distributed and dynamic mobility
   management: (1) Routing via a centralized anchor is often longer, so
   that those mobility protocol deployments that lack optimization
   extensions results in non-optimal routes, affecting performance;
   whereas routing optimization may be an integral part of a distributed
   design. (2) As mobile network becomes more flattened centralized
   mobility management can become more non-optimal, especially as the
   content servers in a content delivery network (CDN) are moving closer
   to the access network; in contrast, distributed mobility management
   can support both hierarchical network and more flattened network as
   it also supports CDN networks. (3) Centralized route maintenance and
   context maintenance for a large number of mobile hosts is more
   difficult to scale. (4) Scalability may worsen when lacking mechanism
   to distinguish whether there are real need for mobility support;
   dynamic mobility management, i.e., to selectively provide mobility
   support, is needed and may be better implemented with distributed
   mobility management. (5) Deployment is complicated with numerous
   variants and extensions of mobile IP; these variants and extensions
   may be better integrated in a distributed and dynamic design which
   can selectively adapt to the needs. (6) Excessive signaling overhead
   should be avoided when end nodes are able to communicate end-to-end;
   capability to selectively turn off signaling that are not needed by
   the end hosts will reduce the handover delay. (7) Centralized
   approach is generally more vulnerable to a single point of failure
   and attack often requiring duplication and backups, whereas a
   distributed approach intrinsically mitigates the problem to a local
   network so that the needed protection can be simpler.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions used in this document  . . . . . . . . . . . . . .  5
   3.  Centralized versus distributed mobility management . . . . . .  6
     3.1.  Centralized mobility management  . . . . . . . . . . . . .  6
     3.2.  Distributed mobility management  . . . . . . . . . . . . .  7
   4.  Problem statement  . . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Non-optimal routes . . . . . . . . . . . . . . . . . . . .  9
     4.2.  Non-optimality in Evolved Network Architecture . . . . . . 10
     4.3.  Low scalability of centralized route and mobility
           context maintenance  . . . . . . . . . . . . . . . . . . . 11
     4.4.  Wasting resources to support mobile nodes not needing
           mobility support . . . . . . . . . . . . . . . . . . . . . 11
     4.5.  Complicated deployment with too many variants and
           extensions of MIP  . . . . . . . . . . . . . . . . . . . . 12
     4.6.  Mobility signaling overhead with peer-to-peer
           communication  . . . . . . . . . . . . . . . . . . . . . . 12
     4.7.  Single point of failure and attack . . . . . . . . . . . . 13
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
   7.  Co-authors and Contributors  . . . . . . . . . . . . . . . . . 14
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16

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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, among other tasks, ensures forwarding of packets destined
   to or sent from the mobile device.  As such, most of the deployed
   architectures today have a small number of centralized anchors
   managing the traffic of millions of mobile subscribers.  Coompared
   with a distributed approach, a centralized approach have several
   issues or limitations affecting performance and scalability, which
   require costly network dimensioning and engineering to fix them.

   To optimize handovers for mobile users, 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 signalling overhead.  Unfortunately today we
   witness difficulties in getting such protocols deployed, often
   leading to sub-optimal choices.

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

   Mobile users are, more than ever, consuming Internet content, and
   impose new requirements on mobile core networks for data traffic
   delivery.  When this 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 Providers
   network requires taking into account local Content Delivery Networks
   (CDNs) while providing mobility services.

   As long as demand exceeds capactity, both offloading and CDN
   techniques could benefit from the development of more flat mobile

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   architectures (i.e., fewer levels of routing hierarchy introduced
   into the data path by the mobility management system).  This view is
   reinforced by the shift in users!_ traffic behavior, aimed at
   increasing direct communications among peers in the same geographical
   area.  The development of truly flat mobile architectures would
   result in anchoring the traffic closer to point of attachment of the
   user and overcoming 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, in which
   case specific IP mobility management support is not required for
   applications that launch and complete while 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 work 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 anchors
   topologically distant.

   This document discusses the issues with centralized IP mobility
   management compared with distributed and dynamic mobility management.
   A companion document [dmm-senario] discusses the use case senarios.

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT",

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   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 OSI stack.  At the IP layer, they may reside in the network or
   in the mobile node.  In particular, network-based solution resides in
   the network only.  It therefore enables mobility for hosts and
   network applications which lack mobility support in them but are
   already in deployment.

   At the IP layer, a mobility management protocol to achieve session
   continuity are typically based on the principle of distinguishing
   between session identifier and routing address and maintaining a
   mapping between them.  With Mobile IP, the home address takes the
   role of session identifier 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.

   Mobility management functions in the network may be centralized or
   distributed, as is explained in the next two subsections.

3.1.  Centralized mobility management

   With centralized mobility management, the mapping information for the
   stable session identifier and the changing IP address of an 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 leverage on 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 IP
   [RFC3775] and Proxy Mobile IP [RFC5213] , respectively.  Current
   mobile networks such as the Third Generation Partnership Project
   (3GPP) UMTS networks, CDMA networks, and 3GPP Evolve Packet System
   (EPS) networks also employs 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.

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          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.

   Distributed 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.dmm-scenario].

   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] .

   While it is possible to design new mobility management protocols for
   the future flat IP architecture, one may first ask whether the
   existing mobility management protocols that have already been
   deployed for the hierarchical mobile networks can be extended to

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   serve the flat IP architecture.  Indeed, 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 will then ease the
   migration of the current mobile networks towards the future 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 a HoA from any 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 find out where the location information of an MN is

   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
   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.PMIP-DMC] 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 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 Binidng
   Query message to all of the MAGs in its local PMIP domain so as to
   get the Proxy-CoA of the MN.

4.  Problem statement

   This section describes the problems or limitations in a centralized

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   mobility approach and compares it against the distributed approach.

4.1.  Non-optimal routes

   Routing via a centralized anchor often results in a longer route.
   Figure 3 shows two cases of non-optimized routes.

           /\ \  \                   +---+
          /  \   \    \              |CDN|
         /    \     \      \         +---+
        /      \       \        \      |
       /        \         \          \ |
   +------+  +------+  +------+   +------+
   |FA/MAG|  |FA/MAG|  |FA/MAG|   |FA/MAG|
   +------+  +------+  +------+   +------+
                          |          |
                        ----       ----
                       | CN |     | MN |
                        ----       ----

   Figure 3.  Non-optimized route when communicating with CN and when
   accessing local content.

   In the first case, the mobile node and the correspondent node are
   close to each other but are both far from the mobility anchor.
   Packets destined to the mobile node need to be routed via the
   mobility anchor, which is not in the shortest path.  The second case
   involves a content delivery network (CDN).  A user may obtain content
   from a server, such as when watching a video.  As such usage becomes
   more popular, resulting in an increase in the core network traffic,
   service providers may relieve the core network traffic by placing
   these contents closer to the users in the access network in the form
   of cache or local CDN servers.  Yet as the MN is getting content from
   a local or cache server of a CDN, even though the server is close to
   the MN, packets still need to go through the core network to route
   via the mobility anchor in the home network of the MN, if the MN uses
   the HoA as the session identifier.

   In a distributed mobility management design, mobility anchors are
   distributed in different access networks so that packets may be
   routed via a nearby mobility anchor function, as shown in Figure 4.

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

   Figure 4.  Mobile node in any network is served by a close by
   mobility function.

   Due to the above limitation, with the centralized mobility anchor
   design, route optimization extensions to mobility protocols are
   therefore needed.  Whereas the location privacy of each MN may be
   compromised when the CoA of an MN is given to the CN, those mobility
   protocol deployments that lack such optimization extensions will
   encounter non-optimal routes, which affect the performance.

   In contrast, route optimization may be naturally an integral part of
   a distributed mobility management design.  With the help of such
   intrinsic route optimization, the data transmission delay will be
   reduced, by which the data transmission throughputs can be enhanced.
   Furthermore, the data traffic overhead at the mobility agents such as
   the HA and the LMA in the core network can be alleviated

4.2.  Non-optimality in Evolved Network Architecture

   Centralized mobility management is currently deployed to support the
   existing hierarchical mobile data networks.  It leverages on the
   hierarchical architecture.  However, the volume of wireless data
   traffic continues to increase exponentially.  The data traffic
   increase would require costly capacity upgrade of centralized
   architectures.  It is thus predictable that the data traffic increase
   will soon overload the centralized data anchor point, e.g., the P-GW
   in 3GPP EPS.  In order to address this issue, a trend in the
   evolution of mobile networks is to distribute network functions close
   to access networks.  These network functions can be the content
   servers in a CDN, and also the data anchor point.

   Mobile networks have been evolving from a hierarchical architecture
   to a more flattened architecture.  In the 3GPP standards, the GPRS
   network has the hierarchy GGSN "C SGSN "C RNC "C NB (Node B).  In

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   3GPP EPS networks, the hierarchy is reduced to P-GW "C S-GW "C eNB
   (Evolved NB).  In some deployments, the P-GW and the S-GW are
   collocated to further reduce the hierarchy.  Reducing the hierarchy
   this way reduces the number of different physical network elements in
   the network, contributing to easier system maintenance and lower
   cost.  As mobile networks become more flattened, the centralized
   mobility management can become non-optimal.  Mobility management
   deployment with distributed architecture is then needed to support
   the more flattened network and the CDN networks.

4.3.  Low scalability of centralized route and mobility context

   Special routes are set up to enable session continuity when a
   handover occurs.  Packets sent from the CN need to be tunneled
   between the HA and FA in MIP and between the LMA and MAG in PMIP.
   However, these network elements at the ends of the tunnel are also
   routers performing the regular routing tasks for ordinary packets not
   involving a mobile node.  These ordinary packets need to be directly
   routed according to the routing table in the routers without
   tunneling.  Therefore, the network must be able to distinguish those
   packets requiring tunneling from the regular packets.  For each
   packet that requires tunneling owing to mobility, the network will
   encapsulate it with a proper outer IP header with the proper source
   and destination IP addresses.  The network therefore needs to
   maintain and manage the mobility context of each MN, which is the
   relevant information needed to characterize the mobility situation of
   that MN to allow the network to distinguish their packets from other
   packets and to perform the required tunneling.

   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.

4.4.  Wasting resources to support mobile nodes not needing mobility

   The problem of centralized route and mobility context maintenance is
   aggravated when the via routes are set up for many more MNs that are
   not requiring IP mobility support.  On the one hand, the network
   needs to provide mobility support for the increasing number of mobile
   devices because the existing mobility management has been designed to
   always provide such support as long as a mobile device is attached to
   the network.  On the other hand, many nomadic users connected to a
   network in an office or meeting room are not even going to move for
   the entire network session.  It has been studied that over two-thirds

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   of a user mobility is local [Paper-Locating.User] .  In addition, it
   is possible to have the intelligence for applications to manage
   mobility without needing help from the network.  Network resources
   are therefore wasted to provide mobility support for the devices that
   do not really need it at the moment.

   It is necessary to dynamically set up the via routes only for MNs
   that actually undergo handovers and lack higher-layer mobility
   support.  With distributed mobility anchors, such dynamic mobility
   management mechanism may then also be distributed.  Therefore,
   dynamic mobility and distributed mobility may complement each other
   and may be integrated.

4.5.  Complicated deployment with too many variants and extensions of

   Mobile IP, which has primarily been deployed in a centralized manner
   for the hierarchical mobile networks, already has numerous variants
   and extensions including PMIP, Fast MIP (FMIP) [RFC4068] [RFC4988] ,
   Proxy-based FMIP (PFMIP) [RFC5949] , hierarchical MIP (HMIP)
   [RFC5380] , Dual-Stack Mobile IP (DSMIP) [RFC5454] [RFC5555] and
   there may be more to come.  These different modifications or
   extensions of MIP have been developed over the years owing to the
   different needs that are found afterwards.  Deployment can then
   become complicated, especially if interoperability with different
   deployments is an issue.

   A desirable feature of mobility management is to be able to work with
   network architectures of both hierarchical networks and flattened
   networks, so that the mobility management protocol possesses enough
   flexibility to support different networks.  In addition, one goal of
   dynamic mobility management is the capability to selectively turn on
   and off mobility support and certain different mobility signaling.
   Such flexibility in the design is compatible with the goal to
   integrate different mobility variants as options.  Some additional
   extensions to the base protocols may then be needed to improve the

4.6.  Mobility signaling overhead with peer-to-peer communication

   In peer-to-peer communications, end users communicate by sending
   packets directly addressed to each other!_s IP address.  However,
   they need to find each other!_s IP address first through signaling in
   the network.  While different schemes for this purpose may be used,
   MIP already has a mechanism to locate an MN and may be used in this
   way.  In particular, MIPv6 Route Optimization (RO) mode enables a
   more efficient data packets exchange than the bidirectional tunneling
   (BT) mode, as shown in Figure 5.

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           /\ \  \
          /  \   \    \
         /    \     \      \
        /      \       \        \
       /        \         \          \
   +------+  +------+  +------+   +------+
   |FA/MAG|  |FA/MAG|  |FA/MAG|   |FA/MAG|
   +------+  +------+  +------+   +------+
                          |          |
                        ----       ----
                       | MN |<--->| CN |
                        ----       ----

   Figure 5.  Non-optimized route when communicating with CN and when
   accessing local content.

   This RO mode is expected to be used whenever possible unless the MN
   is not interested in disclosing its topological location, i.e., the
   CoA, to the CN (e.g., for privacy reasons) or some other network
   constraints are put in place.  However, MIPv6 RO mode requires
   exchanging a significant amount of signaling messages in order to
   establish and periodically refresh a bidirectional security
   association (BSA) between an MN and its CN.  While the mobility
   signaling exchange impacts the overall handover latency, the BSA is
   needed to authenticate the binding update and acknowledgment messages
   (note that the latter is not mandatory).  In addition, the amount of
   mobility signaling messages increases further when both endpoints are

   A dynamic mobility management capability to turn off these signaling
   when they are not needed will enable the RO mode between two mobile
   endpoints at minimum or no cost.  It will also reduce the handover
   latency owing to the removal of the extra signaling.  These benefits
   for peer-to-peer communications will encourage the adoption and
   large-scale deployment of dynamic mobility management.

4.7.  Single point of failure and attack

   A centralized anchoring architecture is generally more vulnerable to
   a single point of failure or attack, requiring duplication and
   backups of the support functions.

   On the other hand, a distributed mobility management architecture has
   intrinsically mitigated the problem to a local network which is then

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   of a smaller scope.  In addition, the availability of such functions
   in neighboring networks has already provided the needed architecture
   to support protection.

5.  Security Considerations


6.  IANA Considerations


7.  Co-authors and Contributors

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

   Dapeng Liu: liudapeng@chinamobile.com

   Pierrick Seite: pierrick.seite@orange-ftgroup.com

   Hidetoshi Yokota: yokota@kddilabs.jp

   Charles E. Perkins: charles.perkins@tellabs.com

   Melia Telemaco: telemaco.melia@alcatel-lucent.com

   Hui Deng: denghui@chinamobile.com

   Elena Demaria: elena.demaria@telecomitalia.it

   Zhen Cao: caozhen@chinamobile.com

   Wassim Michel Haddad: Wassam.Haddad@ericsson.com

   Seok Joo Koh: sjkoh@knu.ac.kr

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.

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8.2.  Informative References

              Koh, S., Kim, J., Jung, H., and Y. Han, "Use of Proxy
              Mobile IPv6 for Distributed Mobility Control",
              draft-sjkoh-mext-pmip-dmc-01 (work in progress),
              March 2011.

              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.

              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.

              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.

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   [RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.

   [RFC4068]  Koodli, R., "Fast Handovers for Mobile IPv6", RFC 4068,
              July 2005.

   [RFC4988]  Koodli, R. and C. Perkins, "Mobile IPv4 Fast Handovers",
              RFC 4988, October 2007.

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

   [RFC5380]  Soliman, H., Castelluccia, C., ElMalki, K., and L.
              Bellier, "Hierarchical Mobile IPv6 (HMIPv6) Mobility
              Management", RFC 5380, October 2008.

   [RFC5454]  Tsirtsis, G., Park, V., and H. Soliman, "Dual-Stack Mobile
              IPv4", RFC 5454, March 2009.

   [RFC5555]  Soliman, H., "Mobile IPv6 Support for Dual Stack Hosts and
              Routers", RFC 5555, June 2009.

   [RFC5949]  Yokota, H., Chowdhury, K., Koodli, R., Patil, B., and F.
              Xia, "Fast Handovers for Proxy Mobile IPv6", RFC 5949,
              September 2010.

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Author's Address

   H Anthony Chan (editor)
   Huawei Technologies
   5340 Legacy Dr Building 3, Plano, TX 75024, USA
   Email: h.a.chan@ieee.org
   Dapeng Liu
   China Mobile
   Unit2, 28 Xuanwumenxi Ave, Xuanwu District, Beijing 100053, China
   Email: liudapeng@chinamobile.com
   Pierrick Seite
   France Telecom - Orange
   4, rue du Clos Courtel, BP 91226, Cesson-Sevigne 35512, France
   Email: pierrick.seite@orange-ftgroup.com
   Hidetoshi Yokota
   KDDI Lab
   2-1-15 Ohara, Fujimino, Saitama, 356-8502 Japan
   Email: yokota@kddilabs.jp
   Charles E. Perkins
   Tellabs Inc.
   3590 N. 1st Street, Suite 300, San Jose, CA 95134, USA
   Email: charles.perkins@tellabs.com
   Melia Telemaco
   Alcatel-Lucent Bell Labs
   Email: telemaco.melia@alcatel-lucent.com
   Wassim Michel Haddad
   300 Holger Dr, San Jose, CA 95134, USA
   Email: Wassam.Haddad@ericsson.com
   Elena Demaria
   Telecom Italia
   via G. Reiss Romoli, 274, TORINO, 10148, Italy
   Email: elena.demaria@telecomitalia.it
   Seok Joo Koh
   Kyungpook National University, Korea
   Email: sjkoh@knu.ac.kr

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