Network Working Group                                      H. Chan (Ed.)
Internet-Draft                                 Huawei Technologies (more
Intended status: Informational                      co-authors on P. 17)
Expires: June 5, August 4, 2014                                           D. Liu
                                                            China Mobile
                                                                P. Seite
                                                                  Orange
                                                               H. Yokota
                                                                KDDI Lab
                                                             J. Korhonen
                                                 Broadcom Communications
                                                        December 2, 2013
                                                        January 31, 2014

            Requirements for Distributed Mobility Management
                     draft-ietf-dmm-requirements-12
                     draft-ietf-dmm-requirements-13

Abstract

   This document defines the requirements for Distributed Mobility
   Management (DMM). (DMM) at the network layer.  The hierarchical structure in
   traditional wireless networks has led primarily to centralized
   deployment models.  As some wireless networks are evolving away from
   the hierarchical structure, a distributed model for mobility
   management can be useful to them.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 RFC 2119
   [RFC2119].

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on June 5, August 4, 2014.

Copyright Notice

   Copyright (c) 2013 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3  4
   2.  Conventions used in this document  . . . . . . . . . . . . . .  4  5
     2.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  4  5
   3.  Centralized versus distributed mobility management . . . . . .  5  6
     3.1.  Centralized mobility management  . . . . . . . . . . . . .  6  7
     3.2.  Distributed mobility management  . . . . . . . . . . . . .  7  8
   4.  Problem Statement  . . . . . . . . . . . . . . . . . . . . . .  8  9
   5.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 10
     5.1.  Distributed processing . . . . . . . . . . . . . . . . . . 10
     5.2.  Transparency to Upper Layers when needed . . . . . . . . . 10
     5.3.  IPv6 deployment  . . . . . . . . . . . . . . . . . . . . . 11
     5.4.  Existing mobility protocols  . . . . . . . . . . . . . . . 11
     5.5.  Co-existence . . . . . . . . . . . . . . . . . . . . . . . 11
     5.6.  Security considerations  . . . . . . . . . . . . . . . . . 12
     5.7.  Multicast  . . . . . . . . . . . . . . . . . . . . . . . . 12
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13 14
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13 14
   8.  Co-authors and Contributors  . . . . . . . . . . . . . . . . . 13 14
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 14
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 13 14
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 17

1.  Introduction

   In the past decade a fair number of network-layer mobility protocols
   have been standardized [RFC6275] [RFC5944] [RFC5380] [RFC6301]
   [RFC5213].  Although the protocols differ in terms of functions and
   associated message formats, they all employ a mobility anchor to
   allow a mobile node to remain reachable after it has moved to a
   different network.  The anchor point, among other tasks, ensures
   connectivity by forwarding packets destined to, or sent from, the
   mobile node.  It is a centrally deployed mobility anchor in the sense
   that the deployed architectures today have a small number of these
   anchors and the traffic of millions of mobile nodes in an operator
   network are typically managed by the same anchor.

   Distributed mobility management (DMM) is an alternative to the above
   centralized deployment.  The background behind the interests to study
   DMM are primarily in the following.

   (1)  Mobile users are, more than ever, consuming Internet content
        including that of local Content Delivery Networks (CDNs) which
        had not taken mobility service into account before.  Such
        traffic imposes new requirements on mobile core networks for
        data traffic delivery.  To prevent exceeding the available core
        network capacity, service providers need to implement new
        strategies such as selective IPv4 traffic offload (e.g.
        [RFC6909], 3GPP work items LIPA/SIPTO Local IP Access (LIPA) and Selected
        IP Traffic Offload (SIPTO) [TS.23.401]) through alternative
        access networks (e.g.  WLAN) [Paper-
        Mobile.Data.Offloading]. [Paper-Mobile.Data.Offloading].  In
        addition, a gateway selection mechanism takes the user proximity
        into account within EPC [TS.29303].  Yet these mechanisms were
        not pursued in the past owing to charging and billing which
        require solutions beyond the mobility protocol.  Consequently,
        assigning a gateway anchor node from a visited network in
        roaming scenario has until recently been done and are limited to
        voice services only.

        Both traffic offloading and CDN mechanisms 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 towards so-called "flat networks"
        works best for 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.

   (2)  Today's mobile networks present service providers with new
        challenges.  Mobility patterns indicate that mobile nodes often
        remain attached to the same point of attachment for considerable
        periods of time [Paper-Locating.User].  Specific IP mobility
        management support is not required for applications that launch
        and complete their sessions while the mobile node is connected
        to the same point of attachment.  However, currently, IP
        mobility support is designed for always-on operation,
        maintaining all parameters of the context for each mobile
        subscriber for as long as they are connected to the network.
        This can result in a waste of resources and unnecessary costs
        for the service provider.  Infrequent node mobility coupled with
        application intelligence suggest that mobility support could be
        provided selectively such as in [I-D.bhandari-dhc-class-based-
        prefix] and [I-D.korhonen-6man-prefix-properties], thus reducing
        the amount of context maintained in the network.

   The distributed mobility management (DMM) charter addresses two
   complementary aspects of mobility management procedures:

   DMM may distribute the
   distribution of mobility anchors in the data-plane towards a
   more flat network and such that the selective activation/deactivation of mobility
   protocol support as an enabler to distributed mobility management.
   The former aims at positioning mobility anchors (e.g., HA, LMA) are positioned
   closer to the user; ideally, mobility agents could be collocated with
   the first-hop router.  The latter, facilitated  Facilitated by the distribution of mobility
   anchors, identifies DMM may also selectively activate/deactivate mobility
   protocol support.  There is need to identify when mobility support
   must be activated and when sessions do not require mobility
   management support -- support.  It can thus
   reducing reduce the amount of state
   information that must be maintained in various mobility agents of the
   mobile network.  It can then avoid the unnecessary establishment of
   mechanisms to forward traffic from an old to a new mobility anchor.

   This document compares distributed mobility management with
   centralized mobility management in Section 3.  The problems that can
   be addressed with DMM are summarized in Section 4.  The mandatory
   requirements as well as the optional requirements for network-layer
   distributed mobility management are given in Section 5.  Finally,
   security considerations are discussed in Section 6.

   The problem statement and the use cases [I-D.yokota-dmm-scenario] can
   be found in [Paper-Distributed.Mobility.Review].

2.  Conventions used in this document

2.1.  Terminology

   All the general mobility-related terms and their acronyms used in
   this document are to be interpreted as defined in the Mobile IPv6
   base specification [RFC6275], in the Proxy mobile IPv6 specification
   [RFC5213], and in Mobility Related Terminology [RFC3753].  These
   terms include the following: mobile node (MN), correspondent node
   (CN), and home agent (HA) as per [RFC6275]; local mobility anchor
   (LMA) and mobile access gateway (MAG) as per [RFC5213], and context
   as per [RFC3753].

   In addition, this draft introduces the following terms.

   Centrally deployed mobility anchors

      refer to the mobility management deployments in which there are
      very few mobility anchors and the traffic of millions of mobile
      nodes in an operator network are managed by the same anchor.

   Centralized mobility management

      makes use of centrally deployed mobility anchors.

   Distributed mobility management

      is not centralized so that traffic does not need to traverse
      centrally deployed mobility anchors far from the optimal route.

   Flat mobile network

      has few levels of routing hierarchy introduced into the data path
      by the mobility management system.

   Mobility context

      is the collection of information required to provide mobility
      management support for a given mobile node.

3.  Centralized versus distributed mobility management

   Mobility management is needed because the IP address of a mobile node
   may change as the node moves.  Mobility management functions may be
   implemented at different layers of the protocol stack.  At the IP
   (network) layer, mobility management can be client-based or network-based. network-
   based.

   An IP-layer mobility management protocol is typically based on the
   principle of distinguishing between a session identifier and a
   routing address and maintaining a mapping between the two.  In Mobile
   IP, the
   home new IP address serves as of the session identifier mobile node after the node has moved is
   the routing address, whereas the care-of- original IP address (CoA) takes before the role of
   mobile node moves serves as the routing address. session identifier.  The binding
   between these two location
   management (LM) information is maintained at kept by associating the home agent (mobility anchor).
   If packets routing
   address with the session identifier.  Packets addressed to the home address of a mobile node can be
   continuously delivered
   session identifier will first route to the node, then all sessions original network which re-
   directs them using that home the routing address are unaffected even though to deliver to the session.
   Re-directing packets this way can result in long routes.  An existing
   optimization routes directly using the routing address (CoA) changes. of the host,
   and such is a host-based solution.

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

3.1.  Centralized mobility management

   In centralized mobility management, the mapping location information in terms
   of a mapping between the session identifier and the locator IP routing address of a mobile node
   (MN)
   is kept at a single mobility anchor.  At the same time, anchor, and packets destined to the MN
   session identifier are routed via this anchor.  In other words, such
   mobility management systems are centralized in both the control plane
   and the data plane (mobile node IP traffic).

   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) serving as the anchors for the mobile node (MN) and
   Mobile Access Gateway (MAG) in Mobile IPv6 [RFC6275] and in Proxy
   Mobile IPv6 [RFC5213], [RFC5213] respectively.  Current
   cellular  Cellular networks such as the
   Third Generation Partnership Project (3GPP) GPRS networks, CDMA networks, General Packet Radio
   System (GPRS) networks and 3GPP Evolved Packet System (EPS) networks
   employ centralized mobility management too.  In
   particular, the 3GPP GPRS
   network, the Gateway GPRS Support Node (GGSN), Serving GPRS Support
   Node (SGSN) and Radio Network Controller (RNC) in constitute a hierarchy
   of anchors.  In the 3GPP
   GPRS hierarchical EPS network, and the Packet Data Network Gateway
   (P-GW) and Serving Gateway (S-GW) in the 3GPP EPS network all act as anchors
   in a hierarchy. constitute another hierarchy of
   anchors.

         3G GPRS                 3GPP EPS                MIP/PMIP
         +------+                +------+                +------+
         | GGSN |                | P-GW |                |HA/LMA|
         +------+                +------+                +------+
            /\                      /\                      /\
           /  \                    /  \                    /  \
          /    \                  /    \                  /    \
         /      \                /      \                /      \
        /        \              /        \              /        \
       /          \            /          \            /          \
      /            \          /            \          /            \
  +------+      +------+  +------+      +------+  +------+      +------+
  | SGSN |      | SGSN |  | S-GW |      | S-GW |  |MN/MAG|      |MN/MAG|
  +------+      +------+  +------+      +------+  +------+      +------+
     /\            /\
    /  \          /  \
   /    \        /    \
+---+  +---+  +---+  +---+
|RNC|  |RNC|  |RNC|  |RNC|
+---+  +---+  +---+  +---+

   Figure 1.  Centralized mobility management.

3.2.  Distributed mobility management

   Mobility management functions may also be distributed to multiple
   networks as shown in Figure 2, so that a mobile node in any of these
   networks may be served by a nearby function with appropriate routing/
   mobility
   mobility/routing management (RM) capability.

                    +------+  +------+  +------+  +------+
                    |  RM  |  |  RM  |  |  RM  |  |  RM  |
                    +------+  +------+  +------+  +------+
                                           |
                                         +----+
                                         | MN |
                                         +----+

   Figure 2.  Distributed mobility management.

   Mobility management may be partially or fully distributed
   [I-D.yokota-dmm-scenario].  In the former case only the data plane is
   distributed, implicitly assuming separation of data and control
   planes as described in [I-D.wakikawa-netext-pmip-cp-up-separation].
   Fully distributed mobility management implies that both the data
   plane and the control plane are distributed.  While mobility
   management can be distributed, it is not necessary for other
   functions such as subscription management, subscription database, and
   network access authentication to be similarly distributed.

   A distributed mobility management scheme for a flat mobile network of
   access nodes is proposed in [Paper-Distributed.Dynamic.Mobility].
   Its benefits over centralized mobility management have been shown
   through simulations [Paper-Distributed.Centralized.Mobility].
   Moreover, the (re)use and extension of existing protocols in the
   design of both fully distributed mobility management [Paper-
   Migrating.Home.Agents] [Paper-Distributed.Mobility.SAE] and partially
   distributed mobility management [Paper-Distributed.Mobility.PMIP]
   [Paper-Distributed.Mobility.MIP] have been reported in the
   literature.  Therefore, before designing new mobility management
   protocols for a future distributed architecture, it is recommended to
   first consider whether existing mobility management protocols can be
   extended.

4.  Problem Statement

   The problems that can be addressed with DMM are summarized in the
   following:

   PS1:  Non-optimal routes

         Routing via a centralized anchor often results in non-optimal
         routes, thereby increasing the end-to-end delay.  The problem
         is manifested, for example, when accessing a nearby server or
         servers of a Content Delivery Network (CDN), or when receiving
         locally available IP multicast or sending IP multicast packets.
         (Existing route optimization is only a host-based solution.  On
         the other hand, localized routing with PMIPv6 [RFC6705]
         addresses only a part of the problem where both the MN and the
         CN
         correspondent node (CN) are attached to the same MAG, and it is
         not applicable when the CN does not behave like an MN.)

   PS2:  Divergence from other evolutionary trends in network
         architectures such as distribution of content delivery.

         Mobile networks have generally been evolving towards a flat
         network.  Centralized mobility management, which is non-optimal
         with a flat network architecture, does not support this
         evolution.

   PS3:  Scalability  Lack of scalability of centralized tunnel management and
         mobility context maintenance

         Setting up tunnels through a central anchor and maintaining
         mobility context for each MN usually requires more concentrated
         resources in a centralized design, thus reducing scalability.
         Distributing the tunnel maintenance function and the mobility
         context maintenance function among different network entities
         with proper signaling protocol design can avoid increasing the
         concentrated resources with an increasing number of MNs.

   PS4:  Single point of failure and attack

         Centralized anchoring designs may be more vulnerable to single
         points of failures and attacks than a distributed system.  The
         impact of a successful attack on a system with centralized
         mobility management can be far greater as well.

   PS5:  Unnecessary mobility support to clients that do not need it

         IP mobility support is usually provided to all MNs.  Yet it is
         not always required, and not every parameter of mobility
         context is always used.  For example, some applications or
         nodes do not need a stable IP address during a handover to
         maintain session continuity.  Sometimes, the entire application
         session runs while the terminal MN does not change the point of
         attachment.  Besides, some sessions, e.g.  SIP-based sessions,
         can handle mobility at the application layer and hence do not
         need IP mobility support; it is then unnecessary to provide IP
         mobility support for such sessions.

   PS6:  (Related problem)  Mobility signaling overhead with peer-to-peer communication

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

   PS7:  (Related problem)  Deployment with multiple mobility solutions

         There are already many variants and extensions of MIP. MIP as well
         mobility solutions at other layers.  Deployment of new mobility
         management solutions can be challenging, and debugging
         difficult, when they co-exist with solutions already deployed
         in the field.

   PS8:  Duplicate multicast traffic

         IP multicast distribution over architectures using IP mobility
         solutions (e.g., [RFC6224]) may lead to convergence of
         duplicated multicast subscriptions towards the downstream
         tunnel entity (e.g.  MAG in PMIPv6).  Concretely, when
         multicast subscription for individual mobile nodes is coupled
         with mobility tunnels (e.g.  PMIPv6 tunnel), duplicate
         multicast subscription(s) is prone to be received through
         different upstream paths.  This problem may also exist or be
         more severe in a distributed mobility environment.

5.  Requirements

   After comparing distributed mobility management against centralized
   deployment in Section 3, 3 and describing the problems in Section 4,
   this section identifies the following requirements:

5.1.  Distributed processing

   REQ1:  Distributed processing

          IP mobility, network access and routing solutions provided by
          DMM MUST enable distributed processing for mobility management
          so that traffic can avoid traversing single mobility anchor
          far from the optimal route.

          Motivation: This requirement is motivated by current trends in
          network evolution: (a) it is cost- and resource-effective to
          cache contents, and distribute content by combining distributed mobility
          anchors with the caching systems (e.g., CDN); CDN) servers are
          distributed so that each user in any location can be close to
          one of the servers; (b) the significantly larger number of
          mobile nodes and flows call for improved scalability; (c)
          single points of failure are avoided in a distributed system;
          (d) threats against centrally deployed anchors, e.g., home
          agent and local mobility anchor, are mitigated in a
          distributed system.

   This requirement addresses the problems PS1, PS2, PS3, and PS4
   described in Section 4.

5.2.  Transparency to Upper Layers when needed

   REQ2:  Transparency to Upper Layers when needed  Bypassable network-layer mobility support

          DMM solutions MUST provide transparent enable network-layer mobility but it MUST
          be possible to not use it.  Mobility support above
          the IP layer when needed.  Such transparency is needed, for
          example, when, upon change of point of attachment to the
          network, when a mobile host moves and an application flow cannot
          cope with a change in the IP address.  However, it  Mobility support is
          also needed, for example, when a mobile router moves together
          with a host and an application in the host is interrupted by a
          change of IP address of the mobile router.  However mobility
          support at the network-layer is not always needed; a mobile
          node can often be stationary, and mobility support can also be
          provided at other layers.  It is then not always necessary to
          maintain a stable home IP address or prefix for every application or at
          all times for a mobile node. prefix.

          Motivation: The motivation of this requirement is to enable
          more efficient routing and more efficient use of network
          resources by selecting an IP address or prefix according to
          whether mobility support is needed and by not maintaining
          context at the mobility anchor when there is no such need.

   This requirement addresses the problem problems PS5 as well as the related
   problem and PS6 stated described in
   Section 4.

5.3.  IPv6 deployment

   REQ3:  IPv6 deployment

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

          Motivation: This requirement conforms to the general
          orientation of IETF work.  DMM deployment is foreseen in mid-
          to long-term horizon, when IPv6 is expected to be far more
          common than today.

   This requirement avoids the unnecessarily complexity in solving the
   problems in Section 4 for IPv4, which will not be able to use some of
   the IPv6-specific features.

5.4.  Existing mobility protocols

   REQ4:  Existing mobility protocols

          A DMM solution SHOULD MUST first consider reusing and extending
          IETF-standardized IETF-
          standardized protocols before specifying new protocols.

          Motivation: Reuse of existing IETF work is more efficient and
          less error-prone.

   This requirement attempts to avoid the need of new protocols
   development and therefore their potential problems of being time-
   consuming and error-prone.

5.5.  Co-existence

   REQ5:  Co-existence  Coexistence with deployed networks and hosts

          The DMM solution may require loose, tight or no integration
          into existing mobility protocols and host IP stack.
          Regardless of the integration level, the DMM solution MUST be
          able to co-exist coexist with existing network deployments and deployments, end hosts.  For example, depending on
          the environment in which DMM is deployed, DMM solutions hosts
          and routers that may
          need to be compatible with other deployed mobility protocols or may need to co-exist with a network or mobile hosts/routers
          that do not support DMM protocols.  The mobile node may also
          move between different access networks, where some of them may
          support neither DMM nor another implement existing mobility protocol.
          protocols.  Furthermore, a DMM solution SHOULD work across
          different networks, possibly operated as separate
          administrative domains, when allowed by the trust relationship
          between them.

          Motivation: (a) to preserve backwards compatibility so that
          existing networks and hosts are not affected and continue to
          function as usual, and (b) enable inter-domain operation if
          desired.

   This requirement addresses the related problem PS7 described in Section 4.

5.6.  Security considerations

   REQ6:  Security considerations

          A DMM solution MUST NOT introduce new security risks risks, or
          amplify existing security risks against which the risks, that cannot be mitigated by
          existing security mechanisms/protocols cannot offer sufficient
          protection. mechanisms or protocols.

          Motivation: Various attacks such as impersonation, denial of
          service, man-in-the-middle attacks, and so on, may be launched
          in a DMM deployment.  For instance, an illegitimate node may
          attempt to access a network providing DMM.  Another example is
          that a malicious node can forge a number of signaling messages
          thus redirecting traffic from its legitimate path.
          Consequently, the specific node is under a denial of service
          attack, whereas other nodes do not receive their traffic.
          Accordingly, security mechanisms/protocols providing access
          control, integrity, authentication, authorization,
          confidentiality, etc. can be used to protect the DMM entities
          as they are already used to protect against existing networks
          and existing mobility protocols defined in IETF.

   This requirement prevents a DMM solution from introducing
   uncontrollable problems of potentially insecure mobility management
   protocols which make deployment infeasible because platforms
   conforming to the protocols are at risk for data loss and numerous
   other dangers, including financial harm to the users.

5.7.  Multicast

   REQ7:  Multicast considerations

          DMM SHOULD enable multicast solutions to be developed to avoid
          network inefficiency in multicast traffic delivery.

          Motivation: Existing multicast deployment have been introduced
          after completing the design of the reference mobility
          protocol, often leading to network inefficiency and non-
          optimal routing for the multicast traffic.  Instead DMM should
          consider multicast early so that the multicast solutions can
          better consider efficiency nature in the multicast traffic
          delivery (such as duplicate multicast subscriptions towards
          the downstream tunnel entities).  The multicast solutions
          should then avoid restricting the management of all IP
          multicast traffic to a single host through a dedicated
          (tunnel) interface on multicast-capable access routers.

   This requirement addresses the problems PS1 and PS8 described in
   Section 4.

6.  Security Considerations

   Please refer to the discussion under Security requirement in Section
   5.6.

7.  IANA Considerations

   None

8.  Co-authors and Contributors

   This problem statement document is a joint effort among the numerous
   participants.  Each individual has made significant contributions to
   this work and have been listed as co-authors.

9.  References

9.1.  Normative References

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

9.2.  Informative References

   [I-D.bhandari-dhc-class-based-prefix]
              Bhandari, S., Halwasia, G., Gundavelli, S., Deng, H.,
              Thiebaut, L., Korhonen, J., and I. Farrer, "DHCPv6 class
              based prefix", draft-bhandari-dhc-class-based-prefix-05
              (work in progress), July 2013.

   [I-D.korhonen-6man-prefix-properties]
              Korhonen, J., Patil, B., Gundavelli, S., Seite, P., and D.
              Liu, "IPv6 Prefix Properties",
              draft-korhonen-6man-prefix-properties-02 (work in
              progress), July 2013.

   [I-D.wakikawa-netext-pmip-cp-up-separation]
              Wakikawa, R., Pazhyannur, R., and S. Gundavelli,
              "Separation of Control and User Plane for Proxy Mobile
              IPv6", draft-wakikawa-netext-pmip-cp-up-separation-00
              (work in progress), July 2013.

   [I-D.yokota-dmm-scenario]
              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.

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

   [Paper-Distributed.Dynamic.Mobility]
              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.

   [Paper-Distributed.Mobility.MIP]
              Chan, H., "Distributed Mobility Management with Mobile
              IP",  Proceedings of IEEE International Communication
              Conference (ICC) Workshop on Telecommunications: from
              Research to Standards, June 2012.

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

   [Paper-Distributed.Mobility.Review]
              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, February 2011.

   [Paper-Distributed.Mobility.SAE]
              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),
              2008.

   [Paper-Locating.User]
              Kirby, G., "Locating the User",  Communication
              International, 1995.

   [Paper-Migrating.Home.Agents]
              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.

   [Paper-Mobile.Data.Offloading]
              Lee, K., Lee, J., Yi, Y., Rhee, I., and S. Chong, "Mobile
              Data Offloading: How Much Can WiFi Deliver?",  SIGCOMM
              2010, 2010.

   [RFC3753]  Manner, J. and M. Kojo, "Mobility Related Terminology",
              RFC 3753, June 2004.

   [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.

   [RFC5944]  Perkins, C., "IP Mobility Support for IPv4, Revised",
              RFC 5944, November 2010.

   [RFC6224]  Schmidt, T., Waehlisch, M., and S. Krishnan, "Base
              Deployment for Multicast Listener Support in Proxy Mobile
              IPv6 (PMIPv6) Domains", RFC 6224, April 2011.

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

   [RFC6301]  Zhu, Z., Wakikawa, R., and L. Zhang, "A Survey of Mobility
              Support in the Internet", RFC 6301, July 2011.

   [RFC6705]  Krishnan, S., Koodli, R., Loureiro, P., Wu, Q., and A.
              Dutta, "Localized Routing for Proxy Mobile IPv6",
              RFC 6705, September 2012.

   [RFC6909]  Gundavelli, S., Zhou, X., Korhonen, J., Feige, G., and R.
              Koodli, "IPv4 Traffic Offload Selector Option for Proxy
              Mobile IPv6", RFC 6909, April 2013.

   [TS.23.401]
              3GPP, "General Packet Radio Service (GPRS) enhancements
              for Evolved Universal Terrestrial Radio Access Network
              (E-UTRAN) access", 3GPP TR 23.401 10.10.0, March 2013.

   [TS.29303]
              3GPP, "Domain Name System Procedures; Stage 3", 3GPP
              TR 23.303 11.2.0, September 2012.

Authors' Addresses

   H Anthony Chan (editor)
   Huawei Technologies (more co-authors on P. 17)
   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
   Orange
   4, rue du Clos Courtel, BP 91226, Cesson-Sevigne 35512, France
   Email: pierrick.seite@orange.com

   Hidetoshi Yokota
   KDDI Lab
   2-1-15 Ohara, Fujimino, Saitama, 356-8502 Japan
   Email: yokota@kddilabs.jp

   Jouni Korhonen
   Broadcom Communications
   Porkkalankatu 24, FIN-00180 Helsinki, Finland
   Email: jouni.nospam@gmail.com
   -
   Charles E. Perkins
   Huawei Technologies
   Email: charliep@computer.org
   -
   Melia Telemaco
   Alcatel-Lucent Bell Labs
   Email: telemaco.melia@alcatel-lucent.com telemaco.melia@googlemail.com
   -
   Elena Demaria
   Telecom Italia
   via G. Reiss Romoli, 274, TORINO, 10148, Italy
   Email: elena.demaria@telecomitalia.it
   -
   Jong-Hyouk Lee
   Sangmyung University University, Korea
   Email: hurryon@gmail.com jonghyouk@smu.ac.kr
   -
   Kostas Pentikousis
   EICT GmbH
   Email: k.pentikousis@eict.de
   -
   Tricci So
   ZTE
   Email: tso@zteusa.com
   -
   Carlos J. Bernardos
   Universidad Carlos III de Madrid
   Av. Universidad, 30, Leganes, Madrid 28911, Spain
   Email: cjbc@it.uc3m.es
   -
   Peter McCann
   Huawei Technologies
   Email: Peter.McCann@huawei.com
   -
   Seok Joo Koh
   Kyungpook National University, Korea
   Email: sjkoh@knu.ac.kr
   -
   Wen Luo
   ZTE
   No.68, Zijinhua RD,Yuhuatai District, Nanjing, Jiangsu 210012, China
   Email: luo.wen@zte.com.cn
   -
   Sri Gundavelli
   Cisco
   sgundave@cisco.com
   -
   Marco Liebsch
   NEC Laboratories Europe
   Email: liebsch@neclab.eu
   -
   Carl Williams
   MCSR Labs
   Email: carlw@mcsr-labs.org
   -
   Seil Jeon
   Instituto de Telecomunicacoes, Aveiro
   Email: seiljeon@av.it.pt
   -
   Sergio Figueiredo
   Universidade de Aveiro
   Email: sfigueiredo@av.it.pt
   -
   Stig Venaas
   Email: stig@venaas.com
   -
   Luis Miguel Contreras Murillo
   Telefonica I+D
   Email: lmcm@tid.es
   -
   Juan Carlos Zuniga
   InterDigital
   Email: JuanCarlos.Zuniga@InterDigital.com
   -
   Alexandru Petrescu
   Email: alexandru.petrescu@gmail.com
   -
   Georgios Karagiannis
   University of Twente
   Email: g.karagiannis@utwente.nl
   -
   Julien Laganier
   Juniper
   jlaganier@juniper.net
   julien.ietf@gmail.com
   -
   Wassim Michel Haddad
   Ericsson
   Wassam.Haddad@ericsson.com
   Wassim.Haddad@ericsson.com
   -
   Dirk von Hugo
   Deutsche Telekom Laboratories
   Dirk.von-Hugo@telekom.de
   -
   Ahmad Muhanna
   Award Solutions
   amuhanna@awardsolutions.com
   asmuhanna@yahoo.com
   -
   Byoung-Jo Kim
   ATT Labs
   macsbug@research.att.com
   -
   Hassan Ali-Ahmad
   Orange
   hassan.aliahmad@orange.com
   -
   Alper Yegin
   Samsung
   alper.yegin@partner.samsung.com
   -