Network Working Group                                      H. Chan (Ed.)
Internet-Draft                                 Huawei Technologies (more
Intended status: Informational                      co-authors on P. 17)
Expires: April 1, May 11, 2014                                             D. Liu
                                                            China Mobile
                                                                P. Seite
                                                                  Orange
                                                               H. Yokota
                                                                KDDI Lab
                                                             J. Korhonen
                                                          Renesas Mobile
                                                      September 28,
                                                        November 7, 2013

            Requirements for Distributed Mobility Management
                     draft-ietf-dmm-requirements-09
                     draft-ietf-dmm-requirements-10

Abstract

   This document defines the requirements for Distributed Mobility
   Management (DMM).  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,
   such as in moving the content delivery servers closer to the users, 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 April 1, May 11, 2014.

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

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Conventions used in this document  . . . . . . . . . . . . . .  6
     2.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Centralized versus distributed mobility management . . . . . .  7
     3.1.  Centralized mobility management  . . . . . . . . . . . . .  7
     3.2.  Distributed mobility management  . . . . . . . . . . . . .  8
   4.  Problem Statement  . . . . . . . . . . . . . . . . . . . . . .  9
   5.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 11
     5.1.  Distributed processing . . . . . . . . . . . . . . . . . . 11
     5.2.  Transparency to Upper Layers when needed . . . . . . . . . 11
     5.3.  IPv6 deployment  . . . . . . . . . . . . . . . . . . . . . 12
     5.4.  Existing mobility protocols  . . . . . . . . . . . . . . . 12
     5.5.  Co-existence . . . . . . . . . . . . . . . . . . . . . . . 13
     5.6.  Security considerations  . . . . . . . . . . . . . . . . . 13
     5.7.  Multicast  . . . . . . . . . . . . . . . . . . . . . . . . 14
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 14
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15 14
   8.  Co-authors and Contributors  . . . . . . . . . . . . . . . . . 15 14
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 15
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 15
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17

1.  Introduction

   In the past decade a fair number of 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;
        such traffic imposes new requirements on mobile core networks
        for data traffic delivery.  The presence of content providers
        closer to Internet Service Providers (ISP) network requires
        taking into account local Content Delivery Networks (CDNs) while
        providing mobility services.  Moreover, when the traffic demand
        exceeds available capacity, service providers need to implement
        new strategies such as selective IPv4 traffic offload (e.g.
        [RFC6909], 3GPP work items LIPA/SIPTO [TS.23.401]) through
        alternative access networks (e.g.  WLAN) [Paper-
        Mobile.Data.Offloading].  A gateway selection mechanism also
        takes the user proximity into account within EPC [TS.29303].
        These mechanisms were not pursued in the past owing to charging
        and billing reasons.  Assigning a gateway anchor node from a
        visited network in roaming scenario has until recently been done
        and are limited to voice services only.  Charging and billing
        require solutions beyond the mobility protocol.

        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.

   In addition, considerations in the study of DMM are in the following.

   (1)  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 have stringent
        requirements in terms of delay.  Notions of localization and
        distribution of local agents have been introduced to reduce
        signaling overhead at the centralized routing anchor point
        [Paper-Distributed.Centralized.Mobility].  Unfortunately, such
        protocols have not been deployed today.

   (2)  Most existing mobility protocols have not been designed for
        multiple-interface hosts which are capable to use multiple
        interfaces simultaneously.  Retrofitting the required
        functionality can result in an unnecessary increase in the
        protocol complexity.

   (3)  IP multicast support, including optimizations, have been
        introduced as an effective transport method for multimedia data
        delivery, but by "patching-up" procedure after completing the
        design of reference mobility protocol, leading to network
        inefficiency and non-optimal routing.

   The distributed mobility management (DMM) charter addresses two
   complementary aspects of mobility management procedures: the
   distribution of mobility anchors in the data-plane towards a more
   flat network and 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)
   closer to the user; ideally, mobility agents could be collocated with
   the first-hop router.  The latter, facilitated by the distribution of
   mobility anchors, identifies when mobility support must be activated
   and when sessions do not require mobility management support -- thus
   reducing 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 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.

   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 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.

   An IP-layer mobility management protocol is typically based on the
   principle of distinguishing between session identifier and routing
   address and maintaining a mapping between the two.  In Mobile IP, the
   home address serves as the session identifier whereas the care-of-
   address (CoA) takes the role of the routing address.  The binding
   between these two is maintained at the home agent (mobility anchor).
   If packets addressed to the home address of a mobile node can be
   continuously delivered to the node, then all sessions using that home
   address are unaffected even though the routing address (CoA) changes.

   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 information between
   the session identifier and the locator IP address of a mobile node
   (MN) is kept at a single mobility anchor.  At the same time, packets
   destined to the MN 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) in Mobile IPv6
   [RFC6275] and Proxy Mobile IPv6 [RFC5213], respectively.  Current
   cellular networks such as the Third Generation Partnership Project
   (3GPP) GPRS networks, CDMA networks, and 3GPP Evolved Packet System
   (EPS) networks employ centralized mobility management too.  In
   particular, the Gateway GPRS Support Node (GGSN), Serving GPRS
   Support Node (SGSN) and Radio Network Controller (RNC) in the 3GPP
   GPRS hierarchical 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.

         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 mobility function (MF).

                    +------+  +------+  +------+  +------+
                    |  MF  |  |  MF  |  |  MF  |  |  MF  |
                    +------+  +------+  +------+  +------+
                                           |
                                         +----+
                                         | 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-separtion].
   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 are shown through
   simulations in [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 are located in the PMIP domain and attached to a MAG, and is
         not applicable when the CN is outside the PMIP domain or does
         not behave like an MN.)

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

         Centralized mobility management can become non-optimal with a
         flat network architecture.

   PS3:  Low 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 increase scalability.

   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 nodes that do not need it

         IP mobility support is not always required, and not every
         parameter of mobility context is always used.  For example,
         some applications do not need a stable IP address during a
         handover to maintain session continuity.  Sometimes, the entire
         application session runs while the terminal 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 more
         efficient to deactivate 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.  Peer-to-peer communications have
         particular traffic patterns that often do not benefit from
         mobility support from the network.  Thus, the associated
         mobility support signaling (e.g., maintenance of the tunnel,
         keep alive signaling, etc.) wastes network resources for no
         application gain.

   PS7:  (Related problem) Deployment with multiple mobility solutions

         There are already many variants and extensions of MIP.
         Deployment of new mobility management solutions can be
         challenging, and debugging difficult, when they must co-exist
         with solutions already 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, 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 does not need to traverse centrally deployed
          mobility anchors and thereby can avoid non-optimal routes. 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 and distribute content by combining distributed mobility
          anchors with caching systems (e.g., CDN); (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

          DMM solutions MUST provide transparent mobility support above
          the IP layer when needed.  Such transparency is needed, for
          example, when, upon change of point of attachment to the
          network, an application flow cannot cope with a change in the
          IP address.  However, it is not always necessary to maintain a
          stable home IP address or prefix for every application or at
          all times for a mobile node.

          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 PS5 as well as the related
   problem PS6 stated 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 first consider reusing and extending
          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 with deployed networks and hosts

          The DMM solution MUST be able to co-exist with existing
          network deployments and end hosts.  For example, depending on
          the environment in which DMM is deployed, DMM solutions 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 mobility protocol.
          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 or
          amplify existing security risks against which the existing
          security mechanisms/protocols cannot offer sufficient
          protection.

          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.  In addition,
          end-to-end security measures between communicating nodes may
          already be used when deploying existing mobility protocols
          where the signaling messages travel over the Internet.  For
          instance, EAP-based authentication can be used for network
          access security, while IPsec can be used for end-to-end
          security.  When the existing security mechanisms/protocols are
          applied to protect the DMM entities, the security risks that
          may be introduced by DMM MUST be considered to be eliminated.
          Else the security protection would be degraded in the DMM
          solution versus in existing mobility protocols.

   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 consider multicast early so that solutions can be
          developed not only to provide IP mobility support when it is
          needed, but also to avoid network inefficiency issues in
          multicast traffic delivery (such as duplicate multicast
          subscriptions towards the downstream tunnel entities).  The
          multicast solutions should therefore avoid restricting the
          management of all IP multicast traffic to a single host
          through a dedicated (tunnel) interface on multicast-capable
          access routers.

          Motivation: Existing multicast deployment have been introduced
          after completing the design of the reference mobility
          protocol, then optimization and extensions have been followed
          by "patching-up" procedure, thus leading to network
          inefficiency and non-optimal routing.  The multicast solutions
          should therefore be required to consider efficiency nature in
          multicast traffic delivery.

   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, Feb 2011.",
               Proceedings of GlobeCom Workshop  on Seamless Wireless
              Mobility, 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
   Renesas Mobile
   Porkkalankatu 24, FIN-00180 Helsinki, Finland
   Email: jouni.korhonen@nsn.com
   -
   Charles E. Perkins
   Huawei Technologies
   Email: charliep@computer.org
   -
   Melia Telemaco
   Alcatel-Lucent Bell Labs
   Email: telemaco.melia@alcatel-lucent.com
   -
   Elena Demaria
   Telecom Italia
   via G. Reiss Romoli, 274, TORINO, 10148, Italy
   Email: elena.demaria@telecomitalia.it
   -
   Jong-Hyouk Lee
   Sangmyung University
   Email: hurryon@gmail.com
   -
   Kostas Pentikousis
   Huawei Technologies
   Carnotstr. 4 10587 Berlin, Germany
   EICT GmbH
   Email: k.pentikousis@huawei.com 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: PeterMcCann@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
   -
   Wassim Michel Haddad
   Ericsson
   Wassam.Haddad@ericsson.com
   -
   Dirk von Hugo
   Deutsche Telekom Laboratories
   Dirk.von-Hugo@telekom.de
   -
   Ahmad Muhanna
   Award Solutions
   amuhanna@awardsolutions.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
   -