Internet Engineering Task Force (IETF)                      H. Chan, Ed.
Request for Comments: 7333                           Huawei Technologies
Category: Informational                                           D. Liu
ISSN: 2070-1721                                             China Mobile
                                                                P. Seite
                                                                  Orange
                                                               H. Yokota
                                                              Landis+Gyr
                                                             J. Korhonen
                                                 Broadcom Communications
                                                             August 2014

Requirements for Distributed Mobility Management

Abstract

   This document defines the requirements for Distributed Mobility
   Management (DMM) at the network layer.  The hierarchical structure in
   traditional wireless networks has led primarily to centrally deployed
   mobility anchors.  As some wireless networks are evolving away from
   the hierarchical structure, it can be useful to have a distributed
   model for mobility management in which traffic does not need to
   traverse centrally deployed mobility anchors far from the optimal
   route.  The motivation and the problems addressed by each requirement
   are also described.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7333.

Copyright Notice

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

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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   1. Introduction ....................................................2
   2. Conventions Used in This Document ...............................4
      2.1. Requirements Language ......................................4
      2.2. Terminology ................................................4
   3. Centralized versus Distributed Mobility Management ..............5
      3.1. Centralized Mobility Management ............................6
      3.2. Distributed Mobility Management ............................7
   4. Problem Statement ...............................................8
   5. Requirements ...................................................10
   6. Security Considerations ........................................16
   7. Contributors ...................................................17
   8. References .....................................................20
      8.1. Normative References ......................................20
      8.2. Informative References ....................................21

1. Introduction

   In the past decade, a fair number of network-layer mobility protocols
   have been standardized [RFC6275] [RFC5944] [RFC5380] [RFC6301]
   [RFC5213].  Although these 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.  Among other tasks that the anchor point performs,
   the anchor point 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 is typically managed by the same
   anchor.  Such a mobility anchor may still have to reside in the
   subscriber's provider network even when the subscriber is roaming to

   a visited network, in order that certain functions such as charging
   and billing can be performed more readily by the provider's network.
   An example provider network is a Third Generation Partnership Project
   (3GPP) network.

   Distributed mobility management (DMM) is an alternative to the above-
   mentioned centralized deployment.  The background behind the interest
   in studying DMM is primarily as follows.

   (1)  More than ever, mobile users are consuming Internet content,
        including that of local Content Delivery Networks (CDNs).  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 Local IP Access (LIPA) and Selected IP Traffic
        Offload (SIPTO) work items [TS.23.401]) through alternative
        access networks such as Wireless Local Area Networks (WLANs)
        [MOB-DATA-OFFLOAD].  In addition, a gateway selection mechanism
        takes user proximity into account within the Evolved Packet Core
        (EPC) [TS.29.303].  However, these mechanisms were not pursued
        in the past, owing to charging and billing considerations that
        require solutions beyond the mobility protocol.  Consequently,
        assigning a gateway anchor node from a visited network when
        roaming to the visited network has only recently been done and
        is limited to voice services.

        Both traffic offloading and CDN mechanisms could benefit from
        the development of mobile architectures with fewer hierarchical
        levels introduced into the data path by the mobility management
        system.  This trend of "flattening" the mobile networks works
        best for direct communications among peers in the same
        geographical area.  Distributed mobility management in the
        flattening mobile networks 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 [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, IP mobility support
        is currently 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, e.g., as described in [DHCPv6-CLASS-BASED-PREFIX]
        and [IPv6-PREFIX-PROPERTIES], thus reducing the amount of
        context maintained in the network.

   DMM may distribute the mobility anchors in the data plane in
   flattening the mobility network such that the mobility anchors are
   positioned closer to the user; ideally, mobility agents could be
   collocated with the first-hop router.  Facilitated by the
   distribution of mobility anchors, it may be possible to selectively
   use or not use mobility protocol support, depending on whether such
   support is needed or not.  DMM can thus reduce the amount of state
   information that must be maintained in various mobility agents of the
   mobile network and can then avoid the unnecessary establishment of
   mechanisms to forward traffic from an old mobility anchor 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.  Security
   considerations are mentioned in Section 6.

   The problem statement and use cases [DMM-SCENARIO] can be found in
   [DIST-MOB-REVIEW].

2. Conventions Used in This Document

2.1. 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 [RFC2119].

2.2. Terminology

   All of the general mobility-related terms, and their acronyms as used
   in this document, are to be interpreted as defined in the Mobile IPv6
   base specification [RFC6275], the Proxy Mobile IPv6 (PMIPv6)
   specification [RFC5213], and "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 document introduces the following terms:

   Centrally deployed mobility anchors

      refers 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 is 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.

   Hierarchical mobile network

      has a hierarchy of network elements arranged into multiple
      hierarchical levels that are introduced into the data path by the
      mobility management system.

   Flattening mobile network

      refers to the hierarchical mobile network that is going through
      the trend of reducing its number of hierarchical levels.

   Flatter mobile network

      has fewer hierarchical levels compared to a hierarchical mobile
      network.

   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.

   An IP-layer mobility management protocol is typically based on the
   principle of distinguishing between a session identifier and a
   forwarding address and maintaining a mapping between the two.  In
   Mobile IP, the new IP address of the mobile node after the node has
   moved is the forwarding address, whereas the original IP address
   before the mobile node moves serves as the session identifier.  The
   location management (LM) information is kept by associating the
   forwarding address with the session identifier.  Packets addressed to
   the session identifier will first route to the original network,
   which redirects them using the forwarding address to deliver to the
   session.  Redirecting packets this way can result in long routes.  An
   existing optimization routes directly, using the forwarding address
   of the host, and as 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 location information in terms
   of a mapping between the session identifier and the forwarding
   address is kept at a single mobility anchor, and packets destined to
   the session identifier are forwarded 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 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], respectively.  Cellular networks, such as 3GPP
   General Packet Radio System (GPRS) networks and 3GPP Evolved Packet
   System (EPS) networks, also employ centralized mobility management.
   In the 3GPP GPRS network, the Gateway GPRS Support Node (GGSN),
   Serving GPRS Support Node (SGSN), and Radio Network Controller (RNC)
   constitute a hierarchy of anchors.  In the 3GPP EPS network, the
   Packet Data Network Gateway (P-GW) and Serving Gateway (S-GW)
   constitute another hierarchy of anchors.

        3GPP 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 in the data
   plane 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 forwarding management (FM) capability.

                   +------+  +------+  +------+  +------+
                   |  FM  |  |  FM  |  |  FM  |  |  FM  |
                   +------+  +------+  +------+  +------+
                                          |
                                        +----+
                                        | MN |
                                        +----+

                 Figure 2: Distributed Mobility Management

   DMM is distributed in the data plane, whereas the control plane may
   be either centralized or distributed [DMM-SCENARIO].  The former case
   implicitly assumes separation of data and control planes as described
   in [PMIP-CP-UP-SPLIT].  While mobility management can be distributed,
   it is not necessary for other functions such as subscription
   management, subscription databases, and network access authentication
   to be similarly distributed.

   A distributed mobility management scheme for a flattening mobile
   network consisting of access nodes is proposed in [DIST-DYNAMIC-MOB].
   Its benefits over centralized mobility management have been shown
   through simulations [DIST-CENTRAL-MOB].  Moreover, the (re)use and
   extension of existing protocols in the design of both fully
   distributed mobility management [MIGRATING-HAs] [DIST-MOB-SAE] and
   partially distributed mobility management [DIST-MOB-PMIP]
   [DIST-MOB-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 as
   follows:

   PS1:  Non-optimal routes

         Forwarding 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 packets 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 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 flatter
         and flatter network.  Centralized mobility management, which is
         non-optimal with a flatter network architecture, does not
         support this evolution.

   PS3:  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 a
         single point of failure 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.  However,
         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 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:  Mobility signaling overhead with peer-to-peer communication

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

   PS7:  Deployment with multiple mobility solutions

         There are already many variants and extensions of MIP as well
         as mobility solutions at other layers.  Deployment of new
         mobility management solutions can be challenging, and debugging
         difficult, when they coexist 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., a 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

   Now that distributed mobility management has been compared with
   centralized deployment (Section 3) and the problems have been
   described (Section 4), this section identifies the following
   requirements:

   REQ1:  Distributed mobility management

          IP mobility, network access solutions, and forwarding
          solutions provided by DMM MUST enable traffic to avoid
          traversing a single mobility anchor far from the optimal
          route.

          This requirement on distribution applies to the data plane
          only.  It does not impose constraints on whether the control
          plane should be distributed or centralized.  However, if the
          control plane is centralized while the data plane is
          distributed, it is implied that the control plane and data
          plane need to separate (Section 3.2).

          Motivation: This requirement is motivated by current trends in
          network evolution: (a) it is cost- and resource-effective to
          cache contents, and the caching (e.g., 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;
          and (d) threats against centrally deployed anchors, e.g., a
          home agent and a local mobility anchor, are mitigated in a
          distributed system.

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

   REQ2:  Bypassable network-layer mobility support for each application
          session

          DMM solutions MUST enable network-layer mobility, but it MUST
          be possible for any individual active application session
          (flow) to not use it.  Mobility support is needed, for
          example, when a mobile host moves and an application cannot
          cope with a change in the IP address.  Mobility support is
          also needed when a mobile router changes its IP address as it
          moves together with a host and, in the presence of ingress
          filtering, an application in the host is interrupted.
          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 IP address or prefix for
          an active application session.

          Different active sessions can also differ in whether network-
          layer mobility support is needed.  IP mobility, network access
          solutions, and forwarding solutions provided by DMM MUST then
          provide the possibility of independent handling for each
          application session of a user or mobile device.

          The handling of mobility management to the granularity of an
          individual session of a user/device SHOULD need proper session
          identification in addition to user/device identification.

          Motivation: The motivation of this requirement is to enable
          more efficient forwarding 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 problems PS5 and PS6 described
          in Section 4.

   REQ3:  IPv6 deployment

          DMM solutions SHOULD target IPv6 as the primary deployment
          environment and SHOULD NOT be tailored specifically to support
          IPv4, particularly 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 as "on
          the mid- to long-term horizon", when IPv6 is expected to be
          far more common than today.

          This requirement avoids the unnecessarily complex solution of
          trying to provide the same level of functionality to both IPv4
          and IPv6.  Some of the IPv6-specific features are not
          available for IPv4.

   REQ4:  Existing mobility protocols

          A DMM solution MUST first consider reusing and extending IETF
          standard 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 for development of
          new protocols and therefore their potential for being time-
          consuming and error-prone.

   REQ5:  Coexistence with deployed networks/hosts and operability
          across different networks

          A DMM solution may require loose, tight, or no integration
          into existing mobility protocols and host IP stacks.
          Regardless of the integration level, DMM implementations MUST
          be able to coexist with existing network deployments, end
          hosts, and routers that may or may not implement existing
          mobility protocols.  Furthermore, a DMM solution SHOULD work
          across different networks, possibly operated as separate
          administrative domains, when the needed mobility management
          signaling, forwarding, and network access are allowed by the
          trust relationship between them.

          Motivation: to (a) 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 problem PS7 described in
          Section 4.

   REQ6:  Operation and management considerations

          A DMM solution needs to consider configuring a device,
          monitoring the current operational state of a device, and
          responding to events that impact the device, possibly by
          modifying the configuration and storing the data in a format
          that can be analyzed later.  Different management protocols
          are available.  For example:

          (a)  the Simple Network Management Protocol (SNMP) [RFC1157],
               with definitions of standardized management information
               base (MIB) objects for DMM that allow the monitoring of
               traffic steering in a consistent manner across different
               devices

          (b)  the Network Configuration Protocol (NETCONF) [RFC6241],
               with definitions of standardized YANG [RFC6020] modules
               for DMM to achieve a standardized configuration

          (c)  syslog [RFC5424], which is a one-way protocol allowing a
               device to report significant events to a log analyzer in
               a network management system

          (d)  the IP Flow Information Export (IPFIX) Protocol, which
               serves as a means for transmitting traffic flow
               information over the network [RFC7011], with a formal
               description of IPFIX Information Elements [RFC7012]

          It is not the goal of this requirements document to impose
          which management protocol(s) should be used.  An inventory of
          the management protocols and data models is covered in
          [RFC6632].

          The following paragraphs list the operation and management
          considerations required for a DMM solution; this list of
          considerations may not be exhaustive and may be expanded
          according to the needs of the solutions:

          A DMM solution MUST describe how, and in what types of
          environments, it can be scalably deployed and managed.

          A DMM solution MUST support mechanisms to test whether the DMM
          solution is working properly.  For example, when a DMM
          solution employs traffic indirection to support a mobility
          session, implementations MUST support mechanisms to test that
          the appropriate traffic indirection operations are in place,

          including the setup of traffic indirection and the subsequent
          teardown of the indirection to release the associated network
          resources when the mobility session has closed.

          A DMM solution SHOULD expose the operational state of DMM to
          the administrators of the DMM entities.  For example, when a
          DMM solution employs separation between a session identifier
          and forwarding address, it should expose the association
          between them.

          When flow mobility is supported by a DMM solution, the
          solution SHOULD support means to correlate the flow routing
          policies and the observed forwarding actions.

          A DMM solution SHOULD support mechanisms to check the liveness
          of a forwarding path.  If the DMM solution sends periodic
          update refresh messages to configure the forwarding path, the
          refresh period SHOULD be configurable and a reasonable default
          configuration value proposed.  Information collected can be
          logged or made available with protocols such as SNMP
          [RFC1157], NETCONF [RFC6241], IPFIX [RFC7011], or syslog
          [RFC5424].

          A DMM solution MUST provide fault management and monitoring
          mechanisms to manage situations where an update of the
          mobility session or the data path fails.  The system must also
          be able to handle situations where a mobility anchor with
          ongoing mobility sessions fails.

          A DMM solution SHOULD be able to monitor usage of the DMM
          protocol.  When a DMM solution uses an existing protocol, the
          techniques already defined for that protocol SHOULD be used to
          monitor the DMM operation.  When these techniques are
          inadequate, new techniques MUST be developed.

          In particular, the DMM solution SHOULD

          (a)  be able to monitor the number of mobility sessions per
               user, as well as their average duration

          (b)  provide an indication of DMM performance, such as

               (1)  handover delay, which includes the time necessary to
                    reestablish the forwarding path when the point of
                    attachment changes

               (2)  protocol reactivity, which is the time between
                    handover events such as the attachment to a new
                    access point and the completion of the mobility
                    session update

          (c)  provide means to measure the signaling cost of the DMM
               protocol

          (d)  if tunneling is used for traffic redirection, monitor

               (1)  the number of tunnels

               (2)  their transmission and reception information

               (3)  the encapsulation method used, and its overhead

               (4)  the security used at the node level

          DMM solutions SHOULD support standardized configuration with
          NETCONF [RFC6241], using YANG [RFC6020] modules, which SHOULD
          be created for DMM when needed for such configuration.
          However, if a DMM solution creates extensions to MIPv6 or
          PMIPv6, the allowed addition of definitions of management
          information base (MIB) objects to the MIPv6 MIB [RFC4295] or
          the PMIPv6 MIB [RFC6475] that are needed for the control and
          monitoring of the protocol extensions SHOULD be limited to
          read-only objects.

          Motivation: A DMM solution that is designed from the beginning
          for operability and manageability can implement efficient
          operations and management solutions.

          These requirements avoid DMM designs that make operations and
          management difficult or costly.

   REQ7:  Security considerations

          A DMM solution MUST support any security protocols and
          mechanisms needed to secure the network and to make continuous
          security improvements.  In addition, with security taken into
          consideration early in the design, a DMM solution MUST NOT
          introduce new security risks or amplify existing security
          risks that cannot be mitigated by existing security protocols
          and mechanisms.

          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 or nodes to which the traffic
          is redirected may be under a denial-of-service attack and
          other nodes do not receive their traffic.  Accordingly,
          security mechanisms/protocols providing access control,
          integrity, authentication, authorization, confidentiality,
          etc. should be used to protect the DMM entities as they are
          already used to protect existing networks and existing
          mobility protocols defined in the IETF.  However, if a
          candidate DMM solution is such that these existing security
          mechanisms/protocols are unable to provide sufficient security
          protection even when properly used, then that candidate DMM
          solution is causing uncontrollable security problems.

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

   REQ8:  Multicast considerations

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

          Motivation: Existing multicast deployments have been
          introduced after completing the design of the reference
          mobility protocol, often leading to network inefficiency and
          non-optimal forwarding for the multicast traffic.  DMM should
          instead consider multicast early in the process, so that the
          multicast solutions can better consider the efficient nature
          of 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 REQ7 in Section 5.

7. Contributors

   This requirements document is a joint effort among numerous
   participants working as a team.  Valuable comments and suggestions in
   various reviews from the following area directors and IESG members
   have also contributed to many improvements: Russ Housley, Catherine
   Meadows, Adrian Farrel, Barry Leiba, Alissa Cooper, Ted Lemon, Brian
   Haberman, Stephen Farrell, Joel Jaeggli, Alia Atlas, and Benoit
   Claise.

   In addition to the authors, each of the following has made very
   significant and important contributions to this work:

  Charles E. Perkins
  Huawei Technologies
  EMail: charliep@computer.org

  Melia Telemaco
  Alcatel-Lucent Bell Labs
  EMail: 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, Korea
  EMail: 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

  Hui Deng
  China Mobile
  EMail: denghui@chinamobile.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
  EMail: julien.ietf@gmail.com

  Wassim Michel Haddad
  Ericsson
  EMail: Wassim.Haddad@ericsson.com

  Dirk von Hugo
  Deutsche Telekom Laboratories
  EMail: Dirk.von-Hugo@telekom.de

  Ahmad Muhanna
  Award Solutions
  EMail: asmuhanna@yahoo.com

  Byoung-Jo Kim
  ATT Labs
  EMail: macsbug@research.att.com

  Hassan Ali-Ahmad
  Orange
  EMail: hassan.aliahmad@orange.com

  Alper Yegin
  Samsung
  EMail: alper.yegin@partner.samsung.com

  David Harrington
  Effective Software
  EMail: ietfdbh@comcast.net

8. References

8.1. Normative References

   [RFC1157]  Case, J., Fedor, M., Schoffstall, M., and J. Davin,
              "Simple Network Management Protocol (SNMP)", STD 15,
              RFC 1157, May 1990.

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

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

   [RFC4295]  Keeni, G., Koide, K., Nagami, K., and S. Gundavelli,
              "Mobile IPv6 Management Information Base", RFC 4295,
              April 2006.

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

   [RFC5424]  Gerhards, R., "The Syslog Protocol", RFC 5424, March 2009.

   [RFC6020]  Bjorklund, M., "YANG - A Data Modeling Language for the
              Network Configuration Protocol (NETCONF)", RFC 6020,
              October 2010.

   [RFC6241]  Enns, R., Bjorklund, M., Schoenwaelder, J., and A.
              Bierman, "Network Configuration Protocol (NETCONF)",
              RFC 6241, June 2011.

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

   [RFC6475]  Keeni, G., Koide, K., Gundavelli, S., and R. Wakikawa,
              "Proxy Mobile IPv6 Management Information Base", RFC 6475,
              May 2012.

   [RFC6632]  Ersue, M. and B. Claise, "An Overview of the IETF Network
              Management Standards", RFC 6632, June 2012.

   [RFC7011]  Claise, B., Trammell, B., and P. Aitken, "Specification of
              the IP Flow Information Export (IPFIX) Protocol for the
              Exchange of Flow Information", STD 77, RFC 7011,
              September 2013.

   [RFC7012]  Claise, B. and B. Trammell, "Information Model for IP Flow
              Information Export (IPFIX)", RFC 7012, September 2013.

8.2. Informative References

   [DHCPv6-CLASS-BASED-PREFIX]
              Bhandari, S., Halwasia, G., Gundavelli, S., Deng, H.,
              Thiebaut, L., Korhonen, J., and I. Farrer, "DHCPv6 class
              based prefix", Work in Progress, July 2013.

   [DIST-CENTRAL-MOB]
              Bertin, P., Bonjour, S., and J-M. Bonnin, "Distributed or
              Centralized Mobility?", Proceedings of the 28th IEEE
              Conference on Global Telecommunications (GlobeCom),
              December 2009.

   [DIST-DYNAMIC-MOB]
              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.

   [DIST-MOB-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.

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

   [DIST-MOB-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.

   [DIST-MOB-SAE]
              Fischer, M., Andersen, 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.

   [DMM-SCENARIO]
              Yokota, H., Seite, P., Demaria, E., and Z. Cao, "Use case
              scenarios for Distributed Mobility Management", Work in
              Progress, October 2010.

   [IPv6-PREFIX-PROPERTIES]
              Korhonen, J., Patil, B., Gundavelli, S., Seite, P., and
              D. Liu, "IPv6 Prefix Properties", Work in Progress,
              July 2013.

   [LOCATING-USER]
              Kirby, G., "Locating the User", Communications
              International, 1995.

   [MIGRATING-HAs]
              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.

   [MOB-DATA-OFFLOAD]
              Lee, K., Lee, J., Yi, Y., Rhee, I., and S. Chong, "Mobile
              Data Offloading: How Much Can WiFi Deliver?", Proceedings
              of the ACM SIGCOMM 2010 Conference, 2010.

   [PMIP-CP-UP-SPLIT]
              Wakikawa, R., Pazhyannur, R., and S. Gundavelli,
              "Separation of Control and User Plane for Proxy Mobile
              IPv6", Work in Progress, July 2013.

   [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.

   [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 TS 23.401 12.5.0, June 2014,
              <http://www.3gpp.org/ftp/Specs/html-info/23401.htm>.

   [TS.29.303]
              3GPP, "Domain Name System Procedures; Stage 3", 3GPP
              TS 29.303 12.3.0, June 2014, <http://www.3gpp.org/ftp/
              Specs/html-info/29303.htm>.

Authors' Addresses

   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
   Unit 2, 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
   Landis+Gyr

   EMail: hidetoshi.yokota@landisgyr.com

   Jouni Korhonen
   Broadcom Communications
   Porkkalankatu 24
   Helsinki  FIN-00180
   Finland

   EMail: jouni.nospam@gmail.com