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Versions: (draft-liu-dmm-best-practices-gap-analysis) 00 01 02 03 04 05 06 07 08 09 RFC 7429

DMM                                                          D. Liu, Ed.
Internet-Draft                                              China Mobile
Intended status: Informational                           JC. Zuniga, Ed.
Expires: May 8, 2015                                        InterDigital
                                                                P. Seite
                                                                  Orange
                                                                 H. Chan
                                                     Huawei Technologies
                                                           CJ. Bernardos
                                                                    UC3M
                                                        November 4, 2014


  Distributed Mobility Management: Current practices and gap analysis
             draft-ietf-dmm-best-practices-gap-analysis-09

Abstract

   This document analyzes deployment practices of existing IP mobility
   protocols in a distributed mobility management environment.  It then
   identifies existing limitations when compared to the requirements
   defined for a distributed mobility management solution.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 8, 2015.

Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Functions of existing mobility protocols  . . . . . . . . . .   3
   4.  DMM practices . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Assumptions . . . . . . . . . . . . . . . . . . . . . . .   5
     4.2.  IP flat wireless network  . . . . . . . . . . . . . . . .   6
       4.2.1.  Host-based IP DMM practices . . . . . . . . . . . . .   7
       4.2.2.  Network-based IP DMM practices  . . . . . . . . . . .  11
     4.3.  Flattening 3GPP mobile network approaches . . . . . . . .  13
   5.  Gap analysis  . . . . . . . . . . . . . . . . . . . . . . . .  16
     5.1.   Distributed mobility management - REQ1 . . . . . . . . .  16
     5.2.   Bypassable network-layer mobility support for each
           application session - REQ2  . . . . . . . . . . . . . . .  19
     5.3.   IPv6 deployment - REQ3 . . . . . . . . . . . . . . . . .  20
     5.4.   Considering existing mobility protocols - REQ4 . . . . .  20
     5.5.   Coexistence with deployed networks/hosts  and
           operability across different networks - REQ5  . . . . . .  21
     5.6.   Operation and management considerations - REQ6 . . . . .  21
     5.7.   Security considerations - REQ7 . . . . . . . . . . . . .  22
     5.8.   Multicast - REQ8 . . . . . . . . . . . . . . . . . . . .  22
     5.9.  Summary . . . . . . . . . . . . . . . . . . . . . . . . .  23
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  25
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  25
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  26
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  26
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  26
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

1.  Introduction

   Existing network-layer mobility management protocols have primarily
   employed a mobility anchor to ensure connectivity of a mobile node by
   forwarding packets destined to, or sent from, the mobile node after
   the node has moved to a different network.  The mobility anchor has
   been centrally deployed in the sense that the traffic of millions of
   mobile nodes in an operator network is typically managed by the same
   anchor.  This centralized deployment of mobility anchors to manage IP
   sessions poses several problems.  In order to address these problems,
   a distributed mobility management (DMM) architecture has been



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   proposed.  This document investigates whether it is feasible to
   deploy current IP mobility protocols in a DMM scenario in a way that
   can fulfill the requirements as defined in [RFC7333].  It discusses
   current deployment practices of existing mobility protocols and
   identifies the limitations (gaps) in these practices from the
   standpoint of satisfying DMM requirements.  The analysis is primarily
   towards IPv6 deployment, but can be seen to also apply to IPv4
   whenever there are IPv4 counterparts equivalent to the IPv6 mobility
   protocols.

   The rest of this document is organized as follows.  Section 3
   analyzes existing IP mobility protocols by examining their functions
   and how these functions can be configured and used to work in a DMM
   environment.  Section 4 presents the current practices of IP wireless
   networks and 3GPP architectures.  Both network- and host-based
   mobility protocols are considered.  Section 5 presents the gap
   analysis with respect to the current practices.

2.  Terminology

   All 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 the Distributed Mobility Management Requirements
   [RFC7333].  These terms include mobile node (MN), correspondent node
   (CN), home agent (HA), Local Mobility Anchor (LMA), Mobile Access
   Gateway (MAG), centrally depoyed mobility anchors, distributed
   mobility management, hierarchical mobile network, flatter mobile
   network, and flattening mobile network.

   In addition, this document also introduces some definitions of IP
   mobility functions in Section 3.

   In this document there are also references to a "distributed mobility
   management environment."  By this term, we refer to a scenario in
   which the IP mobility, access network and routing solutions allow for
   setting up IP networks so that traffic is distributed in an optimal
   way, without relying on centrally deployed mobility anchors to manage
   IP mobility sessions.

3.  Functions of existing mobility protocols

   The host-based Mobile IPv6 (MIPv6) [RFC6275] and its network-based
   extension, Proxy Mobile IPv6 (PMIPv6) [RFC5213], as well as
   Hierarchical Mobile IPv6 (HMIPv6) [RFC5380] are logically centralized
   mobility management approaches addressing primarily hierarchical
   mobile networks.  Although these approaches are centralized, they
   have important mobility management functions resulting from years of



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   extensive work to develop and to extend these functions.  It is
   therefore useful to take these existing functions and examine them in
   a DMM scenario in order to understand how to deploy the existing
   mobility protocols to provide distributed mobility management.

   The main mobility management functions of MIPv6, PMIPv6, and HMIPv6
   are the following:

   1.  Anchoring Function (AF): allocation to a mobile node of an IP
       address, i.e., Home Address (HoA), or prefix, i.e., Home Network
       Prefix (HNP) topologically anchored by the advertising node.
       That is, the anchor node is able to advertise a connected route
       into the routing infrastructure for the allocated IP prefixes.
       This function is a control plane function.

   2.  Internetwork Location Information (LI) function: managing and
       keeping track of the internetwork location of an MN.  The
       location information may be a binding of the IP advertised
       address/prefix, e.g., HoA or HNP, to the IP routing address of
       the MN or of a node that can forward packets destined to the MN.
       It is a control plane function.

       In a client-server protocol model, location query and update
       messages may be exchanged between a location information client
       (LIc) and a location information server (LIs).

   3.  Forwarding Management (FM) function: packet interception and
       forwarding to/from the IP address/prefix assigned to the MN,
       based on the internetwork location information, either to the
       destination or to some other network element that knows how to
       forward the packets to their destination.

       FM may optionally be split into the control plane (FM-CP) and
       data plane (FM-DP).

   In Mobile IPv6, the home agent (HA) typically provides the anchoring
   function (AF); the location information server (LIs) is at the HA
   whereas the location information client (LIc) is at the MN; the
   Forwarding Management (FM) function is distributed between the ends
   of the tunnel at the HA and the MN.

   In Proxy Mobile IPv6, the Local Mobility Anchor (LMA) provides the
   anchoring function (AF); the location information server (LIs) is at
   the LMA whereas the location information client (LIc) is at the
   mobile access gateway (MAG); the Forwarding Management (FM) function
   is distributed between the ends of the tunnel at the HA and the MAG.





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   In Hierarchical Mobile IPv6 (HMIPv6) [RFC5380], the Mobility Anchor
   Point (MAP) serves as a location information aggregator between the
   LIs at the HA and the LIc at the MN.  The MAP also provides the FM
   function to enable tunneling between HA and itself as well as
   tunneling between MN and itself.

4.  DMM practices

   This section documents deployment practices of existing mobility
   protocols to satisfy distributed mobility management requirements.
   This description considers both IP wireless, e.g., evolved Wi-Fi
   hotspots, and 3GPP flattening mobile network.

   While describing the current DMM practices, the section provides
   references to the generic mobility management functions described in
   Section 3 as well as some initial hints on the identified gaps with
   respect to the DMM requirements documented in [RFC7333].

4.1.  Assumptions

   There are many different approaches that can be considered to
   implement and deploy a distributed anchoring and mobility solution.
   The focus of the gap analysis is on certain current mobile network
   architectures and standardized IP mobility solutions, considering any
   kind of deployment options which do not violate the original protocol
   specifications.  In order to limit the scope of our analysis of DMM
   practices, we consider the following list of technical assumptions:

   1.  Both host- and network-based solutions are considered.

   2.  Solutions should allow selecting and using the most appropriate
       IP anchor among a set of available candidates.

   3.  Mobility management should be realized by the preservation of the
       IP address across the different points of attachment (i.e.,
       provision of IP address continuity).  This is in contrast to
       certain transport-layer based approaches such as Stream Control
       Transmission Protocol (SCTP) [RFC4960] or application-layer
       mobility.

   Applications which can cope with changes in the MN's IP address do
   not depend on IP mobility management protocols such as DMM.
   Typically, a connection manager together with the operating system
   will configure the source address selection mechanism of the IP
   stack.  This might involve identifying application capabilities and
   triggering the mobility support accordingly.  Further considerations
   on application management and source address selection are out of the
   scope of this document, but the reader might consult [RFC6724].



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4.2.  IP flat wireless network

   This section focuses on common IP wireless network architectures and
   how they can be flattened from an IP mobility and anchoring point of
   view using common and standardized protocols.  We take Wi-Fi as an
   useful wireless technology, since it is widely known and deployed
   nowadays.  Some representative examples of Wi-Fi deployment
   architectures are depicted in Figure 1.

                     +-------------+             _----_
    +---+            |   Access    |           _(      )_
    |AAA|. . . . . . | Aggregation |----------( Internet )
    +---+            |   Gateway   |           (_      _)
                     +-------------+             '----'
                        |  |   |
                        |  |   +-------------+
                        |  |                 |
                        |  |              +-----+
        +---------------+  |              | AR  |
        |                  |              +--+--+
     +-----+            +-----+         *----+----*
     | RG  |            | WLC |        (    LAN    )
     +-----+            +-----+         *---------*
        .                /   \            /     \
       / \          +-----+ +-----+  +-----+   +-----+
      /   \         |Wi-Fi| |Wi-Fi|  |Wi-Fi|   |Wi-Fi|
    MN1   MN2       | AP1 | | AP2 |  | AP3 |   | AP4 |
                    +-----+ +-----+  +-----+   +-----+
                       .                .
                      / \              / \
                     /   \            /   \
                    MN3  MN4         MN5  MN6

                 Figure 1: IP Wi-Fi network architectures

   In Figure 1, three typical deployment options are shown
   [I-D.gundavelli-v6ops-community-wifi-svcs].  On the left hand side of
   the figure, mobile nodes MN1 and MN2 directly connect to a
   Residential Gateway (RG) at the customer premises.  The RG hosts the
   802.11 Access Point (AP) function to enable wireless layer-2 access
   connectivity and also provides layer-3 routing functions.  In the
   middle of the figure, mobile nodes MN3 and MN4 connect to Wi-Fi
   Access Points (APs) AP1 and AP2 that are managed by a Wireless LAN
   Controller (WLC), which performs radio resource management on the
   APs, domain-wide mobility policy enforcement and centralized
   forwarding function for the user traffic.  The WLC could also
   implement layer-3 routing functions, or attach to an access router
   (AR).  Last, on the right-hand side of the figure, access points AP3



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   and AP4 are directly connected to an access router.  This can also be
   used as a generic connectivity model.

   IP mobility protocols can be used to provide heterogeneous network
   mobility support to users, e.g., handover from Wi-Fi to cellular
   access.  Two kinds of protocols can be used: Proxy Mobile IPv6
   [RFC5213] or Mobile IPv6 [RFC5555], with the role of mobility anchor,
   e.g., Local Mobility Anchor or home agent, typically being played by
   the edge router of the mobile network [SDO-3GPP.23.402].

   Although this section has made use of the example of Wi-Fi networks,
   there are other flattening mobile network architectures specified,
   such as WiMAX [IEEE.802-16.2009], which integrates both host- and
   network-based IP mobility functions.

   Existing IP mobility protocols can also be deployed in a flatter
   manner, so that the anchoring and access aggregation functions are
   distributed.  We next describe several practices for the deployment
   of existing mobility protocols in a distributed mobility management
   environment.  The analysis in this section is limited to protocol
   solutions based on existing IP mobility protocols, either host- or
   network-based, such as Mobile IPv6 [RFC6275], [RFC5555], Proxy Mobile
   IPv6 (PMIPv6) [RFC5213], [RFC5844] and Network Mobility Basic Support
   protocol (NEMO) [RFC3963].  Extensions to these base protocol
   solutions are also considered.  The analysis is divided into two
   parts: host- and network-based practices.

4.2.1.  Host-based IP DMM practices

   Mobile IPv6 (MIPv6) [RFC6275] and its extension to support mobile
   networks, the NEMO Basic Support protocol (hereafter, simply referred
   to as NEMO) [RFC3963] are well-known host-based IP mobility
   protocols.  They depend on the function of the Home Agent (HA), a
   centralized anchor, to provide mobile nodes (hosts and routers) with
   mobility support.  In these approaches, the Home Agent typically
   provides the Anchoring Function (AF), Forwarding Management (FM), and
   Internetwork Location Information server (LIs) functions.  The mobile
   node possesses the Location Information client (LIc) function and the
   FM function to enable tunneling between HA and itself.  We next
   describe some practices that show how MIPv6/NEMO and several other
   protocol extensions can be deployed in a distributed mobility
   management environment.

   One approach to distribute the anchors can be to deploy several HAs
   (as shown in Figure 2), and assign the topologically closest anchor
   to each MN [RFC4640], [RFC5026], [RFC6611].  In the example shown in
   Figure 2, the mobile node MN1 is assigned to the home agent HA1 and
   uses a home address anchored by HA1 to communicate with the



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   correspondent node CN1.  Similarly, the mobile node MN2 is assigned
   to the home agent HA2 and uses a home address anchored by HA2 to
   communicate with the correspondent node CN2.  Note that MIPv6/NEMO
   specifications do not prevent the simultaneous use of multiple home
   agents by a single mobile node.  In this deployment model, the mobile
   node can use several anchors at the same time, each of them anchoring
   IP flows initiated at a different point of attachment.  However,
   there is currently no mechanism specified in IETF standard to enable
   an efficient dynamic discovery of available anchors and the selection
   of the most suitable one.

   <-INTERNET-> <- HOME NETWORK -> <------- ACCESS NETWORK ------->
    +-----+                            +-----+       +--------+
    | CN1 |---                      ===| AR1 |=======|   MN1  |
    +-----+   \   +-----------+   //   +-----+       |(FM,LMc)|
               ---|    HA1    |===                   +--------+
                  |(AF,FM,LMs)|        +-----+       (anchored
                  +-----------+        | AR2 |          at HA1)
    +-----+                            +-----+
    | CN2 |--------------
    +-----+              \             +-----+       +--------+
                          -------------| AR3 |-------|   MN2  |
                  +-----------+        +-----+       |(FM,LMc)|
                  |    HA2    |                      +--------+
                  |(AF,FM,LMs)|        +-----+       (anchored
                  +-----------+        | AR4 |          at HA2)
                                       +-----+

   CN1   CN2        HA1   HA2         AR1   AR3      MN1    MN2
    |     |          |     |           |     |        |      |
    |<-------------->|<======tunnel====+=============>|      | BT mode
    |     |          |     |           |     |        |      |
    |     |<---------------------------------+-------------->| RO mode
    |     |          |     |           |     |        |      |

     Figure 2: Distributed operation of Mobile IPv6 (BT and RO) / NEMO

   One goal of the deployment of mobility protocols in a distributed
   mobility management environment is to avoid the suboptimal routing
   caused by centralized anchoring.  Here, the Route Optimization (RO)
   support provided by Mobile IPv6 can be used to achieve a flatter IP
   data forwarding.  By default, Mobile IPv6 and NEMO use the so-called
   Bidirectional Tunnel (BT) mode, in which data traffic is always
   encapsulated between the MN and its HA before being directed to any
   other destination.  The RO mode allows the MN to update its current
   location on the CNs, and then use the direct path between them.
   Using the example shown in Figure 2, MN1 is using BT mode with CN1,




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   while MN2 is in RO mode with CN2.  However, the RO mode has several
   drawbacks:

   o  The RO mode is only supported by Mobile IPv6.  There is no route
      optimization support standardized for the NEMO protocol because of
      the security problems posed by extending return routability tests
      for prefixes, although many different solutions have been proposed
      [RFC4889].

   o  The RO mode requires signaling that adds some protocol overhead.

   o  The signaling required to enable RO involves the home agent and is
      repeated periodically for security reasons [RFC4225].  Therefore
      the HA remains a single point of failure.

   o  The RO mode requires support from the CN.

   Notwithstanding these considerations, the RO mode does offer the
   possibility of substantially reducing traffic through the Home Agent,
   in cases when it can be supported by the relevant correspondent
   nodes.  Note that a mobile node can also use its care-of-address
   (CoA) directly [RFC5014] when communicating with CNs on the same link
   or anywhere in the Internet, although no session continuity support
   would be provided by the IP stack in this case.

   Hierarchical Mobile IPv6 (HMIPv6) [RFC5380] (as shown in Figure 3),
   is another host-based IP mobility extension which can be considered
   as a complement to provide a less centralized mobility deployment.
   It allows the reduction of the amount of mobility signaling as well
   as improving the overall handover performance of Mobile IPv6 by
   introducing a new hierarchy level to handle local mobility.  The
   Mobility Anchor Point (MAP) entity is introduced as a local mobility
   handling node deployed closer to the mobile node.  It provides LI
   intermediary function between the LI server (LIs) at the HA and the
   LI client (LIc) at the MN.  It also performs the FM function to
   tunnel with the HA and also with the MN.















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   <INTERNET> <- HOME NETWORK -> <---------- ACCESS NETWORK ---------->
                                                  LCoA anchored
                                                     at AR1
                                                      +---+  +--------+
                                                   ===|AR1|==|   MN1  |
    +-----+    +-----------+      +----------+   //   +---+  |(FM,LMc)|
    | CN1 |----|    HA1    |======|   MAP1   |===            +--------+
    +-----+    |(AF,FM,LMs)|     /|(AF,FM,LM)|        +---+        HoA,
               +-----------+    / +----------+        |AR2|       RCoA,
                HoA anchored   /  RCoA anchored       +---+       LCoA
                   at HA1     /      at MAP1
                             /                        +---+
                            /                         |AR3|
    +-----+                /      +----------+        +---+
    | CN2 |----------------       |   MAP2   |
    +-----+                       |(AF,FM,LM)|        +---+
                                  +----------+        |AR4|
                                                      +---+
   CN1   CN2        HA1               MAP1             AR1     MN1
    |     |          |                 |                |       |
    |<-------------->|<===============>|<====tunnel============>| HoA
    |     |          |                 |                |       |
    |     |<-------------------------->|<====tunnel============>| RCoA
    |     |          |                 |                |       |

                    Figure 3: Hierarchical Mobile IPv6

   When HMIPv6 is used, the MN has two different temporary addresses:
   the Regional Care-of Address (RCoA) and the Local Care-of Address
   (LCoA).  The RCoA is anchored at one MAP, which plays the role of
   local home agent, while the LCoA is anchored at the access router
   level.  The mobile node uses the RCoA as the CoA signaled to its home
   agent.  Therefore, while roaming within a local domain handled by the
   same MAP, the mobile node does not need to update its home agent,
   i.e., the mobile node does not change its RCoA.

   The use of HMIPv6 enables a form of route optimization, since a
   mobile node may decide to directly use the RCoA as source address for
   a communication with a given correspondent node, particularly if the
   MN does not expect to move outside the local domain during the
   lifetime of the communication.  This can be seen as a potential DMM
   mode of operation, though it fails to provide session continuity if
   and when the MN moves outside the local domain.  In the example shown
   in Figure 3, MN1 is using its global HoA to communicate with CN1,
   while it is using its RCoA to communicate with CN2.

   Furthermore, a local domain might have several MAPs deployed,
   enabling therefore a different kind of HMIPv6 deployments which are



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   flattening and distributed.  The HMIPv6 specification supports a
   flexible selection of the MAP, including those based on the distance
   between the MN and the MAP, or taking into consideration the expected
   mobility pattern of the MN.

   Another extension that can be used to help with distributing mobility
   management functions is the Home Agent switch specification
   [RFC5142], which defines a new mobility header for signaling a mobile
   node that it should acquire a new home agent.  [RFC5142] does not
   specify the case of changing the mobile node's home address, as that
   might imply loss of connectivity for ongoing persistent connections.
   Nevertheless, that specification could be used to force the change of
   home agent in those situations where there are no active persistent
   data sessions that cannot cope with a change of home address.

   There are other host-based approaches standardized that can be used
   to provide mobility support.  For example MOBIKE [RFC4555] allows a
   mobile node encrypting traffic through IKEv2 [RFC5996] to change its
   point of attachment while maintaining a Virtual Private Network (VPN)
   session.  The MOBIKE protocol allows updating the VPN Security
   Associations (SAs) in cases where the base connection initially used
   is lost and needs to be re-established.  The use of the MOBIKE
   protocol avoids having to perform an IKEv2 re-negotiation.  Similar
   considerations to those made for Mobile IPv6 can be applied to
   MOBIKE; though MOBIKE is best suited for situations where the address
   of at least one endpoint is relatively stable and can be discovered
   using existing mechanisms such as DNS.

   Extensions have been defined to the mobility protocol to optimize the
   handover performance.  Mobile IPv6 Fast Handovers (FMIPv6) [RFC5568]
   is the extension to optimize handover latency.  It defines new access
   router discovery mechanism before handover to reduce the new network
   discovery latency.  It also defines a tunnel between the previous
   access router and the new access router to reduce the packet loss
   during handover.  The Candidate Access Router Discovery (CARD)
   [RFC4066] and Context Transfer Protocol (CXTP) [RFC4067] protocols
   were standardized to improve the handover performance.  The DMM
   deployment practice discussed in this section can also use those
   extensions to improve the handover performance.

4.2.2.  Network-based IP DMM practices

   Proxy Mobile IPv6 (PMIPv6) [RFC5213] is the main network-based IP
   mobility protocol specified for IPv6.  Proxy Mobile IPv4 [RFC5844]
   defines some IPv4 extensions.  With network-based IP mobility
   protocols, the Local Mobility Anchor (LMA) typically provides the
   Anchoring Function (AF), Forwarding Management (FM) function, and
   Internetwork Location Information server (LIs) function.  The mobile



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   access gateway (MAG) provides the Location Information client (LIc)
   function and Forwarding Management (FM) function to tunnel with LMA.
   PMIPv6 is architecturally almost identical to MIPv6, as the mobility
   signaling and routing between LMA and MAG in PMIPv6 is similar to
   those between HA and MN in MIPv6.  The required mobility
   functionality at the MN is provided by the MAG so that the
   involvement in mobility support by the MN is not required.

   We next describe some practices that show how network-based mobility
   protocols and several other protocol extensions can be deployed in a
   distributed mobility management environment.

   One way to decentralize Proxy Mobile IPv6 operation can be to deploy
   several Local Mobility Anchors and use some selection criteria to
   assign LMAs to attaching mobile nodes.  An example of this type of
   assignment is shown in Figure 4.  As with the client based approach,
   a mobile node may use several anchors at the same time, each of them
   anchoring IP flows initiated at a different point of attachment.
   This assignment can be static or dynamic.  The main advantage of this
   simple approach is that the IP address anchor, i.e., the LMA, could
   be placed closer to the mobile node.  Therefore the resulting paths
   are close-to-optimal.  On the other hand, as soon as the mobile node
   moves, the resulting path will start deviating from the optimal one.

   <INTERNET> <--- HOME NETWORK ---> <------ ACCESS NETWORK ------->
                                               +--------+      +---+
                                        =======|  MAG1  |------|MN1|
    +-----+       +-----------+       //       |(FM,LMc)|      +---+
    | CN1 |-------|    LMA1   |=======         +--------+
    +-----+       |(AF,FM,LMs)|
                  +-----------+                +--------+
    +-----+                                    |  MAG2  |
    | CN2 |---                                 |(FM,LMc)|
    +-----+   \   +-----------+                +--------+
               ---|    LMA2   |=======
    +-----+       |(AF,FM,LMs)|       \\       +--------+      +---+
    | CN3 |       +-----------+         =======|  MAG3  |------|MN2|
    +-----+                                    |(FM,LMs)|      +---+
                                               +--------+
   CN1   CN2        LMA1  LMA2                  MAG1 MAG3     MN1  MN2
    |     |          |     |                     |    |        |    |
    |<-------------->|<===========tunnel========>|<----------->|    |
    |     |          |     |                     |    |        |    |
    |     |<-------------->|<=====tunnel=============>|<----------->|
    |     |          |     |                     |    |        |    |

           Figure 4: Distributed operation of Proxy Mobile IPv6




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   In a similar way to the host-based IP mobility case, network-based IP
   mobility has some extensions defined to mitigate the suboptimal
   routing issues that may arise due to the use of a centralized anchor.
   The Local Routing extensions [RFC6705] enable optimal routing in
   Proxy Mobile IPv6 in three cases: i) when two communicating MNs are
   attached to the same MAG and LMA, ii) when two communicating MNs are
   attached to different MAGs but to the same LMA, and iii) when two
   communicating MNs are attached to the same MAG but have different
   LMAs.  In these three cases, data traffic between the two mobile
   nodes does not traverse the LMA(s), thus providing some form of path
   optimization since the traffic is locally routed at the edge.  The
   main disadvantage of this approach is that it only tackles the MN-to-
   MN communication scenario, and only under certain circumstances.

   An interesting extension that can also be used to facilitate the
   deployment of network-based mobility protocols in a distributed
   mobility management environment is the support of LMA runtime
   assignment described in [RFC6463].  This extension specifies a
   runtime Local Mobility Anchor assignment functionality and
   corresponding mobility options for Proxy Mobile IPv6.  This runtime
   Local Mobility Anchor assignment takes place during the Proxy Binding
   Update / Proxy Binding Acknowledgment message exchange between a
   mobile access gateway and a local mobility anchor.  While this
   mechanism is mainly aimed for load-balancing purposes, it can also be
   used to select an optimal LMA from the routing point of view.  A
   runtime LMA assignment can be used to change the assigned LMA of an
   MN, for example, in cases when the mobile node does not have any
   active session, or when the running sessions can survive an IP
   address change.  Note that several possible dynamic Local Mobility
   Anchor discovery solutions can be used, as described in [RFC6097].

4.3.  Flattening 3GPP mobile network approaches

   The 3rd Generation Partnership Project (3GPP) is the standards
   development organization that specifies the 3rd generation mobile
   network and the Evolved Packet System (EPS) [SDO-3GPP.23.402], which
   mainly comprises the Evolved Packet Core (EPC) and a new radio access
   network, usually referred to as LTE (Long Term Evolution).

   Architecturally, the 3GPP Evolved Packet Core (EPC) network is
   similar to an IP wireless network running PMIPv6 or MIPv6, as it
   relies on the Packet Data Network Gateway (PGW) anchoring services to
   provide mobile nodes with mobility support (see Figure 5).  There are
   client-based and network-based mobility solutions in 3GPP, which for
   simplicity will be analyzed together.  We next describe how 3GPP
   mobility protocols and several other completed or ongoing extensions
   can be deployed to meet some of the DMM requirements [RFC7333].




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            +---------------------------------------------------------+
            |                           PCRF                          |
            +-----------+--------------------------+----------------+-+
                        |                          |                |
   +----+   +-----------+------------+    +--------+-----------+  +-+-+
   |    |   |          +-+           |    |  Core Network      |  |   |
   |    |   | +------+ |S|__         |    | +--------+  +---+  |  |   |
   |    |   | |GERAN/|_|G|  \        |    | |  HSS   |  |   |  |  |   |
   |    +-----+ UTRAN| |S|   \       |    | +---+----+  |   |  |  | E |
   |    |   | +------+ |N|  +-+-+    |    |     |       |   |  |  | x |
   |    |   |          +-+ /|MME|    |    | +---+----+  |   |  |  | t |
   |    |   | +---------+ / +---+    |    | |  3GPP  |  |   |  |  | e |
   |    +-----+ E-UTRAN |/           |    | |  AAA   |  |   |  |  | r |
   |    |   | +---------+\           |    | | SERVER |  |   |  |  | n |
   |    |   |             \ +---+    |    | +--------+  |   |  |  | a |
   |    |   |   3GPP AN    \|SGW+----- S5---------------+ P |  |  | l |
   |    |   |               +---+    |    |             | G |  |  |   |
   |    |   +------------------------+    |             | W |  |  | I |
   | UE |                                 |             |   |  |  | P |
   |    |   +------------------------+    |             |   +-----+   |
   |    |   |+-------------+ +------+|    |             |   |  |  | n |
   |    |   || Untrusted   +-+ ePDG +-S2b---------------+   |  |  | e |
   |    +---+| non-3GPP AN | +------+|    |             |   |  |  | t |
   |    |   |+-------------+         |    |             |   |  |  | w |
   |    |   +------------------------+    |             |   |  |  | o |
   |    |                                 |             |   |  |  | r |
   |    |   +------------------------+    |             |   |  |  | k |
   |    +---+  Trusted non-3GPP AN   +-S2a--------------+   |  |  | s |
   |    |   +------------------------+    |             |   |  |  |   |
   |    |                                 |             +-+-+  |  |   |
   |    +--------------------------S2c--------------------|    |  |   |
   |    |                                 |                    |  |   |
   +----+                                 +--------------------+  +---+

             Figure 5: EPS (non-roaming) architecture overview

   The GPRS Tunneling Protocol (GTP) [SDO-3GPP.29.060] [SDO-3GPP.29.281]
   [SDO-3GPP.29.274] is a network-based mobility protocol specified for
   3GPP networks (S2a, S2b, S5 and S8 interfaces).  In a similar way to
   PMIPv6, it can handle mobility without requiring the involvement of
   the mobile nodes.  In this case, the mobile node functionality is
   provided in a proxy manner by the Serving Data Gateway (SGW), Evolved
   Packet Data Gateway (ePDG), or Trusted Wireless Access Gateway (TWAG
   [SDO-3GPP.23.402]) .

   3GPP specifications also include client-based mobility support, based
   on adopting the use of Dual-Stack Mobile IPv6 (DSMIPv6) [RFC5555] for
   the S2c interface [SDO-3GPP.24.303].  In this case, the User



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   Equipment (UE) implements the binding update functionality, while the
   home agent role is played by the PGW.

   A Local IP Access (LIPA) and Selected IP Traffic Offload (SIPTO)
   enabled network [SDO-3GPP.23.401] allows offloading some IP services
   at the local access network above the Radio Access Network (RAN)
   without the need to travel back to the PGW (see Figure 6).

     +---------+ IP traffic to mobile operator's CN
     |  User   |....................................(Operator's CN)
     | Equipm. |..................
     +---------+                 . Local IP traffic
                                 .
                           +-----------+
                           |Residential|
                           |enterprise |
                           |IP network |
                           +-----------+

                          Figure 6: LIPA scenario

   SIPTO enables an operator to offload certain types of traffic at a
   network node close to the UE's point of attachment to the access
   network, by selecting a set of GWs (SGW and PGW) that are
   geographically/topologically close to the UE's point of attachment.

                        SIPTO Traffic
                             |
                             .
                             .
                         +-------+        +------+
                         | L-PGW |   ---- | MME  |
                         +-------+  /     +------+
                              |    /
   +------+     +-----+    +-----+/       +-----+
   |  UE  |.....| eNB |....| SGW |........| PGW |.... CN Traffic
   +------+     +-----+    +-----+        +-----+

                       Figure 7: SIPTO architecture

   LIPA, on the other hand, enables an IP addressable UE connected via a
   Home eNB (HeNB) to access other IP addressable entities in the same
   residential/enterprise IP network without traversing the mobile
   operator's network core in the user plane.  In order to achieve this,
   a Local GW (LGW) collocated with the HeNB is used.  LIPA is
   established by the UE requesting a new Public Data Network (PDN)
   connection to an access point name for which LIPA is permitted, and




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   the network selecting the Local GW associated with the HeNB and
   enabling a direct user plane path between the Local GW and the HeNB.

   +---------------+------+  +----------+  +-------------+    =====
   |Residential |  | HeNB |  | Backhaul |  |Mobile       |   ( IP  )
   |Enterprise  |..|------|..|          |..|Operator     |..(Network)
   |Network     |  | LGW  |  |          |  |Core network |   =======
   +---------------+------+  +----------+  +-------------+
                      /
                      |
                      /
                  +-----+
                  | UE  |
                  +-----+

                        Figure 8: LIPA architecture

   The 3GPP architecture specifications also provide mechanisms to allow
   discovery and selection of gateways [SDO-3GPP.29.303].  These
   mechanisms enable decisions taking into consideration topological
   location and gateway collocation aspects, relying upon the DNS as a
   "location database."

   Both SIPTO and LIPA have a very limited mobility support, especially
   in 3GPP specifications up to Rel-12.  Briefly, LIPA mobility support
   is limited to handovers between HeNBs that are managed by the same
   LGW (i.e., mobility within the local domain).  There is no guarantee
   of IP session continuity for SIPTO.

5.  Gap analysis

   This section identifies the limitations in the current practices,
   described in Section 4, with respect to the DMM requirements listed
   in [RFC7333].

5.1.  Distributed mobility management - REQ1

   According to requirement REQ1 stated in [RFC7333], IP mobility,
   network access and forwarding solutions provided by DMM must make it
   possible for traffic to avoid traversing a single mobility anchor far
   from the optimal route.

   From the analysis performed in Section 4, a DMM deployment can meet
   the requirement "REQ1 Distributed mobility management" usually
   relying on the following functions:

   o  Multiple (distributed) anchoring: ability to anchor different
      sessions of a single mobile node at different anchors.  In order



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      to provide improved routing, some anchors might need to be placed
      closer to the mobile node or the corresponding node.

   o  Dynamic anchor assignment/re-location: ability to i) assign the
      initial anchor, and ii) dynamically change the initially assigned
      anchor and/or assign a new one (this may also require the transfer
      of mobility context between anchors).  This can be achieved either
      by changing anchor for all ongoing sessions or by assigning new
      anchors just for new sessions.

   GAP1-1:  Both the main client- and network-based IP mobility
            protocols, namely (DS)MIPv6 and PMIPv6 allow deploying
            multiple anchors (i.e., home agents and localized mobility
            anchors), thereby providing the multiple anchoring function.
            However, existing solutions only provide an initial anchor
            assignment, thus the lack of dynamic anchor change/new
            anchor assignment is a gap.  Neither the HA switch nor the
            LMA runtime assignment allows changing the anchor during an
            ongoing session.  This actually comprises several gaps:
            ability to perform anchor assignment at any time (not only
            at the initial MN's attachment), ability of the current
            anchor to initiate/trigger the relocation, and ability to
            transfer registration context between anchors.

   GAP1-2:  Dynamic anchor assignment may lead the MN to manage
            different mobility sessions served by different mobility
            anchors.  This is not an issue with client based mobility
            management where the mobility client natively knows the
            anchor associated with each of its mobility sessions.
            However, there is one gap, as the MN should be capable of
            handling IP addresses in a DMM-friendly way, meaning that
            the MN can perform smart source address selection (i.e.,
            deprecating IP addresses from previous mobility anchors, so
            they are not used for new sessions).  Besides, managing
            different mobility sessions served by different mobility
            anchors may raise issues with network based mobility
            management.  In this case, the mobile client located in the
            network, e.g., MAG, usually retrieves the MN's anchor from
            the MN's policy profile as described in Section 6.2 of
            [RFC5213].  Currently, the MN's policy profile implicitly
            assumes a single serving anchor and thus does not maintain
            the association between home network prefix and anchor.

   GAP1-3:  The consequence of the distribution of the mobility anchors
            is that there might be more than one available anchor for a
            mobile node to use, which leads to an anchor discovery and
            selection issue.  Currently, there is no efficient mechanism
            specified to allow the dynamic discovery of the presence of



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            nodes that can play the anchor role, discovering their
            capabilities and selecting the most suitable one.  There is
            also no mechanism to allow selecting a node that is
            currently anchoring a given home address/prefix (capability
            sometimes required to meet REQ#2).  However, there are some
            mechanisms that could help to discover anchors, such as the
            Dynamic Home Agent Address Discovery (DHAAD) [RFC6275], the
            use of the home agent flag (H) in Router Advertisements
            (which indicates that the router sending the Router
            Advertisement is also functioning as a Mobile IPv6 home
            agent on the link) or the MAP option in Router
            Advertisements defined by HMIPv6.  Note that there are 3GPP
            mechanisms providing that functionality defined in
            [SDO-3GPP.29.303].

   Regarding the ability to transfer registration context between
   anchors, there are already some solutions that could be reused or
   adapted to fill that gap, such as Fast Handovers for Mobile IPv6
   [RFC5568] -- to enable traffic redirection from the old to the new
   anchor --, the Context Transfer protocol [RFC4067] -- to enable the
   required transfer of registration information between anchors --, or
   the Handover Keying architecture solutions [RFC6697], to speed up the
   re-authentication process after a change of anchor.  Note that some
   extensions might be needed in the context of DMM, as these protocols
   were designed in the context of centralized client IP mobility,
   focusing on the access re-attachment and authentication.

   GAP1-4:  Also note that REQ1 is intended to prevent the data plane
            traffic from taking a suboptimal route.  Distributed
            processing of the traffic may then be needed only in the
            data plane.  Provision of this capability for distributed
            processing should not conflict with the use of a centralized
            control plane.  Other control plane solutions such as
            charging, lawful interception, etc.  should not be
            constrained by the DMM solution.  On the other hand
            combining the control plane and data plane forwarding
            management (FM) function may limit the choice of solutions
            to those that distribute both data plane and control plane
            together.  In order to enable distribution of only the data
            plane without distributing the control plane, it would be
            necessary to split the forwarding management function into
            the control plane (FM-CP) and data plane (FM-DP) components;
            there is currently a gap here.








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5.2.  Bypassable network-layer mobility support for each application
      session - REQ2

   The requirement REQ2 for "bypassable network-layer mobility support
   for each application session" introduced in [RFC7333] requires
   flexibility in determining whether network-layer mobility support is
   needed.  This requirement enables one to choose whether or not to use
   network-layer mobility support.  The following two functions are also
   needed:

   o  Dynamically assign/relocate anchor: a mobility anchor is assigned
      only to sessions which use the network-layer mobility support.
      The MN may thus manage more than one session; some of them may be
      associated with anchored IP address(es), while the others may be
      associated with local IP address(es).

   o  Multiple IP address management: this function is related to the
      preceding and is about the ability of the mobile node to
      simultaneously use multiple IP addresses and select the best one
      (from an anchoring point of view) to use on a per-
      session/application/service basis.  This requires MN to acquire
      information regarding the properties of the available IP
      addresses.

   GAP2-1:  The dynamic anchor assignment/relocation needs to ensure
            that IP address continuity is guaranteed for sessions that
            uses such mobility support (e.g., in some scenarios, the
            provision of mobility locally within a limited area might be
            enough from the mobile node or the application point of
            view) at the relocated anchor.  Implicitly, when no
            applications are using the network-layer mobility support,
            DMM may release the needed resources.  This may imply having
            the knowledge of which sessions at the mobile node are
            active and are using the mobility support.  This is
            something typically known only by the MN, e.g., by its
            connection manager, and would also typically require some
            signaling support such as socket API extensions from
            applications to indicate to the IP stack whether mobility
            support is required or not.  Therefore, (part of) this
            knowledge might need to be transferred to/shared with the
            network.

   GAP2-2:  Multiple IP address management provides the MN with the
            choice to pick the correct address, e.g., from those
            provided or not provided with mobility support, depending on
            the application requirements.  When using client based
            mobility management, the mobile node is itself aware of the
            anchoring capabilities of its assigned IP addresses.  This



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            is not necessarily the case with network based IP mobility
            management; current mechanisms do not allow the MN to be
            aware of the properties of its IP addresses.  For example,
            the MN does not know whether the allocated IP addresses are
            anchored.  However, there are proposals, such as
            [I-D.bhandari-dhc-class-based-prefix],
            [I-D.korhonen-6man-prefix-properties] and
            [I-D.anipko-mif-mpvd-arch] that the network could indicate
            such IP address properties during assignment procedures.
            Although these individual efforts exist and they could be
            considered as attempts to fix the gap, there is no solution
            adopted as a work item within any IETF working group.

   GAP2-3:  The handling of mobility management to the granularity of an
            individual session of a user/device needs proper session
            identification in addition to user/device identification.

5.3.  IPv6 deployment - REQ3

   This requirement states that DMM solutions should primarily target
   IPv6 as the primary deployment environment.  IPv4 support is not
   considered mandatory and solutions should not be tailored
   specifically to support IPv4.

   All analyzed DMM practices support IPv6.  Some of them, such as
   MIPv6/NEMO including the support of dynamic HA selection, MOBIKE,
   SIPTO also have IPv4 support.  Some solutions, e.g., PMIPv6, also
   have some limited IPv4 support.  In conclusion, this requirement is
   met by existing DMM practices.

5.4.  Considering existing mobility protocols - REQ4

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

   As stated in [RFC7333], a DMM solution could reuse existing IETF and
   standardized protocols before specifying new protocols.  Besides,
   Section 4 of this document discusses various ways to flatten and
   distribute current mobility solutions.  Actually, nothing prevents
   the distribution of mobility functions within IP mobility protocols.
   However, as discussed in Section 5.1 and Section 5.2, limitations
   exist.

   The 3GPP data plane anchoring function, i.e., the PGW, can also be
   distributed, but with limitations; e.g., no anchoring relocation, no
   context transfer between anchors and centralized control plane.  The
   3GPP architecture is also going in the direction of flattening with
   SIPTO and LIPA, though they do not provide full mobility support.



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   For example, mobility support for SIPTO traffic can be rather
   limited, and offloaded traffic cannot access operator services.
   Thus, the operator must be very careful in selecting which traffic to
   offload.

5.5.  Coexistence with deployed networks/hosts and operability across
      different networks - REQ5

   According to [RFC7333], DMM implementations are required to co-exist
   with existing network deployments, end hosts and routers.
   Additionally, DMM solutions are expected to work across different
   networks, possibly operated as separate administrative domains, when
   the necessary mobility management signaling, forwarding, and network
   access are allowed by the trust relationship between them.  All
   current mobility protocols can co-exist with existing network
   deployments and end hosts.  There is no gap between existing mobility
   protocols and this requirement.

5.6.  Operation and management considerations - REQ6

   This requirement actually comprises several aspects, as summarized
   below.

   o  A DMM solution needs to consider configuring a device, monitoring
      the current operational state of a device, responding to events
      that impact the device, possibly by modifying the configuration
      and storing the data in a format that can be analyzed later.

   o  A DMM solution has to describe in what environment and how it can
      be scalably deployed and managed.

   o  A DMM solution has to support mechanisms to test if the DMM
      solution is working properly.

   o  A DMM solution is expected to expose the operational state of DMM
      to the administrators of the DMM entities.

   o  A DMM solution, which supports flow mobility, is also expected to
      support means to correlate the flow routing policies and the
      observed forwarding actions.

   o  A DMM solution is expected to support mechanisms to check the
      liveness of the forwarding path.

   o  A DMM solution has to provide fault management and monitoring
      mechanisms to manage situations where update of the mobility
      session or the data path fails.




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   o  A DMM solution is expected to be able to monitor the usage of the
      DMM protocol.

   o  DMM solutions have to support standardized configuration with
      NETCONF [RFC6241], using YANG [RFC6020] modules, which are
      expected to be created for DMM when needed for such configuration.

   GAP6-1:  Existing mobility management protocols have not thoroughly
            documented how, or whether, they support the above list of
            operation and management considerations.  Each of the above
            needs to be considered from the beginning in a DMM solution.

   GAP6-2:  Management information base (MIB) objects are currently
            defined in [RFC4295] for MIPv6 and in [RFC6475] for PMIPv6.
            Standardized configuration with NETCONF [RFC6241], using
            YANG [RFC6020] modules is lacking.

5.7.  Security considerations - REQ7

   As stated in [RFC7333], a DMM solution has to 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 cannot
   introduce new security risks, or privacy concerns, or amplify
   existing security risks, that cannot be mitigated by existing
   security protocols and mechanisms.

   Any solutions that are intended to fill in gaps identified in this
   document need to meet this requirement.  At present, it does not
   appear that using existing solutions to support DMM has introduced
   any new security issues.  For example, Mobile IPv6 defines security
   features to protect binding updates both to home agents and
   correspondent nodes.  It also defines mechanisms to protect the data
   packets transmission for Mobile IPv6 users.  Proxy Mobile IPv6 and
   other variations of mobile IP also have similar security
   considerations.

5.8.  Multicast - REQ8

   It is stated in [RFC7333] that DMM solutions are expected to allow
   the development of multicast solutions to avoid network inefficiency
   in multicast traffic delivery.

   Current IP mobility solutions address mainly the mobility problem for
   unicast traffic.  Solutions relying on the use of an anchor point for
   tunneling multicast traffic down to the access router, or to the
   mobile node, introduce the so-called "tunnel convergence problem."
   This means that multiple instances of the same multicast traffic can



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   converge to the same node, diminishing the advantage of using
   multicast protocols.

   [RFC6224] documents a baseline solution for the previous issue, and
   [RFC7028] a routing optimization solution.  The baseline solution
   suggests deploying a Multicast Listener Discovery (MLD) proxy
   function at the MAG, and either a multicast router or another MLD
   proxy function at the LMA.  The routing optimization solution
   describes an architecture where a dedicated multicast tree mobility
   anchor or a direct routing option can be used to avoid the tunnel
   convergence problem.

   Besides the solutions highlighted before, there are no other
   mechanisms for mobility protocols to address the multicast tunnel
   convergence problem.

5.9.  Summary

   We next list the main gaps identified from the analysis performed
   above:

   GAP1-1:  Existing solutions only provide an optimal initial anchor
            assignment, a gap being the lack of dynamic anchor change/
            new anchor assignment.  Neither the HA switch nor the LMA
            runtime assignment allows changing the anchor during an
            ongoing session.  MOBIKE allows change of GW but its
            applicability has been scoped to a very narrow use case.

   GAP1-2:  The MN needs to be able to perform source address selection.
            Proper mechanism to inform the MN is lacking to provide the
            basis for the proper selection.

   GAP1-3:  Currently, there is no efficient mechanism specified by the
            IETF that allows the dynamic discovery of the presence of
            nodes that can play the role of anchor, discover their
            capabilities and allow the selection of the most suitable
            one.  However, the following mechanisms could help
            discovering anchors:

            Dynamic Home Agent Address Discovery (DHAAD): the use of the
            home agent (H) flag in Router Advertisements (which
            indicates that the router sending the Router Advertisement
            is also functioning as a Mobile IPv6 home agent on the link)
            and the MAP option in Router Advertisements defined by
            HMIPv6.

   GAP1-4:  While existing network-based DMM practices may allow the
            deployment of multiple LMAs and dynamically select the best



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            one, this requires to still keep some centralization in the
            control plane, to access the policy database (as defined in
            RFC5213).  Although [I-D.ietf-netext-pmip-cp-up-separation]
            allows a MAG to perform splitting of its control and user
            planes, there is a lack of solutions/extensions that support
            a clear control and data plane separation for IETF IP
            mobility protocols in a DMM context.

   GAP2-1:  The information of which sessions at the mobile node are
            active and are using the mobility support need to be
            transferred to or shared with the network.  Such mechanism
            has not been defined.

   GAP2-2:  The mobile node needs to simultaneously use multiple IP
            addresses with different properties.  There is a lack of
            mechanism to expose this information to the mobile node
            which can then update accordingly its source address
            selection mechanism.

   GAP2-3:  The handling of mobility management has not been to the
            granularity of an individual session of a user/device
            before.  The combination of session identification and user/
            device identification may be lacking.

   GAP6-1:  Mobility management protocols have not thoroughly documented
            how, or whether, they support the following list of
            operation and management considerations:

            *  A DMM solution needs to consider configuring a device,
               monitoring the current operational state of a device,
               responding to events that impact the device, possibly by
               modifying the configuration and storing the data in a
               format that can be analyzed later.

            *  A DMM solution has to describe in what environment and
               how it can be scalably deployed and managed.

            *  A DMM solution has to support mechanisms to test if the
               DMM solution is working properly.

            *  A DMM solution is expected to expose the operational
               state of DMM to the administrators of the DMM entities.

            *  A DMM solution, which supports flow mobility, is also
               expected to support means to correlate the flow routing
               policies and the observed forwarding actions.





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            *  A DMM solution is expected to support mechanisms to check
               the liveness of the forwarding path.

            *  A DMM solution has to provide fault management and
               monitoring mechanisms to manage situations where update
               of the mobility session or the data path fails.

            *  A DMM solution is expected to be able to monitor the
               usage of the DMM protocol.

            *  DMM solutions have to support standardized configuration
               with NETCONF [RFC6241], using YANG [RFC6020] modules,
               which are expected to be created for DMM when needed for
               such configuration.

   GAP6-2:  Management information base (MIB) objects are currently
            defined in [RFC4295] for MIPv6 and in [RFC6475] for PMIPv6.
            Standardized configuration with NETCONF [RFC6241], using
            YANG [RFC6020] modules is lacking.

6.  Security Considerations

   The deployment of DMM using existing IP mobility protocols raises
   similar security threats as those encountered in centralized mobility
   management systems.  Without authentication, a malicious node could
   forge signaling messages and redirect traffic from its legitimate
   path.  This would amount to a denial of service attack against the
   specific node or nodes for which the traffic is intended.
   Distributed mobility anchoring, while keeping current security
   mechanisms, might require more security associations to be managed by
   the mobility management entities, potentially leading to scalability
   and performance issues.  Moreover, distributed mobility anchoring
   makes mobility security problems more complex, since traffic
   redirection requests might come from previously unconsidered origins,
   thus leading to distributed points of attack.  Consequently, the DMM
   security design needs to account for the distribution of security
   associations between additional mobility entities and fulfill the
   security requirement of [RFC7333].

7.  Contributors

   This document has benefited to valuable contributions from

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





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   who had produced a matrix to compare the different mobility protocols
   and extensions against a list of desired DMM properties.  They were
   useful inputs in the early work of gap analysis.  He had continued to
   give suggestions as well as extensive review comments to this
   documents.

8.  References

8.1.  Normative References

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

   [RFC7333]  Chan, H., Liu, D., Seite, P., Yokota, H., and J. Korhonen,
              "Requirements for Distributed Mobility Management", RFC
              7333, August 2014.

8.2.  Informative References

   [I-D.anipko-mif-mpvd-arch]
              Anipko, D., "Multiple Provisioning Domain Architecture",
              draft-anipko-mif-mpvd-arch-05 (work in progress), November
              2013.

   [I-D.bhandari-dhc-class-based-prefix]
              Systems, C., 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.gundavelli-v6ops-community-wifi-svcs]
              Gundavelli, S., Grayson, M., Seite, P., and Y. Lee,
              "Service Provider Wi-Fi Services Over Residential
              Architectures", draft-gundavelli-v6ops-community-wifi-
              svcs-06 (work in progress), April 2013.

   [I-D.ietf-netext-pmip-cp-up-separation]
              Wakikawa, R., Pazhyannur, R., Gundavelli, S., and C.
              Perkins, "Separation of Control and User Plane for Proxy
              Mobile IPv6", draft-ietf-netext-pmip-cp-up-separation-07
              (work in progress), August 2014.

   [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.





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   [IEEE.802-16.2009]
              "IEEE Standard for Local and metropolitan area networks
              Part 16: Air Interface for Broadband Wireless Access
              Systems", IEEE Standard 802.16, 2009,
              <http://standards.ieee.org/getieee802/
              download/802.16-2009.pdf>.

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

   [RFC4066]  Liebsch, M., Singh, A., Chaskar, H., Funato, D., and E.
              Shim, "Candidate Access Router Discovery (CARD)", RFC
              4066, July 2005.

   [RFC4067]  Loughney, J., Nakhjiri, M., Perkins, C., and R. Koodli,
              "Context Transfer Protocol (CXTP)", RFC 4067, July 2005.

   [RFC4225]  Nikander, P., Arkko, J., Aura, T., Montenegro, G., and E.
              Nordmark, "Mobile IP Version 6 Route Optimization Security
              Design Background", RFC 4225, December 2005.

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

   [RFC4555]  Eronen, P., "IKEv2 Mobility and Multihoming Protocol
              (MOBIKE)", RFC 4555, June 2006.

   [RFC4640]  Patel, A. and G. Giaretta, "Problem Statement for
              bootstrapping Mobile IPv6 (MIPv6)", RFC 4640, September
              2006.

   [RFC4889]  Ng, C., Zhao, F., Watari, M., and P. Thubert, "Network
              Mobility Route Optimization Solution Space Analysis", RFC
              4889, July 2007.

   [RFC4960]  Stewart, R., "Stream Control Transmission Protocol", RFC
              4960, September 2007.

   [RFC5014]  Nordmark, E., Chakrabarti, S., and J. Laganier, "IPv6
              Socket API for Source Address Selection", RFC 5014,
              September 2007.

   [RFC5026]  Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6
              Bootstrapping in Split Scenario", RFC 5026, October 2007.





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   [RFC5142]  Haley, B., Devarapalli, V., Deng, H., and J. Kempf,
              "Mobility Header Home Agent Switch Message", RFC 5142,
              January 2008.

   [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.

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

   [RFC5568]  Koodli, R., "Mobile IPv6 Fast Handovers", RFC 5568, July
              2009.

   [RFC5844]  Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
              Mobile IPv6", RFC 5844, May 2010.

   [RFC5996]  Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
              "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC
              5996, September 2010.

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

   [RFC6097]  Korhonen, J. and V. Devarapalli, "Local Mobility Anchor
              (LMA) Discovery for Proxy Mobile IPv6", RFC 6097, February
              2011.

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

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

   [RFC6463]  Korhonen, J., Gundavelli, S., Yokota, H., and X. Cui,
              "Runtime Local Mobility Anchor (LMA) Assignment Support
              for Proxy Mobile IPv6", RFC 6463, February 2012.

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




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   [RFC6611]  Chowdhury, K. and A. Yegin, "Mobile IPv6 (MIPv6)
              Bootstrapping for the Integrated Scenario", RFC 6611, May
              2012.

   [RFC6697]  Zorn, G., Wu, Q., Taylor, T., Nir, Y., Hoeper, K., and S.
              Decugis, "Handover Keying (HOKEY) Architecture Design",
              RFC 6697, July 2012.

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

   [RFC6724]  Thaler, D., Draves, R., Matsumoto, A., and T. Chown,
              "Default Address Selection for Internet Protocol Version 6
              (IPv6)", RFC 6724, September 2012.

   [RFC7028]  Zuniga, JC., Contreras, LM., Bernardos, CJ., Jeon, S., and
              Y. Kim, "Multicast Mobility Routing Optimizations for
              Proxy Mobile IPv6", RFC 7028, September 2013.

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

   [SDO-3GPP.23.402]
              3GPP, "Architecture enhancements for non-3GPP accesses",
              3GPP TS 23.402 10.8.0, September 2012.

   [SDO-3GPP.24.303]
              3GPP, "Mobility management based on Dual-Stack Mobile
              IPv6; Stage 3", 3GPP TS 24.303 10.0.0, June 2013.

   [SDO-3GPP.29.060]
              3GPP, "General Packet Radio Service (GPRS); GPRS
              Tunnelling Protocol (GTP) across the Gn and Gp interface",
              3GPP TS 29.060 3.19.0, March 2004.

   [SDO-3GPP.29.274]
              3GPP, "3GPP Evolved Packet System (EPS); Evolved General
              Packet Radio Service (GPRS) Tunnelling Protocol for
              Control plane (GTPv2-C); Stage 3", 3GPP TS 29.274 10.11.0,
              June 2013.

   [SDO-3GPP.29.281]
              3GPP, "General Packet Radio System (GPRS) Tunnelling
              Protocol User Plane (GTPv1-U)", 3GPP TS 29.281 10.3.0,
              September 2011.



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   [SDO-3GPP.29.303]
              3GPP, "Domain Name System Procedures; Stage 3", 3GPP TS
              29.303 10.4.0, September 2012.

Authors' Addresses

   Dapeng Liu (editor)
   China Mobile
   Unit2, 28 Xuanwumenxi Ave, Xuanwu District
   Beijing  100053
   China

   Email: liudapeng@chinamobile.com


   Juan Carlos Zuniga (editor)
   InterDigital Communications, LLC
   1000 Sherbrooke Street West, 10th floor
   Montreal, Quebec  H3A 3G4
   Canada

   Email: JuanCarlos.Zuniga@InterDigital.com
   URI:   http://www.InterDigital.com/


   Pierrick Seite
   Orange
   4, rue du Clos Courtel, BP 91226
   Cesson-Sevigne  35512
   France

   Email: pierrick.seite@orange.com


   H Anthony Chan
   Huawei Technologies
   5340 Legacy Dr. Building 3
   Plano, TX  75024
   USA

   Email: h.a.chan@ieee.org










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   Carlos J. Bernardos
   Universidad Carlos III de Madrid
   Av. Universidad, 30
   Leganes, Madrid  28911
   Spain

   Phone: +34 91624 6236
   Email: cjbc@it.uc3m.es
   URI:   http://www.it.uc3m.es/cjbc/










































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