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Mobility Practices and DMM Gap Analysis
draft-zuniga-dmm-gap-analysis-02

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Authors Juan-Carlos Zúñiga , Carlos J. Bernardos , Telemaco Melia , Charles E. Perkins
Last updated 2012-10-22
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draft-zuniga-dmm-gap-analysis-02
DMM WG                                                        JC. Zuniga
Internet-Draft                                              InterDigital
Intended status: Informational                             CJ. Bernardos
Expires: April 26, 2013                                             UC3M
                                                                T. Melia
                                                          Alcatel-Lucent
                                                              C. Perkins
                                                               Futurewei
                                                        October 23, 2012

                Mobility Practices and DMM Gap Analysis
                    draft-zuniga-dmm-gap-analysis-02

Abstract

   This document describes practices for the deployment of existing
   mobility protocols in a distributed mobility management environment,
   and identifies the limitations in the current practices with respect
   to providing the expected functionality.

   The practices description and gap analysis are performed for IP-based
   mobility protocols, dividing them into two main solution families:
   client- and network-based.

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 April 26, 2013.

Copyright Notice

   Copyright (c) 2012 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

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   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   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.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Practices: deployment of existing solutions in a DMM
       fashion  . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Client-based mobility  . . . . . . . . . . . . . . . . . .  4
       2.1.1.  Mobile IPv6 / NEMO . . . . . . . . . . . . . . . . . .  5
       2.1.2.  Mobile IPv6 Route Optimization . . . . . . . . . . . .  5
       2.1.3.  Hierarchical Mobile IPv6 . . . . . . . . . . . . . . .  7
       2.1.4.  Home Agent switch  . . . . . . . . . . . . . . . . . .  8
       2.1.5.  Flow Mobility  . . . . . . . . . . . . . . . . . . . .  8
       2.1.6.  Source Address Selection . . . . . . . . . . . . . . .  8
     2.2.  Network-based mobility . . . . . . . . . . . . . . . . . .  9
       2.2.1.  Proxy Mobile IPv6  . . . . . . . . . . . . . . . . . .  9
       2.2.2.  Local Routing  . . . . . . . . . . . . . . . . . . . . 10
       2.2.3.  LMA runtime assignment . . . . . . . . . . . . . . . . 10
       2.2.4.  Source Address Selection . . . . . . . . . . . . . . . 11
       2.2.5.  Multihoming in PMIPv6  . . . . . . . . . . . . . . . . 11
   3.  Gap Analysis: limitations in current practices . . . . . . . . 12
     3.1.  Client-based mobility  . . . . . . . . . . . . . . . . . . 12
       3.1.1.  REQ1: Distributed deployment . . . . . . . . . . . . . 12
       3.1.2.  REQ2: Transparency to Upper Layers when needed . . . . 13
       3.1.3.  REQ3: IPv6 deployment  . . . . . . . . . . . . . . . . 14
       3.1.4.  REQ4: Existing mobility protocols  . . . . . . . . . . 14
       3.1.5.  REQ5: Compatibility  . . . . . . . . . . . . . . . . . 15
       3.1.6.  REQ6: Security considerations  . . . . . . . . . . . . 15
     3.2.  Network-based mobility . . . . . . . . . . . . . . . . . . 15
       3.2.1.  REQ1: Distributed deployment . . . . . . . . . . . . . 15
       3.2.2.  REQ2: Transparency to Upper Layers when needed . . . . 17
       3.2.3.  REQ3: IPv6 deployment  . . . . . . . . . . . . . . . . 17
       3.2.4.  REQ4: Existing mobility protocols  . . . . . . . . . . 18
       3.2.5.  REQ5: Compatibility  . . . . . . . . . . . . . . . . . 18
       3.2.6.  REQ6: Security considerations  . . . . . . . . . . . . 18
   4.  Summary  . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 19
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 20
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 21
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 22
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22

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1.  Introduction

   The Distributed Mobility Management (DMM) approach aims at setting up
   IP networks so that traffic is distributed in an optimal way and does
   not rely on centrally deployed anchors to manage IP mobility
   sessions.

   A first step towards the definition of DMM solutions is the
   definition of the problem of distributed mobility management and the
   identification of the main requirements for a distributed mobility
   management solution [I-D.ietf-dmm-requirements].

   We first analyze existing practices of deployment of IP mobility
   solutions from a DMM perspective [I-D.perkins-dmm-matrix],
   [I-D.patil-dmm-issues-and-approaches2dmm].  After that, a gap
   analysis is carried out, identifying what can be achieved with
   existing solutions and what is missing in order to meet the DMM
   requirements identified in [I-D.ietf-dmm-requirements].

2.  Practices: deployment of existing solutions in a DMM fashion

   This section documents practices for the deployment of existing
   mobility protocols in a distributed mobility management (DMM)
   fashion.  The scope is limited to existing IPv6-based mobility
   protocols, such as Mobile IPv6 [RFC6275], NEMO Basic Support Protocol
   [RFC3963], Proxy Mobile IPv6 [RFC5213], and their extensions, such as
   Hierarchical Mobile IPv6 [RFC5380], Mobile IPv6 Fast Handovers
   [RFC5568] or Localized Routing for Proxy Mobile IPv6 [RFC6705], among
   others [RFC6301].

   The section is divided in two parts: client-based and network-based
   mobility solutions.

2.1.  Client-based mobility

   Mobile IPv6 (MIPv6) [RFC6275] and its extension to support mobile
   networks, the NEMO Basic Support protocol (hereafter, simply NEMO)
   [RFC3963] are well-known client-based IP mobility protocols.  They
   heavily rely on the function of the Home Agent (HA), a centralized
   anchor, to provide mobile nodes (hosts and routers) with mobility
   support.  We next describe how Mobile IPv6/NEMO and several
   additional protocol extensions can be deployed to meet some of the
   DMM requirements [I-D.ietf-dmm-requirements].

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2.1.1.  Mobile IPv6 / NEMO

    <- INTERNET -> <- HOME NETWORK -> <---- ACCESS NETWORK ---->
       -------                          -------
       | CN1 |         -------          | AR1 |-(o) zzzz (o)
       -------         | HA1 |          -------           |
                       -------   (MN1 anchored at HA1) -------
                                        -------        | MN1 |
                                        | AR2 |-(o)    -------
                                        -------
                       -------
                       | HA2 |          -------
                       -------          | AR3 |-(o) zzzz (o)
                                        -------           |
       -------                   (MN2 anchored at HA2) -------
       | CN2 |                          -------        | MN2 |
       -------                          | AR4 |-(o)    -------
                                        -------

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

     Figure 1: Distributed operation of Mobile IPv6 (BT and RO) / NEMO

   Due to the heavy dependence on the home agent role, the base Mobile
   IPv6 and NEMO protocols (i.e., without additional extensions) cannot
   be easily deployed in a distributed fashion.  One approach would be
   to deploy several HAs (as shown in Figure 1), and assign to each MN
   the one closest to its topological location [RFC4640], [RFC5026],
   [RFC6611].  In the example shown in Figure 1, MN1 is assigned HA1
   (and a home address anchored by HA1), while MN2 is assigned HA2.
   Note that current Mobile IPv6 / NEMO specifications do not allow the
   use of multiple home agents by a mobile node simultaneously, and
   therefore the benefits of this deployment model shown here are
   limited.  For example, if MN1 moves and attaches to AR3, the path
   followed by data packets would be suboptimal, as they have to
   traverse HA1, which is no longer close to the topological attachment
   point of MN1.

2.1.2.  Mobile IPv6 Route Optimization

   One of the main goals of DMM is to avoid the suboptimal routing
   caused by centralized anchoring.  By default, Mobile IPv6 and NEMO
   use the so-called Bidirectional Tunnel (BT) mode, in which data

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   traffic is always encapsulated between the MN and its HA.  Mobile
   IPv6 also specifies the Route Optimization (RO) mode, which 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 1, MN1
   is using BT mode with CN2 and MN2 is in RO mode with CN1.  Note that
   this 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, although
      many different solutions have been proposed.

   o  The RO mode requires additional signaling, which adds some
      protocol overhead.

   o  The signaling required to enable RO involves the home agent, and
      it is repeated periodically because of security reasons [RFC4225].
      This basically means that the HA remains as single point of
      failure, because the Mobile IPv6 RO mode does not mean HA-less
      operation.

   o  The RO mode requires additional support on the correspondent node
      (CN).

   Notwithstanding these considerations, RO mode does offer the
   possibility of substantially reducing traffic through the Home Agent,
   when it can be supported on the relevant network nodes.

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2.1.3.  Hierarchical Mobile IPv6

     <- INTERNET -> <- HOME NETWORK -> <------- ACCESS NETWORK ------->
                                                    -----
                                                   /|AR1|-(o) zz (o)
                                         -------- / -----         |
                                         | MAP1 |<             -------
                                         -------- \ -----      | MN1 |
        -------                                    \|AR2|      -------
        | CN1 |                                     -----  HoA anchored
        -------                                     -----     at HA1
                        -------                    /|AR3|  RCoA anchored
                        | HA1 |          -------- / -----     at MAP1
                        -------          | MAP2 |<         LCoA anchored
                                         -------- \ -----     at AR1
                                                   \|AR4|
        -------                                     -----
        | CN2 |                                     -----
        -------                                    /|AR5|
                                         -------- / -----
                                         | MAP3 |<
                                         -------- \ -----
                                                   \|AR6|
                                                    -----

     CN1      CN2         HA1              MAP1      AR1         MN1
      |        |           |                | ________|__________ |
      |<------------------>|<==============>|<________+__________>| HoA
      |        |           |                |         |           |
      |        |<-------------------------->|<===================>| RCoA
      |        |           |                |         |           |

                    Figure 2: Hierarchical Mobile IPv6

   Hierarchical Mobile IPv6 (HMIPv6) [RFC5380] allows reducing 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.

   When HMIPv6 is used, the MN has two different temporal addresses: the
   Regional Care-of Address (RCoA) and the Local Care-of Address (LCoA).
   The RCoA is anchored at one MAP, that 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.,

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   the mobile node does not change RCoA).

   The use of HMIPv6 allows some route optimization, as a mobile node
   may decide to directly use the RCoA as source address for a
   communication with a given correspondent node, notably 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.  In the example shown in Figure 2, MN1 is using its global
   HoA to communicate with CN1, while it is using its RCoA to
   communicate with CN2.

   Additionally, a local domain might have several MAPs deployed,
   enabling hence different kind of HMIPv6 deployments (e.g., flat and
   distributed).  The HMIPv6 specification supports a flexible selection
   of the MAP (e.g., based on the distance between the MN and the MAP,
   taking into consideration the expected mobility pattern of the MN,
   etc.).

2.1.4.  Home Agent switch

   The Home Agent switch specification [RFC5142] defines a new mobility
   header for signaling a mobile node that it should acquire a new home
   agent.  Although the purposes of this specification do not include
   the case of changing the mobile node's home address, as that might
   imply loss of connectivity for ongoing connections, it could be used
   to force the change of home agent in those situations where there are
   no active data sessions running that cannot cope themselves with a
   change of home address.

2.1.5.  Flow Mobility

   There exist different protocols meant to support flow mobility with
   Mobile IPv6, namely the multiple care-of address registration
   [RFC5648], the flow bindings in Mobile IPv6 and NEMO [RFC6089] and
   the traffic selectors for flow bindings [RFC6088].  The use of these
   extensions allows a mobile node to associate different flows with
   different care-of addresses that the mobile owns at a given time.
   This could also be used, combined with the route optimization
   support, to improve the paths followed by data packets.

2.1.6.  Source Address Selection

   The IPv6 socket API for source address selection [RFC5014], [RFC6724]
   can be used by an application running on a mobile node to express its
   preference of using a home address or a care-of address in a given
   connection.  This allows, for example, an application which can
   survive an IP address change to always prefer the use of a care-of
   address.  Similarly, and as mentioned in [RFC6275], a mobile node can

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   also prefer the use of a care-of address for sessions that are going
   to finish before the mobile node hands off to a different attachment
   point (e.g., short-lived connections like DNS dialogs).  This could
   be based on user or operator policies, and it is typically performed
   by a connection manager (e.g., [I-D.seite-mif-cm]).

2.2.  Network-based mobility

   Proxy Mobile IPv6 (PMIPv6) [RFC5213] and GPRS Tunneling Protocol
   (GTP) [3GPP.29.060] are the main network-based IP mobility protocols
   specified for IPv6.  Architecturally, both solutions are similar, as
   they rely on the function of the Local Mobility Anchor (LMA) or
   Packet Data Gateway (PDG) to provide mobile nodes with mobility
   support, without requiring the involvement of the mobile nodes, and
   providing the required functionality by the Mobile Access Gateway
   (MAG), Service Data Gateway (SGW), or Evolved Packet Data Gateway
   (ePDG).  We next describe how network-based mobility protocols and
   several additional protocol extensions can be deployed to meet some
   of the DMM requirements [I-D.ietf-dmm-requirements].

2.2.1.  Proxy Mobile IPv6

   <- INTERNET -><- HOME NET -><----------- ACCESS NETWORK ------------>
       -------
       | CN1 |                      --------      --------      --------
       -------      --------        | MAG1 |      | MAG2 |      | MAG3 |
                    | LMA1 |        ---+----      ---+----      ---+----
       -------      --------           |             |             |
       | CN2 |                        (o)           (o)           (o)
       -------      --------          x                           x
                    | LMA2 |         x                           x
       -------      --------       (o)                          (o)
       | CN3 |                      |                            |
       -------                   ---+---                      ---+---
                      Anchored   | MN1 |          Anchored    | MN2 |
                      at LMA1 -> -------          at LMA2 ->  -------

     CN1    CN2     LMA1   LMA2        MAG1   MN1     MAG3    MN2
      |      |       |      |           |      |       |       |
      |<------------>|<================>|<---->|       |       |
      |      |       |      |           |      |       |       |
      |      |<------------>|<========================>|<----->|
      |      |       |      |           |      |       |       |

           Figure 3: Distributed operation of Proxy Mobile IPv6

   As with Mobile IPv6, plain Proxy Mobile IPv6 operation cannot be
   easily decentralized.  One simple, but still suboptimal, approach

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   would be to deploy several local mobility anchors and use a
   topological position-based assignment to attach mobile nodes (an
   example of this type of assignment is shown in Figure 3.  This
   assignment can be static or dynamic (as described in Section 2.2.3).
   The main advantage of this simple approach is that the IP address
   anchor (i.e., the LMA) is placed close to the mobile node, and
   therefore resulting paths are close-to-optimal.  On the other hand,
   as soon as the mobile node moves, the resulting path starts to
   deviate from the optimal one.

2.2.2.  Local Routing

   [RFC6705] enables 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 distribution, 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.

   In the context of 3GPP, the closest analogy is the use of the X2
   interface between two eNBs to directly exchange data traffic during
   handover procedures. 3GPP does not foresee the use of local routing
   at any other point of the network given the structure of the EPS
   bearer model.

2.2.3.  LMA runtime assignment

   [RFC6463] 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 case when the mobile
   node does not have any session active, or when running sessions can
   survive an IP address change.

   In the context of 3GPP networks, similar considerations have been
   discussed with respect to Selective IP Traffic Offload (SIPTO) above
   the RAN or at the macro.  When an MN is allowed to get some SIPTO

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   service, a geographically close PGW is selected.  That is, upon
   establishment of the Packet Data Network (PDN) connection, the MN is
   configured with an IP address belonging to an optimal P-GW from a
   routing point of view.  The drawback is that if the MN moves out of
   the region covered by that PGW, the mobile node will have to
   disconnect from the network and reconnect again, since no seamless
   session continuity is provided.  In this sense, applications that
   cannot not survive an IP address change will present an unpredictable
   behavior.

2.2.4.  Source Address Selection

   Also in the context of network-based mobility, the use of a source
   address selection API can be considered as means to achieve better
   routing (by using different anchors).  For instance, an MN connected
   to a PMIPv6 domain could attach two different wireless network
   interfaces to two different MAGs, hence configuring a different set
   of HNPs on both interfaces (potentially combining both IPv4 and
   IPv6).  Based on application requirements or operator's policies the
   connection manager logic could instruct the IP stack on the MN to
   route selected traffic on a specific wireless interface
   [I-D.seite-mif-cm].  It should be noted that source address selection
   mostly provides for better routing but not session continuity.

   In the context of 3GPP networks, two ongoing study items are
   currently addressing the issue of selecting a wireless interface or
   an IP address for a specific application.  The study item DIDA (Data
   IDentification in ANDSF) is addressing the need to map an application
   ID to a specific wireless interface, while the study item Operator
   Policies for IP Interface Selection (OPIIS) is addressing the need of
   selecting the right APN for a given application.  Taking into account
   that there is a one to one link between APN and PDN connection (IP
   address) the second study item clearly addresses from a 3GPP
   perspective the same problem space as [RFC6724].

2.2.5.  Multihoming in PMIPv6

   PMIPv6 provides some multihoming support.  RFC 5213 specifies that
   the LMA can maintain one mobility session per attached interface and
   that upon handover the full set of HNPs can be moved to another
   interface in case of inter-technology handover (MAGs providing
   different wireless access technology) or maintained on the same
   interface in case of intra-technology handover (MAGs providing the
   same wireless access technology).  An MN can also attach two
   different interfaces to the PMIPv6 domain (as described in
   Section 2.2.4) two different interfaces to the PMIPv6 domain, hence
   resulting in a multihomed device being able to send/receive traffic
   sequentially or simultaneously from both network interfaces.

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   [I-D.ietf-netext-pmipv6-flowmob] extends the base RFC5213
   capabilities so that a mobility session can be shared across two
   different access networks.  It derives that a selected flow could be
   routed through different paths, hence achieving some sort of better
   routing.  Yet all the traffic is anchored at centralized anchor
   points.

   In the context of 3GPP networks the Multi-Access PDN Connectivity
   (MAPCON) feature addresses the use of multiple PDN connections, hence
   the use of multiple wireless interfaces either sequentially or
   simultaneously.

3.  Gap Analysis: limitations in current practices

   This section identifies the limitations in the current practices
   (documented in Section 2) with respect to the requirements listed in
   [I-D.ietf-dmm-requirements].

   The section is also divided in two parts: client-based and network-
   based mobility.  Each part analyzes how well the requirements listed
   in [I-D.ietf-dmm-requirements] are covered/met by the current
   practices, highlighting existing limitations and gaps.

3.1.  Client-based mobility

3.1.1.  REQ1: Distributed deployment

   MIPv6 / NEMO  A careful home agent deployment and policy
      configuration of the Mobile IPv6 / NEMO protocols can achieve some
      distribution.  However, as soon as the mobile node moves and
      changes its initial attachment point, the anchors are no longer
      placed optimally, incurring in sub-optimal routes.  If the mobile
      node is not expected to move within a limited area, this
      configuration might be considered sufficient.  Otherwise,
      additional mechanisms to support dynamic anchoring would be
      needed.

   Mobile IPv6 RO  The use of route optimization support enables a
      close-to anchor-less operation, which effectively can be
      considered as a fully distributed configuration.  However, as
      explained before in this document, the home agent is still used
      for the signaling and therefore remains as a critical centralized
      component.  Additionally, there is no standardized RO support for
      network mobility.

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   HMIPv6  The use of hierarchical mobile IPv6 can be seen as a step
      forward compared to a careful deployment of multiple home agents
      and its proper configuration, as it allows a mobile node to roam
      within a local domain, reducing the handover latency as well as
      the signaling overhead.  If used together with mobile IPv6,
      traffic still has to traverse the centralized home agent, and
      therefore no distributed operation is achieved.

   HA switch  The home agent switch specification can be used to enable
      obtaining more benefits from a multiple-HA deployment, as the
      mobile node could be instructed to switch to a closer home agent.
      To avoid packet loss, this switch must be performed at periods of
      time in which the mobile node does not have any active connection
      running.  Even if some packet loss were acceptable for active
      sessions, the change of home address would also require the mobile
      node to re-establish those sessions.

   Flow mobility  Considerations made for previous scenarios (e.g. for
      Route Optimization) could also apply here, extending those
      scenarios by the use of multiple attached interfaces.

   SA selection API  The use of proper source address selection
      decisions, enabled by smart connection managers
      [I-D.seite-mif-cm], or mobility aware applications using a
      selection API [RFC5014], [RFC6724], would allow the mobile node to
      realize substantial benefits from deployments providing multiple
      anchors.

3.1.2.  REQ2: Transparency to Upper Layers when needed

   MIPv6 / NEMO  As a mobility protocol, the solution is transparent to
      the upper layers.  However, as described before, this transparency
      comes with the cost of suboptimal routes if the MN moves away from
      its initial attachment point.

   Mobile IPv6 RO  The use of the route optimization support is
      transparent to the upper layers.

   HMIPv6  The use of HMIPv6 is transparent to the upper layers.

   HA switch  The use of the home agent switch functionality is not
      transparent to the upper layers, as a change of home agent
      normally implies a change of home address.  Therefore, it is only
      recommended to switch home agent when there is no active session
      running on the mobile node.

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   Flow mobility  The use of flow mobility mechanisms is transparent to
      the upper layers.

   SA selection API  The use of an intelligent source address mechanisms
      is transparent to the upper layers if performed by the connection
      manager.  However if the selection is performed by the
      applications themselves, via the use of the API, then applications
      have to be mobility-aware.

3.1.3.  REQ3: IPv6 deployment

   MIPv6 / NEMO  Mobile IPv6 / NEMO protocols primarily support IPv6,
      although there are some extensions defined to also offer some IPv4
      support [RFC5555].

   Mobile IPv6 RO  Route optimization only supports IPv6.

   HMIPv6  HMIPv6 is only defined for IPv6.

   HA switch  The home agent switch specification supports only IPv6,
      although the use of the defined mechanisms to support dual stack
      IPv4/IPv6 mobile nodes would also enable some IPv4 support.

   Flow mobility  Flow mobility is only defined for IPv6.

   SA selection API  The use of source address selection mechanisms
      supports both IPv6 and IPv4.

3.1.4.  REQ4: Existing mobility protocols

   MIPv6 / NEMO  These approaches are ones of the base IETF-standardized
      mobility protocols: [RFC6275] and [RFC3963].

   Mobile IPv6 RO  This approach is based on an existing protocol
      [RFC6275].

   HMIPv6  This approach is based on an existing protocol [RFC5380].

   HA switch  This approach is based on an existing protocol [RFC5142].

   Flow mobility  This approach is based on existing protocols
      [RFC5648], [RFC6089] and [RFC6088].

   SA selection API  This approach is based on existing protocols
      [RFC6724] and [RFC5014].

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3.1.5.  REQ5: Compatibility

   MIPv6 / NEMO  This approach would be compatible with other protocols
      and work between trusted administrative domains, although as
      described before its operation would not provide the benefits of a
      fully distributed mechanism.  The combination of different IP
      mobility protocols might have a performance/complexity cost
      associated, as described in [A. de la Oliva, et al.].

   Mobile IPv6 RO  This approach would be compatible with other
      protocols and work between trusted administrative domains, as long
      as mobile IPv6 is allowed.  However, as highlighted before, mobile
      IPv6 route optimization requires specific support at the
      correspondent nodes.

   HMIPv6  HMIPv6 is compatible with other protocols.

   HA switch  This approach would be compatible with other protocols and
      work between trusted administrative domains.

   Flow mobility  This approach would be compatible with other protocols
      and work between trusted administrative domains.

   SA selection API  This approach has no impact in terms of
      compatibility or use between trusted administrative domains.

3.1.6.  REQ6: Security considerations

   MIPv6 / NEMO  This approach includes security considerations.

   Mobile IPv6 RO  This approach includes security considerations.

   HMIPv6  This approach includes security considerations.

   HA switch  This approach includes security considerations.

   Flow mobility  This approach includes security considerations.

   SA selection API  This approach does not have security issues.

3.2.  Network-based mobility

3.2.1.  REQ1: Distributed deployment

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   PMIPv6  As for the case of MIPv6, a careful deployment of the local
      mobility anchors and policy configuration of the Proxy Mobile IPv6
      protocol can achieve some distribution.  However, as soon as the
      mobile node moves and changes its initial attachment point, the
      anchor is no longer placed optimally, incurring in sub-optimal
      routes, which might be quite noticeable in case of medium to large
      PMIPv6 domains.  If the mobile node movement is restricted to a
      well known limited area and/or the PMIPv6 domain is not large,
      this configuration might be considered sufficient.  Otherwise,
      additional mechanisms to support dynamic anchoring would be
      needed.

   Local Routing  As mentioned before, it enables optimal routing in
      three cases: the LMA manages the traffic of two mobile nodes
      connected to the same MAG, the LMA manages the traffic of two
      mobile nodes connected to different MAGs, the MAG manages the
      traffic of two mobile nodes connected to different LMAs.  LR does
      not consider the case where the traffic should be optimized
      considering different MAGs and different LMAs.  Inter LMA
      communication is not in scope.  LR only enables better routing and
      does not consider the distribution of mobility anchors as such.

   LMA Runtime Assignment  The LMA runtime assignment is used to
      allocate an optimal LMA mostly for load balancing purposes, for
      instance in scenarios where LMAs run in a datacenter-like
      infrastructure.  It can be used to allocate a different LMA based
      on other policies such as routing although is not clear how the
      technology can be used to achieve distributed mobility management,
      especially considering scalability issues.

   Source Address Selection  It can help in selecting a given IP source
      address although the current specifications have many limitations
      (for instance prefer IPv6 over IPv4, prefer HoA instead of CoA)
      and the socket extensions [RFC5014] require changes in the node.
      This solution alone is not sufficient to achieve anchors
      distribution in case of session continuity requirements, as some
      control logic (e.g., from a connection manager [I-D.seite-mif-cm])
      is needed to intelligently perform source address selection.

   Multihoming in PMIPv6  As summarized in the previous section a single
      mobility session belongs to a single LMA (at the most the same
      mobility session is shared across two access networks).  As of
      today there is no possibility to distribute anchors and to move
      the session between different LMAs.

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3.2.2.  REQ2: Transparency to Upper Layers when needed

   PMIPv6  As a mobility protocol, the solution provides transparent
      mobility support for a mobile node while roaming within the PMIPv6
      domain (e.g., if a mobile node moves outside the domain,
      established sessions cannot be maintained, unless the MN
      implements Mobile IPv6).  However, as for the MIPv6 case, this
      transparent mobility support comes with the cost of suboptimal
      routes if the MN moves away from its initial attachment point,
      especially in large PMIPv6 domains.

   Local Routing  During HO the standard mechanisms are used.  In this
      sense if there is a MAG change while LR is enabled signaling is
      exchanged to inform the target MAG that upon handover LR should be
      re-established.  The inter LMA case is not supported.  For this
      solution the mobility context is always up, all the traffic
      receive seamless service.

   LMA Runtime Assignment  Seamless support is provided as per RFC 5213.
      For this solution the mobility context is always up, all the
      traffic receive seamless service.

   Source Address Selection  No seamless support is currently provided,
      since it requires solutions such as IP flow mobility for PMIPv6
      [I-D.ietf-netext-pmipv6-flowmob].

   Multihoming in PMIPv6  Seamless support falls back to standard PMIPv6
      operations extended for IP flow mobility support.  For this
      solution the mobility context is always up, all the traffic
      receive seamless service.

3.2.3.  REQ3: IPv6 deployment

   PMIPv6  Although Proxy Mobile IPv6 primarily support IPv6, there are
      also extensions defined to also offer some limited IPv4 support
      [RFC5844].

   Local Routing  It supports both IPv4 (limited to the support provided
      by [RFC5844]) and IPv6.

   LMA Runtime Assignment  It supports both IPv4 (limited to the support
      provided by [RFC5844]) and IPv6.

   Source Address Selection  It supports both IPv4 and IPv6.

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   Multihoming in PMIPv6  It supports both IPv4 (limited to the support
      provided by [RFC5844]) and IPv6.

3.2.4.  REQ4: Existing mobility protocols

   PMIPv6  This approach is one of the base IETF-standardized mobility
      protocols: [RFC5213].

   Local Routing  It reuses [RFC5213].

   LMA Runtime Assignment  It reuses [RFC5213].

   Source Address Selection  This approach is based on local support on
      the terminal only.

   Multihoming in PMIPv6  It reuses [RFC5213].

3.2.5.  REQ5: Compatibility

   PMIPv6  This protocol is compatible with other protocols and can
      operate between trusted administrative domains, although there may
      be an associated penalty in terms of performance and/or complexity
      [A. de la Oliva, et al.].

   Local Routing  Since it extends [RFC5213], compatibility with
      existing network deployments and end hostsis provided.

   LMA Runtime Assignment  Since it extends [RFC5213], compatibility
      with existing network deployments and end hostsis provided.

   Source Address Selection  To enable the full set of use cases
      mentioned above extensions are required thus impacting the
      landscape of mobile devices.  The extensions should not impact the
      network.

   Multihoming in PMIPv6  Since it extends [RFC5213], compatibility is
      provided.

3.2.6.  REQ6: Security considerations

   PMIPv6  This approach includes security considerations.

   Local Routing  It reuses [RFC5213].  As such, the same security
      considerations apply.

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   LMA Runtime Assignment  It reuses [RFC5213].  As such, the same
      security considerations apply.

   Source Address Selection  There is not signaling involved to perform
      this action.

   Multihoming in PMIPv6  It reuses [RFC5213].  As such, the same
      security considerations apply.

4.  Summary

   This section summarizes the identified IP-mobility protocols and
   their mappings (YES, NO, LIMITED) to the different dynamic mobility
   management requirements listed in [I-D.ietf-dmm-requirements].

      +-------------+------+------+-----------+------+------+------+
      |             | REQ1 | REQ2 | REQ3      | REQ4 | REQ5 | REQ6 |
      +-------------+------+------+-----------+------+------+------+
      | MIPv6/NEMO  | NO   | LIM  | v6/v4     | YES  | LIM  | YES  |
      | MIPv6 RO    | NO   | YES  | v6        | YES  | LIM  | YES  |
      | HMIPv6      | NO   | YES  | v6        | YES  | LIM  | YES  |
      | HA switch   | NO   | NO   | v6        | YES  | YES  | YES  |
      | FlowMob     | NO   | YES  | v6/LIM v4 | YES  | YES  | YES  |
      | SAS w/ CB   | NO   | YES  | v6/v4     | YES  | YES  | YES  |
      | PMIPv6      | NO   | LIM  | v6/LIM v4 | YES  | LIM  | YES  |
      | LR          | NO   | LIM  | v6/LIM v4 | YES  | YES  | YES  |
      | LMA RA      | LIM  | LIM  | v6/LIM v4 | YES  | YES  | YES  |
      | SAS w/ NB   | NO   | NO   | v6/v4     | YES  | YES  | YES  |
      | MuHo PMIPv6 | NO   | LIM  | v6/LIM v4 | YES  | YES  | YES  |
      +-------------+------+------+-----------+------+------+------+

5.  IANA Considerations

   No IANA considerations.

6.  Security Considerations

   This is an informational document that analyzes practices for the
   deployment of existing mobility protocols in a distributed mobility
   management environment, and identifies the limitations in the current
   practices.  One of the requirements that these practices has to meet
   is to take into account security aspects, including confidentiality
   and integrity.  This is briefly analyzed for each of the considered
   practices, and will be extended in future versions of this document.

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7.  References

7.1.  Normative References

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

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

   [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.

   [RFC5648]  Wakikawa, R., Devarapalli, V., Tsirtsis, G., Ernst, T.,
              and K. Nagami, "Multiple Care-of Addresses Registration",
              RFC 5648, October 2009.

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

   [RFC6088]  Tsirtsis, G., Giarreta, G., Soliman, H., and N. Montavont,
              "Traffic Selectors for Flow Bindings", RFC 6088,
              January 2011.

   [RFC6089]  Tsirtsis, G., Soliman, H., Montavont, N., Giaretta, G.,
              and K. Kuladinithi, "Flow Bindings in Mobile IPv6 and
              Network Mobility (NEMO) Basic Support", RFC 6089,
              January 2011.

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

   [RFC6463]  Korhonen, J., Gundavelli, S., Yokota, H., and X. Cui,

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              "Runtime Local Mobility Anchor (LMA) Assignment Support
              for Proxy Mobile IPv6", RFC 6463, February 2012.

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

7.2.  Informative References

   [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.

   [A. de la Oliva, et al.]
              de la Oliva, A., Soto, I., Calderon, M., Bernardos, C.,
              and M. Sanchez, "The costs and benefits of combining
              different IP mobility standards", Computer Standards &
              Interfaces, accepted for publication, doi:10.1016/
              j.csi.2012.08.003 , 2012.

   [I-D.ietf-dmm-requirements]
              Chan, A., "Requirements for Distributed Mobility
              Management", draft-ietf-dmm-requirements-02 (work in
              progress), September 2012.

   [I-D.ietf-netext-pmipv6-flowmob]
              Bernardos, C., "Proxy Mobile IPv6 Extensions to Support
              Flow Mobility", draft-ietf-netext-pmipv6-flowmob-05 (work
              in progress), October 2012.

   [I-D.patil-dmm-issues-and-approaches2dmm]
              Patil, B., Williams, C., and J. Korhonen, "Approaches to
              Distributed mobility management using Mobile IPv6 and its
              extensions", draft-patil-dmm-issues-and-approaches2dmm-00
              (work in progress), March 2012.

   [I-D.perkins-dmm-matrix]
              Perkins, C., Liu, D., and W. Luo, "DMM Comparison Matrix",
              draft-perkins-dmm-matrix-04 (work in progress), July 2012.

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   [I-D.seite-mif-cm]
              Seite, P. and J. Zuniga, "MIF API Conn Mngr
              Considerations", draft-seite-mif-cm-00 (work in progress),
              September 2012.

   [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.

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

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

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

Appendix A.  Acknowledgments

   The work of Carlos J. Bernardos and Telemaco Melia has been partially
   supported by the European Community's Seventh Framework Programme
   (FP7-ICT-2009-5) under grant agreement n. 258053 (MEDIEVAL project).
   The work of Carlos J. Bernardos has also been partially supported by
   the Ministry of Science and Innovation of Spain under the QUARTET
   project (TIN2009-13992-C02-01).  The authors would like to thank
   Konstantinos Pentikousis, Georgios Karagian, Jouni Korhonen and Jong-
   Hyouk Lee for their valuable comments.

Authors' Addresses

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

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

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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/

   Telemaco Melia
   Alcatel-Lucent Bell Labs
   Route de Villejust
   Nozay, Ile de France  91620
   France

   Email: telemaco.melia@alcatel-lucent.com

   Charles E. Perkins
   Futurewei
   USA

   Email: charliep@computer.org

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