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MULTIMOB Group                                               J.C. Zuniga
INTERNET-DRAFT                                                 A. Rahman
Intended Status: Standards Track        InterDigital Communications, LLC
Expires: January 2012                                     L.M. Contreras
                                                          C.J. Bernardos
                                        Universidad Carlos III de Madrid
                                                                 I. Soto
                                       Universidad Politecnica de Madrid
                                                           July 11, 2011



           Support Multicast Services Using Proxy Mobile IPv6
                 <draft-zuniga-multimob-smspmip-06.txt>


Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   Drafts.

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Copyright and License Notice

   Copyright (c) 2011 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
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   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.


Abstract

   The MULTIMOB group has specified a base solution to support IP
   multicasting in a PMIPv6 domain [RFC6224]. In this document, an
   enhancement is proposed to the base solution to use a multicast tree
   mobility anchor as the topological anchor point for multicast
   traffic, while the MAG remains as an IGMP/MLD proxy. This enhancement
   provides benefits such as reducing multicast traffic replication and
   supporting different PMIPv6 deployments scenarios.


Table of Contents

   1  Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2  Conventions and Terminology  . . . . . . . . . . . . . . . . . . 3
   3  Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
      3.1  Architecture  . . . . . . . . . . . . . . . . . . . . . . . 5
      3.2  Deployment Scenarios  . . . . . . . . . . . . . . . . . . . 6
         3.2.1  PMIPv6 domain with ratio 1:1 . . . . . . . . . . . . . 7
         3.2.2  PMIPv6 domain with ratio N:1 . . . . . . . . . . . . . 7
         3.2.3  PMIPv6 domain with ratio 1:N . . . . . . . . . . . . . 9
         3.2.4  PMIPv6 domain with H-LMA . . . . . . . . . . . . . .  10
      3.3  Multicast Establishment . . . . . . . . . . . . . . . . .  12
      3.4  Multicast Mobility  . . . . . . . . . . . . . . . . . . .  14
      3.5  PMIPv6 enhancements . . . . . . . . . . . . . . . . . . .  15
         3.5.1  New Binding Update List in MAG . . . . . . . . . . .  15
         3.5.2  Policy Profile Information with Multicast Parameters  16
         3.5.3  MAG to MTMA attach requirements  . . . . . . . . . .  16
         3.5.4. Data structure stored by MTMA  . . . . . . . . . . .  16
      3.6  Advantages  . . . . . . . . . . . . . . . . . . . . . . .  16
   4  Consideration of MAG as multicast router in the tunnel
      interface to MTMA  . . . . . . . . . . . . . . . . . . . . . .  20
   5  Security Considerations  . . . . . . . . . . . . . . . . . . .  20
   6  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  20
   7  References . . . . . . . . . . . . . . . . . . . . . . . . . .  20
      7.1  Normative References  . . . . . . . . . . . . . . . . . .  20
      7.2  Informative References  . . . . . . . . . . . . . . . . .  21
   Appendix A. Overhead analysis of the proposed MTMA architecture.   21
   Author's Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22






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1  Introduction

   Proxy Mobile IPv6 [RFC5213] is a network-based approach to solving
   the IP mobility problem. In a Proxy Mobile IPv6 (PMIPv6) domain, the
   Mobile Access Gateway (MAG) behaves as a proxy mobility agent in the
   network and does the mobility management on behalf of the Mobile Node
   (MN). The Local Mobility Anchor (LMA) is the home agent for the MN
   and the topological anchor point. PMIPv6 was originally designed for
   unicast traffic.

   The Internet Group Management Protocol (IGMPv3) [RFC3376] is used by
   IPv4 hosts to report their IP multicast group memberships to
   neighboring multicast routers. Multicast Listener Discovery (MLDv2)
   [RFC3810] is used in a similar way by IPv6 routers to discover the
   presence of IPv6 multicast hosts. Also, the IGMP/MLD proxy [RFC4605]
   allows an intermediate (edge) node to appear as a multicast router to
   downstream hosts, and as a host to upstream multicast routers. IGMP
   and MLD related protocols were not originally designed to address IP
   mobility of multicast listeners (i.e. IGMP and MLD protocols were
   originally designed for fixed networks).

   The MULTIMOB group has specified a base solution to support IP
   multicast listener mobility in a PMIPv6 domain [RFC6224]. In this
   document, an enhancement is proposed to the base solution to use a
   multicast tree mobility anchor (MTMA) as the topological anchor point
   for multicast traffic, while the MAG remains as an IGMP/MLD proxy.
   This enhancement allows different PMIPv6 deployment scenarios.  It
   also eliminates the so called "Tunnel Convergence problem" where the
   MAG may receive the same multicast packet from several LMAs. There
   are no impacts to the MN to support multicast listener mobility from
   this document.


2  Conventions and Terminology

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

   This document uses the terminology defined in [RFC5213], [RFC3775],
   and [RFC3810]. Specifically, the definition of PMIPv6 domain is
   reused from [RFC5213] and reproduced here for completeness.

      - Proxy Mobile IPv6 Domain (PMIPv6-Domain): Proxy Mobile IPv6
      domain refers to the network where the mobility management of a
      mobile node is handled using the Proxy Mobile IPv6 protocol as
      defined in [RFC5213]. The Proxy Mobile IPv6 domain includes local
      mobility anchors and mobile access gateways between which security



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      associations can be set up and authorization for sending Proxy
      Binding Updates on behalf of the mobile nodes can be ensured.

   In this draft we refine such definition from the point of view of the
   kind of traffic served to the MN in the following way:

      - PMIPv6 unicast domain: PMIPv6 unicast domain refers to the
      network covered by one LMA for unicast service in such a way that
      an MN using that service is not aware of mobility as it moves from
      one MAG to another associated to that LMA regarding its unicast
      traffic.

      - PMIPv6 multicast domain: PMIPv6 multicast domain refers to the
      network covered by one network element named MTMA (defined below)
      for multicast service in such a way that an MN using that service
      is not aware of mobility as it moves from one MAG to another.

   This means that a PMIPv6 domain can have several PMIPv6 unicast
   domains and PMIPv6 multicast domains.

   Additionally, some other definitions are introduced, as follows.

      - MTMA or multicast tree mobility anchor: an entity working as
      topological anchor point for multicast traffic exclusively.

      - H-LMA or Hybrid-LMA: an entity dedicated to both unicast and
      multicast services, that is, it is able to work as both LMA and
      MTMA simultaneously.


3  Solution

   A PMIPv6 domain may handle data from both unicast and multicast
   sources. This document addresses an optimization of the base solution
   specified for multicast support in PMIPv6 domains [RFC6224] by
   introducing a complementary network entity, named multicast tree
   mobility anchor (MTMA), and defining the architecture and protocol
   flows derived from it. An MTMA can be used to serve as the mobility
   anchor for multicast traffic. The MTMA connects to the MAG as
   described in [RFC6224] and it can reuse native PMIPv6 features such
   as tunnel establishment and security [RFC5213], heartbeat [RFC5847],
   etc. Unicast traffic will go normally to the LMAs in the PMIPv6
   domain.

   This section describes how the MTMA works in scenarios of MN
   attachment and multicast mobility. We first concentrate on the case
   of both LMA and MTMA defining a unique PMIPv6 domain, and then
   different deployment scenarios are presented.



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3.1  Architecture

   Figure 1 shows an example of a PMIPv6 domain supporting multicast
   mobility. LMA1 is dedicated to unicast traffic, and MTMA1 is
   dedicated to multicast traffic. The tree mobility anchor MTMA1 can be
   considered to be a form of upstream multicast router with tunnel
   interfaces allowing remote subscription for the MNs. Note that there
   can be multiple LMAs for unicast traffic (not shown in Figure 1) in a
   given PMIPv6 domain. Similarly, more than one MTMAs can be deployed
   by the operator (not shown in Figure 1).

   Also in this architecture, all MAGs that are connected to the MTMA
   must support the MLD proxy [RFC4605] function. Specifically in Figure
   1, each of the MAG1-MTMA1 and MAG2-MTMA1 tunnel interfaces defines an
   MLD proxy domain.  The MNs are considered to be on the downstream
   interface of the MLD proxy (in the MAG), and MTMA1 is considered to
   be on the upstream interface (of the MAG) as per [RFC4605].  Note
   that MAG could also be an IGMP proxy.  For brevity this document will
   refer primarily to MLD proxy, but all references to "MLD proxy"
   should be understood to also include "IGMP/MLD proxy" functionality.

   As shown in Figure 1, MAG1 may connect to both unicast (LMAs) and
   multicast (MTMAs) entities. Thus, a given MN may simultaneously
   receive both unicast and multicast traffic. In Figure 1, MN1 and MN2
   receive unicast traffic, multicast traffic, or both, whereas MN3
   receives multicast traffic only, despite of that, this draft
   considers that every MN demanding multicast-only services is
   previously registered in a PMIPv6 unicast domain to get a unicast IP
   address. This registration can be required also for several purposes
   such as remote management, billing, etc.





















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                                   +--------------+
                                   |Content Source|
                                   +--------------+
                                          |
                                          |
         ***  ***  ***  ***      ***  ***  ***  ***
        *   **   **   **   *    *   **   **   **    *
       *                    *  *                     *
       *  Unicast Traffic   *  *  Multicast Traffic  *
       *                    *  *                     *
        *   **   **   **   *    *   **   **   **   *
         ***  ***  ***  ***      ***  ***  ***  ***
                 |                       |
                 |                       |
                 |                       |
              +-----+                 +------+
     Unicast  | LMA1|                 | MTMA1|     Multicast
      Anchor  +-----+                 +------+      Anchor
                  \\                    // ||
                   \\                  //  ||
                    \\                //   ||
                     \\              //    ||
                      \\            //     ||
                       \\          //      ||
                        \\        //       ||
                         \\      //        ||
                          \\    //         ||
                          +-----+       +-----+
                          | MAG1|       | MAG2|      MLD Proxy
                          +-----+       +-----+
                          |     |          |
                          |     |          |
                        {MN1} {MN2}      {MN3}

      Figure 1. Architecture of Multicast Tree Mobility Anchor (MTMA)


3.2  Deployment Scenarios

   From the network architecture point of view, there are several
   options when considering the multicast tree mobility anchor (MTMA)
   approach. These options can be distinguished in terms of the number
   of LMAs and MTMAs present in a PMIPv6 domain and the service
   relationship that a set of MNs gets from them, in the form of a "LMA
   : MTMA" ratio. According to that, it is possible to differentiate the
   following approaches:

      - A set of MNs is served in a PMIPv6 domain by two entities, one



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      MTMA for multicast service, and one LMA for unicast, in such a way
      that the ratio is 1:1 (one common PMIPv6 unicast and multicast
      domain).

      - A set of MNs is served in a PMIPv6 domain by several entities,
      one MTMA for multicast service, while the others (LMAs) for
      unicast, in such a way that the ratio is N:1 (N PMIPv6 unicast
      domains coexist with a unique multicast domain).

      - A set of MNs is served in a PMIPv6 domain by several entities,
      one LMA for unicast, while the others (MTMAs) are devoted to
      multicast service, in such a way that the ratio is 1:N (one single
      PMIPv6 unicast domain coexists with multiple multicast domains).

   Scenarios with an N:M ratio are considered to be a combination of the
   previous ones.


3.2.1  PMIPv6 domain with ratio 1:1

   This approach basically refers to the architecture presented in
   figure 1. Within this approach, a common set of MNs is served by a
   couple of entities, one LMA for unicast and one MTMA for multicast.
   All the MNs of the set are served by these two elements as they move
   in the PMIPv6 domain.


3.2.2  PMIPv6 domain with ratio N:1

   This approach basically refers to the situation where a common set of
   MNs is served by a unique MTMA for multicast service, but
   simultaneously there are subsets from that group of MNs which are
   served by distinct LMAs for unicast service as they move in the
   PMIPv6 domain. Each particular MN association with the LMAs (unicast)
   and MTMA (multicast) remains always the same as it moves in the
   PMIPv6 domain.

   Figure 2 shows the scenario here described.













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            +----------------+       +----------------+
            |Content Source A|       |Content Source B|
            +----------------+       +----------------+
                   |                      |
                   |                      |
         ***  ***  ***  ***  ***  ***  ***  *** *** *** ***
        *   **   **   **   **  **   **   **   **   **  **  *
       *                                                    *
       *                 Fixed Internet                     *
       *        (Unicast & Multicast Traffic)               *
        *   **   **   **   **  **   **   **   **   **  **  *
         ***  ***  ***  *** *** ***  ***  ***  ***  ***  ***
           |                     |                      |
           |                     |                      |
           |                     |                      |
        +-------+       +-----------------+          +-------+
        |  LMA1 |       |      MTMA2      |          |  LMA3 |
        +-------+       +-----------------+          +-------+
          || \\        oo    oo      oo   oo          //  ||
          ||  \\      oo     oo      oo    oo        //   ||
          ||   \\    oo      oo      oo     oo      //    ||
          ||    \\  oo       oo      oo      oo    //     ||
          ||     \\oo        oo      oo       oo  //      ||
          ||      \\         oo      oo        oo//       ||
          ||     oo\\        oo      oo         //        ||
          ||    oo  \\       oo      oo        //oo       ||
          ||   oo    \\      oo      oo       //  oo      ||
          ||  oo      \\     oo      oo      //    oo     ||
        +------+      +--------+     +--------+     +--------+
        | MAG1 |      |  MAG2  |     |  MAG3  |     |  MAG4  |
        +------+      +--------+     +--------+     +--------+
        |      |       |      |       |      |       |      |
        |      |       |      |       |      |       |      |
     {MN10}  {MN11}  {MN20} {MN21}  {MN30} {MN31} {MN40} {MN41}

                 Figure 2. PMIPv6 domain with ratio N:1

   The figure 2 proposes an architecture where there are two entities
   acting as LMAs, LMA1 and LMA3, while there is another one, named
   MTMA2, working as multicast tree mobility anchor. LMA1 and LMA3
   constitute two distinct unicast domains, whereas MTMA2 forms a single
   multicast domain. The tunnels among MAGs and LMAs represented by
   lines ("||") indicate a tunnel transporting unicast traffic, while
   the tunnels among MAGs and MTMA2 depicted with circles ("o") show a
   tunnel transporting multicast traffic.

   In the figure it can be observed that all the MNs are served by MTMA2
   for the incoming multicast traffic from sources A or B. However,



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   there are different subsets regarding unicast traffic which maintain
   distinct associations within the PMIPv6 domain. For instance, the
   subset formed by MN10, MN11, MN20 and MN21 is served by LMA1 for
   unicast, and the rest of MNs are being served by LMA3. For the
   scenario described above, the association between each MN and the
   corresponding LMA and MTMA is permanently maintained.


3.2.3  PMIPv6 domain with ratio 1:N

   This approach is related to a scenario where a common group of MNs is
   served by a unique LMA for unicast service, but simultaneously there
   are subsets from that group of MNs which are served by distinct MTMAs
   for multicast service as they move in the PMIPv6 domain. Each
   particular MN association with the LMA and MTMAs (unicast and
   multicast respectively) remains always the same as it moves in the
   PMIPv6 domain.

   Figure 3 shows the scenario here described.

   The figure 3 proposes an architecture where the LMA2 is the unique
   LMA for a certain group of MNs, while there are two others entities,
   MTMA1 and MTMA3, acting as MTMAs for different subsets of MNs of the
   same group. MTMA1 and MTMA3 constitute two distinct multicast
   domains, whereas LMA2 forms a single unicast domain. Each MTMA could
   be devoted to carry on a different content (for instance, MTMA1 for
   source A and MTMA3 for source B) or not. Looking at the picture, the
   subset formed by MN10, MN11, MN20 and MN21 is served by MTMA1 for
   multicast. The rest of MNs are being served by MTMA3 also for
   multicast. Finally, all of them are served by LMA2 for unicast. For
   the scenario described above, the association between each MN and the
   corresponding LMA and MTMA is permanently maintained.



















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            +----------------+       +----------------+
            |Content Source A|       |Content Source B|
            +----------------+       +----------------+
                   |                      |
                   |                      |
         ***  ***  ***  ***  ***  ***  ***  *** *** *** ***
        *   **   **   **   **  **   **   **   **   **  **  *
       *                                                    *
       *                 Fixed Internet                     *
       *        (Unicast & Multicast Traffic)               *
        *   **   **   **   **  **   **   **   **   **  **  *
         ***  ***  ***  *** *** ***  ***  ***  ***  ***  ***
           |                     |                      |
           |                     |                      |
           |                     |                      |
        +-------+       +-----------------+          +-------+
        | MTMA1 |       |       LMA2      |          | MTMA3 |
        +-------+       +-----------------+          +-------+
          oo oo        //    ||      ||   \\          oo  oo
          oo  oo      //     ||      ||    \\        oo   oo
          oo   oo    //      ||      ||     \\      oo    oo
          oo    oo  //       ||      ||      \\    oo     oo
          oo     oo//        ||      ||       \\  oo      oo
          oo      oo         ||      ||        \\oo       oo
          oo     //oo        ||      ||         \\        oo
          oo    //  oo       ||      ||        oo\\       oo
          oo   //    oo      ||      ||       oo  \\      oo
          oo  //      oo     ||      ||      oo    \\     oo
        +------+      +--------+     +--------+     +--------+
        | MAG1 |      |  MAG2  |     |  MAG3  |     |  MAG4  |
        +------+      +--------+     +--------+     +--------+
        |      |       |      |       |      |       |      |
        |      |       |      |       |      |       |      |
     {MN10}  {MN11}  {MN20} {MN21}  {MN30} {MN31} {MN40} {MN41}

                 Figure 3. PMIPv6 domain with ratio 1:N

3.2.4  PMIPv6 domain with H-LMA

   The H-LMA is defined as an entity which simultaneously transports
   unicast and multicast service, that is, it simultaneously works as
   LMA and MTMA. In the context of the MTMA solution, an H-LMA can play
   the role of MTMA for an entire group of MNs in a PMIPv6 domain, while
   acting simultaneously as LMA for a subset of them. The figure 4
   adapts the PMIPv6 domain with ratio N:1 scenario of figure 2 to the
   case where MTMA2 is an H-LMA, which serves multicast traffic to all
   the MNs in the picture, and simultaneously, it is able to serve
   unicast traffic to the subset formed by MN30, MN40 and MN41.



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            +----------------+       +----------------+
            |Content Source A|       |Content Source B|
            +----------------+       +----------------+
                   |                      |
                   |                      |
         ***  ***  ***  ***  ***  ***  ***  *** *** *** ***
        *   **   **   **   **  **   **   **   **   **  **  *
       *                                                    *
       *                 Fixed Internet                     *
       *        (Unicast & Multicast Traffic)               *
        *   **   **   **   **  **   **   **   **   **  **  *
         ***  ***  ***  *** *** ***  ***  ***  ***  ***  ***
           |                     |                      |
           |                     |                      |
           |                     |                      |
        +-------+       +-----------------+          +-------+
        |  LMA1 |       |      H-LMA      |          |  LMA3 |
        +-------+       +-----------------+          +-------+
          || \\        oo    db      db   oo          //  ||
          ||  \\      oo     db      db    oo        //   ||
          ||   \\    oo      db      db     oo      //    ||
          ||    \\  oo       db      db      oo    //     ||
          ||     \\oo        db      db       oo  //      ||
          ||      \\         db      db        oo//       ||
          ||     oo\\        db      db         //        ||
          ||    oo  \\       db      db        //oo       ||
          ||   oo    \\      db      db       //  oo      ||
          ||  oo      \\     db      db      //    oo     ||
        +------+      +--------+     +--------+     +--------+
        | MAG1 |      |  MAG2  |     |  MAG3  |     |  MAG4  |
        +------+      +--------+     +--------+     +--------+
        |      |       |      |       |      |       |      |
        |      |       |      |       |      |       |      |
     {MN10}  {MN11}  {MN20} {MN21}  {MN30} {MN31} {MN40} {MN41}

                   Figure 4. PMIPv6 domain with H-LMA

   Figure 4 presents a PMIPv6 network where there are two pure unicast
   LMAs, LMA1 and LMA3, and a hybrid LMA, labeled as H-LMA in the
   figure. The H-LMA is an MTMA from the perspective of MAG1 and MAG4.
   The tunnels among MAGs and LMAs represented by lines ("||") indicate
   a tunnel transporting exclusively unicast traffic, the tunnels
   depicted with circles ("o") show a tunnel transporting exclusively
   multicast traffic, and the tunnels with mixed lines and circles
   ("db") describe a tunnel transporting both types of traffic
   simultaneously.

   All of the MNs in the figure receive the multicast traffic from H-LMA



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   (one single multicast domain), but it is possible to distinguish
   three subsets from the unicast service perspective (that is, three
   unicast domains). The first subset is the one formed by MN10, MN11
   and MN 20, which receives unicast traffic from LMA1. A second subset
   is the one formed by MN21 and MN30, which receives unicast traffic
   from H-LMA. And finally, a third subset is built on MN31, MN40 and
   MN41, which receives unicast traffic from LMA3. For the scenario
   described above, the association between each MN and the
   corresponding LMA and H-LMA is permanently maintained.


3.3  Multicast Establishment

   Figure 5 shows the procedure when MN1 attaches to MAG1, and
   establishes associations with LMA (unicast) and MTMA (multicast).




































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           MN1                   MAG1       LMA       MTMA
            |                (MLD Proxy) (Unicast) (Multicast)
        MN attaches to MAG1       |          |          |
            |                     |          |          |
            |------Rtr Sol----- ->|          |          |
            |                     |--PBU -- >|          |
            |                     |          |          |
            |                     |<-- PBA --|          |
            |                     |          |          |
            |                     |=Unicast= |          |
            |                     |  Tunnel  |          |
            |<-----Rtr Adv ------ |          |          |
            |                     |          |          |
            |< ------ Unicast Traffic------ >|          |
            |                     |          |          |
            |                     |==Multicast Tunnel ==|
            |                     |          |          |
            |<--MLD Query --------|          |          |
            |                     |          |          |
        MN requires               |          |          |
        multicast services        |          |          |
            |                     |          |          |
            |---MLD Report (G) -->|          |          |
            |                     |          |          |
            |                     |---- Aggregated ---> |
            |                     |    MLD Report (G)   |
            |                     |          |          |
            |                     |          |          |
            |< --------- Multicast Traffic ----------- >|
            |                     |          |          |


      Figure 5. MN Attachment and Multicast Service Establishment

   In Figure 5, MAG1 first establishes the PMIPv6 tunnel with LMA for
   unicast traffic as defined in [RFC5213] after being triggered by the
   Router Solicitation message from MN1. Unicast traffic will then flow
   between MN1 and LMA.

   For multicast traffic, a multicast tunnel may have been pre-
   configured between MAG1 and MTMA. Or the multicast tunnel may be
   dynamically established when the first MN appears at the MAG.

   MN1 sends the MLD report message (when required by its upper layer
   applications) as defined in [RFC3810] in response to an MLD Query
   from MAG1.  MAG1 acting as a MLD Proxy as defined in [RFC4605] will
   then send an Aggregated MLD Report to the multicast anchor, MTMA
   (assuming that this is a new multicast group which MAG1 had not



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   previously subscribed to).  Multicast traffic will then flow from
   MTMA towards MN1.


3.4  Multicast Mobility

   Figure 6 illustrates the mobility scenario for multicast traffic.
   Specifically, MN2 with ongoing multicast subscription moves from MAG1
   to MAG2.  Note that, for simplicity, in this scenario we only
   consider the tunnel of MAG2 with MTMA (for multicast traffic) and we
   assume that MN2 does not receive unicast traffic.  Of course, if it
   was desired to support unicast traffic, this is served by a tunnel
   between  MAG2 and LMA to transfer unicast traffic.

   According to baseline solution signaling method described in
   [RFC6224], after MN2 mobility, MAG2 acting in its role of MLD proxy
   will send an MLD Query to the newly observed MN on its downlink.
   Assuming that the subsequent MLD Report from MN2 requests membership
   of a new multicast group (from MAG2's point of view), this will then
   result in an Aggregated MLD Report being sent to MTMA from MAG2. This
   message will be sent through a pre-established (or dynamically
   established) multicast tunnel between MAG2 and MTMA.

   When MN2 detaches, MAG1 may keep the multicast tunnel with the
   multicast MTMA if there are still other MNs using the multicast
   tunnel. Even if there are no MNs currently on the multicast tunnel,
   MAG1 may decide to keep the multicast tunnel for potential future
   use.

   As discussed above, existing MLD (and Proxy MLD) signaling will
   handle a large part of the multicast mobility management for the MN.




















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           MN2          MAG1       MAG2         LMA      MTMA
            |        (MLD Proxy) (MLD Proxy) (Unicast)(Multicast)
            |            |           |            |          |
          MN Attached    |           |            |          |
           To MAG1       |           |            |          |
            |            |           |            |          |
            |            |========= Multicast Tunnel ======= |
            |            |           |            |          |
          MN Detaches    |           |            |          |
           From MAG1     |           |            |          |
            |            |           |            |          |
            |            |           |            |          |
          MN Attaches    |           |            |          |
           To MAG2       |           |            |          |
            |            |           |            |          |
            |            |           |==Multicast Tunnel === |
            |            |           |            |          |
            |---------Rtr Sol------ >|            |          |
            |            |           |--- PBU --->|          |
            |            |           |            |          |
            |            |           |<-- PBA ----|          |
            |<-----Rtr Adv --------- |            |          |
            |            |           |            |          |
            |            |           |            |          |
            |<---------MLD Query---- |            |          |
            |            |           |            |          |
            |---MLD Report (G) ----> |            |          |
            |            |           |            |          |
            |            |           |---- Aggregated -----> |
            |            |           |    MLD Report (G)     |
            |            |           |            |          |
            |< --------- Multicast Traffic ---------------- >|
            |            |           |            |          |
            |            |           |            |          |


                 Figure 6. Multicast Mobility Signaling


3.5  PMIPv6 enhancements

   This section describes the enhancements to the Proxy Mobile IPv6
   [RFC5213] protocol required to support the MTMA architecture.


3.5.1  New Binding Update List in MAG

   The Binding Update List in the MAG must be updated to be able to



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   handle the fact that more than one entity (i.e. LMA and MTMA) may be
   serving the mobile node.


3.5.2  Policy Profile Information with Multicast Parameters

   A given mobile node's policy profile information must be updated to
   be able to store the IPv6 addresses of both the LMA and MTMA.


3.5.3  MAG to MTMA attach requirements

   The MAG procedures must be updated to be able to handle simultaneous
   attach for a given mobile node to both the LMA and MTMA. For example,
   packets coming from a given mobile node must be screened to determine
   if it should be sent to the LMA or to the MTMA.


3.5.4. Data structure stored by MTMA

   The MTMA does not directly interact with the MNs attached to any of
   the MAGs. The MTMA only manages the multicast groups subscribed per
   MAG on behalf of the MNs attached to it. Having this in mind, the
   relevant information to be stored in the MTMA should be the tunnel
   interface identifier (tunnel-if-id) of the bi-directional tunnel for
   multicast between the MTMA and every MAG (as stated in [RFC5213] for
   the unicast case), the IP addresses of the multicast group delivered
   per tunnel to each of the MAGs, and the IP addresses of the sources
   injecting the multicast traffic per tunnel to the multicast domain
   defined by the MTMA.


3.6  Advantages

   An advantage of the proposed MTMA architecture is that it allows a
   PMIPv6 domain to closely follow a simple multicast tree topology for
   Proxy MLD forwarding (cf., sections 1.1 and 1.2 of [RFC4605]).  In
   contrast, the combined unicast/multicast LMA as proposed in [RFC6224]
   will be a more complex set of trees.

   Another advantage of the proposed dedicated multicast solution is
   that it allows a gradual network upgrade of a PMIPv6 domain to
   support multicast functionality.  This is because the operator does
   not have to upgrade all the LMAs in the network to support multicast
   functionality.  Only certain nodes (MTMAs), dedicated to multicast
   support, will have to be upgraded to support the new multicast
   functionality. Also, multiple deployment scenarios are supported as
   required by the operator for expected traffic distributions.



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   A final advantage is that a specific multicast elements minimize the
   replication of multicast packets (the Tunnel Convergence problem), in
   certain scenarios, compared to [RFC6224]. Figures 7 and 8 illustrate
   this point visually.  For this simple scenario, it can be observed
   that the multicast MTMA topology (Figure 7) generates 6 packets for
   one input multicast packet. In comparison, the combined
   unicast/multicast LMA topology (Figure 8) generates 8 packets for one
   input multicast packet.

   In general, it can be seen that the extra multiplication of packets
   in the combined unicast/multicast LMA topology will be proportional
   to the number of LMAs, and the number of MNs (in a given MAG)
   associated to different LMAs, for a given multicast group.  The
   packet multiplication problem aggravates as more MNs associated to
   different LMAs receive the same multicast traffic when attached to
   the same MAG.  Hence, the MTMA architecture significantly decreases
   the network capacity requirements in this scenario.

   (Note that in Figure 7, it is assumed that MN1 and MN2 are associated
   with MAG1-LMA1, and MN3 is associated with MAG2-MTMA2 for multicast
   traffic.  In Figure 8, it is assumed that MN1 is associated with
   MAG1-LMA1, MN2 is associated with MAG1-LMA2, and MN3 is associated
   with MAG2-LMA2 for multicast traffic.  In both Figures 7 and 8, it is
   assumed that the packets are transmitted point to point on the last
   hop wireless link.)

   Additional results can be found in [ERCIM], where both solutions are
   compared by simulation under realistic traffic conditions. It can be
   shown that, for multicast traffic, the number of channels that a node
   (LMA in the base solution, MTMA in the proposed multicast
   architecture) has to serve does not decrease linearly with the
   reduction of the number of MNs associated to that node. The key
   factor is the set of channels subscribed by the MNs. In fact, as the
   number of MNs increases in the PMIPv6 domain, we have less advantage
   for having several nodes serving multicast, as each of them will
   probably manage all the multicast channels (or at least the popular
   ones) anyway.














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                                   +--------------+
                                   |Content Source|
                                   +--------------+
                                          |
                                          |
                                        +---+     Packet destined
                                        | 1 |   for Multicast group "G"
                                        +---+
                                          |
         ***  ***  ***  ***      ***  ***  ***  ***
        *   **   **   **   *    *   **   **   **    *
       *                    *  *                     *
       *  Unicast Traffic   *  *  Multicast Traffic  *
       *                    *  *                     *
        *   **   **   **   *    *   **   **   **   *
         ***  ***  ***  ***      ***  ***  ***  ***
                 |                       |
                 |                     +---+
                 |                     | 2 |
                 |                     +---+
                 |                       |
              +-----+                 +------+
     Unicast  | LMA1|                 | MTMA2|     Multicast
      Anchor  +-----+                 +------+      Anchor
                 \\                     //||
                  \\                   // ||
                   \\                 //  ||
                    \\               //   ||
                     \\          +---+  +---+
                      \\         | 3 |  | 4 |
                       \\        +---+  +---+
                        \\       //       ||
                         \\     //        ||
                          \\   //         ||
                           \\ //          ||
                          +-----+       +-----+
                          | MAG1|       | MAG2|      MLD Proxy
                          +-----+       +-----+
                          |     |          |
                        +---+ +---+      +---+
                        | 5 | | 6 |      | 7 |
                        +---+ +---+      +---+
                          |     |          |         All MNs in same
                          |     |          |       multicast group "G"
                        {MN1} {MN2}      {MN3}


           Figure 7. Packet Flow in the MTMA architecture



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                       +--------------+
                       |Content Source|
                       +--------------+
                              |
                              |
                            +---+      Packet destined
                            | 1 |    for Multicast group "G"
                            +---+
                              |
         ***  ***  ***  ***  ***  ***  ***  *** ***
        *   **   **   **   **  **   **   **   **   *
       *                                            *
       *                 Fixed Internet             *
       *        (Unicast & Multicast Traffic)       *
        *   **   **   **   **  **   **   **   **   *
         ***  ***  ***  ***      *** ***  ***  ***
                 |                       |
               +---+                   +---+
               | 2 |                   | 3 |
               +---+                   +---+
                 |                       |
              +-----+                 +------+
              | LMA1|                 | LMA2 |     Combined
              +-----+                 +------+     Unicast/Multicast
                 \\                   //  ||       Anchor
                  \\                 //   ||
                   \\               //    ||
                    \\             //     ||
                    +---+        +---+  +---+
                    | 4 |        | 5 |  | 6 |
                    +---+        +---+  +---+
                        \\       //       ||
                         \\     //        ||
                          \\   //         ||
                           \\ //          ||
                          +-----+       +-----+
                          | MAG1|       | MAG2|      MLD Proxy
                          +-----+       +-----+
                          |     |          |
                        +---+ +---+      +---+
                        | 7 | | 8 |      | 9 |
                        +---+ +---+      +---+
                          |     |          |         All MNs in same
                          |     |          |       multicast group "G"
                        {MN1} {MN2}      {MN3}

       Figure 8. Packet Flow in a Combined Unicast/Multicast LMA




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4  Consideration of MAG as multicast router in the tunnel interface to MTMA

   In the architecture described before, all MAGs that are connected to
   the MTMA are considered to act as MLD proxies. This follows the MAG
   characterization provided in [RFC6224]. However, interesting
   advantages can be derived from the fact of converting the MAG node in
   a multicast router in the tunnel interface towards the MTMA, that is,
   in implementing PIM protocol ([RFC4601], [RFC4607]) in the tunnel
   interface, in case the MAG connects to more than one MTMA in the
   PMIPv6 domain.

   This could be the case, for instance, in which a PMIPv6 domain
   provides access to MNs of different home networks, each home network
   using a distinct MTMA to provide multicast service in the PMIPv6
   domain. With the MAG working as a multicast router in the tunnel
   interface, in a source-specific multicast scenario [RFC4607], the MAG
   could send the PIM request to the corresponding MTMA based on the
   multicast source address.

   Another possible scenario for connecting more than one MTMA to a MAG
   could be the case of a home network using different MTMAs to serve
   different content over the same PMIPv6 domain for scalability
   reasons, or as a way to provide backup in case of MTMA failure.


5  Security Considerations

   This draft discusses the operations of existing protocols without
   modifications. It does not introduce new security threats beyond the
   current security considerations of PMIPv6 [RFC5213], MLD [RFC3810],
   IGMP [RFC3376] and IGMP/MLD Proxying [RFC4605].


6  IANA Considerations

   This document makes no request of IANA.


7  References

7.1  Normative References

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

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



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   [RFC3775]   Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
               in Ipv6", RFC 3775, June 2004.

   [RFC3810]   Vida, R. and L.Costa, "Multicast Listener Discovery
               Version 2 (MLDv2) for IPv6", RFC 3810, June 2004.

   [RFC3376]   Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
               Thyagarajan, "Internet Group Management Protocol, Version
               3", RFC 3376, October 2002.

   [RFC4605]   Fenner, B., He, H., Haberman, B., and H. Sandick,
               "Internet Group Management Protocol (IGMP)/ Multicast
               Listener Discovery (MLD)-Based Multicast Forwarding
               ("IGMP/MLD Proxying")", RFC 4605, August 2006.

   [RFC5847]   Devarapalli, V., Koodli, R., Lim, H., Kant, N., Krishnan,
               S., Laganier, J., "Heartbeat Mechanism for Proxy Mobile
               IPv6", RFC 5847, June 2010.

   [RFC4601]   Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
               "Protocol Independent Multicast - Sparse Mode (PIM-SM):
               Protocol Specification (Revised)", RFC 4601, August 2006.

   [RFC4607]   Holbrook, H., and B. Cain, "Source-Specific Multicast for
               IP", RFC 4607, August 2006.


7.2  Informative References

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

   [ERCIM]     L.M. Contreras, C.J. Bernardos, I. Soto, "On the
               efficiency of a dedicated LMA for multicast traffic
               distribution in PMIPv6 domains", 5th ERCIM Workshop in
               eMobility, Vilanova i la Geltru, Spain, June 2011.

   [ETSI]      ETSI TS 102 034, "Digital Video Broadcasting (DVB);
               Transport of MPEG-2 TS Based DVB Services over IP Based
               Networks", v1.4.1, August, 2009.


Appendix A. Overhead analysis of the proposed MTMA architecture.

   This appendix provides an analysis of the overhead introduced by the
   proposed multicast architecture. In this solution an MTMA is used to
   serve the multicast traffic to the MNs. The MAGs in the PMIPv6 domain



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   are connected to the MTMA through a tunnel which is used to deliver
   the multicast flows subscribed by the MNs attached to the MAG.

   A very common way for video delivery over IP networks is the
   transport of MPEG-2 Transport Streams (TS) encapsulated in RTP/UDP/IP
   datagrams, as described in [ETSI].

   An MPEG-2 transport stream is a packet of 188 bytes. So, an Ethernet
   frame with 1500 bytes of payload can carry a maximum of up to 7 MPEG-
   2 TS packets.

   When encapsulating those 7 MPEG-2 TS packets in RTP/UDP/IP datagrams
   we are forming a datagram of length 7*188 (MPEG-2 TS) + 12 (RTP) + 8
   (UDP) + 40 (IPv6) = 1376 bytes.

   In the proposed multicast architecture, such datagram should be
   transported over the tunnel existing between a MAG and the MTMA. That
   tunnel implies an IP-in-IP encapsulation, that is, an additional 40
   byte length header should be added to the datagram. In this
   situation, the overhead caused by the MTMA approach can be calculated
   as 40 / (40 + 1376) = 2,8%.

   This results in a minimal overhead derived from the use of the tunnel
   between MTMA and MAG.


Author's Addresses

   Juan Carlos Zuniga
   InterDigital Communications, LLC
   Email: JuanCarlos.Zuniga@InterDigital.com

   Akbar Rahman
   InterDigital Communications, LLC
   Email: Akbar.Rahman@InterDigital.com

   Luis M. Contreras
   Universidad Carlos III de Madrid
   Email: contreras.uc3m@gmail.com

   Carlos J. Bernardos
   Universidad Carlos III de Madrid
   Email: cjbc@it.uc3m.es

   Ignacio Soto
   Universidad Politecnica de Madrid
   Email: isoto@dit.upm.es




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