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MULTIMOB Group                                                JC.Zuniga
Internet Draft                                                     G.Lu
Intended status: Standards Track                               A.Rahman
Expires: November 30, 2010             InterDigital Communications, LLC
                                                           May 31, 2010


            Support Multicast Services Using Proxy Mobile IPv6
                   draft-zuniga-multimob-smspmip-03.txt


Abstract

   The MULTIMOB group has specified a base solution to support IP
   multicasting in a PMIPv6 domain [I-D.draft-ietf-multimob-pmipv6-base-
   solution]. In this document, an enhancement is proposed to the base
   solution to use a dedicated multicast LMA 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 reducing complexity of PMIPv6 deployments.



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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   This Internet-Draft will expire on November 30, 2010.






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Copyright Notice

   Copyright (c) 2010 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
   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 BSD License.



Table of Contents


   1. Introduction...................................................2
   2. Conventions and Terminology....................................3
   3. Solution.......................................................3
      3.1. Architecture..............................................3
      3.2. Multicast Establishment...................................5
      3.3. Multicast Mobility........................................7
      3.4. Advantages................................................8
   4. Security Considerations.......................................12
   5. IANA Considerations...........................................12
   6. References....................................................12
      6.1. Normative References.....................................12
      6.2. Informative References...................................12
   7. Acknowledgments...............................................13



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.




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   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 [I-D.draft-ietf-
   multimob-pmipv6-base-solution]. In this document, an enhancement is
   proposed to the base solution to use a dedicated multicast LMA as the
   topological anchor point for multicast traffic, while the MAG remains
   as an IGMP/MLD proxy. This enhancement reduces complexity of PMIPv6
   deployments.  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 [RFC2119].

   This document uses the terminology defined in [RFC5213], [RFC3775],
   and [RFC3810].

3. Solution

   A PMIPv6 domain may receive data from both unicast and multicast
   sources.  A dedicated multicast LMA can be used to serve as the
   mobility anchor for multicast traffic. Unicast traffic will go
   normally to the other LMAs in the PMIPv6 domain. This section
   describes how the multicast LMA works in scenarios of MN attachment
   and multicast mobility.

3.1. Architecture

   Figure 1 shows an example of a PMIPv6 domain supporting multicast
   mobility. LMA1 is dedicated to unicast traffic, and LMA2 is dedicated
   to multicast traffic. The multicast traffic LMA (LMA2) can be
   considered to be a form of upstream multicast router with tunnel
   interfaces allowing remote subscription for the MNs. Note that there


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   can multiple LMAs for unicast traffic (not shown in Figure 1) in a
   given PMIPv6 domain. Similarly, more than one multicast dedicated LMA
   can be deployed by the operator (not shown in Figure 1).

   Also in this architecture, all MAGs that are connected to the
   multicast LMA must support the MLD proxy [RFC4605] function.
   Specifically in Figure 1, each of the MAG1-LMA2 and MAG2-LMA2 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 LMA2
   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 and multicast
   LMAs. 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.





























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                                   +--------------+
                                   |Content Source|
                                   +--------------+
                                          |
                                          |
         ***  ***  ***  ***      ***  ***  ***  ***
        *   **   **   **   *    *   **   **   **    *
       *                    *  *                     *
       *  Unicast Traffic   *  *  Multicast Traffic  *
       *                    *  *                     *
        *   **   **   **   *    *   **   **   **    *
         ***  ***  ***  ***      ***  ***  ***  ***
                 |                       |
                 |                       |
                 |                       |
              +-----+                 +------+
     Unicast  | LMA1|                 | LMA2 |     Multicast
      Anchor  +-----+                 +------+      Anchor
                  \\                    // ||
                   \\                  //  ||
                    \\                //   ||
                     \\              //    ||
                      \\            //     ||
                       \\          //      ||
                        \\        //       ||
                         \\      //        ||
                          \\    //         ||
                          +-----+       +-----+
                          | MAG1|       | MAG2|      MLD Proxy
                          +-----+       +-----+
                          |     |          |
                          |     |          |
                        {MN1} {MN2}      {MN3}

        Figure 1 Architecture of Dedicated LMA as Multicast Anchor

3.2. Multicast Establishment

   Figure 2 shows the procedure when MN1 attaches to MAG1, and
   establishes associations with LMA1 (unicast) and LMA2 (multicast).







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      MN1                   MAG1       LMA1       LMA2
       |                (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 2 MN Attachment and Multicast Service Establishment

   In Figure 2, MAG1 first establishes the PMIPv6 tunnel with LMA1 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 LMA1.

   For multicast traffic, a multicast tunnel may have been pre-
   configured between MAG1 and the multicast LMA (LMA2).  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


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   then send an Aggregated MLD Report to the multicast anchor, LMA2
   (assuming that this is a new multicast group which MAG1 had not
   previously subscribed to).  Multicast traffic will then flow from
   LMA2 towards MN1.



3.3. Multicast Mobility

   Figure 3 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 MAG2 is
   connected only to LMA2 (multicast) and does not receive unicast
   traffic.  Of course, if it was desired to support unicast traffic,
   the architecture will easily allow MAG2 to also connect to LMA1 to
   support unicast traffic.

   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 LMA2 from MAG2. This message
   will be sent through a pre-established (or dynamically established)
   multicast tunnel between MAG2 and LMA2.

   When MN2 detaches, MAG1 may keep the multicast tunnel with the
   multicast LMA2 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         LMA1       LMA2
       |        (MLD Proxy) (MLD Proxy)  (Unicast)(Multicast)
       |            |           |            |          |
     MN Attached    |           |            |          |
      To MAG1       |           |            |          |
       |            |           |            |          |
       |            |========= Multicast Tunnel ======= |
       |            |           |            |          |
     MN Detaches    |           |            |          |
      From MAG1     |           |            |          |
       |            |           |            |          |
       |            |           |            |          |
     MN Attaches    |           |            |          |
      To MAG2       |           |            |          |
       |            |           |            |          |
       |            |           |==Multicast Tunnel === |
       |            |           |            |          |
       |---------Rtr Sol------ >|            |          |
       |            |           |            |          |
       |<-----Rtr Adv --------- |            |          |
       |            |           |            |          |
       |            |           |            |          |
       |<---------MLD Query---- |            |          |
       |            |           |            |          |
       |---MLD Report (G) ----> |            |          |
       |            |           |            |          |
       |            |           |---- Aggregated -----> |
       |            |           |    MLD Report (G)     |
       |            |           |            |          |

       |            |           |            |          |
       |< --------- Multicast Traffic ---------------- >|
       |            |           |            |          |
       |            |           |            |          |

                   Figure 3 Multicast Mobility Signaling

3.4. Advantages

   An advantage of the proposed dedicated multicast LMA 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 [I-D.draft-ietf-multimob-pmipv6-base-solution] will be a
   more complex set of trees.




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   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 LMAs, dedicated to multicast support,
   will have to be upgraded to support the new multicast functionality.

   A final advantage is that a dedicated multicast LMA minimizes
   replication of multicast packets (the Tunnel Convergence problem), in
   certain scenarios, compared to [I-D.draft-ietf-multimob-pmipv6-base-
   solution]. Figures 4 and 5 illustrate this point visually.  For this
   simple scenario, it can be observed that the dedicated multicast LMA
   topology (Figure 4) generates 6 packets for one input multicast
   packet. In comparison, the combined unicast/multicast LMA topology
   (Figure 5) 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 dedicated multicast architecture
   significantly decreases the network capacity requirements in this
   scenario.

   (Note that in Figure 4, it is assumed that MN1 and MN2 are associated
   with MAG1-LMA1, and MN3 is associated with MAG2-LMA2 for multicast
   traffic.  In Figure 5, 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 4 and 5, it is
   assumed that the packets are transmitted point to point on the last
   hop wireless link.)
















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

             Figure 4 Packet Flow in a Dedicated Multicast LMA


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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 5 Packet Flow in a Combined Unicast/Multicast LMA


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4. 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].

5. IANA Considerations

   This document makes no request of IANA.

6. References

6.1. 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.

   [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.

6.2. Informative References

    [I-D.draft-ietf-multimob-pmipv6-base-solution] Schmidt, T.C.,
             Waehlisch, M., and S.Krishnan, "Base Deployment for
             Multicast Listener Support in PMIPv6 Domains", draft-ietf-
             multimob-pmipv6-base-solution-01 (Work in progress), May
             25, 2010.




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7. Acknowledgments

   This document was prepared using 2-Word-v2.0.template.dot.

Authors' Addresses

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


   Guang Lu
   InterDigital Communications, LLC
   Email: Guang.Lu@InterDigital.com


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






























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