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Versions: (draft-schmidt-multimob-pmipv6-source) 00 01 02 03 04 05 06 07 08 09 RFC 7287

MULTIMOB Group                                         T C. Schmidt, Ed.
Internet-Draft                                               HAW Hamburg
Intended status: Standards Track                                  S. Gao
Expires: April 25, 2013                                         H. Zhang
                                             Beijing Jiaotong University
                                                            M. Waehlisch
                                                    link-lab & FU Berlin
                                                        October 22, 2012


 Mobile Multicast Sender Support in Proxy Mobile IPv6 (PMIPv6) Domains
                  draft-ietf-multimob-pmipv6-source-02

Abstract

   Multicast communication can be enabled in Proxy Mobile IPv6 domains
   via the Local Mobility Anchors by deploying MLD Proxy functions at
   Mobile Access Gateways, via a direct traffic distribution within an
   ISP's access network, or by selective route optimization schemes.
   This document describes the support of mobile multicast senders in
   Proxy Mobile IPv6 domains for all three scenarios.  Protocol
   optimizations for synchronizing PMIPv6 with PIM, as well as extended
   MLD Proxy functions are presented.  Mobile sources always remain
   agnostic of multicast mobility operations.

Requirements Language

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

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 25, 2013.




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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
   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.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Base Solution for Source Mobility and PMIPv6 Routing . . . . .  5
     3.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.2.  Base Solution for Source Mobility: Details . . . . . . . .  9
       3.2.1.  Operations of the Mobile Node  . . . . . . . . . . . .  9
       3.2.2.  Operations of the Mobile Access Gateway  . . . . . . .  9
       3.2.3.  Operations of the Local Mobility Anchor  . . . . . . .  9
       3.2.4.  IPv4 Support . . . . . . . . . . . . . . . . . . . . . 10
       3.2.5.  Efficiency of the Distribution System  . . . . . . . . 11
   4.  Direct Multicast Routing . . . . . . . . . . . . . . . . . . . 11
     4.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . 12
     4.2.  MLD Proxies at MAGs  . . . . . . . . . . . . . . . . . . . 13
       4.2.1.  Considerations for PIM-SM on the Upstream  . . . . . . 14
       4.2.2.  SSM Considerations . . . . . . . . . . . . . . . . . . 14
     4.3.  PIM-SM . . . . . . . . . . . . . . . . . . . . . . . . . . 14
       4.3.1.  Routing Information Base for PIM-SM  . . . . . . . . . 14
       4.3.2.  Operations of PIM in Phase One . . . . . . . . . . . . 15
       4.3.3.  Operations of PIM in Phase Two . . . . . . . . . . . . 16
       4.3.4.  Operations of PIM in Phase Three . . . . . . . . . . . 16
       4.3.5.  PIM-SSM Considerations . . . . . . . . . . . . . . . . 17
       4.3.6.  Handover Optimizations for PIM . . . . . . . . . . . . 17
     4.4.  BIDIR-PIM  . . . . . . . . . . . . . . . . . . . . . . . . 17
       4.4.1.  Routing Information Base for BIDIR-PIM . . . . . . . . 18
       4.4.2.  Operations of BIDIR-PIM  . . . . . . . . . . . . . . . 18
   5.  Extended MLD Proxy Functions for Optimized Source Mobility
       in PMIPv6  . . . . . . . . . . . . . . . . . . . . . . . . . . 18
     5.1.  Multiple Upstream Interface Proxy  . . . . . . . . . . . . 19
       5.1.1.  Operations for Local Multicast Sources . . . . . . . . 19
       5.1.2.  Operations for Local Multicast Subscribers . . . . . . 20
     5.2.  Peering Function for MLD Proxies . . . . . . . . . . . . . 20
       5.2.1.  Operations at the Multicast Sender . . . . . . . . . . 20
       5.2.2.  Operations at the Multicast Listener . . . . . . . . . 21
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 22
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 22
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 23
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 23
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 23
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 24
   Appendix A.  Evaluation of Traffic Flows . . . . . . . . . . . . . 24
   Appendix B.  Change Log  . . . . . . . . . . . . . . . . . . . . . 24
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25







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1.  Introduction

   Proxy Mobile IPv6 (PMIPv6) [RFC5213] extends Mobile IPv6 (MIPv6)
   [RFC6275] by network-based management functions that enable IP
   mobility for a host without requiring its participation in any
   mobility-related signaling.  Additional network entities called the
   Local Mobility Anchor (LMA), and Mobile Access Gateways (MAGs), are
   responsible for managing IP mobility on behalf of the mobile node
   (MN).  An MN connected to a PMIPv6 domain, which only operates
   according to the base specifications of [RFC5213], cannot participate
   in multicast communication, as MAGs will discard group packets.

   Multicast support for mobile listeners can be enabled within a PMIPv6
   domain by deploying MLD Proxy functions at Mobile Access Gateways,
   and multicast routing functions at Local Mobility Anchors [RFC6224].
   This base deployment option is the simplest way to PMIPv6 multicast
   extensions in the sense that it follows the common PMIPv6 traffic
   model and neither requires new protocol operations nor additional
   infrastructure entities.  Standard software functions need to be
   activated on PMIPv6 entities, only, at the price of possibly non-
   optimal multicast routing.

   Alternate solutions leverage performance optimization by providing
   multicast routing at the access gateways directly, or by selective
   route optimization schemes.  Such approaches (partially) follow the
   business model of providing multicast data services in parallel to
   PMIPv6 unicast routing.

   Multicast listener support satisfies the needs of receptive use cases
   such as IPTV or sever-centric gaming on mobiles.  However, current
   trends in the Internet enfold towards user-centric, highly
   interactive group applications like user generated streaming,
   conferencing, collective mobile sensing, etc.  Many of these popular
   applications create group content at end systems and can largely
   profit from a direct data transmission to a multicast-enabled
   network.

   This document describes the support of mobile multicast senders in
   Proxy Mobile IPv6 domains subsequently for the base deployment
   scenario [RFC6224], for direct traffic distribution within an ISP's
   access network, as well as for selective route optimization schemes.
   The contribution of this work reflects the source mobility problem as
   discussed in [RFC5757].  Mobile Nodes in this setting remain agnostic
   of multicast mobility operations.







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2.  Terminology

   This document uses the terminology as defined for the mobility
   protocols [RFC6275], [RFC5213] and [RFC5844], as well as the
   multicast edge related protocols [RFC3376], [RFC3810] and [RFC4605].


3.  Base Solution for Source Mobility and PMIPv6 Routing

3.1.  Overview

   The reference scenario for multicast deployment in Proxy Mobile IPv6
   domains is illustrated in Figure 1.  MAGs play the role of first-hop
   access routers that serve multiple MNs on the downstream while
   running an MLD/IGMP proxy instance for every LMA upstream tunnel.




































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                       +-------------+
                       | Multicast   |
                       | Listeners   |
                       +-------------+
                              |
                     ***  ***  ***  ***
                    *   **   **   **   *
                   *                    *
                    *  Fixed Internet  *
                   *                    *
                    *   **   **   **   *
                     ***  ***  ***  ***
                      /            \
                  +----+         +----+
                  |LMA1|         |LMA2|                 Multicast Anchor
                  +----+         +----+
             LMAA1  |              |  LMAA2
                    |              |
                    \\           //\\
                     \\         //  \\
                      \\       //    \\                 Unicast Tunnel
                       \\     //      \\
                        \\   //        \\
                         \\ //          \\
               Proxy-CoA1 ||            ||  Proxy-CoA2
                       +----+          +----+
                       |MAG1|          |MAG2|           MLD Proxy
                       +----+          +----+
                        |  |             |
                MN-HNP1 |  | MN-HNP2     | MN-HNP3
                        |  |             |
                       MN1 MN2          MN3

                 Multicast Sender + Listener(s)

   Figure 1: Reference Network for  Multicast Deployment in PMIPv6 with
                              Source Mobility

   An MN in a PMIPv6 domain will decide on multicast data transmission
   completely independent of its current mobility conditions.  It will
   send packets as initiated by applications, using its source address
   with Home Network Prefix (HNP) and a multicast destination address
   chosen by application needs.  Multicast packets will arrive at the
   currently active MAG via one of its downstream local (wireless)
   links.  A multicast unaware MAG would simply discard these packets in
   the absence of a multicast routing information base (MRIB).

   An MN can successfully distribute multicast data in PMIPv6, if MLD



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   proxy functions are deployed at the MAG as described in [RFC6224].
   In this set-up, the MLD proxy instance serving a mobile multicast
   source has configured its upstream interface at the tunnel towards
   MN's corresponding LMA.  For each LMA, there will be a separate
   instance of an MLD proxy.

   According to the specifications given in [RFC4605], multicast data
   arriving from a downstream interface of an MLD proxy will be
   forwarded to the upstream interface and to all but the incoming
   downstream interfaces that have appropriate forwarding states for
   this group.  Thus multicast streams originating from an MN will
   arrive at the corresponding LMA and directly at all mobile receivers
   co-located at the same MAG and MLD Proxy instance.  Serving as the
   designated multicast router or an additional MLD proxy, the LMA
   forwards data to the fixed Internet, whenever forwarding states are
   maintained by multicast routing.  If the LMA is acting as another MLD
   proxy, it will forward the multicast data to its upstream interface,
   and to downstream interfaces with matching subscriptions,
   accordingly.

   In case of a handover, the MN (unaware of IP mobility) can continue
   to send multicast packets as soon as network connectivity is
   reconfigured.  At this time, the MAG has determined the corresponding
   LMA, and IPv6 unicast address configuration (including PMIPv6
   bindings) has been performed .  Still multicast packets arriving at
   the MAG are discarded (if not buffered) until the MAG has completed
   the following steps.

   1.  The MAG has determined that the MN is admissible to multicast
       services.

   2.  The MAG has added the new downstream link to the MLD proxy
       instance with up-link to the corresponding LMA.

   As soon as the MN's uplink is associated with the corresponding MLD
   proxy instance, multicast packets are forwarded again to the LMA and
   eventually to receivers within the PMIP domain (see the call flow in
   Figure 2).  In this way, multicast source mobility is transparently
   enabled in PMIPv6 domains that deploy the base scenario for
   multicast.











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   MN1             MAG1             MN2             MAG2             LMA
   |                |                |               |                |
   |                | Mcast Data     |               |                |
   |                |<---------------+               |                |
   |                |     Mcast Data |               |                |
   |  Join(G)       +================================================>|
   +--------------> |                |               |                |
   | Mcast Data     |                |               |                |
   |<---------------+                |               |                |
   |                |                |               |                |
   |           <  Movement of MN 2 to MAG2  &  PMIP Binding Update  > |
   |                |                |               |                |
   |                |                |--- Rtr Sol -->|                |
   |                |                |<-- Rtr Adv ---|                |
   |                |                |               |                |
   |                |                |   < MLD Proxy Configuration >  |
   |                |                |               |                |
   |                |                |  (MLD Query)  |                |
   |                |                |<--------------+                |
   |                |                |  Mcast Data   |                |
   |                |                +-------------->|                |
   |                |                |               | Mcast Data     |
   |                |                |               +===============>|
   |                |                |               |                |
   |                |   Mcast Data   |               |                |
   |                |<================================================+
   |  Mcast Data    |                |               |                |
   |<---------------+                |               |                |
   |                |                |               |                |

   Figure 2: Call Flow for Group Communication in Multicast-enabled PMIP

   These multicast deployment considerations likewise apply for mobile
   nodes that operate with their IPv4 stack enabled in a PMIPv6 domain.
   PMIPv6 can provide IPv4 home address mobility support [RFC5844].
   IPv4 multicast is handled by an IGMP proxy function at the MAG in an
   analogous way.

   Following these deployment steps, multicast traffic distribution
   transparently inter-operates with PMIPv6.  It is worth noting that an
   MN - while being attached to the same MAG as the mobile source, but
   associated with a different LMA - cannot receive multicast traffic on
   a shortest path.  Instead, multicast streams flow up to the LMA of
   the mobile source, are transferred to the LMA of the mobile listener
   and tunneled downwards to the MAG again (see Appendix A for further
   considerations).





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3.2.  Base Solution for Source Mobility: Details

   Incorporating multicast source mobility in PMIPv6 requires to deploy
   general multicast functions at PMIPv6 routers and to define their
   interaction with the PMIPv6 protocol in the following way.

3.2.1.  Operations of the Mobile Node

   A Mobile Node willing to send multicast data will proceed as if
   attached to the fixed Internet.  No specific mobility or other
   multicast related functionalities are required at the MN.

3.2.2.  Operations of the Mobile Access Gateway

   A Mobile Access Gateway is required to have MLD proxy instances
   deployed, one for each tunnel to an LMA, which serves as its unique
   upstream link (cf., [RFC6224]).  On the arrival of an MN, the MAG
   decides on the mapping of downstream links to a proxy instance and
   the upstream link to the LMA based on the regular Binding Update List
   as maintained by PMIPv6 standard operations.  When multicast data is
   received from the MN, the MAG MUST identify the corresponding proxy
   instance from the incoming interface and forwards multicast data
   upstream according to [RFC4605].

   The MAG MAY apply special admission control to enable multicast data
   transition from an MN.  It is advisable to take special care that MLD
   proxy implementations do not redistribute multicast data to
   downstream interfaces without appropriate subscriptions in place.

3.2.3.  Operations of the Local Mobility Anchor

   For any MN, the Local Mobility Anchor acts as the persistent Home
   Agent and at the same time as the default multicast upstream for the
   corresponding MAG.  It will manage and maintain a multicast
   forwarding information base for all group traffic arriving from its
   mobile sources.  It SHOULD participate in multicast routing functions
   that enable traffic redistribution to all adjacent LMAs within the
   PMIPv6 domain and thereby ensure a continuous receptivity while the
   source is in motion.

3.2.3.1.  Local Mobility Anchors Operating PIM

   Local Mobility Anchors that operate the PIM-SM routing protocol
   [RFC4601] will require sources to be directly connected for sending
   PIM registers to the RP.  This does not hold in a PMIPv6 domain, as
   MAGs are routers intermediate to MN and the LMA.  In this sense, MNs
   are multicast sources external to the PIM-SM domain.




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   To mitigate this incompatibility common to all subsidiary MLD proxy
   domains, the LMA should act as a PIM Border Router and activate the
   Border-bit.  In this case, the DirectlyConnected(S) is treated as
   being TRUE for mobile sources and the PIM-SM forwarding rule "iif ==
   RPF_interface(S)" is relaxed to be TRUE, as the incoming tunnel
   interface from MAG to LMA is considered as not part of the PIM-SM
   component of the LMA (see A.1 of [RFC4601] ).

   In addition, an LMA serving as PIM Designated Router is connected to
   MLD proxies via individual IP-tunnel interfaces and will experience
   changing PIM source states on handover.  As the incoming interface
   connects to a point-to-point link, PIM Assert contention is not
   active, and incoming interface validation is only performed by RPF
   checks.  Consequently, a PIM DR should update incoming source states,
   as soon as RPF inspection succeeds, i.e., after PMIPv6 forwarding
   state update.  Consequently, PIM routers SHOULD be able to manage
   these state changes, but some implementations are expected to
   incorrectly refuse packets until the previous state has timed out.

   Notably, running BIDIR PIM [RFC5015] on LMAs remains robust with
   respect to source location and does not require special
   configurations or state management for sources.

3.2.4.  IPv4 Support

   An MN in a PMIPv6 domain may use an IPv4 address transparently for
   communication as specified in [RFC5844].  For this purpose, an LMA
   can register an IPv4-Proxy-CoA in its Binding Cache and the MAG can
   provide IPv4 support in its access network.  Correspondingly,
   multicast membership management will be performed by the MN using
   IGMP.  For multicast support on the network side, an IGMP proxy
   function needs to be deployed at MAGs in exactly the same way as for
   IPv6.  [RFC4605] defines IGMP proxy behaviour in full agreement with
   IPv6/MLD.  Thus IPv4 support can be transparently provided following
   the obvious deployment analogy.

   For a dual-stack IPv4/IPv6 access network, the MAG proxy instances
   SHOULD choose multicast signaling according to address configurations
   on the link, but MAY submit IGMP and MLD queries in parallel, if
   needed.  It should further be noted that the infrastructure cannot
   identify two data streams as identical when distributed via an IPv4
   and IPv6 multicast group.  Thus duplicate data may be forwarded on a
   heterogeneous network layer.

   A particular note is worth giving the scenario of [RFC5845] in which
   overlapping private address spaces of different operators can be
   hosted in a PMIP domain by using GRE encapsulation with key
   identification.  This scenario implies that unicast communication in



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   the MAG-LMA tunnel can be individually identified per MN by the GRE
   keys.  This scenario still does not impose any special treatment of
   multicast communication for the following reasons.

   Multicast streams from and to MNs arrive at a MAG on point-to-point
   links (identical to unicast).  Multicast data transmission from the
   MAG to the corresponding LMA is link-local between the routers and
   routing/forwarding remains independent of any individual MN.  So the
   MAG-proxy and the LMA SHOULD NOT use GRE key identifiers, but plain
   GRE encapsulation in multicast communication (including MLD queries
   and reports).  Multicast traffic sent upstream and downstream of MAG-
   to-LMA tunnels proceeds as router-to-router forwarding according to
   the multicast routing information base (MRIB) of the MAG or LMA and
   independent of MN's unicast addresses, while the MAG proxy instance
   re-distributes multicast data down the point-to-point links
   (interfaces) according to its own MRIB, independent of MN's IP
   addresses.

3.2.5.  Efficiency of the Distribution System

   The distribution system of the base solution directly follows PMIPv6
   routing rules, and organizes multicast domains with respect to LMAs.
   Thus, no coordination between address spaces or services is required
   between the different instances, provided their associated LMAs
   belong to disjoint multicast domains.  Routing is optimal for
   communication between MNs of the same domain, or stationary
   subscribers.

   In the following efficiency-related issues remain.

   Multicast reception at LMA  In the current deployment scenario, the
      LMA will receive all multicast traffic originating from its
      associated MNs.  There is no mechanism to suppress upstream
      forwarding in the absence of receivers.

   MNs on the same MAG using different LMAs  For a mobile receiver and a
      source that use different LMAs, the traffic has to go up to one
      LMA, cross over to the other LMA, and then be tunneled back to the
      same MAG, causing redundant flows in the access network and at the
      MAG.


4.  Direct Multicast Routing

   There are deployment scenarios, where multicast services are
   available throughout the access network independent of the PMIPv6
   routing system [I-D.ietf-multimob-pmipv6-ropt].  In these cases, the
   visited networks grant a local content distribution service (in



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   contrast to LMA-based home subscription) with locally optimized
   traffic flows.  It is also possible to deploy a mixed service model
   of local and LMA-based subscriptions, provided a unique way of
   service selection is implemented.  For example, access routers (MAGs)
   could decide on service access based on the multicast address G or
   the SSM channel (S,G) under request (see Section 5 for a further
   discussion).

4.1.  Overview

   Direct multicast access can be supported by

   o  native multicast routing provided by one multicast router that is
      neighboring MLD proxies deployed at MAGs within a flat access
      network, or via tunnel uplinks,

   o  a multicast routing protocol such as PIM-SM [RFC4601] or BIDIR-PIM
      [RFC5015] deployed at the MAGs.


               ***  ***  ***  ***
              *   **   **   **   *
             *                    *
             *      Multicast     *
    +----+   *   Infrastructure   *                               +----+
    |LMA |    *   **   **   **   *                                |LMA |
    +----+     ***  ***  ***  ***                                 +----+
         |          //  \\                                             |
         \\        //    \\       PMIP (unicast)                       |
  PMIP    \\      //      \\      //          \\   **  ***  *** **    //
(unicast)  \\    //        \\    //            \\ *   **   **     ** //
            \\  //          \\  //              \\*    Multicast   *//
            || ||           || ||              * ||     Routing    || *
           +----+          +----+              * +----+         +----+ *
 MLD Proxy |MAG1|          |MAG2|              * |MAG1|         |MAG2| *
           +----+          +----+               *+----+ **   ** +----+*
            |  |             |                    |  |***  ***   ***|
            |  |             |                    |  |              |
           MN1 MN2          MN3                 MN1 MN2            MN3

 (a) Multicast Access at Proxy Uplink      (b) Multicast Routing at MAG

   Figure 3: Reference Networks for (a) Proxy-assisted Direct Multicast
             Access and (b) Dynamic Multicast Routing at MAGs

   Figure 3 displays the corresponding deployment scenarios, which
   separate multicast from PMIPv6 unicast routing.  It is assumed
   throughout these scenarios that all MAGs (MLD proxies) are linked to



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   a single multicast routing domain.  Noteworthy, this scenario
   requires coordination of multicast address utilization and service
   bindings.

   Multicast traffic distribution can be simplified in these scenarios.
   A single proxy instance at MAGs with up-link into the multicast
   domain will serve as a first hop multicast gateway and avoid traffic
   duplication or detour routing.  Multicast routing functions at MAGs
   will seamlessly embed access gateways within a multicast cloud.
   However, mobility of the multicast source in this scenario will
   require some multicast routing protocols to rebuild distribution
   trees.  This can cause significant service disruptions or delays (see
   [RFC5757] for further aspects).  Deployment details are specific to
   the multicast routing protocol in use, in the following described for
   common protocols.

4.2.  MLD Proxies at MAGs

   In a PMIPv6 domain, single MLD proxy instances can be deployed at
   each MAG that enable multicast service at the access via an uplink to
   a multicast service infrastructure (see Figure 3 (a) ).  To avoid
   service disruptions on handovers, the uplinks of all proxies SHOULD
   be adjacent to the same next-hop multicast router.  This can either
   be achieved by arranging proxies within a flat access network, or by
   upstream tunnels that terminate at a common multicast router.

   Multicast data submitted by a mobile source will reach the MLD proxy
   at the MAG that subsequently forwards flows to the upstream, and all
   downstream interfaces with appropriate subscriptions.  Traversing the
   upstream will lead traffic into the multicast infrastructure (e.g.,
   to a PIM Designated Router) which will route packets to all local
   MAGs that have joined the group, as well as further upstream
   according to protocol procedures and forwarding states.

   On handover, a mobile source will reattach at a new MAG and can
   continue to send multicast packets as soon as PMIPv6 unicast
   configurations have completed.  Like at the previous MAG, the new MLD
   proxy will forward data upstream and downstream to subscribers.
   Listeners local to the previous MAG will continue to receive group
   traffic via the local multicast distribution infrastructure following
   aggregated listener reports of the previous proxy.  In general,
   traffic from the mobile source continues to be transmitted via the
   same next-hop router using the same source address and thus remains
   unchanged when seen from the wider multicast infrastructure.







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4.2.1.  Considerations for PIM-SM on the Upstream

   A mobile source that transmits data via an MLD proxy will not be
   directly connected to a PIM Designated Router as discussed in
   Section 3.2.3.1.  Countermeasures apply correspondingly.

   A PIM Designated Router that is connected to MLD proxies via
   individual IP-tunnel interfaces will experience invalid PIM source
   states on handover.  In some implementations of PIM-SM this could
   lead to interim packet loss (see Section Section 3.2.3.1).  This
   problem can be mitigated by aggregating proxies on a lower layer.

4.2.2.  SSM Considerations

   Source-specific subscriptions invalidate with routes, whenever the
   source moves from or to the MAG/proxy of a subscriber.  Multicast
   forwarding states will rebuild with unicast route changes.  However,
   this may lead to noticeable service disruptions for locally
   subscribed nodes.

4.3.  PIM-SM

   The full-featured multicast routing protocol PIM-SM MAY be deployed
   in the access network for providing multicast services in parallel to
   unicast routes.  Throughout this section, it is assumed that the
   PMIPv6 mobility domain is part of a single PIM-SM multicast routing
   domain with PIM-SM routing functions present at all MAGs and all
   LMAs.  The PIM routing instance at a MAG SHALL then serve as the
   Designated Router (DR) for all directly attached Mobile Nodes.  For
   expediting handover operations, it is advisable to position PIM
   Rendezvous Points (RPs) in the core of the PMIPv6 network domain.
   However, regular IP routing tables need not be present in a PMIPv6
   deployment, and additional effort is required to establish reverse
   path forwarding rules as required by PIM-SM.

4.3.1.  Routing Information Base for PIM-SM

   In this scenario, PIM-SM will rely on a Multicast Routing Information
   Base (MRIB) that is generated independently of the policy-based
   routing rules of PMIPv6.  The granularity of mobility-related routing
   locators required in PIM depends on the complexity (phases) of its
   deployment.

   The following information is needed for all phases of PIM.

   o  All routes to networks and nodes (including RPs) that are not
      mobile members of the PMIPv6 domain MUST be defined consistently
      among PIM routers and remain uneffected by node mobility.  The



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      setup of these general routes is expected to follow the topology
      of the operator network and is beyond the scope of this document.

   The following route entries are required at a PIM-operating MAG when
   phases two or three of PIM, or PIM-SSM are in operation.

   o  All MNs that are directly attached to the MAG generate local
      routes to their Home Network Prefixes (HNPs) at the corresponding
      point-to-point attachments that MUST be included into the local
      MRIB.

   o  All routes to MNs that are attached to distant MAGs of the PMIPv6
      domain point towards their corresponding LMAs.  These routes MUST
      be made available in the MRIB of all PIM routers (except for the
      local MAG of attachment), but MAY be eventually expressed by an
      appropriate default entry.

4.3.2.  Operations of PIM in Phase One

   A new mobile source S will transmit multicast data of group G towards
   its MAG of attachment.  Acting as a PIM DR, the access gateway will
   unicast-encapsulate the multicast packets and forward the data to the
   Virtual Interface (VI) with encapsulation target RP(G), a process
   known as PIM source registering.  The RP will decapsulate and
   natively forward the packets down the RP-based distribution tree
   towards (mobile and stationary) subscribers.

   On handover, the point-to-point link connecting the mobile source to
   the old MAG will go down and all (S,*) flows terminate.  In response,
   the previous DR (MAG) deactivates the data encapsulation channels for
   the transient source (e.g., all DownstreamJPState(S,*,VI) are set to
   NoInfo state).  After reattaching and completing unicast handover
   negotiations, the mobile source can continue to transmit multicast
   packets, while being treated as a new source at its new DR (MAG).
   Source register encapsulation will be immediately initiated, and
   (S,G) data continue to flow natively down the (*,G) RP-based tree.

   Source handover management in PIM phase one admits low complexity and
   remains transparent to receivers.  In addition, the source register
   tunnel management of PIM is a fast protocol operation and little
   overhead is induced thereof.  In a PMIPv6 deployment, PIM RPs MAY be
   configured to not initiated (S,G) shortest path tress for mobile
   sources, and thus remain in phase one of the protocol.  The price to
   pay for such simplified deployment lies in possible routing detours
   by an overall RP-based packet distribution.






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4.3.3.  Operations of PIM in Phase Two

   After receiving source register packets, a PIM RP eventually will
   initiated a source-specific Join for creating a shortest path tree to
   the (mobile) source S, and issue a source register stop at the native
   arrival of data from S. For initiating an (S,G) tree, the RP, as well
   as all intermediate routers, require route entries for MN's HNP that
   - unless the RP coincides with the MAG of S - point towards the
   corresponding LMA of S. Consequently, the (S,G) tree will proceed
   from the RP via the (stable) LMA, the LMA-MAG tunnel to the mobile
   source.  This tree can be of lesser routing efficiency than the PIM
   source register tunnel established in phase one, but provides the
   advantage of immediate data delivery to receivers that share a MAG
   with S.

   On handover, the mobile source reattaches to a new MAG (DR), and
   PMIPv6 unicast management will transfer the LMA-MAG tunnel to the new
   point of attachment.  However, in the absence of a corresponding
   multicast forwarding state, the new DR will treat S as a new source
   and initiate a source registering of PIM phase one.  In consequence,
   the PIM transition from phase one to two will be iterated per
   handover, leading to an enhanced signaling load and repeated delay
   variations.

4.3.4.  Operations of PIM in Phase Three

   In response to an exceeded threshold of packet transmission, DRs of
   receivers eventually will initiated a source-specific Join for
   creating a shortest path tree to the (mobile) source S, thereby
   transitioning PIM into the final short-cut phase three.  For all
   receivers not sharing a MAG with S, this (S,G) tree will proceed from
   the receiving DR via the (stable) LMA, the LMA-MAG tunnel to the
   mobile source.  This tree is of higher routing efficiency than
   established in the previous phase two, but need not outperform the
   PIM source register tunnel established in phase one.  It provides the
   advantage of immediate data delivery to receivers that share a MAG
   with S.

   On handover, the mobile source reattaches to a new MAG (DR), and
   PMIPv6 unicast management will transfer the LMA-MAG tunnel to the new
   point of attachment.  However, in the absence of a corresponding
   multicast forwarding state, the new DR will treat S as a new source
   and initiate a source registering of PIM phase one.  In consequence,
   the PIM transition from phase one to two and three will be iterated
   per handover, leading to an enhanced signaling load and repeated
   delay variations.





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4.3.5.  PIM-SSM Considerations

   Source-specific Joins of receivers will guide PIM to operate in SSM
   mode and lead to an immediate establishment of source-specific
   shortest path trees.  Such (S,G) trees will equal the distribution
   system of PIM's final phase three (see Section 4.3.4).  However, on
   handover and in the absence of RP-based data distribution, SSM data
   delivery cannot be resumed via source registering as in PIM phase
   one.  Consequently, data packets transmitted after a handover will be
   discarded at the MAG until regular tree maintenance has re-
   established the (S,G) forwarding state at the new MAG.

4.3.6.  Handover Optimizations for PIM

   Source-specific shortest path trees are constructed in PIM-SM (phase
   two and three), and in PIM-SSM that follow LMA-MAG tunnels towards a
   source.  As PIM remains unaware of source mobility management, these
   trees invalidate under handovers with each tunnel re-establishment at
   a new MAG.  Regular tree maintenance of PIM will recover the states,
   but remains unsynchronized and too slow to seamlessly preserve PIM
   data dissemination.

   A method to quickly recover PIM (S,G) trees under handover SHOULD
   synchronize multicast state maintenance with unicast handover
   operations and MAY proceed as follows.  On handover, an LMA reads all
   (S,G) Join states from its corresponding tunnel interface and
   identifies those source addresses S_i that match moving HNPs.  After
   re-establishing the new tunnel, it SHOULD associate the (S_i,*) Join
   states with the new tunnel endpoint and immediately trigger a state
   maintenance (PIM Join) message.  In proceeding this way, the source-
   specific PIM states are transferred to the new tunnel end point and
   propagated to the new MAG in synchrony with unicast handover
   procedures.

4.4.  BIDIR-PIM

   BIDIR-PIM MAY be deployed in the access network for providing
   multicast services in parallel to unicast routes.  Throughout this
   section, it is assumed that the PMIPv6 mobility domain is part of a
   single BIDIR-PIM multicast routing domain with BIDIR-PIM routing
   functions present at all MAGs and all LMAs.  The PIM routing instance
   at a MAG SHALL then serve as the Designated Forwarder (DF) for all
   directly attached Mobile Nodes.  For expediting handover operations,
   it is advisable to position BIDIR-PIM Rendezvous Point Addresses
   (RPAs) in the core of the PMIPv6 network domain.  As regular IP
   routing tables need not be present in a PMIPv6 deployment, reverse
   path forwarding rules as required by BIDIR-PIM need to be
   established.



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4.4.1.  Routing Information Base for BIDIR-PIM

   In this scenario, BIDIR-PIM will rely on a Multicast Routing
   Information Base (MRIB) that is generated independently of the
   policy-based routing rules of PMIPv6.  The following information is
   needed.

   o  All routes to networks and nodes (including RPAs) that are not
      mobile members of the PMIPv6 domain MUST be defined consistently
      among BIDIR-PIM routers and remain uneffected by node mobility.
      The setup of these general routes is expected to follow the
      topology of the operator network and is beyond the scope of this
      document.

4.4.2.  Operations of BIDIR-PIM

   BIDIR-PIM will establish spanning trees across its network domain in
   conformance to its preconfigured RPAs and the routing information
   provided.  Multicast data transmitted by a mobile source will
   immediately be forwarded by its DF (MAG) onto the spanning group tree
   without further protocol operations.

   On handover, the mobile source re-attaches to a new MAG (DF), which
   completes unicast network configurations.  Thereafter, the source can
   immediately proceed with multicast packet transmission onto the pre-
   established distribution tree.  BIDIR-PIM does neither require
   protocol signaling nor additional reconfiguration delays to adapt to
   source mobility and can be considered the protocol of choice for
   mobile multicast operations in the access.  As multicast streams
   always flow up to the Rendezvous Point Link, some care should be
   taken to configure RPAs compliant with network capacities.


5.  Extended MLD Proxy Functions for Optimized Source Mobility in PMIPv6

   A deployment of MLD Proxies (see [RFC4605]) at MAGs has proven a
   useful and appropriate approach to multicast in PMIPv6, see
   [RFC6224], [I-D.ietf-multimob-pmipv6-ropt].  However, unmodified
   standard solutions can go along with significant performance
   degradation for mobile senders as discussed along the lines of this
   document.  To overcome these deficits, optimizing approaches to
   multicast source mobility are introduced in this section.  In
   particular, uplink capabilities of MLD proxies are extended to allow
   for rapid, optimized multicast traffic flows from mobile sources.

   Solutions that extend MLD Proxies by additional uplinking functions
   need to comply to the following requirements.




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   Prevention of Routing Loops  In the absence of a full-featured
      routing logic at an MLD Proxy, simple and locally decidable rules
      need to prevent source traffic from traversing the network in
      loops as potentially enabled by multiple uplinks.

   Unique coverage of receivers  Listener functions at Proxies require
      simple, locally decidable rules to initiate a unique delivery of
      multicast packets to all receivers.

   Following different techniques, these requirements are met in the
   following solutions.

5.1.  Multiple Upstream Interface Proxy

   In this section, we define upstream extensions for an MLD proxy.
   Multiple proxy instances deployed at a single MAG (see Section 3) can
   be avoided by adding multiple upstream interfaces to a single MLD
   Proxy.  In a typical PMIPv6 deployment, each upstream of a single
   proxy instance can interconnect to one of the LMAs.  With such
   ambiguous upstream options, appropriate forwarding rules MUST be
   supplied to

   o  unambiguously guide traffic forwarding from directly attached
      mobile sources, and

   o  lead listener reports to initiating unique traffic subscriptions.

   This can be achieved by a complete set of source- and group-specific
   filter rules (e.g., (S,*), (*,G)) installed at proxy interfaces.
   These filters MAY be derived in parts from PMIPv6 routing policies,
   and can include a default behavior (e.g., (*,*)).

5.1.1.  Operations for Local Multicast Sources

   Packets from a locally attached multicast source will be forwarded to
   all downstream interfaces with appropriate subscriptions, as well as
   up the interface with the matching source-specific filter.

   Typically, the upstream interface for a mobile multicast source is
   chosen based on the policy routing (e.g., the MAG-LMA tunnel
   interface for LMA-based routing or the interface towards the
   multicast router for direct routing), but alternate configuriations
   MAY be applied.  Packets from a locally attached multicast source
   will be forwarded to the corresponding upstream interface with the
   matching source-specific filter, as well as all the downstream
   interfaces with appropriate subscriptions.





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5.1.2.  Operations for Local Multicast Subscribers

   Multicast listener reports are group-wise aggregated by the MLD
   proxy.  The aggregated report is issued to the upstream interface
   with matching group/channel-specific filter.  The choice of the
   corresponding upstream interface for aggregated group membership
   reports MAY be additionally based on some administrative scoping
   rules for scoped multicast group addresses.

   In detail, a Multiple Upstream Interface Proxy will provide and
   maintain a Multicast Subscription Filter Table that maps source- and
   group-specific filters to upstream interfaces.  The forwarding
   decision for an aggregated MLD listener report is based on the first
   matching entry from this table, with the understanding that for
   IGMPv3/MLDv2 the MLD Proxy performs a state decomposition , if needed
   (i.e., a (*,G) subscription is split into (S,G) and (* \ S,G) in the
   presence of (*,G) after (S,G) interface entries), and that
   (S,*)-filters are always false in the absence of source-specific
   signaling, i.e. in IGMPv2/MLDv1 only domains.

   In typical deployment scenarios, specific group services (channels)
   could be either associated with selected uplinks to remote LMAs,
   while a (*,*) default subscription entry (in the last table line) is
   bound to a local routing interface, or selected groups are configured
   as local services first, while a (*,*) default entry (in the last
   table line) points to a remote uplink that provides the general
   multicast support.

5.2.  Peering Function for MLD Proxies

   In this section, we define a peering interface for MLD proxies that
   allows for a direct data exchange of locally attached multicast
   sources.  Such peering interfaces can be configured - as a direct
   link or a bidirectional tunnel - between any two proxy instances
   (locally deployed as in [RFC6224] or remotely) and remain as silent
   virtual links in regular proxy operations.  Data on such link is
   exchanged only in cases, where one peering proxy directly connects on
   the downstream to a source of multicast traffic, which the other
   peering proxy actively subscribes to.  Operations are defined for ASM
   and SSM, but provide superior performance in the presence of source-
   specific signaling (IGMPv3/MLDv2).

5.2.1.  Operations at the Multicast Sender

   An MLD Proxy in the perspective of a sender will see peering
   interfaces as restricted downstream interfaces.  It will install and
   maintain source filters at its peering links that will restrict data
   transmission to those packets that originate from a locally attached



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   source at the downstream.  In detail, a proxy will extract from its
   configuration the network prefixes attached to its downstream
   interfaces and MUST implement a source filter base at its peering
   interfaces that restricts data transmission to IP source addresses
   from its local prefixes.  This filter base Must be updated, if and
   only if the downstream configuration changes.  In this way, a
   multihop forwarding on peering links is prevented.  Multicast packets
   that arrive from the upstream interface of the proxy are thus only
   forwarded to regular downstream interfaces with appropriate
   subscription states.

   Multicast traffic arriving from a locally attached source will be
   forwarded to the regular upstream interface and all downstreams with
   appropriate subscription states (i.e., regular Proxy operations).  In
   addition, local multicast packets are transferred to those peering
   interfaces with appropriate subscription states.

5.2.2.  Operations at the Multicast Listener

   From the listener side, peering interfaces appear as preferred
   upstream links.  Thus an MLD proxy with peering interconnects will
   offer several interfaces for pulling remote traffic: the regular
   upstream and the peerings.  Traffic arriving from any of the peering
   links will be mutually disjoint, but normally also available from the
   upstream.  To prevent duplicate traffic from arriving at the listener
   side, the proxy

   o  MAY delay aggregated reports to the upstream, and

   o  MUST apply appropriate filters to exclude duplicate streams.

   In detail, it first issues listener reports (in parallel) to its
   peering links, which only span one (virtual) hop.  Whenever the
   expected traffic (e.g., SSM channels) does not completely arrive from
   the peerings after a waiting time (default: 10 ms), additional
   (complementary, in the case of SSM) reports are sent to the standard
   upstream interface.

   After the arrival of traffic from peering links, an MLD proxy MUST
   install source filters at the upstream in the following way.

   ASM with IGMPv2/MLDv1  In the presence of Any Source Multicast using
      IGMPv2/MLDv1, only, the proxy cannot signal source filtering to
      its upstream.  Correspondingly, it applies (S,*) ingress filters
      at its upstream interface for all sources S seen in traffic of the
      peering links.  It is noteworthy that unwanted traffic is still
      replicated to the proxy via the access network.




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   ASM with IGMPv3/MLDv2  In the presence of source-specific signaling
      (IGMPv3/MLDv2), the upstream interface is set to (S,*) exclude
      mode for all sources S seen in traffic of the peering links.  The
      corresponding source-specific signaling will prevent duplicate
      traffic forwarding throughout the access network.

   SSM  In the presence of Source Specific Multicast, the proxy will
      subscribe on its uplink interface to those (S,G) channels, only,
      that do not arrive via the peering links.

   In proceeding this way, multicast group data arrive from peering
   interfaces first, while only peer-wise unavailable traffic is
   retrieved from the regular upstream interface.


6.  IANA Considerations

   TODO.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.


7.  Security Considerations

   TODO

   Consequently, no new threats are introduced by this document in
   addition to those identified as security concerns of [RFC3810],
   [RFC4605], [RFC5213], and [RFC5844].

   However, particular attention should be paid to implications of
   combining multicast and mobility management at network entities.  As
   this specification allows mobile nodes to initiate the creation of
   multicast forwarding states at MAGs and LMAs while changing
   attachments, threats of resource exhaustion at PMIP routers and
   access networks arrive from rapid state changes, as well as from high
   volume data streams routed into access networks of limited
   capacities.  In addition to proper authorization checks of MNs, rate
   controls at replicators MAY be required to protect the agents and the
   downstream networks.  In particular, MLD proxy implementations at
   MAGs SHOULD carefully procure for automatic multicast state
   extinction on the departure of MNs, as mobile multicast listeners in
   the PMIPv6 domain will not actively terminate group membership prior
   to departure.






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8.  Acknowledgements

   The authors would like to thank (in alphabetical order) Luis M.
   Contreras, Muhamma Omer Farooq, Bohao Feng, Dirk von Hugo, Ning Kong,
   Jouni Korhonen, He-Wu Li, Akbar Rahman, Stig Venaas, Li-Li Wang, Qian
   Wu, Zhi-Wei Yan for advice, help and reviews of the document.
   Funding by the German Federal Ministry of Education and Research
   within the G-LAB Initiative (project HAMcast) is gratefully
   acknowledged.


9.  References

9.1.  Normative References

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

   [RFC2710]  Deering, S., Fenner, W., and B. Haberman, "Multicast
              Listener Discovery (MLD) for IPv6", RFC 2710,
              October 1999.

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

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

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

   [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.

   [RFC5015]  Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
              "Bidirectional Protocol Independent Multicast (BIDIR-
              PIM)", RFC 5015, October 2007.

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

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




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

9.2.  Informative References

   [I-D.ietf-multimob-pmipv6-ropt]
              Zuniga, J., Contreras, L., Bernardos, C., Jeon, S., and Y.
              Kim, "Multicast Mobility Routing Optimizations for Proxy
              Mobile IPv6", draft-ietf-multimob-pmipv6-ropt-01 (work in
              progress), September 2012.

   [RFC2236]  Fenner, W., "Internet Group Management Protocol, Version
              2", RFC 2236, November 1997.

   [RFC5757]  Schmidt, T., Waehlisch, M., and G. Fairhurst, "Multicast
              Mobility in Mobile IP Version 6 (MIPv6): Problem Statement
              and Brief Survey", RFC 5757, February 2010.

   [RFC5845]  Muhanna, A., Khalil, M., Gundavelli, S., and K. Leung,
              "Generic Routing Encapsulation (GRE) Key Option for Proxy
              Mobile IPv6", RFC 5845, June 2010.

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


Appendix A.  Evaluation of Traffic Flows

   TODO


Appendix B.  Change Log

   The following changes have been made from version
   draft-ietf-multimob-pmipv6-source-01:

   1.  Added clarifications and details as requested be the working
       group, resolved nits.

   2.  Detailed out operations of Multiple Upstream MLD Proxies.

   3.  Clarified operations of MLD proxies with peering links.

   4.  Many editorial improvements.

   5.  Updated references.




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   The following changes have been made from version
   draft-ietf-multimob-pmipv6-source-00:

   1.  Direct routing with PIM-SM and PIM-SSM has been added.

   2.  PMIP synchronization with PIM added for improved handover.

   3.  Direct routing with BIDIR-PIM has been added.

   4.  MLD Proxy extensions requirements added.

   5.  Peering of MLD Proxies added.

   6.  First sketch of multiple upstream proxy added.

   7.  Editorial improvements.

   8.  Updated references.


Authors' Addresses

   Thomas C. Schmidt
   HAW Hamburg
   Berliner Tor 7
   Hamburg  20099
   Germany

   Email: schmidt@informatik.haw-hamburg.de
   URI:   http://inet.cpt.haw-hamburg.de/members/schmidt


   Shuai Gao
   Beijing Jiaotong University
   Beijing,
   China

   Phone:
   Fax:
   Email: shgao@bjtu.edu.cn
   URI:










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   Hong-Ke Zhang
   Beijing Jiaotong University
   Beijing,
   China

   Phone:
   Fax:
   Email: hkzhang@bjtu.edu.cn
   URI:


   Matthias Waehlisch
   link-lab & FU Berlin
   Hoenower Str. 35
   Berlin  10318
   Germany

   Email: mw@link-lab.net

































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