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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. Schmidt, Ed.
Internet-Draft                                               HAW Hamburg
Intended status: Experimental                                     S. Gao
Expires: October 2, 2014                                        H. Zhang
                                             Beijing Jiaotong University
                                                            M. Waehlisch
                                                    link-lab & FU Berlin
                                                          March 31, 2014


 Mobile Multicast Sender Support in Proxy Mobile IPv6 (PMIPv6) Domains
                  draft-ietf-multimob-pmipv6-source-09

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 a base solution and an experimental protocol
   to support mobile multicast senders in Proxy Mobile IPv6 domains for
   all three scenarios.  Protocol optimizations for synchronizing PMIPv6
   with PIM, as well as a peering function for MLD Proxies are defined.
   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 October 2, 2014.



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Copyright Notice

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

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Base Solution for Source Mobility and PMIPv6 Routing  . . . .   4
     3.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Base Solution for Source Mobility: Details  . . . . . . .   8
       3.2.1.  Operations of the Mobile Node . . . . . . . . . . . .   8
       3.2.2.  Operations of the Mobile Access Gateway . . . . . . .   8
       3.2.3.  Operations of the Local Mobility Anchor . . . . . . .   8
       3.2.4.  IPv4 Support  . . . . . . . . . . . . . . . . . . . .   9
       3.2.5.  Efficiency of the Distribution System . . . . . . . .  10
   4.  Direct Multicast Routing  . . . . . . . . . . . . . . . . . .  11
     4.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .  11
     4.2.  MLD Proxies at MAGs . . . . . . . . . . . . . . . . . . .  12
       4.2.1.  Considerations for PIM-SM on the Upstream . . . . . .  13
       4.2.2.  SSM Considerations  . . . . . . . . . . . . . . . . .  13
     4.3.  PIM-SM at MAGs  . . . . . . . . . . . . . . . . . . . . .  13
       4.3.1.  Routing Information Base for PIM-SM . . . . . . . . .  13
       4.3.2.  Operations of PIM in Phase One (RP Tree)  . . . . . .  14
       4.3.3.  Operations of PIM in Phase Two (Register-Stop)  . . .  15
       4.3.4.  Operations of PIM in Phase Three (Shortest-Path Tree)  15
       4.3.5.  PIM-SSM Considerations  . . . . . . . . . . . . . . .  16
       4.3.6.  Handover Optimizations for PIM  . . . . . . . . . . .  16
     4.4.  BIDIR-PIM . . . . . . . . . . . . . . . . . . . . . . . .  17
       4.4.1.  Routing Information Base for BIDIR-PIM  . . . . . . .  17
       4.4.2.  Operations of BIDIR-PIM . . . . . . . . . . . . . . .  17
   5.  MLD Proxy Peering Function for Optimized Source Mobility in
       PMIPv6  . . . . . . . . . . . . . . . . . . . . . . . . . . .  18
     5.1.  Requirements  . . . . . . . . . . . . . . . . . . . . . .  18
     5.2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .  18
     5.3.  Operations in Support of Multicast Senders  . . . . . . .  19
     5.4.  Operations in Support of Multicast Listeners  . . . . . .  19



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   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  21
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  22
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  22
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  22
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  23
   Appendix A.  Multiple Upstream Interface Proxy  . . . . . . . . .  24
     A.1.  Operations for Local Multicast Sources  . . . . . . . . .  24
     A.2.  Operations for Local Multicast Subscribers  . . . . . . .  24
   Appendix B.  Implementation . . . . . . . . . . . . . . . . . . .  25
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25

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
   [I-D.ietf-multimob-fmipv6-pfmipv6-multicast], or by selective route
   optimization schemes [RFC7028].  Such approaches (partially) follow
   the model of providing multicast data services in parallel to PMIPv6
   unicast routing [I-D.ietf-multimob-handover-optimization].

   Multicast listener support satisfies the needs of receptive use cases
   such as IPTV or server-centric gaming on mobiles.  However, current
   trends in the Internet develop 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




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   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.

2.  Terminology

   This document uses the terminology as defined for the mobility
   protocols [RFC6275], [RFC5213] and [RFC5844], as well as the
   multicast routing [RFC4601] and edge related protocols [RFC3376],
   [RFC3810] and [RFC4605].

   Throught this document, we use the following acronyms

   HNP  Home Network Prefix as defined in [RFC5213].

   MAG  Mobile Access Gateway as defined in [RFC5213]

   MLD  Multicast Listener Discovery as defined in [RFC2710] and
      [RFC3810].

   PIM  Protocol Independent Multicast as defined in [RFC4601].

   PMIPv6  Proxy Mobile IPv6 as defined in [RFC5213].

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.  It displays the general setting
   for source mobility - Mobile Nodes (MNs) with Home Network Prefixes
   (HNPs) that receive services via tunnels, which are spanned between a
   Local Mobility Anchor Address (LMAA) and a Proxy Care-of-Address
   (Proxy-CoA) at a Mobility Access Gateway (MAG).  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

   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 instructions for packet processing, i.e., a multicast
   routing information base (MRIB).





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   An MN can successfully distribute multicast data in PMIPv6, if MLD
   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 (being unaware of IP mobility) can
   continue to send multicast packets as soon as network connectivity is
   re-established.  At this time, the MAG has determined the
   corresponding LMA, and IPv6 unicast address configuration (including
   PMIPv6 bindings) has been completed.  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 Section 5 for further
   optimizations).





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3.2.  Base Solution for Source Mobility: Details

   A support of 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
   transmission 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 MUST 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 (DR) 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
   Reverse Path Forwarding (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



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   identification.  This scenario implies that unicast communication in
   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 is transmitted as router-to-router
   forwarding via the MAG-to-LMA tunnels and according to the multicast
   routing information base (MRIB) of the MAG or the LMA.  It remains
   independent of MN's unicast addresses, while the MAG proxy instance
   redistributes multicast data down the point-to-point links
   (interfaces) according to its local subscription states, independent
   of IP addresses of the MN.

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.

   These remaining deficits in routing efficiency can be resolved by
   adding peering functions to MLD proxies as described in Section 5.







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4.  Direct Multicast Routing

   There are deployment scenarios, where multicast services are
   available throughout the access network independent of the PMIPv6
   routing system [RFC7028].  In these cases, the visited networks grant
   a local content distribution service (in 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 Appendix A for further discussions).

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



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   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
   a single multicast routing domain.  Notably, 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 transfer 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 to a new MAG and can
   continue to send multicast packets as soon as PMIPv6 unicast
   configurations have been 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 multicast 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 an interim packet loss (see 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 at MAGs

   The full-featured multicast routing protocol PIM-SM MAY be deployed
   in the access network for providing multicast services in parallel to
   unicast routes (see Figure 3 b).  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 (specific phase)
   of its deployment.

   For all three phases in the operation of PIM (see [RFC4601]), the
   following information is needed.

   o  All routes to networks and nodes (including RPs) that are not
      mobile members of the PMIPv6 domain MUST be defined consistently



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      among PIM routers and MUST remain unaffected 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.

   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  Local routes to the Home Network Prefixes (HNPs) of all MNs
      associated with their corresponding point-to-point attachments
      that MUST be included in 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 (RP Tree)

   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 (i.e., 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 that introduces
   little overhead.  In a PMIPv6 deployment, PIM RPs MAY be configured
   to not initiated (S,G) shortest path trees 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 (Register-Stop)

   After receiving source register packets, a PIM RP eventually will
   initiate 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 the HNP of the
   MN 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, down the LMA-MAG tunnel to the
   mobile source.  This tree can be of lower routing efficiency than the
   PIM source register tunnel established in phase one.

   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 with the RP.  In
   response, the PIM RP will recognize the known source at a new
   (tunnel) interface and immediately responds with a register stop.  As
   the RP had previously joined the shortest path tree towards the
   source via the LMA, it will see an RPF change when data arrives at a
   new interface.  Implementation-dependent, this can trigger an update
   of the PIM MRIB and trigger a new PIM Join message that will install
   the multicast forwarding state missing at the new MAG.  Otherwise,
   the tree is periodically updated by Joins transmitted towards the new
   MAG on a path via the LMA.  In proceeding this way, a quick recovery
   of PIM transition from phase one to two will be performed per
   handover.

4.3.4.  Operations of PIM in Phase Three (Shortest-Path Tree)

   In response to an exceeded threshold of packet transmission, DRs of
   receivers eventually will initiate 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 range from
   the receiving DR via the (stable) LMA, the LMA-MAG tunnel, and the
   serving MAG to the mobile source.  This tree is of higher routing
   efficiency than that 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



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   and initiate a source registering of PIM phase one.  A PIM
   implementation compliant with this change can recover phase three
   states in the following way.  First, the RP recovers to phase two as
   described in the previous section, and will not forward data arriving
   via the source register tunnel.  Tree maintenance eventually
   triggered by the RPF change (see Section 4.3.3) will generate proper
   states for a native forwarding from the new MAG via the LMA.
   Thereafter, packets arriving at the LMA without source register
   encapsulation are forwarded natively along the shortest path tree
   towards receivers.

   In consequence, the PIM transitions from phase one to two and to
   three will be quickly recovered per handover, but still lead to an
   enhanced signaling load and intermediate packet loss.

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 reestablished
   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 distribution services.

   A method to quickly recover PIM (S,G) trees under handover SHOULD
   synchronize multicast state maintenance with unicast handover
   operations and can 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.



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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.

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 unaffected 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 pre-configured RPAs and the routing information
   provided.  Multicast data transmitted by a mobile source will
   immediately be forwarded by its DF (MAG) onto the spanning tree for
   the multicast group without further protocol operations.

   On handover, the mobile source reattaches 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.





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5.  MLD Proxy Peering Function 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], [RFC7028].  However, deploying unmodified standard proxies
   can go along with significant performance degradation for mobile
   senders as discussed along the lines of this document.  To overcome
   these deficits, an optimized approach to multicast source mobility
   based on extended peering functions among proxies is defined in this
   section.  Based on such direct data exchange between proxy instances
   at MAGs, triangular routing is avoided and multicast streams can be
   disseminated directly within a PMIPv6 access network, and in
   particular within MAG routing machines.  Prior to presenting the
   solution, we will summarize the relevant requirements.

5.1.  Requirements

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

   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 local filter techniques, these requirements are met in the
   following solution.

5.2.  Overview

   A peering interface for MLD proxies 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).  Peerings remain as silent virtual links in regular proxy
   operations.  Data is exchanged on such links only in cases, where one
   peering proxy on its downstream directly connects to a source of
   multicast traffic, which the other peering proxy actively subscribes
   to.  In such cases, the proxy connected to the source will receive a
   listener report on its peering interface and forwards traffic from
   its local source accordingly.  It is worth noting that multicast
   traffic distribution on peering links does not follow reverse unicast
   paths to sources.  In the following, operations are defined for ASM




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   and SSM, but provide superior performance in the presence of source-
   specific signaling (IGMPv3/MLDv2) [RFC4604].

5.3.  Operations in Support of Multicast Senders

   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 source that is
   locally attached at one of its downstream interfaces.

   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 (e.g., due to mobility).  Multicast packets
   that arrive from the upstream interface of the proxy are thus
   prevented from traversing any peering link, but are only forwarded to
   regular downstream interfaces with appropriate subscription states.
   In this way, a multihop forwarding on peering links is prevented.

   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, multicast packets of local origin are transferred to those
   peering interfaces with appropriate subscription states.

5.4.  Operations in Support of Multicast Listeners

   At the listener side, peering interfaces appear as preferred upstream
   links.  The multicast proxy will attempt to receive multicast
   services on peering links for as many groups (channels) as possible.
   The general upstream interface configured according to [RFC4605] will
   be used only for retrieving those groups (channels) that remain
   unavailable from peerings.  From this extension of [RFC4605], an MLD
   proxy with peering interconnects will exhibit several interfaces for
   pulling remote traffic: the regular upstream and the peerings.
   Traffic available 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, an MLD proxy instance at a MAG first issues listener
   reports (in parallel) to all of its peering links.  These links span



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   at most one (virtual) hop.  Whenever certain group traffic (SSM
   channels) does not arrive from the peerings after a waiting time
   (default: 10 ms (node-local) and 25 ms (remote)), additional
   (complementary, in the case of SSM) reports are sent to the standard
   upstream interface.

   Whenever traffic from a peering link arrives, an MLD proxy MUST
   install source filters at its RFC 4605 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 on the
      peering links.  It is noteworthy that unwanted traffic is still
      replicated to the proxy via the (wired) provider backbone, but it
      is not forwarded into the wireless access network.

   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 forwarding of
      duplicate traffic 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.

   MLD proxies will install data-driven timers (source-timeout) for each
   source but common to all peering interfaces to detect interruptions
   of data services from individual sources at proxy peers.  Termination
   of source-specific flows may be application-specific, but also due to
   a source handover, or transmission failures.  After a handover, a
   mobile source may reattach at another MLD proxy with peering relation
   to the listener, or at a proxy that does not peer.  While in the
   first case, traffic reappears on another peering link, in the second
   case data can only be retrieved via the regular upstream.  To account
   for the latter, the MLD proxy revokes the source-specific filter(s)
   at its upstream interface, after the source-timeout fires (default:
   50 ms).  Corresponding traffic will then be pulled from the regular
   upstream.  Source-specific filters MUST be reinstalled, whenever
   traffic of this source arrives at any peering interface.

   There is a noteworthy trade-off between traffic minimization and
   available traffic at the upstream that is locally filtered at the
   proxy.  Implementors can use this relation to optimize for service-
   specific requirements.





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

6.  IANA Considerations

   This document makes no request to IANA..

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

7.  Security Considerations

   This document defines multicast sender mobility based on PMIPv6 and
   common multicast routing protocols.  Consequently, threats identified
   as security concerns of [RFC2236], [RFC2710], , [RFC3810], [RFC4605],
   [RFC5213], and [RFC5844] are inherited by this document.

   In addition, 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 cases of PIM-SM deployment, handover operations of
   the MNs include re-registering sources at the Rendezvous Points at
   possibly high frequency.  In addition to proper authorization checks
   of MNs, rate controls at routing agents and replicators may be needed
   to protect the agents and the downstream networks.  In particular,
   MLD proxy implementations at MAGs SHOULD automatically extinct
   multicast state on the departure of MNs, as mobile multicast
   listeners in the PMIPv6 domain will in general not actively terminate
   group membership prior to departure.

   The deployment of IGMP/MLD proxies for multicast routing requires
   particular care, as routing loops on the upstream are not
   automatically detected.  Peering functions between proxies extend
   this threat in the following way.  Routing loops among peering and
   upstream interfaces are prevented by filters on local sources.  Such
   filtering can fail, whenever prefix configurations for downstream
   interfaces at a proxy are incorrect or inconsistent.  Consequently,
   implementations of peering-enabled proxies SHOULD take particular
   care on keeping IP configurations consistent at the downstream in a
   reliable and timely manner (see [RFC6224] for requirements on
   PMIPv6-compliant implementations of MLD proxies).





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8.  Acknowledgements

   The authors would like to thank (in alphabetical order) David Black,
   Luis M. Contreras, Spencer Dawkins, Muhamma Omer Farooq, Bohao Feng,
   Sri Gundavelli, Dirk von Hugo, Ning Kong, Jouni Korhonen, He-Wu Li,
   Cong Liu, Radia Perlman, Akbar Rahman, Behcet Sarikaya, Stig Venaas,
   Li-Li Wang, Sebastian Woelke, 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 (projects
   HAMcast, Mindstone and SAFEST) 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-fmipv6-pfmipv6-multicast]
              Schmidt, T., Waehlisch, M., Koodli, R., Fairhurst, G., and
              D. Liu, "Multicast Listener Extensions for MIPv6 and
              PMIPv6 Fast Handovers", draft-ietf-multimob-
              fmipv6-pfmipv6-multicast-05 (work in progress), March
              2014.

   [I-D.ietf-multimob-handover-optimization]
              Contreras, L., Bernardos, C., and I. Soto, "PMIPv6
              multicast handover optimization by the Subscription
              Information Acquisition through the LMA (SIAL)", draft-
              ietf-multimob-handover-optimization-07 (work in progress),
              December 2013.

   [Peering-Analysis]
              Schmidt, TC., Woelke, S., and M. Waehlisch, "Peer my Proxy
              - A Performance Study of Peering Extensions for Multicast
              in Proxy Mobile IP Domains", Proc. of 7th IFIP Wireless
              and Mobile Networking Conference (WMNC 2014) IEEEPress,
              May 2014.

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

   [RFC4604]  Holbrook, H., Cain, B., and B. Haberman, "Using Internet
              Group Management Protocol Version 3 (IGMPv3) and Multicast
              Listener Discovery Protocol Version 2 (MLDv2) for Source-
              Specific Multicast", RFC 4604, August 2006.

   [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.






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

Appendix A.  Multiple Upstream Interface Proxy

   In this section, we document upstream extensions for an MLD proxy
   that were originally developed during the work on this document.
   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., (*,*)).

A.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 configurations
   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.

A.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.



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   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.

Appendix B.  Implementation

   An implementation of the extended IGMP/MLD proxy has been provided
   within the MCPROXY project http://mcproxy.realmv6.org/. This open
   source software is written in C++ and uses forwarding capabilities of
   the Linux kernel.  It supports all regular operations according to
   [RFC4605], allows for multiple proxy instances on one node,
   dynamically changing downstream links, as well as proxy-to-proxy
   peerings and multiple upstream links with individual configurations.
   The software can be downloaded from Github at https://github.com/
   mcproxy/mcproxy.  Based on this software, an experimental performance
   evaluation of the proxy peering function has been reported in
   [Peering-Analysis].

Authors' Addresses

   Thomas C. Schmidt (editor)
   HAW Hamburg
   Berliner Tor 7
   Hamburg  20099
   Germany

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








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   Shuai Gao
   Beijing Jiaotong University
   Beijing
   China

   Email: shgao@bjtu.edu.cn


   Hong-Ke Zhang
   Beijing Jiaotong University
   Beijing
   China

   Email: hkzhang@bjtu.edu.cn


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

   Email: mw@link-lab.net




























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