MULTIMOB Group                                                 H. Asaeda
Internet-Draft                                           Keio University
Intended status: Standards Track                                P. Seite
Expires: September 27, 2012                               France Telecom
                                                          March 26, 2012


          Multicast Routing Optimization by PIM-SM with PMIPv6
                draft-asaeda-multimob-pmip6-extension-09

Abstract

   This document describes IP multicast routing optimization using
   PIM-SM in Proxy Mobile IPv6 (PMIPv6) environment.  The Mobile Access
   Gateway (MAG) and the Local Mobility Anchor (LMA) are the mobility
   entities defined in the PMIPv6 protocol and act as PIM-SM routers.
   The proposed protocol optimization addresses the tunnel convergence
   problem and provides seamless handover.

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
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   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 September 27, 2012.

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



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions and Terminology  . . . . . . . . . . . . . . . . .  4
   3.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.1.  Multicast Communication in PMIPv6  . . . . . . . . . . . .  4
     3.2.  Protocol Sequence for Multicast Channel Subscription . . .  6
   4.  Multicast Tunnel (M-Tunnel)  . . . . . . . . . . . . . . . . .  7
     4.1.  Packet Encapsulation . . . . . . . . . . . . . . . . . . .  7
     4.2.  Multiple M-Tunnels and ECMP Routing  . . . . . . . . . . .  8
   5.  Local Mobility Anchor Operation  . . . . . . . . . . . . . . .  9
   6.  Mobile Access Gateway Operation  . . . . . . . . . . . . . . . 10
   7.  Mobile Node Operation  . . . . . . . . . . . . . . . . . . . . 11
   8.  Smooth Handover  . . . . . . . . . . . . . . . . . . . . . . . 11
     8.1.  Handover with Policy Profile . . . . . . . . . . . . . . . 11
     8.2.  Handover with Extended Proxy Binding Update and
           Acknowledgement  . . . . . . . . . . . . . . . . . . . . . 14
   9.  Message Format Extension . . . . . . . . . . . . . . . . . . . 16
     9.1.  Proxy Binding Update with Multicast Extension  . . . . . . 16
     9.2.  Proxy Binding Acknowledgement Message with Multicast
           Extension  . . . . . . . . . . . . . . . . . . . . . . . . 19
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
   11. Security Considerations  . . . . . . . . . . . . . . . . . . . 21
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 21
     13.2. Informative References . . . . . . . . . . . . . . . . . . 22
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22



















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1.  Introduction

   Proxy Mobile IPv6 (PMIPv6) [1] enables network-based mobility for
   IPv6 mobile nodes (MNs) that do not implement any mobility protocols.
   The Local Mobility Anchor (LMA) is the topological anchor point to
   manages the mobile node's binding state.  The Mobile Access Gateway
   (MAG) is an access router or gateway that manages the mobility-
   related signaling for an MN.  An MN is attached to the Proxy Mobile
   IPv6 Domain (PMIPv6-Domain) that includes LMA and MAG(s), and is able
   to receive data coming from outside of the PMIPv6-Domain through LMA
   and MAG.

   Network-based mobility support for unicast is addressed in [1], while
   multicast support in PMIPv6 is not discussed in it.  Since LMA and
   MAG set up a bi-directional IPv6-in-IPv6 tunnel for each mobile node
   and forwards all mobile node's traffic according to [1], it highly
   wastes network resources when a large number of mobile nodes join/
   subscribe the same multicast sessions/channels, because independent
   data copies of the same multicast packet are delivered to the
   subscriber nodes in a unicast manner through MAG.

   The base solution described in [11] provides options for deploying
   multicast listener functions in PMIPv6-Domains without modifying
   mobility and multicast protocol standards.  However, in this
   specification, MAG MUST act as an MLD proxy [2] and hence MUST
   dedicate a tunnel link between LMA and MAG to an upstream interface
   for all multicast traffic.  This limitation does not allow to use
   PIM-SM native routing on MAG, and hence does not solve the tunnel
   convergence problem; MAG receives the same data from multiple LMAs
   when MAG attaches to them for mobile nodes and has subscribed the
   same multicast channel to them.  It does not enable direct routing
   and does not optimize source mobility.

   This document describes IP multicast routing optimization using
   PIM-SM in Proxy Mobile IPv6 (PMIPv6) environment.  The Mobile Access
   Gateway (MAG) and the Local Mobility Anchor (LMA) are the mobility
   entities defined in the PMIPv6 protocol and act as PIM-SM routers.
   The proposed protocol optimization assumes that both LMA and MAG
   enable the Protocol-Independent Multicast - Sparse Mode (PIM-SM)
   multicast routing protocol [3].  The proposed optimization uses a
   dedicated GRE [4] tunnel for multicast, called M-Tunnel, between LMA
   and MAG.  The proposed protocol optimization addresses the tunnel
   convergence problem and provides seamless handover.  It can cooperate
   with local routing and direct routing to deliver IP multicast packets
   for mobile nodes and source mobility.  In this document, because
   multicast listener mobility is mainly focused on, the detail
   specification of source mobility is not described.




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   This document does not require to change unicast communication
   methods or protocols defined in [1], and therefore both unicast and
   multicast communications for mobile nodes in PMIPv6-Domain are
   enabled if this extension is implemented.


2.  Conventions and Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
   NOT","SHOULD", "SHOULD NOT", "RECOMMENDED","MAY", and "OPTIONAL" in
   this document are to be interpreted as described in RFC 2119 [5].

   The following terms used in this document are to be interpreted as
   defined in the Proxy Mobile IPv6 specification [1]; Mobile Access
   Gateway (MAG), Local Mobility Anchor (LMA), Mobile Node (MN), Proxy
   Mobile IPv6 Domain (PMIPv6-Domain), LMA Address (LMAA), Proxy Care-of
   Address (Proxy-CoA), Mobile Node's Home Network Prefix (MN-HNP),
   Mobile Node Identifier (MN-Identifier), Proxy Binding Update (PBU),
   and Proxy Binding Acknowledgement (PBA).


3.  Overview

3.1.  Multicast Communication in PMIPv6

   Required components to enable IP multicast are multicast routing
   protocols and host-and-router communication protocols.  This document
   assumes PIM-SM [3] as the multicast routing protocol and Multicast
   Listener Discovery (MLD) as the host-and-router communication
   protocol.  This document allows mobile nodes to participate in Any-
   Source Multicast (ASM) and Source-Specific Multicast (SSM) [6].
   However, in order to explicitly participate in SSM, mobile nodes MUST
   support either MLDv2 [7] or Lightweight-MLDv2 (LW-MLDv2) [8].

   The architecture of a Proxy Mobile IPv6 domain is shown in Figure 1.
   LMA and MAG are the core functional entities in PMIPv6-Domain.  The
   entire PMIPv6-Domain appears as a single link from the perspective of
   each mobile node.













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                       +---------+
                       | Content |
                       | Source  |
                       +---------+
                            |
                 ***  ***  ***  ***  ***
                *   **   **   **   **   *
               *                         *
                *     Fixed Internet    *
               *                         *
                *   **   **   **   **   *
                 ***  ***  ***  ***  ***
                     /            \
                  +----+        +----+
                  |LMA1|        |LMA2|
                  +----+        +----+
           LMAA1 -> |              | <-- LMAA2
                    |              |
                    \\            //\\
                     \\          //  \\
                      \\        //    \\
                       \\      //      \\
                        \\    //        \\
                         \\  //          \\
             Proxy-CoA1--> |              | <-- Proxy-CoA2
                        +----+          +----+
                        |MAG1|---{MN2}  |MAG2|
                        +----+  |       +----+
                          |     |         |
             MN-HNP1 -->  |   MN-HNP2     |  <-- MN-HNP3, MN-HNP4
                        {MN1}           {MN3}

                    Figure 1: Proxy Mobile IPv6 Domain

   When a mobile node wants to subscribe/unsubscribe a multicast
   channel, it sends MLD Report messages specifying sender and multicast
   addresses to the access link.  The attached MAG detects this
   membership information and sends the PIM Join/Prune message to the
   corresponding LMA over the LMA-MAG bi-directional IPv6-in-IPv6 tunnel
   when the LMA is selected as the previous-hop router for the multicast
   channel, or sends the PIM Join/Prune message to the adjacent upstream
   multicast router for the multicast channel.  When the LMA or the
   adjacent router receives the PIM Join/Prune message, it coordinates
   the corresponding multicast routing tree if necessary and starts
   forwarding the data.

   When the MAG detects mobile node's handover, it can proceed the
   seamless handover procedures.  Since both PMIPv6 and multicast



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   protocols (i.e., MLD and PIM-SM) do not have functions for multicast
   context transfer in their original protocol specifications, the
   external functions or protocols should be used for handover.  One of
   the possibile ways is the use of "mobile node's Policy Profile", as
   it could include "multicast channel information", which expresses
   mobile node's subscribing multicast channel list, as well as the
   mandatory fields of the Policy Profile specified in [1].  Mobile
   node's Policy Profile is provided by "policy store" whose definition
   is the same as of [1].

3.2.  Protocol Sequence for Multicast Channel Subscription

   A mobile node sends unsolicited MLD Report messages including source
   and multicast addresses when it subscribes a multicast channel.
   Although MLDv2 specification [7] permits to use the unspecified
   address (::) for a host whose interface has not acquired a valid
   link-local address yet, MAG SHOULD send MLDv2 Report messages with a
   valid IPv6 link-local source address as defined in [12].  As well,
   MLDv2 Report messages MAY be sent with an IP destination address of
   FF02:0:0:0:0:0:0:16, to which all MLDv2-capable multicast routers
   listen, but the IP unicast address of the attached MAG SHALL be used
   for the destination of MLDv2 Report messages.

   When the MAG operating as a PIM-SM router receives MLD Report
   messages from attached mobile nodes, it joins the multicast delivery
   tree by sending PIM Join messages to its neighboring routers
   (Figure 2).  When the upstream router for the requested channel is
   LMA, the MAG sends the corresponding PIM Join messages over the
   regular LMA-MAG bi-directional tunnel, if the MAG has no multicast
   state for the requested channel.  When the upstream router for the
   requested channel is an adjacent router that is not the LMA, the MAG
   sends the corresponding PIM Join messages to the adjacent upstream
   router natively, if the MAG has no multicast state for the requested
   channel.  The LMA or the adjacent upstream router then joins the
   multicast delivery tree and forwards the packets to the downstream
   MAG.















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   MN1        MN2             MAG                 LMA
    |          |               |                   |
    |------MLD Report--------->|                   |
    |     (S1,G1) join         |  PIM (S1,G1) Join |
    |          |               |===== M-Tunnel ===>|
    |          |               |                   |---> PIM (S1,G1) Join
    |          |               |                   |
    |          |--MLD Report-->|                   |
    |          | (S2,G2) join  |                   |
    |          |               |---> PIM (S2,G2) Join
    |          |               |                   |
    |          |--MLD Report-->|                   |
    |          | (S1,G1) join  |                   |
    |          |               |                   |

                Figure 2: MLD Report Messages Transmission

   The MAG selects only one upstream link for a multicast channel by the
   Reverse Path Forwarding (RPF) algorithm even if the MAG has
   established multiple bi-directional tunnels for unicast transmission
   to different LMAs.  This does not cause the tunnel convergence
   problem, because Multicast Routing Information Base (MRIB) used by
   PIM-SM selects only one incoming interface for each multicast channel
   and hence duplicate packets are not forwarded to the MAG.


4.  Multicast Tunnel (M-Tunnel)

4.1.  Packet Encapsulation

   M-Tunnel is a bi-directional GRE tunnel [4] dedicated for PIM
   messages and IP multicast data transmissions between LMA and MAG.
   M-Tunnel is established between PIM-SM capable LMA and MAG.  It can
   be established in a bootstrap phase of MAG (without detecting a
   multicast channel subscription request from a mobile node) and kept
   while the MAG enables PIM routing functions to forward multicast
   packets.  M-Tunnel is not set up per mobile node basis, but per MAG
   basis; it is shared with mobile nodes attached to the MAG as seen in
   Figure 3.

                   MC1
                      \
                       \-->
                   MC2---->LMA===MC1,MC2 for MNs====>MAG

                   MC: Multicast packets, ==>: M-Tunnel

          Figure 3: Multicast packet forwarding through M-Tunnel



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   In order for the PIM routing protocol to use M-Tunnels for multicast
   forwarding, an M-Tunnel interface must be recognized as the upstream
   multicast interface for MAG.  It is done by the configuration of
   static multicast routes, such as "ip mroute 0.0.0.0 0.0.0.0 gre0".
   By such configuration, MAG enabling the PIM routing function inserts
   the route paths using M-Tunnel into its MRIB and selects a single
   M-Tunnel as the RPF interface and PIM messages, and IP multicast data
   are forwarded over the M-Tunnel.  If operators want to select other
   interface, e.g. a physical interface, as the upstream multicast
   interface for some specific source prefixes, e.g. sources inside the
   PMIPv6-Domain, they can additionally configure the specific multicast
   routes with longer prefixes.  Then the MAG selects as the appropriate
   upstream router according to the MRIB entry.  Note that the case
   having multiple M-Tunnels configured on MAG is described in
   Section 4.2.

   The format of the tunneled multicast packet forwarded from LMA is
   shown below.  "S" and "G" are the same notation used for (S,G)
   multicast channel.

     IPv6 header (src= LMAA, dst= Proxy-CoA) /* Outer Header */
        GRE header                           /* Encapsulation Header */
           IPv6 header (src= S, dst= G)      /* Inner Header */
              Upper layer protocols          /* Packet Content */

        Figure 4: Multicast packet format tunneled from LMA to MAG

   When a PIM message is sent from MAG to LMA, the src and dst addresses
   of the outer tunnel header will be replaced to Proxy-CoA and LMAA,
   respectively.  To convey a PIM message, the src address of the inner
   packet header is changed to either LMA's or MAG's link-local address.
   The dst address of the packet header is assigned based on the PIM's
   condition (see [3]).

   In order to establish M-Tunnel, LMA and MAG need to negotiate GRE
   encapsulation and GRE keys for M-Tunnel.  The GRE Key option to be
   used for the negotiation of GRE tunnel encapsulation mode and
   exchange of the uplink and downlink GRE keys is defined in [9].  It
   is also possible to use the static fixed GRE keys for M-Tunnel.

4.2.  Multiple M-Tunnels and ECMP Routing

   There can be multiple LMAs in a PMIPv6-Domain each serving a
   different group of mobile nodes.  In that case, a MAG will connect to
   multiple LMAs with different M-Tunnels having different GRE keys.
   For example, in Figure 5, MAG1 establishes two M-Tunnels with LMA1
   and LMA2, and MAG2 establishes one M-Tunnel with LMA2.




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   A MAG that has multiple M-Tunnels, such as MAG1 in Figure 5, must
   decide a single upstream M-Tunnel interface for an RP or a source
   address or prefix.  There are two ways to decide a single upstream
   M-Tunnel for a MAG.  One is only with static MRIB configuration by
   operation.  For example, operator can configure one of the M-Tunnel
   interfaces as the RPF interface for specific source adddress(es) or
   prefix(es) to insert into the MRIB for the MAG.

   The other way to select a single upstream M-Tunnel interface is with
   PIM ECMP [13].  A MAG enabling PIM routing functions selects a path
   in the ECMP based on its own implementation specific choice, which
   may refer to the description in [13].  The PIM ECMP function chooses
   the PIM neighbor with the highest IP address, or picks the PIM
   neighbor with the best hash value over the destination and source
   addresses.  When operators decide to use PIM ECMP to select a single
   upstream M-Tunnel from multiple M-Tunnels established between MAG and
   LMAs, both MAG and LMAs MUST enable PIM ECMP for their possiblly
   selecteded M-Tunnels.

                         +----+         +----+
                         |LMA1|         |LMA2|
                         +----+         +----+
                           ||            || ||
                           ||            || ||
                           \\   M-Tunnel // \\
                            \\     |    //   \\
                             \\    +-> //     \\ <-- M-Tunnel
                M-Tunnel ---> \\      //       \\
               (encapsulating  \\    //         \\
               with GRE header) \\  //           \\
                                || ||            ||
                               +----+          +----+
                               |MAG1|---{MN2}  |MAG2|
                               +----+          +----+
                                 |               |
                                 |               |
                               {MN1}           {MN3}

            Figure 5: M-Tunnels established between LMA and MAG


5.  Local Mobility Anchor Operation

   The LMA is responsible for maintaining the mobile node's reachability
   state and is the topological anchor point for the mobile node's home
   network prefix(es).  This document assumes that the LMA is capable of
   forwarding multicast packets to the MAG by enabling the Protocol-
   Independent Multicast - Sparse Mode (PIM-SM) multicast routing



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   protocol [3].  The LMA acting as a PIM-SM multicast router may serve
   MAGs as downstream routers for some multicast channels when a mobile
   node is a multicast data receiver (or as upstream routers when a
   mobile node is a multicast data sender).  The downstream (or
   upstream) MAG is connected to the LMA through the LMA-MAG bi-
   directional tunnel for multicast communication.

   When the LMA sets up the multicast state and joins the group as the
   MAG's upstream router, the multicast packets are tunneled to the MAG
   that requested to receive the corresponding multicast session.  The
   MAG then forwards the packets to the mobile node according to the
   multicast listener state maintained in the MAG. [1] supports only
   point-to-point access link types for MAG and mobile node connection;
   hence a mobile node and the MAG are the only two nodes on an access
   link, where the link is assumed to be multicast capable.


6.  Mobile Access Gateway Operation

   The MAG is the entity that performs the mobility management on behalf
   of a mobile node.  This document assumes that MAG is capable of
   forwarding multicast packets to the corresponding mobile nodes
   attached to MAG by enabling the PIM-SM multicast routing protocol.
   In addition, MAG must maintain multicast membership status for the
   attached mobile nodes at the edge and forwards the multicast data to
   the member mobile nodes.  This condition requires MAG to support
   MLDv2 [7] or LW-MLDv2 [8], as well.

   When mobile nodes subscribe multicast channel(s), they send MLD
   Report messages with their link-local address to the MAG, and the MAG
   sends the corresponding PIM Join messages to the upstream router if
   the MAG has no multicast state for the requested channel(s).  The
   upstream router is selected by the Reverse Path Forwarding (RPF)
   lookup algorithm, and that is either LMA or an adjacent multicast
   router attached to the same link.  If the LMA is the upstream router
   for the channel(s) for the MAG, the MAG encapsulates PIM Join
   messages using the LMA-MAG bi-directional tunnel.

   The MAG also sends MLD Query messages to attached mobile nodes to
   maintain up-to-date membership states.  Since the MAG may deal with a
   large number of the downstream mobile nodes, the MLD protocol
   scalability should be taken into account as described in [12].
   Therefore it is RECOMMENDED that the explicit tracking function [14]
   is enabled on MAG.







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7.  Mobile Node Operation

   Mobile nodes attached to MAG can behave as regular receiver hosts.  A
   mobile node sends MLD messages to MAG when it wants to subscribe and
   unsubscribe IP multicast channels.

   In order to subscribe/unsubscribe multicast channel(s) by unsolicited
   report messages and inform current membersip state by solicited
   report messages, mobile nodes MUST support either MLDv1 [7], MLDv2
   [7], or LW-MLDv2 [8], and SHOULD support MLDv2 or LW-MLDv2.


8.  Smooth Handover

   MAG is responsible for detecting the mobile node's movements to and
   from the access link and for initiating binding registrations to the
   mobile node's LMA.  MAG tracks the mobile node's movements to and
   from the access link and for signaling the mobile node's LMA.  In
   PMIPv6, it SHOULD NOT require for mobile nodes to initiate to re-
   subscribe multicast channels, and MAG SHOULD keep multicast channel
   subscription status for mobile nodes even if they move to a different
   MAG (i.e., n-MAG) in PMIPv6-Domain.

   MAG needs to join the multicast delivery tree when an attached mobile
   node subscribes a multicast channel.  When the mobile node changes
   the network, it should seamlessly receive multicast data from the new
   MAG according to the multicast channel information stored in the
   "MN's Policy Profile" or by the "multicast context transfer
   mechanism".  Whether the MN's Policy Profile or the multicast context
   transfer mechanism mobile operators use depend on their policy or
   implementation.

8.1.  Handover with Policy Profile

   When the multicast channel information subscribed by mobile nodes is
   maintained in "MN's Policy Profile" stored in a policy store [1], MAG
   can use the channel information to provide seamless handover.  The
   procedures are described as follows and illustrated in Figure 6;

   1.   Figure 6 shows the examples that a mobile node has received
        multicast data from an upstream multicast router via p-MAG (*1)
        and from LMA via p-MAG (*2).

   2.   Whenever the mobile node moves a new network and attaches to
        n-MAG, the n-MAG obtains the MN-Identifier (MN-ID) and learns
        multicast channel information described in Mobile Node's Policy
        Profile associated to this MN-Identifier.  Describing the method
        how the n-MAG identifies the p-MAG is out of scope of this



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        document, while using the same mechanism described in [15] would
        be one of the possible methods.

   3.   If there are multicast channels the mobile node has subscribed
        but the n-MAG has not yet subscribed, n-MAG joins the
        corresponding multicast channels by sending the PIM Join message
        to its upstream router.  If the upstream router is LMA, the PIM
        messages are encapsulated and transmitted over the LMA-MAG bi-
        directional tunnel (*4); otherwise the PIM messages are sent
        natively to the adjacent upstream router (*3).

   4.   The multicast data is forwarded from LMA through the bi-
        directional tunnel between the LMA and n-MAG (*4) or from the
        adjacent upstream router (*3).





































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    MN            p-MAG                LMA                n-MAG
     |              |                   |                   |
     |--MLD Report->|                   |                   |
     |              |---> PIM Join (*1)                     |
     |              |   PIM Join (*2)   |                   |
     |              |== Bi-dir tunnel =>|                   |
     |              |                   |---> PIM Join (*2)
     |              |                   |                   |
     |<--Multicast--|                   |                   |
     |   data (*1)  |                   |                   |
     |              |Multicast data (*2)|                   |
     |<-------------|<= Bi-dir tunnel ==|                   |
     |              |                   |                   |
   Detach           |                   |                   |
     |              |                   |                   |
   Attach           |                   |                   |
     |              |                   |          MN attachment event
     |              |                   |     (Acquire MN-ID and Profile)
     |-------------------------RS-------------------------->|
     |              |                   |                   |
     |              |                   |<-------PBU--------|
     |              |                   |                   |
     |              |                   |--------PBA------->|
     |              |                   |                   |---> PIM Join (*3)
     |              |                   |   PIM Join (*4)   |
     |              |                   |<= Bi-dir tunnel ==|
     |              |                   |                   |
     |<------------------------RA---------------------------|
     |              |                   |                   |
     |              |      Multicast data (*3)              |
     |<-----------------------------------------------------|
     |              |                   |Multicast data (*4)|
     |              |                   |== Bi-dir tunnel =>|
     |<-----------------------------------------------------|
     |              |                   |                   |

                Figure 6: Handover with MN's Policy Profile

   After MN attaches to n-MAG, the multicast data will be delivered to
   the MN immediately.  MN's multicast membership state is maintained
   with MLD Query and Report messages exchanged by MN and n-MAG.  If
   p-MAG thinks that the moving mobile node is the last member of
   multicast channel(s) (according to the membership record maintained
   by the explicit tracking function [14]), p-MAG confirms it by sending
   MLD query.  After the confirmation, p-MAG leaves the channel(s) by
   sending the PIM Prune message to its upstream router.





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8.2.  Handover with Extended Proxy Binding Update and Acknowledgement

   This document provides the multicast extension for the PBU message,
   which is named "Proxy Binding Update with multicast extension
   (PBU-M)" (detailed in Section 9.1), and the PBA message, which is
   named "Proxy Binding Acknowledge with multicast extension (PBA-M)"
   (detailed in Section 9.2), to inform n-MAG to subscribe multicast
   channel(s) for moving mobile nodes.

   1.   Figure 7 shows the examples that a mobile node has received
        multicast data from an upstream multicast router via p-MAG (*1)
        and from LMA via p-MAG (*2).

   2.   Whenever the mobile node moves a new network, the p-MAG sends
        de-registration PBU-M message having the lifetime value of zero
        (see Section 9.1) to the LMA.  The LMA then transmits the PBA
        message and keeps the multicast channel information included in
        that message.

   3.   When the mobile node attaches to n-MAG, the n-MAG obtains the
        MN-Identifier (MN-ID) and transmits the regular PBU message.

   4.   Whenever the LMA receives the PBU message, it transmits the
        PBA-M message including multicast channel information that the
        mobile node has joined.

   5.   If there are multicast channels in the channel information the
        mobile node has subscribed but the n-MAG has not yet subscribed,
        the n-MAG joins the corresponding multicast channels by sending
        the PIM Join message to its upstream router.

   6.   Follow the procedures of step 3 and 4 in Section 8.1.



















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    MN            p-MAG                LMA                n-MAG
     |              |                   |                   |
     |              |                   |                   |
     |--MLD Report->|                   |                   |
     |              |---> PIM Join (*1)                     |
     |              |   PIM Join (*2)   |                   |
     |              |== Bi-dir tunnel =>|                   |
     |              |                   |---> PIM Join (*2)
     |              |                   |                   |
     |<--Multicast--|                   |                   |
     |   data (*1)  |                   |                   |
     |              |Multicast data (*2)|                   |
     |<-------------|<= Bi-dir tunnel ==|                   |
     |              |                   |                   |
   Detach           |                   |                   |
     |       MN detachment event        |                   |
     |              |                   |                   |
     |              |----DeReg PBU-M--->|                   |
     |              |                   |                   |
     |              |              Accept PBU               |
     |              |<-------PBA--------|                   |
   Attach           |                   |                   |
     |              |                   |         MN attachment event
     |              |                   |         (Acquire MN-ID)
     |-------------------------RS-------------------------->|
     |              |                   |                   |
     |              |                   |<-------PBU--------|
     |              |                   |                   |
     |              |                   |-------PBA-M------>|
     |              |                 (Acquire multicast channel
     |              |                  information for MN-ID)
     |              |                   |                   |
     |              |                   |                   |---> PIM Join (*3)
     |              |                   |   PIM Join (*4)   |
     |              |                   |<= Bi-dir tunnel ==|
     |              |                   |                   |
     |<------------------------RA---------------------------|
     |              |                   |                   |
     |              |       Multicast data (*3)             |
     |<-----------------------------------------------------|
     |              |                   |Multicast data (*4)|
     |              |                   |== Bi-dir tunnel =>|
     |<-----------------------------------------------------|
     |              |                   |                   |

                  Figure 7: Handover with PBU-M and PBA-M





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9.  Message Format Extension

9.1.  Proxy Binding Update with Multicast Extension

     0               1               2               3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                     |            Sequence #         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |A|H|L|K|M|R|P|C|   Reserved    |            Lifetime           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                                                               .
     .                        Mobility options                       .
     .                                                               .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 8: Proxy Binding Update Message with Multicast Extension

   A Binding Update message that is sent by MAG to LMA is referred to as
   the "Proxy Binding Update" message.  A new flag (C) is included in
   the Proxy Binding Update message with Multicast extension (PBU-M).
   The rest of the Binding Update message format remains the same as
   defined in [16] and with the additional (R), (M), and (P) flags, as
   specified in [17], [18], and [1], respectively.

      Multicast Channel Subscription Flag

      A new flag (C) is included in the Binding Update message to
      indicate to LMA that the Binding Update message is a multicast
      channel subscription.

   The PBU-M message is transfered for binding de-registration from
   p-MAG to LMA as apecified in Section 8.2, the Lifetime value MUST be
   zero.

   When (C) flag is specified in PBU-M message, the Mobility options
   field includes "multicast channel information", which is the same
   information of MLDv2 Report message.  The format of the Mobility
   options field uses the TLV format defined in [16] where the field
   contain Multicast Address Record with the same definitions in [7].









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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Type = TBD   |     Length    |Nr of Mcast Address Records (M)|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                                                               .
     .                  Multicast Address Record [1]                 .
     .                                                               .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                                                               .
     .                  Multicast Address Record [2]                 .
     .                                                               .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                               .                               |
     .                               .                               .
     |                               .                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                                                               .
     .                  Multicast Address Record [M]                 .
     .                                                               .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 9: Multicast channel information

   Each Multicast Address Record has the following internal format,
   where the Record Type MUST be always "1" (i.e., MODE_IS_INCLUDE).



















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     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |Record Type = 1|  Aux Data Len |     Number of Sources (N)     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     *                                                               *
     |                                                               |
     *                       Multicast Address                       *
     |                                                               |
     *                                                               *
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     *                                                               *
     |                                                               |
     *                       Source Address [1]                      *
     |                                                               |
     *                                                               *
     |                                                               |
     +-                                                             -+
     |                                                               |
     *                                                               *
     |                                                               |
     *                       Source Address [2]                      *
     |                                                               |
     *                                                               *
     |                                                               |
     +-                                                             -+
     .                               .                               .
     .                               .                               .
     .                               .                               .
     +-                                                             -+
     |                                                               |
     *                                                               *
     |                                                               |
     *                       Source Address [N]                      *
     |                                                               |
     *                                                               *
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                                                               .
     .                         Auxiliary Data                        .
     .                                                               .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 10: Multicast Address Record format




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9.2.  Proxy Binding Acknowledgement Message with Multicast Extension

     0               1               2               3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
                                     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                                     |   Status      |K|R|P|C|Reserve|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Sequence #            |           Lifetime            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .                                                               .
     .                        Mobility options                       .
     .                                                               .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 11: PBA with Multicast Extension

   A "Proxy Binding Acknowledgement" message is sent from LMA to MAG in
   response to a Proxy Binding Update message.  A new flag (C) is
   included in the Proxy Binding Acknowledgement message with Multicast
   extension (PBA-M).  The rest of the Binding Acknowledgement message
   format remains the same as defined in [16] and with the additional
   (R) flag, as specified in [17] and [1], respectively.

      Multicast Channel Subscription Flag

      A new flag (C) is included in the Binding Acknowledgement message
      to indicate to MAG that the Binding Acknowledgement message is a
      multicast channel subscription.

   When (C) flag is specified in PBA-M message, the mobility options
   field includes "multicast channel information", which is the same
   information of MLDv2 Report message [7] as described in Section 9.1.


10.  IANA Considerations

   This document creates a new registry for the flags in the Binding
   Update message called the "Binding Update Flags".

   The following flags are reserved:









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         (A) 0x8000 [RFC3775]

         (H) 0x4000 [RFC3775]

         (L) 0x2000 [RFC3775]

         (K) 0x1000 [RFC3775]

         (M) 0x0800 [RFC4140]

         (R) 0x0400 [RFC3963]

         (P) 0x0200 [RFC5213]

   This document reserves a new flag (C) for "Proxy Binding Update with
   Multicast Extension" as described in Section 9.1 as follows:

         (C) 0x0100

   The rest of the values in the 16-bit field are reserved.  New values
   can be assigned by Standards Action or IESG approval.

   This document also creates a new registry for the flags in the
   Binding Acknowledgment message called the "Binding Acknowledgment
   Flags".

   The following flags are reserved:

         (K) 0x80 [RFC3775]

         (R) 0x40 [RFC3963]

         (P) 0x20 [RFC5213]

   This document reserves a new flag (C) for "Proxy Binding
   Acknowledgement with Multicast Extension" as described in Section 9.2
   as follows:

         (C) 0x010

   The rest of the values in the 8-bit field are reserved.  New values
   can be assigned by Standards Action or IESG approval.

   The IANA should also allocate the value of the type field of
   "multicast channel information" described in Section 9.1 for the
   Mobility options field upon publication of the first RFC.





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11.  Security Considerations

   TBD.


12.  Acknowledgements

   Many of the specifications described in this document are discussed
   and provided by the multimob mailing-list.


13.  References

13.1.  Normative References

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

   [2]   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.

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

   [4]   Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina,
         "Generic Routing Encapsulation (GRE)", RFC 2784, March 2000.

   [5]   Bradner, S., "Key words for use in RFCs to indicate requirement
         levels", RFC 2119, March 1997.

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

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

   [8]   Liu, H., Cao, W., and H. Asaeda, "Lightweight Internet Group
         Management Protocol Version 3 (IGMPv3) and Multicast Listener
         Discovery Version 2 (MLDv2) Protocols", RFC 5790,
         February 2010.

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




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

13.2.  Informative References

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

   [12]  Asaeda, H., Liu, H., and Q. Wu, "Tuning the Behavior of IGMP
         and MLD for Routers in Mobile and Wireless Networks",
         draft-ietf-multimob-igmp-mld-tuning-04.txt (work in progress),
         March 2012.

   [13]  Thaler, D. and C. Hopps, "Multipath Issues in Unicast and
         Multicast Next-Hop Selection", RFC 2991, November 2000.

   [14]  Asaeda, H. and N. Leymann, "IGMP/MLD-Based Explicit Membership
         Tracking Function for Multicast Routers",
         draft-ietf-pim-explicit-tracking-00.txt (work in progress),
         October 2011.

   [15]  Yokota, H., Chowdhury, K., Koodli, R., Patil, B., and F. Xia,
         "Fast Handovers for Proxy Mobile IPv6", RFC 5949,
         September 2010.

   [16]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
         IPv6", RFC 3775, June 2004.

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

   [18]  Soliman, H., Castelluccia, C., El Malki, K., and L. Bellier,
         "Hierarchical Mobile IPv6 Mobility Management (HMIPv6)",
         RFC 4140, August 2005.

   [19]  Loughney, Ed., J., Nakhjiri, M., Perkins, C., and R. Koodli,
         "Context Transfer Protocol (CXTP)", RFC 4067, July 2005.












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Authors' Addresses

   Hitoshi Asaeda
   Keio University
   Graduate School of Media and Governance
   5322 Endo
   Fujisawa, Kanagawa  252-0882
   Japan

   Email: asaeda@wide.ad.jp
   URI:   http://www.sfc.wide.ad.jp/~asaeda/


   Pierrick Seite
   France Telecom
   4, rue du Clos Courtel
   BP 91226, Cesson-Sevigne  35512
   France

   Email: pierrick.seite@orange-ftgroup.com































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