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MULTIMOB Working Group                                 Luis M. Contreras
INTERNET-DRAFT                                            Telefonica I+D
Intended Status: Proposed Standard                   Carlos J. Bernardos
Expires: April 18, 2013                 Universidad Carlos III de Madrid
                                                      Juan Carlos Zuniga
                                                            InterDigital
                                                       February 25, 2013


     Extension of the MLD proxy functionality to support multiple
                          upstream interfaces
             draft-contreras-multimob-multiple-upstreams-01


Abstract

   This document presents different scenarios of applicability for an
   MLD proxy running more than one upstream interface. Since those
   scenarios impose different requirements on the MLD proxy with
   multiple upstream interfaces, it is important to ensure that the
   proxy functionality addresses all of them for compatibility.

   The purpose of this document is to define the requirements in an MLD
   proxy with multiple interfaces covering a variety of applicability
   scenarios, and to specify the proxy functionality to satisfy all of
   them.


Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   http://www.ietf.org/shadow.html



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Copyright and License 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
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   described in the Simplified BSD License.



Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Problem statement  . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Scenarios of applicability . . . . . . . . . . . . . . . . . .  7
     4.1  Fixed network scenarios . . . . . . . . . . . . . . . . . .  7
       4.1.1  Multicast wholesale offer for residential services  . .  7
         4.1.1.1  Requirements  . . . . . . . . . . . . . . . . . . .  7
       4.1.2  Multicast resiliency  . . . . . . . . . . . . . . . . .  8
         4.1.2.1  Requirements  . . . . . . . . . . . . . . . . . . .  8
       4.1.3  Load balancing for multicast traffic in the metro
              segment . . . . . . . . . . . . . . . . . . . . . . . .  8
         4.1.3.1  Requirements  . . . . . . . . . . . . . . . . . . .  8
       4.1.4  Summary of the requirements needed for mobile network
              scenarios . . . . . . . . . . . . . . . . . . . . . . .  9
     4.2  Mobile network scenarios  . . . . . . . . . . . . . . . . .  9
       4.2.1  Applicability to multicast listener mobility  . . . . . 10
         4.2.1.1  Single MLD proxy instance on MAG  . . . . . . . . . 10
           4.2.1.1.1  Requirements  . . . . . . . . . . . . . . . . . 10
         4.2.1.2  Remote and local multicast subscription . . . . . . 10
           4.2.1.2.1  Requirements  . . . . . . . . . . . . . . . . . 11
         4.2.1.3  Dual subscription to multicast groups during
                  handover  . . . . . . . . . . . . . . . . . . . . . 11
           4.2.1.3.1  Requirements  . . . . . . . . . . . . . . . . . 12
       4.2.2  Applicability to multicast source mobility  . . . . . . 12
         4.2.2.1  Support of remote and direct subscription in
                  basic source mobility . . . . . . . . . . . . . . . 12
           4.2.2.1.1  Requirements  . . . . . . . . . . . . . . . . . 13
         4.2.2.2  Direct communication between source and listener
                  associated with distinct LMAs but on the same MAG . 13



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           4.2.2.3.1  Requirements  . . . . . . . . . . . . . . . . . 14
         4.2.2.3  Route optimization support in source mobility for
                  remote subscribers  . . . . . . . . . . . . . . . . 14
           4.2.2.3.1  Requirements  . . . . . . . . . . . . . . . . . 14
       4.2.3  Summary of the requirements needed for mobile network
              scenarios . . . . . . . . . . . . . . . . . . . . . . . 15
   5  Functional specification of an MLD proxy with multiple
      interfaces  . . . . . . . . . . . . . . . . . . . . . . . . . . 17
   6  Security Considerations . . . . . . . . . . . . . . . . . . . . 17
   7  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 17
   8  Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . 17
   9  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 17
   10  References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     10.1  Normative References . . . . . . . . . . . . . . . . . . . 17
     10.2  Informative References . . . . . . . . . . . . . . . . . . 17
   Appendix A.  Basic support for multicast listener with PMIPv6  . . 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20


































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1  Introduction

   The aim of this document is to define the functionality that an MLD
   proxy with multiple upstream interfaces should have in order to
   support different scenarios of applicability in both fixed and mobile
   networks. This compatibility is needed in order to simplify node
   functionality and to ensure an easier deployment of multicast
   capabilities in all the use cases described in this document.

2.  Terminology

   This document uses the terminology defined in [3]. Specifically, the
   definition of Upstream and Downstream interfaces, which are
   reproduced here for completeness.

   Upstream interface:
      A proxy device's interface in the direction of the root of the
      tree. Also called the "Host interface".

   Downstream interface:
      Each of a proxy device's interfaces that is not in the direction
      of the root of the tree. Also called the "Router interfaces".

3.  Problem statement

   The concept of MLD proxy with several upstream interfaces has emerged
   as a way of optimizing (and in some cases enabling) service delivery
   scenarios where separate multicast service providers are reachable
   through the same access network infrastructure. Figure 1 presents the
   conceptual model under consideration.





















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                  downstream        upstream
                  interface       interface A
                       |               |
                       |               |     _______________
                       |   +-------+   v    /               \
                       |   |       O-------( Multicast Set 1 )
         +----------+  v   |  MLD  |        \_______________/
         | Listener |------|       |         _______________
         +----------+      | Proxy |        /               \
                           |       O-------( Multicast Set 2 )
                           +-------+   ^    \_______________/
                                       |
                                       |
                                    upstream
                                  interface B

    Figure 1. Concept of MLD proxy with multiple upstream interfaces

   For illustrative purposes, two applications for fixed and mobile
   networks are here introduced. They will be elaborated later on the
   document.

   In the case of fixed networks, multicast wholesale services in a
   competitive residential market require an efficient distribution of
   multicast traffic from different operators, i.e. the incumbent
   operator and a number of alternative ones, on the network
   infrastructure of the former. Existing proposals are based on the use
   of PIM routing from the metro network, and multicast traffic
   aggregation on the same tree. A different approach could be achieved
   with the use of an MLD proxy with multiple upstream interfaces, each
   of them pointing to a distinct multicast router in the metro border
   which is part of separated multicast trees deep in the network.
   Figure 2 graphically describes this scenario.

   In the case of mobile networks, IP mobility services guarantee the
   continuity of the IP session while a Mobile Node (MN) changes its
   point of attachment. Proxy Mobile IPv6 (PMIPv6) [1] standardized a
   protocol that allows the network to manage the MN mobility without
   requiring specific support from the mobile terminal. The traffic to
   the MN is tunneled from the Home Network making use of two entities,
   one acting as mobility anchor, and the other as Mobility Access
   Gateway (MAG). Multicast support in PMIPv6 [2] implies the delivery
   of all the multicast traffic from the Home Network, via the mobility
   anchor. However, multicast routing optimization [4] could take
   advantage of an MLD proxy with multiple upstream interfaces by
   supporting the decision of subscribing a multicast content from the
   Home Network or from the local PMIPv6 domain if it is locally
   available. Figure 3 presents this scenario.



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   Informational text is provided in Appendix A summarizing how the
   basic solution for deploying multicast listener mobility with Proxy
   Mobile IPv6 works.

                 downstream       upstream
                 interface       interface A
                    |                |
                    |                |     _______________
                    |   +--------+   v    /               \
                    |   |        O-------( Multicast Set 1 )
                    |   |  Aggr. |        \_______________/
           +----+   v   | Switch |     (e.g. from the Incumbent
           | AN |-------|        |             Operator)
           +----+       |  (MLD  |         _______________
           (e.g.        | Proxy) |        /               \
           DSLAM)       |        O-------( Multicast Set 2 )
                        +--------+   ^    \_______________/
                                     | (e.g. from an Alternative
                                     |         Operator)
                                     |
                                  upstream
                                 interface B

       Figure 2. Example of usage of an MLD proxy with multiple
            upstream interfaces in a fixed network scenario


                 downstream       upstream
                 interface       interface A
                    |                |
                    |                |     _______________
                    |   +--------+   v    /               \
                    |   |        O-------( Multicast Set 1 )
                    |   |        |        \_______________/
           +----+   v   |   MAG  |    e.g. from the Home Network
           | MN |-------|        |     via the mobility anchor)
           +----+       |  (MLD  |         _______________
                        | Proxy) |        /               \
                        |        O-------( Multicast Set 2 )
                        +--------+   ^    \_______________/
                                     | (e.g. from the local PMIPv6
                                     |  domain via direct routing)
                                     |
                                  upstream
                                 interface B

       Figure 3. Example of usage of an MLD proxy with multiple
            upstream interfaces in a mobile network scenario



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   Since those scenarios can motivate distinct needs in terms of MLD
   proxy functionality, it is necessary to consider a comprehensive
   approach, looking at the possible scenarios, and establishing a
   minimum set of requirements which can allow the operation of a
   versatile MLD proxy with multiple upstream interfaces as a common
   entity to all of them (i.e., no different kinds of proxies depending
   on the scenario, but a common proxy applicable to all the potential
   scenarios).

4.  Scenarios of applicability

   This section describes in detail a number of scenarios of
   applicability of an MLD proxy with multiple upstream interfaces in
   place. A number of requirements for the MLD proxy functionality are
   identified from those scenarios.

4.1  Fixed network scenarios

   Residential broadband users get access to multiple IP services
   through fixed network infrastructures. End user's equipment is
   connected to an access node, and the traffic of a number of access
   nodes is collected in aggregation switches.

   For the multicast service, the use of an MLD proxy with multiple
   upstream interfaces in those switches can provide service flexibility
   in a lightweight and simpler manner if compared with PIM-routing
   based alternatives.

4.1.1  Multicast wholesale offer for residential services

   This scenario has been already introduced in the previous section,
   and can be seen in Figure 2. There are two different operators, the
   one operating the fixed network where the end user is connected
   (e.g., typically an incumbent operator), and the one providing the
   Internet service to the end user (e.g., an alternative Internet
   service provider). Both can offer multicast streams that can be
   subscribed by the end user, independently of which provider
   contributes with the content.

   Note that it is assumed that both providers offer distinct multicast
   groups. However, more than one subscription to multicast channels of
   different providers could take place simultaneously.

4.1.1.1  Requirements

   - The MLD proxy should be able to deliver multicast control messages
   sent by the end user to the corresponding provider's multicast
   router.



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   - The MLD proxy should be able to deliver multicast control messages
   sent by each of the providers to the corresponding end user.

4.1.2  Multicast resiliency

   In current PIM-based solutions, the resiliency of the multicast
   distribution relays on the routing capabilities provided by protocols
   like PIM and VRRP. A simpler scheme could be achieved by implementing
   different upstream interfaces on MLD proxies, providing path
   diversity through the connection to distinct leaves of a given
   multicast tree.

   It is assumed that only one of the upstream interfaces is active in
   receiving the multicast content, while the other is up and in standby
   for fast switching.

4.1.2.1  Requirements

   - The MLD proxy should be able to deliver multicast control messages
   sent by the end user to the corresponding active upstream interface.

   - The MLD proxy should be able to deliver multicast control messages
   received in the active upstream to the end users, while ignoring the
   control messages of the standby upstream interface.

   - The MLD proxy should be able of rapidly switching from the active
   to the standby upstream interface in case of network failure,
   transparently to the end user.

4.1.3  Load balancing for multicast traffic in the metro segment

   A single upstream interface in existing MLD proxy functionality
   typically forces the distribution of all the channels on the same
   path in the last segment of the network. Multiple upstream interfaces
   could naturally split the demand, alleviating the bandwidth
   requirements in the metro segment.

4.1.3.1  Requirements

   - The MLD proxy should be able to deliver multicast control messages
   sent by the end user to the corresponding multicast router which
   provides the channel of interest.

   - The MLD proxy should be able to deliver multicast control messages
   sent by each of the multicast routers to the corresponding end user.

   - The MLD proxy should be able to decide which upstream interface is
   selected for any new channel request according to defined criteria



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   (e.g., load balancing).

4.1.4  Summary of the requirements needed for mobile network scenarios

   Following the analysis above, a number of different requirements can
   be identified by the MLD proxy to support multiple upstream
   interfaces in fixed network scenarios. The following table summarizes
   these requirements.

                      +-----------------------------------+
                      |       Fixed Network Scenarios     |
            +---------+-----------+-----------+-----------+
            |Functio- | Multicast | Multicast |   Load    |
            |nality   | Wholesale | Resiliency| Balancing |
            +---------+-----------+-----------+-----------+
            |Upstream |           |           |           |
            |Control  |     X     |     X     |     X     |
            |Delivery |           |           |           |
            +---------+-----------+-----------+-----------+
            |Downstr. |           |           |           |
            |Control  |     X     |     X     |     X     |
            |Delivery |           |           |           |
            +---------+-----------+-----------+-----------+
            |Active / |           |           |           |
            |Standby  |           |     X     |           |
            |Upstream |           |           |           |
            +---------+-----------+-----------+-----------+
            |Upstr i/f|           |           |           |
            |selection|           |           |     X     |
            |per group|           |           |           |
            +---------+-----------+-----------+-----------+
            |Upstr i/f|           |           |           |
            |selection|           |     X     |           |
            |all group|           |           |           |
            +---------+-----------+-----------+-----------+

        Table I. Functionality needed on MLD proxy with multiple
     upstream interfaces per application scenario in fixed networks



4.2  Mobile network scenarios

   The mobile networks considered in this document are supposed to run
   PMIPv6 protocol for IP mobility management. A brief description of
   multicast provision in PMIPv6-based networks can be found in Appendix
   A.




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   The use of an MLD proxy supporting multiple upstream interfaces can
   improve the performance and the scalability of multicast-capable
   PMIPv6 domains.


4.2.1  Applicability to multicast listener mobility

   Three sub-cases can be identified for the multicast listener
   mobility.

4.2.1.1  Single MLD proxy instance on MAG

   The base solution for multicast service in PMIPv6 [2] assumes that
   any MN subscribed to multicast services receive the multicast traffic
   through the associated LMA, as in the unicast case. As standard MLD
   proxy functionality only supports one upstream interface, the MAG
   should implement several separated MLD proxy instances, one per LMA,
   in order to serve the multicast traffic to the MNs, according to any
   particular LMA-MN association.

   A way of avoiding the multiplicity of MLD proxy instance in a MAG is
   to deploy a unique MLD proxy instance with multiple upstream
   interfaces, one per LMA, without any change in the multicast traffic
   distribution.

4.2.1.1.1  Requirements

   - The MLD proxy should be able of delivering the multicast control
   messages sent by the MNs to the associated LMA.

   - The MLD proxy should be able of delivering the multicast control
   messages sent by each of the connected LMAs to the corresponding MN.

   - The MLD proxy should be able of routing the multicast data coming
   from different LMAs to the corresponding MNs according to the MN to
   LMA association.

   - The MLD proxy should be able of maintaining a 1:1 association
   between an MN and LMA (or downstream to upstream).


4.2.1.2  Remote and local multicast subscription

   This scenario has been already introduced in the previous section,
   and can be seen in Figure 3. Standard MLD proxy definition, with a
   unique upstream interface per proxy, does not allow the reception of
   multicast traffic from distinct upstream multicast routers. In other
   words, all the multicast traffic being sent to the MLD proxy in



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   downstream traverses a concrete, unique router before reaching the
   MAG. There are, however, situations where different multicast content
   could reach the MLD proxy through distinct next-hop routers.

   For instance, the solution adopted to avoid the tunnel convergence
   problem in basic multicast PMIPv6 deployments [4] considers the
   possibility of subscription to a multicast source local to the PMIPv6
   domain. In that situation, some multicast content will be accesses
   remotely, through the home network via the multicast tree mobility
   anchor, while some other multicast content will reach the proxy
   directly, via a local router in the domain.

4.2.1.2.1  Requirements

   - The MLD proxy should be able of delivering the multicast control
   messages sent by the MNs to the associated upstream interface based
   on the location of the source, remote or local, for a certain
   multicast group.

   - The MLD proxy should be able of delivering the multicast control
   messages sent either local or remotely to the corresponding MNs.

   - The MLD proxy should be able of routing the multicast data coming
   from different upstream interfaces to a certain MN according to the
   MN subscription, either local or remote. Note that it is assumed that
   a multicast group can be subscribed either locally or remotely, but
   not simultaneously. However more than one subscription could happen,
   being local or remote independently.

   - The MLD proxy should be able of maintaining a 1:N association
   between an MN and the remote and local multicast router (or
   downstream to upstream).

   - The MLD proxy should be able of switching between local or remote
   subscription for per multicast group according to specific
   configuration parameters (out of the scope of this document).

4.2.1.3  Dual subscription to multicast groups during handover

   In the event of an MN handover, once an MN moves from a previous MAG
   (pMAG) to a new MAG (nMAG), the nMAG needs to set up the multicast
   status for the incoming MN, and subscribe the multicast channels it
   was receiving before the handover event. The MN will then experience
   a certain delay until it receives again the subscribed content.

   A generic solution is being defined in [5] to speed up the knowledge
   of the ongoing subscription by the nMAG. However, for the particular
   case that the underlying radio access technology supports layer-2



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   triggers (thus requiring extra capabilities on the mobile node),
   there could be inter-MAG cooperation for handover support if pMAG and
   nMAG are known in advance.

   This could be the case, for instance for those contents not already
   arriving to the nMAG, where the nMAG temporally subscribes the
   multicast groups of the ongoing MN's subscription via the pMAG, while
   the multicast delivery tree among the nMAG and the mobility anchor is
   being established.

   A similar approach is followed in [6] despite the solution proposed
   there differs from this approach (i.e., there is no consideration of
   an MLD proxy with multiple interfaces).

4.2.1.3.1  Requirements

   - The MLD proxy should be able of delivering the multicast control
   messages sent by the MNs to the associated upstream interface based
   on the handover specific moment, for a certain multicast group.

   - The MLD proxy should be able of delivering the multicast control
   messages sent either from pMAG or the multicast anchor to the
   corresponding MNs, based on the handover specific moment.

   - The MLD proxy should be able of handle the incoming packet flows
   from the two simultaneous upstream interfaces, in order to not
   duplicate traffic delivered on the point-to-point link to the MN.

   - The MLD proxy should be able of maintaining a 1:N association
   between an MN and both the remote multicast router and the pMAG (or
   downstream to upstream).

   - The MLD proxy should be able of switching between local or remote
   subscription for all the multicast groups (from pMAG to multicast
   anchor) according to specific configuration parameters (out of the
   scope of this document).

4.2.2  Applicability to multicast source mobility

   A couple of sub-cases can be identified for the multicast source
   mobility.

4.2.2.1  Support of remote and direct subscription in basic source
   mobility

   In the basic case of source mobility, the multicast source is
   connected to one of the downstream interfaces of an MLD proxy.
   According to the standard specification [3] every packet sent by the



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   multicast source will be forwarded towards the root of the multicast
   tree.

   However, linked to the mobility listener problem, there could be the
   case of simultaneous remote subscribers, subscribing to the multicast
   content through the home network, and local subscribers, requesting
   the contents directly via a multicast router residing on the same
   PMIPv6 domain where the source is attached to.

   Then, in order to provide the co-existence of both types of
   subscribers, an MLD proxy with two upstream interfaces could
   simultaneously serve all kind of multicast subscribers.

   Basic source mobility is being defined in [7] but the solution
   proposed there does not allow simultaneous co-existence of remote and
   local subscribers (i.e., the content sent by the source is either
   distributed locally to a multicast router in the PMIPv6 domain, or
   remotely by using the bi-directional tunnel towards the mobility
   anchor, but not both simultaneously).

4.2.2.1.1  Requirements

   - The MLD proxy should be able of forwarding (replicating) the
   multicast content to both upstream interfaces, in case of
   simultaneous remote and local distribution.

   - The MLD proxy should be able of handling control information
   incoming through any of the two upstream interfaces, providing the
   expected behavior for each of the multicast trees.

   - The MLD proxy should be able of routing the multicast data towards
   different upstream interfaces for both remote and local subscriptions
   that could happen simultaneously.

   - The MLD proxy should be able of maintaining a 1:N association
   between an MN and both the remote and local multicast router (or
   downstream to upstream).


4.2.2.2  Direct communication between source and listener associated
   with distinct LMAs but on the same MAG

   In a certain PMIPv6 domain can be MNs associated to distinct LMAs
   using the same MAG to get access to their corresponding home
   networks. For multicast communication, according to the base solution
   [2], each MN <-> LMA association implies a distinct MLD proxy
   instance to be invoked in the MAG.




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   In these conditions, when a mobile source is serving multicast
   content to a mobile listener, both attached to the same MAG but each
   of them associated to different LMAs, the multicast flow must
   traverse the PMIPv6 domain from the MAG to the LMA where the source
   maintains an association, then from that LMA to the LMA where the
   listener is associated to, and finally come back to the same MAG from
   where the flow departed. This routing is extremely inefficient.

   An MLD proxy with multiple upstream interfaces avoids this behavior
   since it allows to invoke a unique MLD proxy instance in the MAG. In
   this case, the multicast source can directly communicate with the
   multicast listener, without need for delivering the multicast traffic
   to the LMAs.

4.2.2.3.1  Requirements

   - The MLD proxy should be able of forwarding (replicating) the
   multicast content to different upstream or downstream interfaces
   where subscribers are present.

   - The MLD proxy should be able of handling control information
   incoming through any of the upstream or downstream interfaces
   requesting a multicast flow being injected in another downstream
   interface.

   - The MLD proxy should be able of maintaining a 1:N association
   between an MN and any of the upstream or downstream interfaces
   demanding the multicast content.

4.2.2.3  Route optimization support in source mobility for remote
   subscribers

   Even in a scenario of remote subscription, there could be the case
   where both the source and the listener are attached to the same
   PMIPv6-Domain (for instance, no possibility of direct routing within
   the PMIPv6, or source and listener pertaining to distinct home
   networks). In this situation there is a possibility of route
   optimization if inter-MAG communication is enabled, in such a way
   that the listeners in the PMIPv6 domain are served through the
   tunnels between MAGs, while the rest of remote listeners are served
   through the mobility anchor.

   A multi-upstream MLD proxy would allow the simultaneous delivery of
   traffic to such kind of remote listeners.

   A similar route optimization approach is proposed in [8].

4.2.2.3.1  Requirements



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   - The MLD proxy should be able of forwarding (replicating) the
   multicast content to both kinds of upstream interfaces, inter-MAG
   tunnel interfaces and MAG to mobility anchor tunnel interface.

   - The MLD proxy should be able of handling control information
   incoming through any of the two types of upstream interfaces,
   providing the expected behavior for each of the multicast trees
   (e.g., no forwarding traffic on one inter-MAG link once there are not
   more listeners requesting the content).

   - The MLD proxy should be able of routing the multicast data towards
   different upstream interfaces for both remote and route optimized
   subscriptions that could happen simultaneously.

   - The MLD proxy should be able of maintaining a 1:N association
   between an MN and both the remote and local MAGs (or downstream to
   upstream).

4.2.3  Summary of the requirements needed for mobile network scenarios

   After the previous analysis, a number of different requirements can
   be identified by the MLD proxy to support multiple upstream
   interfaces in mobile network scenarios. The following table
   summarizes these requirements.



























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              +----------------------------------------------------+
              |               Mobile Network Scenarios             |
              +--------------------------+-------------------------+
              |    Mulicast Listener     |      Mulicast Source    |
    +---------+--------+--------+--------+--------+--------+-------+
    |         |  Single| Remote |  Dual  | Direct |Listener| Route |
    |Functio- |   MLD  |& local | subscr.|& remote|& source|optimi.|
    |nality   |  Proxy | subscr.|  in HO | subscr.| on MAG |       |
    +---------+--------+--------+--------+--------+--------+-------+
    |Upstream |        |        |        |        |        |       |
    |Control  |    X   |    X   |    X   |    X   |    X   |   X   |
    |Delivery |        |        |        |        |        |       |
    +---------+--------+--------+--------+--------+--------+-------+
    |Downstr. |        |        |        |        |        |       |
    |Control  |    X   |    X   |    X   |        |    X   |       |
    |Delivery |        |        |        |        |        |       |
    +---------+--------+--------+--------+--------+--------+-------+
    |Upstream |        |        |        |        |        |       |
    |Data     |        |        |        |    X   |        |   X   |
    |Delivery |        |        |        |        |        |       |
    +---------+--------+--------+--------+--------+--------+-------+
    |Downstr. |        |        |        |        |        |       |
    |Data     |    X   |    X   |    X   |        |    X   |       |
    |Delivery |        |        |        |        |        |       |
    +---------+--------+--------+--------+--------+--------+-------+
    |1:1 MN to|        |        |        |        |        |       |
    |upstream |    X   |        |        |        |        |       |
    |assoc.   |        |        |        |        |        |       |
    +---------+--------+--------+--------+--------+--------+-------+
    |1:N MN to|        |        |        |        |        |       |
    |upstream |        |    X   |    X   |    X   |    X   |   X   |
    |assoc.   |        |        |        |        |        |       |
    +---------+--------+--------+--------+--------+--------+-------+
    |Upstr i/f|        |        |        |        |        |       |
    |selection|        |    X   |        |        |        |       |
    |per group|        |        |        |        |        |       |
    +---------+--------+--------+--------+--------+--------+-------+
    |Upstr i/f|        |        |        |        |        |       |
    |selection|        |        |    X   |        |        |       |
    |all group|        |        |        |        |        |       |
    +---------+--------+--------+--------+--------+--------+-------+
    |Upstream |        |        |        |        |        |       |
    |traffic  |        |        |        |    X   |        |   X   |
    |replicat.|        |        |        |        |        |       |
    +---------+--------+--------+--------+--------+--------+-------+

       Table II. Functionality needed on MLD proxy with multiple
    upstream interfaces per application scenario in mobile networks



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5  Functional specification of an MLD proxy with multiple interfaces

   <To be completed>.

6  Security Considerations

   <To be completed>.

7  IANA Considerations

   <IANA considerations text>.

8  Conclusions

   <To be completed>.

9  Acknowledgements

   The authors thank Stig Venaas for his valuable comments and
   suggestions.

   The research of Carlos J. Bernardos leading to these results has
   received funding from the European Community's Seventh Framework
   Programme (FP7-ICT-2009-5) under grant agreement n. 258053 (MEDIEVAL
   project), being also partially supported by the Ministry of Science
   and Innovation (MICINN) of Spain under the QUARTET project (TIN2009-
   13992-C02-01).


10  References

10.1  Normative References

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

   [2] T.C. Schmidt, M. Waehlisch, and S. Krishnan, "A Minimal
       Deployment Option for Multicast Listeners in PMIPv6 Domains",
       RFC6224, April 2011.

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


10.2  Informative References




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

   [5]  L.M. Contreras, C.J. Bernardos, I. Soto, "PMIPv6 multicast
        handover optimization by the Subscription Information
        Acquisition through the LMA (SIAL)", work in progress, draft-
        ietf-multimob-fast-handover-01, July 2012.

   [6]  T.C. Schmidt, M. Waehlisch, R. Koodli, G. Fairhurst, "Multicast
        Listener Extensions for MIPv6 and PMIPv6 Fast Handovers", work
        in progress, draft-schmidt-multimob-fmipv6-pfmipv6-multicast-06,
        May 2012

   [7]  T.C. Schmidt, S. Gao, H. Zhang, M. Waehlisch, "Mobile Multicast
        Sender Support in Proxy Mobile IPv6 (PMIPv6) Domains", work in
        progress, draft-ietf-multimob-pmipv6-source-01, July 2012.

   [8]  J. Liu, W. Luo, "Routes Optimization for Multicast Sender in
        Proxy Mobile IPv6 Domain", work in progress, draft-liu-multimob-
        pmipv6-multicast-ro-02, July 2012.



Appendix A.  Basic support for multicast listener with PMIPv6

   This section briefly summarizes the operation of Proxy Mobile IPv6
   [1] and how multicast listener support works with PMIPv6 as specified
   in [2].

   Proxy Mobile IPv6 (PMIPv6) [1] is a network-based mobility management
   protocol which enables the network to provide mobility support to
   standard IP terminals residing in the network. These terminals enjoy
   this mobility service without being required to implement any
   mobility-specific IP operations. Namely, PMIPv6 is one of the
   mechanisms adopted by the 3GPP to support the mobility management of
   non-3GPP terminals in future Evolved Packet System (EPS) networks.

   PMIPv6 allows a Media Access Gateway (MAG) to establish a distinct
   bi-directional tunnel with different Local Mobility Anchors (LMAs),
   being each tunnel shared by the attached Mobile Nodes (MNs). Each
   mobile node is associated with a corresponding LMA, which keeps track
   of its current location, that is, the MAG where the mobile node is
   attached. IP-in-IP encapsulation is used within the tunnel to forward
   traffic between the LMA and the MAG. Figure 4 (taken from [1]) shows
   the architecture of a PMIPv6 domain.




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              +----+                +----+
              |LMA1|                |LMA2|
              +----+                +----+
       LMAA1 -> |                      | <-- LMAA2
                |                      |
                \\                    //\\
                 \\                  //  \\
                  \\                //    \\
               +---\\------------- //------\\----+
              (     \\  IPv4/IPv6 //        \\    )
              (      \\  Network //          \\   )
               +------\\--------//------------\\-+
                       \\      //              \\
                        \\    //                \\
                         \\  //                  \\
             Proxy-CoA1--> |                      | <-- Proxy-CoA2
                        +----+                 +----+
                        |MAG1|-----{MN2}       |MAG2|
                        +----+    |            +----+
                          |       |               |
             MN-HNP1 -->  |     MN-HNP2           | <-- MN-HNP3, MN-HNP4
                        {MN1}                   {MN3}


                   Figure 4. Proxy Mobile IPv6 Domain

   The basic solution for the distribution of multicast traffic within a
   PMIPv6 domain [2] makes use of the bi-directional LMA-MAG tunnels.
   The base solution follows the so-called remote subscription model, in
   which the subscribed multicast content is delivered from the Home
   Network. By doing so, an individual copy of every multicast flow is
   delivered through the tunnel connecting the mobility anchor to any of
   the access gateways in the domain. In many cases, these individual
   copies traverse the same routers in the path towards the access
   gateways, incurring in an inefficient distribution, equivalent to the
   unicast distribution of the multicast content in the domain.

   The reference scenario for multicast deployment in Proxy Mobile IPv6
   domains is illustrated in Figure 5 (taken from [2]).

   This fact leads to distribution inefficiencies and higher per-bit
   delivery costs, incurred by the PMIPv6 domain operator offering
   transport capabilities to the Home Network operator for serving their
   MNs when attached to the PMIPv6 domain. As long as the remotely
   subscribed multicast service is not affected, it seems worthy to
   explore more optimal ways of distributing such content within the
   PIMPv6 domain.




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                       +-------------+
                       | Content     |
                       | Source      |
                       +-------------+
                              |
                     ***  ***  ***  ***
                    *   **   **   **   *
                   *                    *
                    *  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


     Figure 5. Reference Network for Multicast Deployment in PMIPv6



Authors' Addresses


    Luis M. Contreras
    Telefonica I+D
    EMail: lmcm@tid.es

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




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
















































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