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Versions: 00 01                                                         
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
                                                        October 15, 2012


     Extension of the MLD proxy functionality to support multiple
                          upstream interfaces
             draft-contreras-multimob-multiple-upstreams-00


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 address 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.

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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
   Provisions Relating to IETF Documents
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   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  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Problem statement  . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Scenarios of applicability . . . . . . . . . . . . . . . . . .  4
     4.1  Applicability to multicast listener mobility  . . . . . . .  4
       4.1.1  Single MLD proxy instance on MAG  . . . . . . . . . . .  4
         4.1.1.1  Requirements  . . . . . . . . . . . . . . . . . . .  5
       4.1.2  Remote and local multicast subscription . . . . . . . .  5
         4.1.2.1  Requirements  . . . . . . . . . . . . . . . . . . .  6
       4.1.3  Dual subscription to multicast groups during handover .  6
         4.1.3.1  Requirements  . . . . . . . . . . . . . . . . . . .  7
     4.2  Applicability to multicast source mobility  . . . . . . . .  7
       4.2.1  Support of remote and direct subscription in basic
              source mobility . . . . . . . . . . . . . . . . . . . .  7
         4.2.1.1  Requirements  . . . . . . . . . . . . . . . . . . .  8
       4.2.2  Direct communication between source and listener
              associated with distinct LMAs but on the same MAG . . .  8
         4.2.3.1  Requirements  . . . . . . . . . . . . . . . . . . .  9
       4.2.3  Route optimization support in source mobility for
              remote subscribers  . . . . . . . . . . . . . . . . . .  9
         4.2.3.1  Requirements  . . . . . . . . . . . . . . . . . . .  9
     4.3  Summary of the requirements needed  . . . . . . . . . . . . 10
   5  Functional specification of an MLD proxy with multiple
      interfaces  . . . . . . . . . . . . . . . . . . . . . . . . . . 12
   6  Security Considerations . . . . . . . . . . . . . . . . . . . . 12
   7  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 12
   8  Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . 12
   9  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 12
   10  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12



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     10.1  Normative References . . . . . . . . . . . . . . . . . . . 12
     10.2  Informative References . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
















































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1  Introduction

   The aim of this document is to specify the functionality that an MLD
   proxy with multiple upstream interfaces should have in order to
   support a set of different scenarios of applicability that have been
   identified on the MULTIMOB working group. Such functional
   specification is required to ensure the compatibility of the MLD
   proxy instances deployed in PMIPv6 domains.

   To do that, a set of requirements are firstly identified to satisfy
   the different scenarios where an MLD proxy instance with multiple
   upstream interfaces can be potentially applied.

2.  Terminology

   <To be completed>.


3.  Problem statement

   The concept of MLD proxy with several upstream interfaces has emerged
   within the MULTIMOB working group as a way of optimizing (and in some
   cases enabling) service delivery scenarios in both multicast listener
   and source mobility cases.

   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

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

4.1  Applicability to multicast listener mobility

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

4.1.1  Single MLD proxy instance on MAG




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   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.

4.1.1.1  Requirements

   These are the requirements identified so far:

      - 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).


4.1.2  Remote and local multicast subscription

   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 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 [3] 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



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   directly, via a local router in the domain.

4.1.2.1  Requirements

   These are the requirements identified so far:

      - 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).

4.1.3  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 [4] 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
   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



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   being established.

   A similar approach is followed in [5] despite the solution proposed
   there differs from this approach (i.e., there is no consideration of
   an MLD proxy with multiple interfaces).

4.1.3.1  Requirements

   These are the requirements identified so far:

      - 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  Applicability to multicast source mobility

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

4.2.1  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 [1] every packet sent by the
   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



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   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 [6] 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).

4.2.1.1  Requirements

   These are the requirements identified so far:

      - 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  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.

   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



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   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.

4.2.3.1  Requirements

   These are the requirements identified so far:

      - 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.

4.2.3  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 [7].

4.2.3.1  Requirements




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   These are the requirements identified so far:

      - 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).

4.3  Summary of the requirements needed

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


























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                +----------------------------------------------------+
                |                     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 |       |
      |         | (4.1.1)|(4.1.2) | (4.1.3)|(4.2.1) |(4.2.2) |(4.2.3)|
      +---------+--------+--------+--------+--------+--------+-------+
      |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 I. Functionality needed on MLD proxy with multiple
              upstream interfaces per application scenario



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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

   Through this document several scenarios of applicability of an MLD
   proxy with multiple upstream interfaces have been presented.

   <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]  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

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



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   [3]  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.

   [4]  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.

   [5]  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

   [6]  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.

   [7]  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.




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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