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Versions: 00 01 02 03 04 draft-ietf-multimob-pmipv6-base-solution

MULTIMOB Group                                              T C. Schmidt
Internet-Draft                                               HAW Hamburg
Intended status: BCP                                        M. Waehlisch
Expires: April 19, 2010                             link-lab & FU Berlin
                                                             B. Sarikaya
                                                              Huawei USA
                                                             S. Krishnan
                                                                Ericsson
                                                        October 16, 2009


 A Minimal Deployment Option for Multicast Listeners in PMIPv6 Domains
           draft-schmidt-multimob-pmipv6-mcast-deployment-02

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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   This Internet-Draft will expire on April 19, 2010.

Copyright Notice

   Copyright (c) 2009 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   Please review these documents carefully, as they describe your rights
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Abstract

   This document describes deployment options for activating multicast
   listener functions in Proxy Mobile IPv6 domains without modifying
   mobility and multicast protocol standards.  Similar to Home Agents in
   Mobile IPv6, PMIPv6 Local Mobility Anchors serve as multicast
   subscription anchor points, while Mobile Access Gateways provide MLD
   proxy functions.  In this scenario, Mobile Nodes remain agnostic of
   multicast mobility operations.

Requirements Language

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


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Deployment Details . . . . . . . . . . . . . . . . . . . . . .  7
     4.1.  Operations of the Mobile Node  . . . . . . . . . . . . . .  7
     4.2.  Operations of the Mobile Access Gateway  . . . . . . . . .  7
     4.3.  Operations of the Local Mobility Anchor  . . . . . . . . .  8
     4.4.  A Note on Explicit Tracking  . . . . . . . . . . . . . . .  9
   5.  Message Source and Destination Address . . . . . . . . . . . .  9
     5.1.  Query  . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     5.2.  Report/Done  . . . . . . . . . . . . . . . . . . . . . . . 10
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12














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1.  Introduction

   Proxy Mobile IPv6 (PMIPv6) [RFC5213] extends Mobile IPv6 [RFC3775] by
   network-based management functions that enable IP mobility for a host
   without requiring its participation in any mobility-related
   signaling.  Additional network entities, i.e., the Local Mobility
   Anchor (LMA), and Mobile Access Gateways (MAGs), are responsible for
   managing IP mobility on behalf of the mobile node (MN).

   With these routing entities in place, the mobile node looses
   transparent end-to-end connectivity to the static Internet, and in
   the particular case of multicast communication, group membership
   management as signaled by the Multicast Listener Discovery protocol
   [RFC3810], [RFC2710] requires a dedicated treatment, see
   [I-D.deng-multimob-pmip6-requirement].

   Multicast routing functions need a careful placement within the
   PMIPv6 domain to augment unicast transmission with group
   communication services.  [RFC5213] does not explicitly address
   multicast communication, whereas bi-directional home tunneling, the
   minimal multicast support arranged by MIPv6, cannot be applied in
   network-based management scenarios: A mobility-unaware node will
   experience no reason to initiate a tunnel with an entity of mobility
   support.

   This document describes deployment options for activating multicast
   listener functions in Proxy Mobile IPv6 domains without modifying
   mobility and multicast protocol standards.  Similar to Home Agents in
   Mobile IPv6, PMIPv6 Local Mobility Anchors serve as multicast
   subscription anchor points, while Mobile Access Gateways provide MLD
   proxy functions.  Mobile Nodes in this scenario remain agnostic of
   multicast mobility operations.  Accrediting the problem space of
   multicast mobility [I-D.irtf-mobopts-mmcastv6-ps], this document does
   not address optimization potentials and efficiency improvements of
   multicast routing in network-centered mobility, as such solutions
   would require changes to the base specification of [RFC5213].


2.  Terminology

   This document uses the terminology as defined for the mobility
   protocols [RFC3775] and [RFC5213], as well as the multicast edge
   related protocols [RFC3810] and [RFC4605].

   The reference scenario for multicast deployment in Proxy Mobile IPv6
   domains is illustrated in Figure 1.





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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 1: Reference Network for Multicast Deployment in PMIPv6


3.  Overview

   An MN in a PMIPv6 domain will decide on multicast group membership
   management completely independent of its current mobility conditions.
   It will submit MLD Report and Done messages following application
   desires, thereby using its link-local source address and multicast
   destinations according to [RFC3810], or [RFC2710].  These link-local
   signaling messages will arrive at the currently active MAG via one of
   its downstream local (wireless) links.  A multicast unaware MAG would
   simply discard these MLD messages.

   To facilitate multicast in a PMIPv6 domain, an MLD proxy function
   [RFC4605] needs to be deployed on the MAG that selects the tunnel



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   interface corresponding to the MN's LMA for its upstream interface
   (cf., section 6 of [RFC5213]).  Thereby, each LMA upstream interface
   defines an MLD proxy domain at the MAG, containing all downstream
   links to MNs that share this LMA.  According to standard proxy
   operations, MLD signaling of the MN will be consequently forwarded
   under aggregation up the tunnel interface to its corresponding LMA.

   Serving as the designated multicast router or an additional MLD
   proxy, the LMA will transpose any MLD message from a MAG into the
   multicast routing infrastructure.  Correspondingly, the LMA will
   implement appropriate multicast forwarding states at its tunnel
   interface.  Traffic arriving for groups under subscription will
   arrive at the LMA, which it will forward according to all its group/
   source states.  In addition, the LMA will naturally act as an MLD
   querier, seeing its downstream tunnel interfaces as multicast enabled
   links.

   At the MAG, MLD queries and multicast data will arrive on the
   (tunnel) interface that is assigned to a group of access links as
   identified by its Binding Update List (cf., section 6 of [RFC5213]).
   As specified for MLD proxies, the MAG will forward multicast traffic
   and initiate related signaling down the appropriate access links to
   the MNs.  In proceeding this way, all multicast-related signaling and
   the data traffic will transparently flow from the LMA to the MN on an
   LMA-specific tree, which is shared among the multicast sources.

   In case of a mobility handover, the MN (unaware of IP mobility) will
   refrain from submitting unsolicited MLD reports.  Instead, the MAG is
   required to maintain group memberships in the following way.  On
   observing a new MN on a downstream link, the MAG sends a General MLD
   Query.  Based on its outcome and the multicast group states
   previously maintained at the MAG, a corresponding Report will be sent
   to the LMA aggregating group states according to the proxy function.
   Additional Reports can be omitted, whenever multicast forwarding
   states previously established at the new MAG already cover the
   subscriptions of the MN.

   After Re-Binding, the LMA is not required to issue a General MLD
   Query on the tunnel link to refresh forwarding states.  Multicast
   state updates SHOULD be triggered by the MAG, which aggregates
   subscriptions of all its MNs (see the call flow in Figure 2).










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   MN1             MAG1             MN2             MAG2             LMA
   |                |                |               |                |
   |    Join(G)     |                |               |                |
   +--------------->|                |               |                |
   |                |     Join(G)    |               |                |
   |                |<---------------+               |                |
   |                |                |               |                |
   |                |     Aggregated Join(G)         |                |
   |                +================================================>|
   |                |                |               |                |
   |                |   Mcast Data   |               |                |
   |                |<================================================+
   |                |                |               |                |
   |  Mcast Data    | Mcast Data     |               |                |
   |<---------------+--------------->|               |                |
   |                |                |               |                |
   |                |      < Movement to MAG2 & PMIP Binding Update > |
   |                |                |               |                |
   |                |                |--- Rtr Sol -->|                |
   |                |                |               |                |
   |                |                |   MLD Query   |                |
   |                |                |<--------------+                |
   |                |                |               |                |
   |                |                |   Join(G)     |                |
   |                |                +-------------->|                |
   |                |                |               Aggregated Join(G)
   |                |                |               +===============>|
   |                |                |               |                |
   |                |   Mcast Data   |               |                |
   |                |<================================================+
   |                |                |               |   Mcast Data   |
   |                |                |               |<===============+
   |  Mcast Data    |                |               |                |
   |<---------------+                |  Mcast Data   |                |
   |                |                |<--------------+                |
   |                |                |               |                |

               Figure 2: Call Flow of Multicast-enabled PMIP

   These multicast deployment considerations likewise apply for mobile
   nodes that operate with its IPv4 stack enabled in a PMIPv6 domain.
   PMIPv6 can provide an IPv4 home address mobility support
   [I-D.ietf-netlmm-pmip6-ipv4-support].  Such mobile node will use
   IGMPv3 [RFC3376] signaling for multicast, which is handled by an IGMP
   proxy function at the MAG in an analogous way.

   Following these deployment steps, multicast management transparently
   interoperates with PMIPv6.  It is worth noting that multicast streams



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   can possibly be distributed on redundant path, leading to duplicate
   traffic arriving from different LMAs at one MAG, and causing multiple
   data transmissions from a MAG over one wireless domain to different
   MNs.


4.  Deployment Details

   Multicast activation in a PMIPv6 domain requires to deploy general
   multicast functions at PMIPv6 routers and to define its interaction
   with the PMIPv6 protocol in the following way:

4.1.  Operations of the Mobile Node

   A Mobile Node willing to manage multicast traffic will join, maintain
   and leave groups as if located in the fixed Internet.  No specific
   mobility actions nor implementations are required at the MN.

4.2.  Operations of the Mobile Access Gateway

   A Mobility Access Gateway is required to assist in MLD signaling and
   data forwarding between the MNs which it serves, and the
   corresponding LMAs associated to each MN.  It therefore needs to
   implement an instance of the MLD proxy function [RFC4605] for each
   upstream tunnel interface that has been established with an LMA.  The
   MAG decides on the mapping of downstream links to a proxy instance
   (and hence an upstream link to an LMA) based on the regular Binding
   Update List as maintained by PMIPv6 standard operations (cf., section
   6.1 of [RFC5213]).

   On the reception of MLD reports from an MN, the MAG MUST identify the
   corresponding proxy instance from the incoming interface and perform
   regular MLD proxy operations: it will insert/update/remove a
   multicast forwarding state on the incoming interface, and state
   updates will be merged into the MLD proxy membership database.  An
   aggregated Report will be sent to the upstream tunnel of the MAG when
   the membership database (cf., section 4.1 of [RFC4605]) changes.
   Conversely, on the reception of MLD Queries, the MAG proxy instance
   will answer the Queries on behalf of all active downstream receivers
   maintained in its membership database.  Queries sent by the LMA do
   not force the MAG to trigger corresponding messages immediately
   towards MNs.  Multicast traffic arriving at the MAG on an upstream
   interface will be forwarded according to the group/source-specific
   forwarding states as acquired for each downstream interface within
   the MLD proxy instance.

   In case of a mobility handover, the MAG will continue to manage
   upstream tunnels and downstream interfaces as foreseen in the PMIPv6



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   specification.  However, it MUST assure consistency of its up- and
   downstream interfaces that change under mobility with MLD proxy
   instances and its multicast forwarding states.  The MAG will observe
   the arrival of a new MN by receiving a router solicitation message or
   by an upcoming link.  To learn about multicast groups subscribed by a
   newly attaching MN, the MAG sends a General Query to the MN's link.
   In case, the access link between MN and MAG goes down, interface-
   specific multicast states change.  Both cases may alter the
   composition of the membership database, which then will trigger
   corresponding Reports towards the LMA.  Note that the actual
   observable state depends on the access link model in use.

   A MN may be unable to answer MAG multicast membership queries due to
   handover procedures.  Such occurrence is equivalent to a General
   Query loss.  To prevent erroneous query timeouts at the MAG, MLD
   parameters SHOULD be carefully adjusted to the mobility regime.  In
   particular, MLD timers and the Robustness Variable (see section 9 of
   [RFC3810]) MUST be chosen to be compliant with the time scale of
   handover operations in the PMIPv6 domain.

   In proceeding this way, the MAG is entitled to aggregate multicast
   subscriptions for each of its MLD proxy instances.  However, this
   deployment approach does not prevent multiple identical streams
   arriving from different LMA upstream interfaces.  Furthermore, a per
   group forwarding into the wireless domain is restricted to the link
   model in use.

4.3.  Operations of the Local Mobility Anchor

   For any MN, the Local Mobility Anchor acts as the persistent Home
   Agent and at the same time as the default multicast querier for the
   corresponding MAG.  It implements the function of the designated
   multicast router or a further MLD proxy.  According to MLD reports
   received from a MAG (on behalf of the MNs), it establishes/maintains/
   removes group/source-specific multicast forwarding states at its
   corresponding downstream tunnel interfaces.  At the same time, it
   procures for aggregated multicast membership maintenance at its
   upstream interface.  Based on the multicast-transparent operations of
   the MAGs, the LMA experiences its tunnel interfaces as multicast
   enabled downstream links, serving zero to many listening nodes.
   Multicast traffic arriving at the LMA is transparently forwarded
   according to its multicast forwarding information base.

   On the occurrence of a mobility handover, the LMA will receive
   Binding Lifetime De-Registrations and Binding Lifetime Extensions
   that will cause a re-mapping of home network prefixes to Proxy-CoAs
   in its Binding Cache (see section 5.3 of [RFC5213]).  The multicast
   forwarding states require updating, as well, if the MN within a MLD



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   proxy domain is the only receiver of a multicast group.  Two cases
   need distinction:

   1.  The mobile node is the only receiver of a group behind the
       interface at which a De-Registration was received: The membership
       database of the MAG changes, which will trigger a Report/Done
       sent via the MAG-to-LMA interface to remove this group.  The LMA
       thus terminates multicast forwarding.

   2.  The mobile node is the only receiver of a group behind the
       interface at which a Lifetime Extension was received: The
       membership database of the MAG changes, which will trigger a
       Report sent via the MAG-to-LMA interface to add this group.  The
       LMA thus starts multicast distribution.

   In proceeding this way, each LMA will provide transparent multicast
   support for the group of MNs it serves.  It will perform traffic
   aggregation at the MN-group level and will assure that multicast data
   streams are uniquely forwarded per individual LMA-to-MAG tunnel.

4.4.  A Note on Explicit Tracking

   IGMPv3/MLDv2 [RFC3376], [RFC3810] may operate in combination with
   explicit tracking, which allows routers to monitor each multicast
   receiver.  This mechanism is not standardized yet, but widely
   implemented by vendors as it supports faster leave latencies and
   reduced signaling.

   Enabling explicit tracking on downstream interfaces of the LMA and
   MAG would track a single MAG and MN respectively per interface.  It
   may be used to preserve bandwidth on the MAG-MN link.


5.  Message Source and Destination Address

   This section describes source and destination addresses of MLD
   messages.  The interface identifier A-B denotes an interface on node
   A, which is connected to node B. This includes tunnel interfaces.













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5.1.  Query
        +===========+================+======================+==========+
        | Interface | Source Address | Destination Address  | Header   |
        +===========+================+======================+==========+
        |           | LMAA           | Proxy-CoA            | outer    |
        + LMA-MAG   +----------------+----------------------+----------+
        |           | LMA-link-local | [RFC2710], [RFC3810] | inner    |
        +-----------+----------------+----------------------+----------+
        | MAG-MN    | MAG-link-local | [RFC2710], [RFC3810] |   --     |
        +-----------+----------------+----------------------+----------+

5.2.  Report/Done
        +===========+================+======================+==========+
        | Interface | Source Address | Destination Address  | Header   |
        +===========+================+======================+==========+
        | MN-MAG    | MN-link-local  | [RFC2710], [RFC3810] |   --     |
        +-----------+----------------+----------------------+----------+
        |           | Proxy-CoA      | LMAA                 | outer    |
        + MAG-LMA   +----------------+----------------------+----------+
        |           | MAG-link-local | [RFC2710], [RFC3810] | inner    |
        +-----------+----------------+----------------------+----------+


6.  IANA Considerations

   This document makes no request of IANA.

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


7.  Security Considerations

   This draft does neither introduce additional messages nor novel
   protocol operations.  Consequently, no new threats arrive from
   procedures described in this document in excess to [RFC3810] and
   [RFC5213] security concerns.


8.  Acknowledgements

   This memo is the outcome of extensive previous discussions and a
   follow-up of several initial drafts on the subject.  The authors
   would like to thank Gorry Fairhurst, Stig Venaas, Jouni Korhonen and
   Liu Hui for advice and reviews of the document.


9.  References



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9.1.  Normative References

   [I-D.ietf-netlmm-pmip6-ipv4-support]
              Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
              Mobile IPv6", draft-ietf-netlmm-pmip6-ipv4-support-17
              (work in progress), September 2009.

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

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

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

   [RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.

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

   [RFC4605]  Fenner, B., He, H., Haberman, B., and H. Sandick,
              "Internet Group Management Protocol (IGMP) / Multicast
              Listener Discovery (MLD)-Based Multicast Forwarding
              ("IGMP/MLD Proxying")", RFC 4605, August 2006.

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

9.2.  Informative References

   [I-D.deng-multimob-pmip6-requirement]
              Deng, H., Chen, G., Schmidt, T., Seite, P., and P. Yang,
              "Multicast Support Requirements for Proxy Mobile IPv6",
              draft-deng-multimob-pmip6-requirement-02 (work in
              progress), July 2009.

   [I-D.irtf-mobopts-mmcastv6-ps]
              Fairhurst, G., "Multicast Mobility in MIPv6: Problem
              Statement and Brief Survey",
              draft-irtf-mobopts-mmcastv6-ps-08 (work in progress),
              August 2009.






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Authors' Addresses

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

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


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

   Email: mw@link-lab.net


   Behcet Sarikaya
   Huawei USA
   1700 Alma Dr. Suite 500
   Plano, TX  75075
   USA

   Email: sarikaya@ieee.org


   Suresh Krishnan
   Ericsson
   8400 Decarie Blvd.
   Town of Mount Royal, QC
   Canada

   Email: suresh.krishnan@ericsson.com














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