Softwire WG                                                      Q. Wang
Internet-Draft                                             China Telecom
Intended status: Standards Track                                  J. Qin
Expires: March 13, May 3, 2012                                                 ZTE
                                                            M. Boucadair
                                                            C. Jacquenet
                                                          France Telecom
                                                                  Y. Lee
                                                                 Comcast
                                                      September 10,
                                                        October 31, 2011

   Multicast Extensions to DS-Lite Technique in Broadband Deployments
                draft-ietf-softwire-dslite-multicast-00
                draft-ietf-softwire-dslite-multicast-01

Abstract

   This document proposes specifies a solution for the delivery of multicast
   service offerings to DS-Lite serviced customers.  The proposed
   solution relies upon a stateless IPv4-in-IPv6 encapsulation scheme
   and does not require performing any NAT operation along uses the path used IPv6 multicast distribution tree to deliver IPv4
   multicast traffic. traffic over an IPv6 multicast-enabled network.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on March 13, May 3, 2012.

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   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4  3
   3.  Context and  Scope  . . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  IPTV-centric View  . . . . . . .  4
   4.  Solution Overview  . . . . . . . . . . . . .  5
     3.2.  Scope . . . . . . . . .  5
     4.1.  IPv4-embedded IPv6 Prefixes  . . . . . . . . . . . . . . .  6
     4.2.  Multicast Distribution Tree Computation  . .  6
   4.  Solution Overview . . . . . . .  7
     4.3.  Multicast Data Forwarding  . . . . . . . . . . . . . . .  6
     4.1.  Rationale .  8
   5.  Address Mapping  . . . . . . . . . . . . . . . . . . . . . . .  7
     4.2.  IPv4-embedded IPv6 Address Prefixes  8
     5.1.  Prefix Assignment  . . . . . . . . . . .  8
     4.3.  Multicast Distribution Tree . . . . . . . . .  8
     5.2.  Examples . . . . . .  9
     4.4.  Multicast Forwarding . . . . . . . . . . . . . . . . . . . 10
     4.5.  9
   6.  Multicast DS-Lite vs. Unicast DS-Lite  . B4 (mB4) . . . . . . . . . 10
   5.  Address Mapping . . . . . . . . . . . . .  9
     6.1.  IGMP-MLD Interworking Function . . . . . . . . . . 10
     5.1.  Prefix Assignment . . . .  9
     6.2.  Multicast Data Forwarding  . . . . . . . . . . . . . . . . 10
     5.2.  Text Representation Examples .
     6.3.  Fragmentation  . . . . . . . . . . . . . . 11
   6.  Multicast B4 (mB4) . . . . . . . . 10
     6.4.  Host built-in mB4 Function . . . . . . . . . . . . . . 11
     6.1.  IGMP-MLD Interworking function . . 10
   7.  Multicast AFTR (mAFTR) . . . . . . . . . . . . 11
     6.2.  De-capsulation and Forwarding . . . . . . . . 11
     7.1.  Routing Considerations . . . . . . 12
     6.3.  Fragmentation . . . . . . . . . . . . 11
     7.2.  Processing PIM Message . . . . . . . . . . 12
     6.4.  Host with mB4 function embedded . . . . . . . . 11
     7.3.  Switching from Shared Tree to Shortest Path Tree . . . . . 12
   7.
     7.4.  Multicast AFTR (mAFTR) Data Forwarding  . . . . . . . . . . . . . . . . 12
     7.5.  TTL/Scope  . . . . . . 13
     7.1.  Routing Considerations . . . . . . . . . . . . . . . . . . 13
     7.2.  Processing PIM/MLD Join Messages
   8.  Security Considerations  . . . . . . . . . . . . . 13
     7.3.  Reliability . . . . . . 13
     8.1.  Firewall Configuration . . . . . . . . . . . . . . . . . . 13
     7.4.  ASM Mode: Building Shared Trees
   9.  Acknowledgements . . . . . . . . . . . . . 14
       7.4.1.  IPv4 Side . . . . . . . . . . 13
   10. IANA Considerations  . . . . . . . . . . . . 14
       7.4.2.  IPv6 Side . . . . . . . . . 13
   11. References . . . . . . . . . . . . . 14
     7.5.  TTL/Scope . . . . . . . . . . . . . 14
     11.1. Normative References . . . . . . . . . . . 15
     7.6.  Encapsulation and forwarding . . . . . . . . 14
     11.2. Informative References . . . . . . . 16
   8.  Optimization in L2 Access Networks . . . . . . . . . . . 15
   Appendix A.  Use Case: IPTV  . . . 16
   9.  Security Considerations . . . . . . . . . . . . . . . . 15
   Appendix B.  Deployment Considerations . . . 16
     9.1.  Firewall Configuration . . . . . . . . . . . 16
     B.1.  Load-Balancing . . . . . . . 17
   10. Acknowledgements . . . . . . . . . . . . . . . 16
     B.2.  RP for IPv4-Embedded IPv6 Multicast Groups . . . . . . . . 17
   11. IANA Considerations 16
     B.3.  mAFTR Policy Configuration . . . . . . . . . . . . . . . . . . . . . 17
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     12.1. Normative References . . . . . . . 16
     B.4.  Static vs. Dynamic PIM Triggering  . . . . . . . . . . . . 17
     12.2. Informative References . . . . . . . . . . . . . . . . . . 18
   Appendix A.  Translation vs. Encapsulation . . . . . . . . . . . . 19
     A.1.  Translation  . . . . . . . . . . . . . . . . . . . . . . . 19
     A.2.  Encapsulation  . . . . . . . . . . . . . . . . . . . . . . 19
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19 17

1.  Introduction

   DS-Lite [RFC6333] is a technique to rationalize that rationalizes the use usage of the
   remaining global IPv4 addresses during the transition period.  The current
   design of period by
   sharing a single IPv4 address with multiple users.  A typical DS-Lite
   scenario is the delivery of an IPv4 service to an IPv4 user over an
   IPv6 network (denoted as a 4-6-4 scenario).  [RFC6333] covers unicast
   services exclusively.

   If customers have to access IPv4 multicast-based service offerings services through a
   DS-Lite DS-
   Lite environment, AFTR (Address Address Family Transition Router) Router (AFTR) devices
   will have to process all the IGMP reports Report messages [RFC2236] [RFC3376] received
   within
   that have been forwarded by the CPE into the IPv4-in-IPv6 tunnels and tunnels.
   From that standpoint, AFTR devices are likely to behave as a
   replication point for downstream multicast traffic.  That is likely to severely affect  And the
   multicast traffic forwarding efficiency by losing packets will be replicated for each tunnel endpoint where
   IPv4 receivers are connected to.

   This kind of DS-Lite environment raises two major issues:

   1.  The IPv6 network loses the benefits of
   deterministic replication of the multicast traffic
       forwarding efficiency because it is unable to deterministically
       replicate the data as close to the receivers as possible.  As a
       consequence, the downstream bandwidth in the IPv6 network will be
       vastly consumed while the AFTR capability may become rapidly overloaded, in
   particular if the by sending multicast data over a unicast
       infrastructure.

   2.  The AFTR capability is deployed in a centralized
   manner.

   This document discusses an extension to responsible for replicating multicast traffic and
       forwarding it into each tunnel endpoint connecting IPv4 receivers
       that have explicitly asked for the corresponding contents.  This
       process may greatly consume AFTR's resources and overload the
       AFTR.

   This document specifies an extension to the DS-Lite model to be used
   for the delivery of deliver
   IPv4 multicast-based service offerings. multicast services to IPv4 clients over an IPv6 multicast-
   enabled network.

1.1.  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].

2.  Terminology

   This document makes use of the following terms:

   o  IPv4-embedded IPv6 address: is an IPv6 address which embeds a 32 32-
      bit-encoded IPv4 address.  An IPv4-embedded IPv6 address can be
      unicast or multicast.

   o  mPrefix64: is a dedicated multicast IPv6 prefix for constructing
      IPv4-embedded IPv6 multicast address addresses
      [I-D.boucadair-behave-64-multicast-address-format]. mPrefix64 can
      be of two types: ASM_mPrefix64 used in ASM Any Source Multicast (ASM)
      mode or SSM_mPrefix64 used in SSM Source Specific Multicast (SSM) mode
      [RFC4607].

   o  uPrefix64: is a dedicated unicast IPv6 unicast prefix for constructing
      IPv4-embedded
      IPv4- embedded IPv6 unicast address addresses [RFC6052].

   o  Multicast AFTR (mAFTR for short): (mAFTR): is a functional entity which is
      part of both the IPv4 and supports
      IPv4- IPv6 multicast distribution trees interworking function (refer to Figure 3).
      It receives and
      which replicates encapsulates the IPv4 multicast streams packets into IPv4-in-IPv6 streams
      in the relevant branches of IPv4-
      in-IPv6 packets and behaves as the corresponding IPv6 multicast distribution tree.
      source for the encapsulated IPv4-in-IPv6 packets.

   o  Multicast B4 (mB4 for short): (mB4): is a functional entity embedded in a CPE,
      which is able to enforce supports an IGMP-MLD interworking function (
      refer (refer to
      Section 6.1) together with a de-capsulation function of
      received multicast IPv4-in-IPv6 packets.

3.  Context and Scope

3.1.  IPTV-centric View

   IPTV generally includes two categories of service offerings:

   1.  VoD (Video on Demand) or Catch-up TV channels streams that are
       delivered using unicast mode to receivers.

   2.  Live TV Broadcast services that are generally multicast to
       receivers.

   Numerous players intervene relays information conveyed in the delivery of this service:

   o  Content Providers: the content can be provided IGMP messages by
      forwarding the same
      provider as corresponding MLD messages towards the one providing MLD Querier
      in the connectivity service or by
      distinct providers;

   o  Network Provider: IPv6 network.  In addition, the one providing network connectivity service
      (e.g., responsible for carrying mB4 decapsulates IPv4-in-
      IPv6 multicast flows from head-ends to
      receivers).  Refer packets.

   o  PIMv4: refers to [I-D.ietf-mboned-multiaaa-framework].

   Many of the current IPTV contents PIM when deployed in an IPv4 infrastructure
      (i.e., IPv4 transfer capabilities are likely used to remain IPv4-formatted
   and out of control of the network providers.  Additionally, there exchange PIM
      messages).

   o  PIMv6: refers to PIM when deployed in an IPv6 infrastructure
      (i.e., IPv6 transfer capabilities are
   numerous legacy receivers (e.g., IPv4-only Set Top Boxes (STB)) that
   can't be upgraded or be easily replaced.  As a consequence, IPv4
   service continuity must be guaranteed during the transition period,
   including the delivery of multicast-based services such as Live TV
   Broadcasting.  The dilemma is the same as in the transition of
   unicast-based Internet services where the customer premises and
   global Internet are out of control of the service providers even if
   they would like to promote the use of IPv6.  The DS-Lite design tries
   to eliminate this issue by decoupling the IPv6 deployments in service
   provider networks from that in global Internet and in customer
   devices and applications.

   DS-Lite can be seen as a catalyst for IPv6 deployment while
   preserving customer's Quality of Experience (QoE).  This is also the
   design goal of the solution proposed in this document for DS-Lite
   serviced customers who have subscribed used to a multicast-based service
   offering.

3.2. exchange PIM
      messages).

3.  Scope

   This document focuses only on issues raised by a DS-Lite networking environment:
   subscription to an IPv4 multicast group and the delivery of IPv4-formatted IPv4-
   formatted content to IPv4 receivers. receivers over an IPv6-only network.  In
   particular, only the following case is covered:

   1.

      An IPv4 receiver accessing accesses IPv4 content (i.e., content formatted
       and reachable in IPv4)

   A viable scenario for this use case in DS-Lite environment: Customers
   with legacy receivers must continue to access the IPv4-enabled multicast services.  This means the traffic should be accessed
   through IPv4 and additional functions are needed to traverse
   operators' contents over an IPv6- enabled network which is the purpose of this
   document.  While since technically, there is no extra function
   required for the scenario of native access (i.e. to access dual-stack
   content natively from the IPv6 receiver), this portion is not taken
   into account.  Refer to [I-D.jaclee-behave-v4v6-mcast-ps] for the
   deployment considerations.
      only multicast-enabled network.

   This document does not cover the case source/receiver heuristics, where an as
   IPv4 host connected to
   a CPE served by a DS-Lite AFTR receiver can be the source of also behave as an IPv4 multicast
   traffic.

   Note source.  This
   document assumes that some contract agreements prevent a network provider to
   alter hosts behind the content as sent by the content provider, in particular for
   copyright, confidentiality and SLA assurance reasons.  The streams
   should be delivered unaltered to requesting users.

4.  Solution Overview

   In mB4 are IPv4 multicast
   receivers only.

4.  Solution Overview

   In the original DS-Lite specification [RFC6333], an IPv4-in-IPv6
   tunnel is used to carry the bidirectional IPv4 unicast traffic between a
   B4 and an AFTR.  This  An extension to DS-Lite is proposed in this document defines
   which specifies an IPv4-in-IPv6 encapsulation scheme to deliver multicast traffic.  Within the
   context of this document, an IPv4 derived IPv6 multicast address is
   used as the destination of the encapsulated
   unidirectional IPv4-in-
   IPv6 IPv4 multicast traffic from the a mAFTR to the a mB4.  The IPv4 address
   of the source

   An overview of the multicast content solution is represented provided in the IPv6
   realm with an IPv4-embedded IPv6 address this section which is
   intended as well.

   See following sections for the multicast distribution tree
   establishment (Section 4.3) and the multicast traffic forwarding
   (Section 4.4).

   Note that IPv4-in-IPv6 encapsulated multicast flows are treated in an
   IPv6 realm like any other IPv6 multicast flow.  Upon completion of introduction to how it works, but is NOT normative.
   For the establishment normative specifications of a multicast distribution tree, no extra function
   is required to be defined to forward IPv4-in-IPv6 multicast traffic
   in the IPv6 network.

4.1.  Rationale

   This document introduces two new functional elements (Figure 1):

   1.  The mAFTR: responsible for replicating IPv4 multicast flows in
       the IPv6 domain owing to a stateless IPv4-in-IPv6 encapsulation
       function.  The mAFTR does not undertake any NAT operation.  The elements:
   mB4 and mAFTR is a demarcation point which connects (Figure 1), refer to both the IPv4 and
       IPv6 multicast networks.

   2.  The mB4: is a functional entity embedded in a CPE responsible for
       the de-capsulation of the received IPv4-in-IPv6 multicast packets Section 6 and forwarding them to the appropriate IPv4 receivers.

                                +-----------+
                                |   IPv4    |
                                |  Source   |
                                +-----------+
                                      | Section 7.

                             ------------
                           /              \
                          |  IPv4 network  |
                           \              /
                             ------------
               IPv4 multicast  :   |   ^  PIMv4 Join
                               v   |   :
                            +-------------+
                            |    mAFTR    |
                            +-------------+
              IPv6 multicast  |:|  |   ^  PIMv6 Join (PIMv6
              (IPv4 embedded) |:|  |   :   routers in between)
                             ------------
                           /              \
                          |  IPv6 network  |
                           \              /
                             ------------
                              |:|  |   :  MLD Report
                              |v|  |   :
                             +-----------+
                             |    mB4    |
                             +-----------+
               IPv4 multicast  :   |   ^  IGMP Report
                               v   |   :
                             +-----------+
                             |   IPv4    |
                             | Receiver receiver  |
                             +-----------+

                     Figure 1: Functional Architecture

4.2.

4.1.  IPv4-embedded IPv6 Address Prefixes

   A dedicated IPv6 multicast prefix (mPrefix64) is needed for forming

   In order to map the addresses of IPv4 multicast traffic with IPv6
   multicast addresses, with IPv4 an IPv6 multicast address embedded.  The
   mPrefix64 can be prefix (mPrefix64) and an IPv6
   unicast prefix (uPrefix64) are provided to mAFTR and mB4 elements,
   both of two types: ASM_mPrefix64 (an mPrefix64 used in
   ASM mode) or SSM_mPrefix64 (an mPrefix64 used in SSM mode), which contribute to the computation and MUST
   be derived from the corresponding maintenance of
   the IPv6 multicast address space
   [I-D.boucadair-behave-64-multicast-address-format].

   In addition, the address of distribution tree that extends the IPv4 multicast source should be
   mapped to IPv6 addresses in
   distribution tree into the IPv6 realm: multicast network.

   The mAFTR and mB4 use mPrefix64 to convert an IPv6 unicast prefix
   (uPrefix64) is therefore needed for forming IPv6 unicast addresses
   with IPv4 unicast multicast address
   (G4) to an IPv4-embedded IPv6 multicast address embedded. (G6).  The mAFTR and
   mB4 use uPrefix64 MUST be derived
   from the to convert an IPv4 multicast source address (S4) to
   an IPv4-embedded IPv6 unicast address space [RFC6052]. (S6).  The mAFTR and mB4 MUST use the
   same mPrefix64 and uPrefix64, and as well as run the same algorithm for
   building IPv4-embedded IPv6 addresses.  Refer to Section 5 for more
   details on about the IPv6 address format.

4.3. mapping.

4.2.  Multicast Distribution Tree

   Assume that Computation

   When an IPv4 receiver connected to the CPE that embeds mB4 wants to
   subscribe to an IPv4 multicast group, it sends an IGMP Report towards message
   to the mB4.  The mB4 to
   join a given creates the IPv6 multicast group.  After receiving group (G6) address
   using mPrefix64 and the IGMP original IPv4 multicast gorup address.  If
   the receiver sends a source-specific IGMPv3 Report message, the mB4 converts
   will create the IGMP message into a IPv6 source address (S6) using uPrefix64 and the
   original IPv4 source address.

   The mB4 uses the G6 (and both S6 and G6 in SSM) to create the
   corresponding MLD Report
   [RFC2710] message.  The mB4 sends the Report message which will then be forwarded upstream towards
   to the MLD Querier. Querier in the IPv6 network.  The MLD Querier is likely to coexist with the PIM DR
   where (typically
   acts as the PIMv6 Join Designated Router) receives the MLD Report message will be triggered
   and sent up hop by hop
   along sends the PIMv6 routers.  Note that Join to join the mAFTR is IPv6 multicast distribution
   tree.  The MLD Querier can send either PIMv6 Join (*,G6) in ASM or
   PIMv6 Join (S6,G6) in SSM to the path mAFTR.

   The mAFTR acts as the DR to reach which the IPv4 source; this uPrefix64-derived S6 is typically achieved by the underlying unicast
   IPv6 routing protocol that advertises
   connected.  The mAFTR will receive the unicast IPv4-embedded IPv6
   addresses: these addresses are used to represent IPv4 sources in source-specific PIMv6 Join
   message (S6,G6) from the IPv6 multicast domain.

   Both network.  If the MLD and mAFTR is the
   Rendezvous Point (RP) of G6, it will receive the any-source PIMv6
   Join messages convey message (*,G6) from the IPv6 address multicast network.  If the mAFTR is
   not the RP of G6, it will send the multicast group PIM Register message to be joined.  The corresponding the RP of
   G6 located in the IPv6 multicast
   group address is constructed by using network.

   When the pre-configured mPrefix64
   and an algorithm so that mAFTR receives the PIMv6 Join message (*,G6), it will
   extract the IPv4 multicast group address (G4).  If the mAFTR is embedded
   accordingly.

   When source-specific multicast is deployed, the IPv6 address
   RP of G4 in the IPv4 multicast source should be constructed network, it will create a (*,G4) entry
   (if there is not yet an existing one) in the same way (using
   uPrefix64, with its own IPv4 multicast source embedded).  Refer to Section
   6.1 for more details of the mB4 function.

   o
   routing table.  If the mAFTR is embedded in not the MLD Querier/PIMv6 DR, RP of G4, it should
      process the received MLD Report message for the IPv4-embedded IPv6
      group and will send the
   corresponding IPv4 PIM PIMv4 Join message.

   o  If message (*,G4) towards the mAFTR is embedded RP of G4 in some upstream PIMv6 router more than
      one hop away from the mB4, it should process
   IPv4 multicast network.

   When the mAFTR receives the received PIMv6 Join message for (S6,G6), it will
   extract the IPv4-embedded IPv6 IPv4 multicast group address (G4) and IPv4 source address
   (S4) and send the corresponding IPv4 PIM (S4,G4) PIMv4 Join message.

   In both cases, an entry for an IPv6 multicast group address is
   created by the mAFTR in its multicast Routing Information Base and is
   used to forward multicast IPv4-in-IPv6 datagrams.  Refer message directly
   to Section
   7.1 for more details about the mAFTR function. IPv4 source.

   A branch of the multicast distribution tree is then established, grafted,
   comprising both an IPv4 part (from the mAFTR upstream) and an IPv6
   part (between (from mAFTR downstream to the mB4 and mB4).

   The mAFTR MUST advertise the route of uPrefix64 with an IPv6 IGP, so
   as to represent the IPv4-embedded IPv6 source in the mAFTR).

4.4. IPv6 multicast
   network.

4.3.  Multicast Data Forwarding

   Whenever

   When the mAFTR receives an IPv4 multicast packet is received on a mAFTR (this
   assumes the RPF Check has passed Section 7.1), packet, it will be
   encapsulated encapsulate
   the packet into an IPv6 multicast packet using the IPv4-embedded IPv6
   multicast address as the destination address and an IPv4-embedded
   IPv6 unicast address as the source of the IPv4-in-IPv6 packet. address.  The
   new encapsulated IPv6
   multicast packet will then be sent through the outgoing
   interface of the matching entry in the multicast routing table and forwarded down the IPv6 multicast
   distribution tree towards and the mB4.

   When receiving mB4 will eventually receive the packet, packet.

   The IPv6 multicast network treats the IPv4-in-IPv6 encapsulated
   multicast packets as native.  The IPv6 multicast routers use the
   outer IPv6 header to make forwarding decisions.

   When the mB4 should de-capsulate receive the IPv6 multicast packet (to G6) derived by
   mPrefix64, it MUST decapsulate it and forward the original IPv4
   multicast packet to the appropriate receiver.  If
   mB4 does not have any route to forward the packet (e.g., change of
   the IPv4 address without cleaning MLD states), the encapsulated IPv4
   datagram is silently dropped.

   Note that: There is an alternative to the encapsulation based
   mechanism (which is detailed in this memo) for Multicast Forwarding:
   Translation based approach, which is per
   [I-D.boucadair-behave-64-multicast-address-format], [RFC6052] and
   [RFC6145].  Refer to Appendix A.

4.5.  Multicast DS-Lite vs. Unicast DS-Lite

   Unlike a unicast AFTR, a mAFTR does not perform any NAT for
   delivering IPv4 multicast traffic.

   Unlike unicast DS-Lite, a mB4 does not need receivers subscribing to discover a mAFTR.

   mAFTR is responsible for encapsulating in a stateless manner the IPv4
   multicast traffic into G4.

5.  Address Mapping

5.1.  Prefix Assignment

   A dedicated IPv6 datagrams. mB4 is responsible for de-
   capsulating in a stateless manner the IPv4-in-IPv6 multicast traffic.
   Further elaboration prefix (mPrefix64) is provided in the following sections about the
   behaviour of provisioned to the
   mAFTR and the mB4.  The corresponding multicast DS-Lite mAFTR and the unicast DS-Lite
   functional elements mB4 use the mPrefix64 to form
   an IPv6 multicast group address from an IPv4 multicast group address.
   The mPrefix64 can be co-located of two types: ASM_mPrefix64 (a mPrefix64 used in the same device
   ASM mode) or
   separated.

5.  Address Mapping

5.1.  Prefix Assignment

   In order to map SSM_mPrefix64 (a mPrefix64 used in SSM mode).  The
   mPrefix64 Must be derived from the addresses corresponding IPv6 multicast
   address space (e.g., the SSM_mPrefix64 MUST be in the range of IPv4
   multicast traffic with address space specified in [RFC4607]).

   The IPv6 part of the multicast addresses, distribution tree can be seen as an IPv6
   extension of the IPv4 part of the multicast prefix (mPrefix64) and distribution tree.  The
   IPv4 multicast source address MUST be mapped to an IPv6 multicast
   source address.  An IPv6 unicast prefix (uPrefix64) are provided is provisioned to
   the mAFTR and the mB4.  The mAFTR and the mB4 elements. use the uPrefix64 to
   form an IPv6 multicast source address from an IPv4 multicast source
   address.  The uPrefix-formed IPv6 multicast source address will
   represent the original IPv4 multicast source in the IPv6 multicast
   network.  The uPrefix64 MUST be derived from the IPv6 unicast address
   space.

   The address format to be used is being left to the responsibility of the service provider as indicated in [RFC6052]
   network provider.  The address synthesizing MUST follow
   [I-D.boucadair-behave-64-multicast-address-format] and
   [I-D.boucadair-behave-64-multicast-address-format]. [RFC6052].

   The mPrefix64 and uPrefix64 together with the address format to be
   used can be configured in the mB4 through using a
   variety of methods, including an out-of-band mechanism, manual
   configuration, or a dedicated provisioning
   protocol, such as DHCPv6 or another protocol.  Two candidate protocol (e.g., using
   DHCPv6
   options are identified in [I-D.ietf-behave-nat64-learn-analysis]. [I-D.qin-softwire-multicast-prefix-option]).

5.2.  Text Representation  Examples

    Group address mapping example when a /96 is used:

   +----------------------+--------------+-----------------------------+

    +---------------------+--------------+----------------------------+
    |      mPrefix64      | IPv4 address | IPv4-Embedded IPv6 address |
   +----------------------+--------------+-----------------------------+
    +---------------------+--------------+----------------------------+
    |    ffxx:abc::/96    |  230.1.2.3   |     ffxx:abc::230.1.2.3    |
   +----------------------+--------------+-----------------------------+
    +---------------------+--------------+----------------------------+

    Source address mapping example when a /96 is used:

   +----------------------+--------------+-----------------------------+

    +---------------------+--------------+----------------------------+
    |      uPrefix64      | IPv4 address | IPv4-Embedded IPv6 address |
   +----------------------+--------------+-----------------------------+
    +---------------------+--------------+----------------------------+
    |    2001:db8::/96    |  192.1.2.3   |     2001:db8::192.1.2.3    |
   +----------------------+--------------+-----------------------------+
    +---------------------+--------------+----------------------------+

6.  Multicast B4 (mB4)

6.1.  IGMP-MLD Interworking function Function

   The IGMP-MLD Interworking function Function combines the IGMP/MLD Proxying
   function specified in [RFC4605] and the IGMP/MLD adaptation translation function.  The IGMP/MLD
   Proxying function
   which is meant to reflect specified in [RFC4605].  The IGMP/MLD
   translation function translates the contents of IGMP messages into
   MLD
   messages.

   Then messages by using a stateless algorithm.  The address
   synthesizing MUST comply with the rules documented in Section 5.  MLD
   messages will be forwarded natively towards the MLD Querier located
   upstream in the IPv6 network.  The mB4 performs the router portion of IGMP-MLD
   Interworking Function to relay between the IGMP protocol on each
   downstream interface messages and performs the host portion of the MLD
   protocol on the upstream interface (Figure 2).

   The output of the operation is a set of membership information which
   is maintained separately on each downstream interface (e.g., Wifi and
   Wired Ethernet).  In addition, the membership information on each
   downstream interface is merged into the membership database on which
   the IPv4 multicast packets are forwarded by mB4.
   messages.

             +----------+   IGMP  +-------+   MLD   +---------+
             |   IPv4   |---------|  CPE  mB4  |---------|   MLD   |
             | Receiver |         |  mB4       |         | Querier |
             +----------+         +-------+         +---------+

                      Figure 2: IGMP-MLD Interworking

   When the mB4 receives an IGMP Report message is received from a receiver to
   subscribe to a given multicast group G (e.g., 230.1.2.3) (and optionally associated to a source 192.1.2.3 if
   in SSM mode is used), the mB4 mode), it MUST
   send an translate the IGMP Report message into a MLD
   Report message to subscribe and send to the corresponding MLD Querier.  The mB4 MUST construct
   the IPv6 multicast group identified by address using the mPrefix64.

   When the mB4 receives an IPv4-embedded IPv6 MLD Listener Query message from the MLD
   Querier, it MUST convert the MLD listener Query message to the IGMP
   Query message and send it to the IPv4 receiver(s).  The mB4 MUST
   retrieve the IPv4 multicast group address using a
   pre-configured prefix and algorithm (e.g., ffxx:abc::230.1.2.3 (and
   optionally source 2001:db8::192.1.2.3 if the mPrefix64.

   If SSM mode is used)). deployed, the mB4 MUST construct the IPv6 source address
   (or retrieve the IPv4 source address) using the uPrefix64.  The MLD
   Report message is sent through mB4
   may create a membership database which associates the upstream interface natively (i.e.,
   without any encapsulation).

6.2.  De-capsulation IPv4-IPv6
   multicast groups with the interfaces (e.g., Wi-Fi and Wired Ethernet)
   facing IPv4 multicast receivers.

6.2.  Multicast Data Forwarding

   When the mB4 receives an IPv6 multicast packet, it checks whether MUST check the
   group address is in the range of mPrefix64 and the source address address.  If the IPv6 multicast group
   prefix is
   in mPrefix64 and the range of uPrefix64.  If it IPv6 source prefix is true, uPrefix64, the mB4
   MUST de-capsulate the IPv4-in-IPv6 packets to extract the original IPv4 multicast
   packets.

   Then IPv6 header and forward the IPv4 multicast
   packet will be forwarded to downstream
   receivers based on information maintained by through each relevant interface.  Otherwise, the mB4 in MUST drop
   the
   membership database.  If no route packet silently.

   As an illustration, if a packet is found, received from source 2001:db8::
   192.1.2.3 and to be forwarded to group ffxx:abc::230.1.2.3, the mB4
   will de-capsulate it into an IPv4 multicast packet is silently
   dropped. using 192.1.2.3 as
   the IPv4 multicast source address and using 230.1.2.3 as the IPv4
   destination address.

6.3.  Fragmentation

   Encapsulating IPv4 over multicast packets into IPv6 from multicast packets that
   will be forwarded by the mAFTR to the mB4 for data forwarding along the IPv6 multicast
   distribution tree reduces the effective MTU size by the size of an
   IPv6 header
   (assuming [RFC2473] encapsulation).  To avoid fragmentation, a
   service provider may increase header.  In this specification, the MTU size by 40 bytes on data flow is unidirection
   from mAFTR to mB4, the IPv6
   network or mAFTR and must fragment the oversized IPv6 packet
   after the encapsulation into two IPv6 packets.  The mB4 may use MUST
   reassemable the IPv6 Path MTU discovery. packets, decapsulate the IPv6 packet, and
   forward the IPv4 packet to the hosts subscribing the multicast group.
   Further considerations about fragmentation issues are documented in
   [RFC6333].

6.4.  Host with built-in mB4 function embedded

   The Function

   If the mB4 function can be embedded is implemented in the CE or in a dual-stack host
   behind the CP router (e.g., STB).  If mB4 which is embedded directly
   connected to an IPv6-only network.  If an IPv4 application running in
   the STB, host requests to subscribe an IPv4 multicast stream, the
   IGMP-MLD interworking function is not needed. host
   MUST implement Section 6.1, Section 6.2, and Section 6.3.  The STB should
   formulate host
   MAY optimize the MLD message correspondingly based on given IPv4 group
   address implemntation to be joint using mPrefix64 (and uPrefix64 for IPv4-embedded
   source if SSM provide an Application Programming
   Interface (API) or kernel module to skip the IGMP-MLD Interworking
   Function.  The optimization is deployed), and de-encapsulate out of scope of the downstream
   multicast traffics received by itself. specification.

7.  Multicast AFTR (mAFTR)

7.1.  Routing Considerations

   Except the need

   The mAFTR is responsible for interconnecting the mAFTR to belong to IPv4 multicast
   distribution trees and to be on the reverse path towards the source
   when performing RPF checks on PIMv6 routers, no further routing
   constraint is to be taken into account.

   Having tree with the corresponding IPv6 multicast distribution
   tree.  The mAFTR in MUST use the reverse path ensures PIM Join sent uPrefix64 to build the IPv6 source (e.g., SSM mode or SPT mode in ASM) will be intercepted by the
   mAFTR.

7.2.  Processing PIM/MLD Join Messages

   Upon receipt
   addresses of the PIM/MLD Join for an IPv6 multicast group (e.g., ffxx:abc::
   230.1.2.3), address derived from mPrefix64.  In
   other words, the mAFTR checks MUST be the corresponding entry in multicast source derived from
   mPrefix64.

   The mAFTR MUST advertise the route of uPrefix64 to the IPv6 IGP.
   This is needed for the IPv6 multicast router to have routing table and adds
   information to discover the source.  In order to pass the Reverse
   Path Forwarding (RPF) check, the IPv6 interface through which routers MUST enable PIM on the
   Join message
   interfaces which has been received into the Out-Interface-List of that
   entry.  If shortest path to the entry does not exist, a new one will be created, as
   per typical uPrefix64.

7.2.  Processing PIM machinery [RFC4601]. Message

   The mAFTR should check whether MUST interwork PIM Join/Prune messages for (*, G6) and (S6,
   G6) on their corresponding (*, G4) and (S4, G4).  The following text
   specifies the expected behavior of mAFTR for PIM Join message.

                                +---------+
                       ---------|  mAFTR  |---------
                         PIMv6  |uPrefix64|  PIMv4
                                |mPreifx64|
                                +---------+

                Figure 3: PIMv6-PIMv4 Interworking Function

   The mAFTR contains two separate multicast routing table (mRIB): IPv4
   multicast routing table (mRIB4) and IPv6 group address belongs to multicast routing table
   (mRIB6), which are bridged by one IPv4-in-IPv6 virtual interface.  It
   should be noted that the mPrefix64 implementations may vary (e.g., ffxx:
   abc::/96).  If so, using one
   integrated mRIB without any virtual interface), while they should
   follow the mAFTR will need to extract specification herein for the IPv4 consistency of overall
   functionality.

   When a mAFTR receives a PIMv6 Join message (*,G6) with an IPv6
   multicast group address (e.g., 230.1.2.3) (G6) that is derived from the IPv4-embedded IPv6 address (e.g.,
   according to [I-D.boucadair-behave-64-multicast-address-format]) and mPrefix64, it
   MUST check the corresponding entry in the IPv4 its IPv6 multicast routing table
   then add (mRIB6).  If there is an
   entry for this G6, it MUST check whether the tunnel interface into through which
   the Out-Interface-List of that
   entry. PIMv6 Join message has been received is on the outgoing interface
   list.  If not, the mAFTR MUST add the interface to the outgoing
   interface list.  If there is no entry does not exist, in the mRIB6, the mAFTR MUST
   create a new entry should be created
   and a PIM join message (*,G6) for that IPv4 group will be sent towards the
   RP multicast group.  While, whether or source connected
   not to set the IPv4 network.

   When SSM IPv4-in-IPv6 virtual interface as the incoming
   interface of the newly created entry is deployed, up to the implementation but
   should comply with the mAFTR's behavior of multicast data forwarding,
   see Section 7.4.

   The mAFTR would in addition check if MUST extract the source
   (e.g., 2001:db8::192.1.2.3) described IPv4 multicast group address (G4) from the
   IPv4-embedded IPv6 multicast address (G6) contained in the PIMv6 Join message
   belongs to uPrefix64 (e.g., 2001:db8::/96).
   message.  The mAFTR MUST check its IPv4 multicast routing table
   (mRIB4).  If so, there is an entry for G4, it can then send
   a PIM (S, G) Join message directly towards the IPv4 source (e.g.,
   192.1.2.3).

   The initialization of MUST check whether the tunnel
   IPv4-in-IPv6 virtual interface (used for encapsulation
   purposes) on the mAFTR is out of the scope of this document.

7.3.  Reliability

   For robustness, reliability and load distribution purposes, several
   nodes in on the network can embed outgoing interface list.  If
   not, the mAFTR function.  In such case, MUST add the
   same IPv6 prefixes (i.e., mPrefix64 and uPrefix64) and algorithm interface to
   build IPv4-embedded IPv6 addresses MUST be configured on those nodes.

7.4.  ASM Mode: Building Shared Trees

7.4.1.  IPv4 Side

   For a given Rendezvous Point (RP) used in the IPv4 realm, outgoing interface list.
   If there is no
   new requirement.  Like any other IPv4 PIM router, the RP of each IPv4
   multicast groups is configured to entry for G4, the mAFTR or discovered using some
   appropriate means.  Moreover, PIM-SM registration MUST create a new (*,G4) entry
   in its mRIB4 and initiate the procedure [RFC4601] for building the shared tree
   in the IPv4 realm is not impacted.

   Shared IPv4 multicast trees network without any additional requirement.

   If mAFTR receives a source-specific Join message, the (S6, G6) will
   be processed rather than (*,G6).  The procedures of processing
   (S6,G6) and (*,G6) are built using almost the procedure defined same.  Differences have been
   detailed in
   [RFC4601] for instance.

7.4.2.  IPv6 Side

   In [RFC4601].

7.3.  Switching from Shared Tree to Shortest Path Tree

   When the IPv6 side, mAFTR receives the RP of IPv4-embedded IPv6 first IPv4 multicast groups is
   configured to all IPv6 PIM routers or discovered using appropriate
   means.  For the sake of simplicity, packet, it is RECOMMENDED to configure may
   extract the multicast source address (S4) from the packet and send an
   Explicit PIMv4 (S4,G4) Join message directly to S4.  The mAFTR as will
   switch from the RP shared Rendezvous Point Tree (RPT) to the Shortest
   Path Tree (SPT) for IPv4-embedded IPv6 multicast groups.

      [Note 1: If some other G4.

   For IPv6 multicast router wants routers to switch to become the
      RP of the IPv4-embedded SPT, there is no new
   requirement.  IPv6 multicast groups, it routers may require send an
      mAFTR Explicit PIMv6 Join
   to emulate the PIM Source Register procedure on behalf of
      IPv4-embedded IPv6 sources with the RP.  The PIM Source Register
      procedure in mAFTR once the IPv4 domain is not altered.]

      [Note 2: How first (S6,G6) multicast packet arrives from
   upstream multicast routers.

7.4.  Multicast Data Forwarding

   When the mAFTR is aware about receives an IPv4 multicast packet, it will look up the sources?  This can be
      considered as deployment-specific:

         (i) By configuration: mAFTR can be configured
   mRIB4 to join find a set of
         IPv4 multicast groups matching entry and then forward the packet to initiate a registration procedure the
   interface(s) on behalf of a set of sources to the RP in outgoing interface list.  If the v6 domain;

         (ii) Dynamic: this assumes that mAFTR is configured IPv4-in-IPv6
   virtual interface also belongs to join a
         set of IPv4 multicast groups.  The source address of received
         flows this list, the packet will be used as a trigger to initiate
   encapsulated with the registration
         procedure mPrefix64-derived and uPrefix64-derived IPv4-
   embedded IPv6 addresses to the RP in the form an IPv6 domain.  There multicast packet.  Then
   another lookup is executed to find a special
         case where mAFTR is the RP of the IPv4 group matching entry in the IPv4
         domain: The registration procedure should then be relayed mRIB6,
   while whether or not to perform RPF check for the RP in second lookup is up
   to the IPv6 domain.

      ]

   Shared implementation and is out of the scope of this document.  The
   IPv6 multicast trees are built using packet is forwarded along the procedure defined IPv6 multicast
   distribution tree, based upon the outgoing interface list of the
   matching entry in
   [RFC4601] for instance.  Switching from the mRIB6.

   As an illustration, if a shared tree packet is received from source 192.1.2.3 and
   to source-based
   tree can be accommodated since the mAFTR is in the path forwarded to join group 230.1.2.3, the
   source.

   The mAFTR will graft to the IPv4 shared tree either because encapsulates it has
   been configured with the list of IPv4 into an
   IPv6 multicast groups that will be
   subscribed by the DS-Lite serviced receivers downstream or upon
   receipt of a PIMv6 Join message.

   An example of packet using ffxx:abc::230.1.2.3 as the exchange of PIM messages is illustrated in
   Figure 3.

                    ------------
                  /              \
                 |  IPv4 network  |
                  \              /
                    ------------
                      :   |   ^
      IPv4 Multicast  :   |   :  PIMv4 Join
                      v   |   :
                   +-------------+
                   |    mAFTR    |
                   +-------------+
                     |:|  |   ^ IPv6 Multicast  |:|  |   : (PIMv6 Join, PIMv6 Routers in between)
     (IPv4 embedded) |.| ...  .
                    ------------
                  /              \
                 |
   destination address and using 2001:db8::192.1.2.3 as the IPv6 network  |
                  \              /
                    ------------
                     |:|  |   :  MLD Report
                     |v|  |   :
                    +-----------+
                    |    mB4    |
                    +-----------+
                      :   |   ^
      IPv4 Multicast  :   |   :  IGMP Report
                      v   |   :
                    +-----------+
                    |   IPv4    |
                    | Receiver  |
                    +-----------+

                       Figure 3: Procedure Overview
   multicast source address.

7.5.  TTL/Scope

   The Scope field of IPv4-in-IPv6 multicast addresses can be valued to
   "E" (Global scope) or to "8" (Organization-local scope).  This is
   left
   specification does not discuss the scope value that should be used.

8.  Security Considerations

   This document does not introduce any new security concern in addition
   to service providers taste.

7.6.  Encapsulation what is discussed in Section 5 of [RFC6052], Section 10 of
   [RFC3810] and forwarding

   When receiving an IPv4 multicast packet, a lookup of the IPv4
   multicast routing table is performed by the PIMv4 router that embeds
   the mAFTR capability.  If an interface used for IPv4-in-IPv6
   encapsulation is found in the Out-Interface-List of the matching
   entry, the encapsulation operation is triggered.  The mAFTR
   encapsulates in a stateless fashion the IPv4 multicast packet into an
   IPv6 multicast datagram.  It MUST use the pre-provisioned mPrefix64/
   uPrefix64 together with an algorithm for building the IPv4-embedded
   IPv6 multicast address that identifies the multicast group, as well
   as the IPv6 source address that represents the IPv4 source in the
   IPv6 network.

   As an illustration, if a packet is received from source 192.1.2.3 and
   forwarded to group 230.1.2.3, the mAFTR encapsulates it into an IPv6
   multicast packet using ffxx:abc::230.1.2.3 as the destination IPv6
   address and 2001:db8::192.1.2.3 as the multicast source address.

   Then a lookup of the IPv6 multicast routing table is performed by the
   PIMv6 router that embeds the mAFTR capability, based on the IPv4-
   embedded IPv6 address.  If a matching entry is found and there exist
   IPv6 interfaces in the Out-Interface-List, the IPv6 multicast packet
   will be sent out through these interfaces and forwarded down the
   multicast distribution tree towards the mB4 devices.

8.  Optimization in L2 Access Networks

   The approach specified in this document is compatible with a Layer-2
   infrastructure which may be involved for deterministic multicast
   replication.

   The IPv4-in-IPv6 encapsulated multicast flows destined to IPv4-
   embedded IPv6 group addresses are treated as any IPv6 multicast flow,
   and can be replicated across Multicast VLANs.  Additionally,
   mechanisms such as MLD Snooping, MLD Proxying, etc., can be
   introduced into the distributed Access Network Nodes (e.g.,
   Aggregation Switches, xPON devices) which then could behave as MLD
   Querier and replicate multicast flows as appropriate.  Thus, the
   multicast replication point is moved downward closer to the
   receivers, so that bandwidth consumption is optimized.

9.  Security Considerations

   This document does not introduce any new security concern in addition
   to what is discussed in Section 5 of [RFC6052], Section 10 of

   [RFC3810] and Section 6 Section 6 of [RFC4601].

9.1.

8.1.  Firewall Configuration

   The CPE should be configured to accept incoming MLD messages and
   traffic forwarded to multicast groups subscribed by receivers located
   in the customer premises.

10.

9.  Acknowledgements

   The authors would like to thank Dan Wing for his guidance in the
   early discussions which initiated this work.  We also appreciate thank Peng Sun,
   Jie Hu, Qiong Sun, Lizhong Jin, Alain Durand, Dean Cheng, Behcet
   Sarikaya, Tina Tsou, and Rajiv Asati Asati, and Xiaohong Deng for their
   valuable comments.

11.

10.  IANA Considerations

   This document includes no request to IANA.

12.

11.  References

12.1.
11.1.  Normative References

   [I-D.boucadair-behave-64-multicast-address-format]
              Boucadair, M., Qin, J., Lee, Y., Venaas, S., Li, X., and
              M. Xu, "IPv4-Embedded IPv6 Multicast Address Format",
              draft-boucadair-behave-64-multicast-address-format-02
              draft-boucadair-behave-64-multicast-address-format-03
              (work in progress), June October 2011.

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

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

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

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

   [RFC4601]  Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
              "Protocol Independent Multicast - Sparse Mode (PIM-SM):
              Protocol Specification (Revised)", RFC 4601, August 2006.

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

   [RFC4607]  Holbrook, H. and B. Cain, "Source-Specific Multicast for
              IP", RFC 4607, August 2006.

   [RFC6052]  Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
              Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
              October 2010.

   [RFC6145]  Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
              Algorithm", RFC 6145, April 2011.

   [RFC6333]  Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual-
              Stack Lite Broadband Deployments Following IPv4
              Exhaustion", RFC 6333, August 2011.

12.2.

11.2.  Informative References

   [I-D.ietf-behave-nat64-learn-analysis]
              Korhonen, J. and T. Savolainen, "Analysis of solution
              proposals for hosts to learn NAT64 prefix",
              draft-ietf-behave-nat64-learn-analysis-00 (work in
              progress), May 2011.

   [I-D.ietf-mboned-multiaaa-framework]
              Satou, H., Ohta, H., Hayashi, T., Jacquenet, C., and H.
              He, "AAA and Admission Control Framework for
              Multicasting", draft-ietf-mboned-multiaaa-framework-12
              (work in progress), August 2010.

   [I-D.jaclee-behave-v4v6-mcast-ps]
              Jacquenet, C., Boucadair, M., Lee, Y., Qin, J., and T.
              ZOU), "IPv4-IPv6 Multicast: Problem Statement and Use
              Cases", draft-jaclee-behave-v4v6-mcast-ps-02 (work in
              progress), June 2011.

   [I-D.qin-softwire-multicast-prefix-option]
              Qin, J., Boucadair, M., and T. Tsou, "DHCPv6 Options for
              IPv6 DS-Lite Multicast Prefix",
              draft-qin-softwire-multicast-prefix-option-01 (work in
              progress), October 2011.

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

   [RFC2473]  Conta, A. and S. Deering, "Generic Packet Tunneling in
              IPv6 Specification", RFC 2473, December 1998.

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

   [RFC4608]  Meyer, D., Rockell, R., and G. Shepherd, "Source-Specific
              Protocol Independent G. Shepherd, "Source-Specific
              Protocol Independent Multicast in 232/8", BCP 120,
              RFC 4608, August 2006.

Appendix A.  Use Case: IPTV

   IPTV generally includes two categories of service offerings:

   o  Video on Demand (VoD) that unicast video content to receivers.

   o  Multicast live TV broadcast services.

   Two players intervene in the delivery of this service:

   o  Content Providers, who usually own the contents that is multicast
      to receivers.  Content providers may contractually define an
      agreement with network providers to deliver contents to receivers.

   o  Network Providers, who provide network connectivity services
      (e.g., network providers are responsible for carrying multicast
      flows from head-ends to receivers).  Refer to
      [I-D.ietf-mboned-multiaaa-framework].

   Note that some contract agreements prevent a network provider from
   altering the content as sent by the content provider for various
   reasons.  Under the contract, multicast streams should be delivered
   unaltered to the requesting users.

   Many current IPTV contents are likely to remain IPv4-formatted and
   out of control of the network providers.  Additionally, there are
   numerous legacy receivers (e.g., IPv4-only Set Top Boxes (STB)) that
   can't be upgraded or be easily replaced to support IPv6.  As a
   consequence, IPv4 service continuity MUST be guaranteed during the
   transition period, including the delivery of multicast services such
   as Live TV Broadcasting to users.

Appendix B.  Deployment Considerations

B.1.  Load-Balancing

   For robustness and load distribution purposes, several nodes in the
   network can embed the mAFTR function.  In such case, the same IPv6
   prefixes (i.e., mPrefix64 and uPrefix64) and algorithm to build IPv4-
   embedded IPv6 addresses MUST be configured on those nodes.

B.2.  RP for IPv4-Embedded IPv6 Multicast in 232/8", BCP 120,
              RFC 4608, August 2006.

Appendix A.  Translation vs. Encapsulation

   In order Groups

   For the sake of simplicity, it is RECOMMENDED to deliver configure mAFTR as
   the RP for the IPv4-embedded IPv6 multicast groups it manages.  No
   registration procedure is required under this configuration.

B.3.  mAFTR Policy Configuration

   mAFTR may be configured with a list of IPv4 multicast groups and
   sources.  Only multicast flows bound to DS-Lite serviced
   receivers, two options can be considered:(1) Translation;
   (2)Encapsulation.

   It the configured addresses
   should be noted that some contract agreement may prevent the
   contents from being altered.  In this case, the employment of handled by the
   translation approach may raise issues e.g., Integrity Check failures.

A.1.  Translation mAFTR.  Otherwise, packets are silently
   drooped.

B.4.  Static vs. Dynamic PIM Triggering

   To delivery IPv4 multicasst contents to an IPv4 receiver: Introduce
   translation functions at optimize the boundaries usage of IPv6 network.  The IPv4-
   translated network resources in current deployments,
   all multicast streams are distributed within conveyed in the IPv6 core network
   natively until the customer premises device where while only
   popular ones are continuously conveyed in the IPv4-translated
   IPv6 aggregation/access
   network (static mode).  Non-popular streams are translated back and passed to IPv4 receivers.
   Multicast Distribution Tree is established by normal machinery of
   control protocols (e.g.  IGMP, MLD, PIMv4/v6) and conveyed in the Interworking
   functions (e.g.  IGMP-MLD, PIMv6-PIMv4), refer to Section 6 and
   Section 7.  The translation function is stateless owing to
   access network upon request (dynamic mode).  Depending on the use
   location of
   IPv4-Embedded IPv6 address
   [I-D.boucadair-behave-64-multicast-address-format] and [RFC6052].

A.2.  Encapsulation

   To deliver IPv4 multicast contents to an IPv4 receiver: Introduce two
   elements at the boundaries of IPv6 network, mAFTR and mB4.  Multicast
   Distribution Tree is established by normal machinery of control
   protocols (e.g.  IGMP, MLD, PIMv4/v6) and in the Interworking functions
   (e.g.  IGMP-MLD, PIMv6-PIMv4), refer to Section 6 network, two modes can be envisaged:
   static and Section 7.
   Multicast streams are forwarded dynamic.

   o  Static Mode: the mAFTR is configured to a receiver by instantiate permanent (S6,
      G6) and (*, G6) entries in its MRIBv6 using an IPv4-in-
   IPv6 encapsulation scheme.  The encapsulation/de-capsulation function a pre-configured (S4,
      G4) list.

   o  Dynamic Mode: the instantiation and deletion of (S6, g6) or (*,
      G6) is stateless owing to triggered by the use receipt of IPv4-Embedded IPv6 address
   [I-D.boucadair-behave-64-multicast-address-format] and [RFC6052]. PIMv6 messages.

Authors' Addresses

   Qian Wang
   China Telecom
   No.118, Xizhimennei
   Beijing,   100035
   China

   Phone: +86 10 5855 2177
   Email: wangqian@ctbri.com.cn

   Jacni Qin
   ZTE
   Shanghai,
   China

   Phone: +86 1391 8619 913
   Email: jacni@jacni.com

   Mohamed Boucadair
   France Telecom
   Rennes,   35000
   France

   Phone:
   Email: mohamed.boucadair@orange-ftgroup.com mohamed.boucadair@orange.com
   Christian Jacquenet
   France Telecom
   Rennes,   35000
   France

   Phone:
   Email: christian.jacquenet@orange-ftgroup.com christian.jacquenet@orange.com

   Yiu L. Lee
   Comcast
   U.S.A.

   Phone:
   Email: yiu_lee@cable.comcast.com
   URI:   http://www.comcast.com