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Versions: (draft-morin-l3vpn-ppvpn-mcast-reqts) 00 01 02 03 04 05 06 07 08 09 10 RFC 4834

l3vpn Working Group                                        T. Morin, Ed.
Internet-Draft                                        France Telecom R&D
Expires: January 14, 2006                                  July 13, 2005

       Requirements for Multicast in L3 Provider-Provisioned VPNs

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
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Copyright Notice

   Copyright (C) The Internet Society (2005).


   This document presents a set of functional requirements for network
   solutions that allow the deployment of IP multicast within L3
   Provider Provisioned virtual private networks (PPVPNs).  It specifies
   requirements both from the end user and service provider standpoints.
   It is intended that potential solutions specifying the support of IP
   multicast within such VPNs will use these requirements as guidelines.

Working group

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   This document is a product of the IETF's Layer 3 Virtual Private
   Network (l3vpn) working group.  Comments should be addressed to WG's
   mailing list at <mailto:l3vpn@ietf.org>.  The charter for l3vpn may
   be found at <http://www.ietf.org/html.charters/l3vpn-charter.html>


   Main contributors to this document are listed below, in alphabetical
   order :


         Christian Jacquenet

         France Telecom

         3, avenue Francois Chateau

         CS 36901 35069 RENNES Cedex


         Email: christian.jacquenet@francetelecom.com


         Yuji Kamite

         NTT Communications Corporation

         Tokyo Opera City Tower 3-20-2 Nishi Shinjuku, Shinjuku-ku

         Tokyo 163-1421, Japan

         Email: y.kamite@ntt.com [3]


         Jean-Louis Le Roux

         France Telecom R & D

         2, avenue Pierre-Marzin

         22307 Lannion Cedex


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         Email: jeanlouis.leroux@francetelecom.com [4]


         Nicolai Leymann

         T-Systems International GmbH

         Engineering Networks, Products & Services

         Goslarer Ufer 35

         10589 Berlin, Germany

         Email: nicolai.leymann@t-systems.com [5]


         Renaud Moignard

         France Telecom R & D

         2, avenue Pierre-Marzin

         22307 Lannion Cedex


         Email: renaud.moignard@francetelecom.com [6]


         Thomas Morin

         France Telecom R & D

         2, avenue Pierre-Marzin

         22307 Lannion Cedex


         Email: thomas.morin@francetelecom.com [7]

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Table of Contents

   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   6
   2.   Conventions used in this document  . . . . . . . . . . . . .   7
     2.1  Terminology  . . . . . . . . . . . . . . . . . . . . . . .   7
     2.2  Conventions  . . . . . . . . . . . . . . . . . . . . . . .   8
   3.   Problem Statement  . . . . . . . . . . . . . . . . . . . . .   9
     3.1  Motivations  . . . . . . . . . . . . . . . . . . . . . . .   9
     3.2  General Requirements . . . . . . . . . . . . . . . . . . .   9
     3.3  Scaling vs. Optimizing Resource Utilization  . . . . . . .   9
   4.   Use cases  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     4.1  Scenarios  . . . . . . . . . . . . . . . . . . . . . . . .  11
       4.1.1  Real-time / Unspecified receivers / Large bandwidth  .  11
       4.1.2  Real-time / Unspecified receivers / Medium bandwidth .  11
       4.1.3  Real-time / Unspecified receivers / Small bandwidth  .  11
       4.1.4  Real-time / Specified receivers  . . . . . . . . . . .  12
       4.1.5  Non-real-time  . . . . . . . . . . . . . . . . . . . .  12
       4.1.6  Content broadcasting / Unspecified Receivers /
              Large Bandwidth  . . . . . . . . . . . . . . . . . . .  12
       4.1.7  Symmetric Low Volume Traffic . . . . . . . . . . . . .  12
       4.1.8  Mixed generic multicast VPN  . . . . . . . . . . . . .  13
     4.2  Scalability orders of magnitude  . . . . . . . . . . . . .  13
   5.   Requirements for supporting IP multicast within L3 PPVPNs  .  15
     5.1  End user/customer standpoint . . . . . . . . . . . . . . .  15
       5.1.1  Service definition . . . . . . . . . . . . . . . . . .  15
       5.1.2  CE-PE Multicast routing and management protocols . . .  15
       5.1.3  Quality of Service (QoS) . . . . . . . . . . . . . . .  15
       5.1.4  SLA parameters measurement . . . . . . . . . . . . . .  16
       5.1.5  Security Requirements  . . . . . . . . . . . . . . . .  17
       5.1.6  Monitoring and Troubleshooting . . . . . . . . . . . .  18
       5.1.7  Extranet . . . . . . . . . . . . . . . . . . . . . . .  18
       5.1.8  Internet Multicast . . . . . . . . . . . . . . . . . .  19
       5.1.9  Carrier's carrier  . . . . . . . . . . . . . . . . . .  19
       5.1.10   Multi-homing, load balancing and resiliency  . . . .  20
       5.1.11   RP Engineering . . . . . . . . . . . . . . . . . . .  20
       5.1.12   Addressing . . . . . . . . . . . . . . . . . . . . .  20
       5.1.13   Minimum MTU  . . . . . . . . . . . . . . . . . . . .  21
     5.2  Service provider standpoint  . . . . . . . . . . . . . . .  21
       5.2.1  Scalability  . . . . . . . . . . . . . . . . . . . . .  21
       5.2.2  Resource optimization  . . . . . . . . . . . . . . . .  23
       5.2.3  Tunneling Requirements . . . . . . . . . . . . . . . .  24
       5.2.4  Control mechanisms . . . . . . . . . . . . . . . . . .  25
       5.2.5  Quality of Service Differentiation . . . . . . . . . .  25
       5.2.6  Infrastructure security  . . . . . . . . . . . . . . .  26
       5.2.7  Robustness . . . . . . . . . . . . . . . . . . . . . .  26
       5.2.8  Management tools, OAM  . . . . . . . . . . . . . . . .  27
       5.2.9  Architectural Considerations . . . . . . . . . . . . .  27
       5.2.10   Compatibility and migration issues . . . . . . . . .  27

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       5.2.11   Troubleshooting  . . . . . . . . . . . . . . . . . .  28
       5.2.12   Inter-AS, inter-provider . . . . . . . . . . . . . .  28
   6.   Security Considerations  . . . . . . . . . . . . . . . . . .  30
   7.   Acknowledgments  . . . . . . . . . . . . . . . . . . . . . .  31
   8.   References . . . . . . . . . . . . . . . . . . . . . . . . .  32
     8.1  Normative references . . . . . . . . . . . . . . . . . . .  32
     8.2  Informative references . . . . . . . . . . . . . . . . . .  33
        Author's Address . . . . . . . . . . . . . . . . . . . . . .  36
   A.   Requirements summary . . . . . . . . . . . . . . . . . . . .  37
   B.   Changelog  . . . . . . . . . . . . . . . . . . . . . . . . .  38
     B.1  Changes between -00 and -01  . . . . . . . . . . . . . . .  38
        Intellectual Property and Copyright Statements . . . . . . .  39

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1.  Introduction

   VPN services satisfying requirement defined in [RFC4031] are now
   being offered by many service providers throughout the world.  VPN
   services are popular because customers need not be aware of VPN
   technologies deployed in the provider network.  They scale well for
   the following reasons:

   o  because P-routers need not be aware of VPN service details

   o  because the addition of a new VPN member requires only limited
      configuration effort

   There is also a growing need for support of IP multicast-based
   services.  Efforts to provide efficient IP multicast routing
   protocols and multicast group management have been done in
   standardization bodies which has led, in particular, to the
   definition of the PIM and IGMP protocols.

   However, multicast traffic is not natively supported within existing
   L3 PPVPN solutions.  Deploying multicast over an L3VPN today, with
   only currently standardized solutions, requires designing customized
   solutions which will be inherently limited in terms of scalability,
   operational efficiency and bandwidth usage.

   This document complements the generic L3 VPN requirements [RFC4031]
   document, by specifying additional requirements specific to the
   deployment of IP multicast-based services within PPVPNs.  It
   clarifies the needs from both VPN client and provider standpoints and
   formulates the problems that should be addressed by technical
   solutions with as a key objective to stay solution agnostic.  There
   is no intent to either specify solution-specific details in this
   document or application-specific requirements.  Also this document
   does NOT aim at expressing multicast-inferred requirements that are
   not specific to L3 PPVPNs.

   It is expected that solutions that specify procedures and protocol
   extensions for multicast in L3 PPVPNs SHOULD satisfy these

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2.  Conventions used in this document

2.1  Terminology

   Although the reader is assumed to be familiar with the terminology
   defined in [RFC4031], [RFC2547] and RFC2547bis [I-D.ietf-l3vpn-
   rfc2547bis], PIM-SM [RFC2362], PIM-SSM [I-D.ietf-ssm-arch] the
   following glossary of terms may be worthwhile.

   Moreover we also propose here generic terms for concept that
   naturally appears when multicast in VPNs is discussed.

   ASM: Any Source Multicast.  One of the two multicast service models
      that denotes the source/receiver heuristic.

   Multicast-enabled VPN, or multicast VPN: a VPN which supports IP
      multicast capabilities, i.e. for which some PE devices (if not
      all) are multicast-enabled and whose core architecture support
      multicast VPN routing and forwarding

   PPVPN: Provider-Provisioned Virtual Private Network

   PE/CE: Provider/Customer edge Equipment ([RFC4026])

   VRF or VR: By this phrase, we refer to the entity defined in a PE
      dedicated to a specific VPN instance.  "VRF" refers to [RFC2547]
      terminology, and "VR" to the VR [I-D.ietf-l3vpn-vpn-vr]

   MD Tunnel: Multicast Distribution Tunnel, the means by which the
      customer's multicast traffic will be conveyed across the SP
      network.  This is meant in a generic way: such tunnels can be
      either point-to-point or point-to-multipoint.  Although this
      definition may seems to assume that distribution tunnels are
      unidirectional, but the wording encompasses bi-directional tunnels
      as well.

   G: Denotes a multicast group

   Multicast channel: (S,G) in the SSM model

   Participating device: Refers to any network device that not only
      participates to the deployment and the maintenance of the VPN
      infrastructure, but also to the establishment and the maintenance
      of the MD Tunnel (see above).

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   S: Denotes a multicast source

   SP: Service provider

   SSM: Source Specific Multicast.  One of the two multicast service
      models where each corresponding service relies upon the use of a
      single source.

   RP: Rendez-vous point (PIM-SM [RFC2362])

   Please refer to [RFC4026] for details about terminology specifically
   relevant to VPN aspects, and to [RFC2432] for multicast performance
   or QoS related terms.

2.2  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

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3.  Problem Statement

3.1  Motivations

   More and more L3 VPN customers use IP multicast services within their
   private infrastructures.  Naturally, they want to extend these
   multicast services to remote sites that are connected via a VPN.

   For instance, the customer could be a national TV channel with
   several geographical locations that wants to broadcast a TV program
   from a central point to several regional locations within its VPN.

   A solution to support multicast traffic would consist in using point-
   to-point tunnels across the provider network and requiring the PE
   routers (provider's routers) to replicate traffic.  This is obviously
   sub-optimal as it places the replication burden on the PE and hence
   has very poor scaling characteristics.  It may also waste bandwidth
   and control plane resources in the provider's network.

   Thus, to provide multicast services for L3 VPN networks in an
   efficient manner (that is, with scalable impact on signaling and
   protocol state as well as bandwidth usage), in a large scale
   environment, new mechanisms are required to enhance existing L3 VPN
   solutions for proper support of multicast-based services.

3.2  General Requirements

   This document sets out requirements for L3 provider-provisioned VPN
   solutions designed to carry customers' multicast traffic.  The main
   requirement is that a solution SHOULD first satisfy requirements
   documented in [RFC4031]: as far as possible, a multicast service
   should have the same flavor as the unicast equivalent, including the
   same simplicity (technology unaware), the same quality of service (if
   any), the same management (e.g. monitoring of performances), etc.

   Moreover, it also has to be clear that a multicast VPN solution MUST
   interoperate seamlessly with current unicast solutions.  It would
   also make sense that multicast VPN solutions define themselves as
   extensions to existing L3 provider-provisioned VPN solutions (such as
   for instance, RFC2547bis [I-D.ietf-l3vpn-rfc2547bis] or VR [I-D.ietf-
   l3vpn-vpn-vr]) and retain consistency with those, although this is
   not a core requirement.

3.3  Scaling vs. Optimizing Resource Utilization

   When transporting multicast VPN traffic over a service provider
   network, there intrinsically is tension between scalability and
   resource optimization, since the latter likely requires maintaining

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   multicast state in the core network.

   Consequently, some trade-off has to be made and this document will
   express some requirements related to this trade-off.

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4.  Use cases

   The goal of this section is to highlight how different applications
   and network contexts may have a different impact on how a trade-off
   is made.  We aim here at presenting a few representative examples of
   multicast VPN deployments, and to express expectations about orders
   of magnitude of relevant scalability parameters.

4.1  Scenarios

4.1.1  Real-time / Unspecified receivers / Large bandwidth

   Broadcasting companies, which want to send their programs in real-
   time, would need large bandwdith and reachability to many unspecified
   nodes on VPN.  This does expect not only bandwidth guarantee, low
   delay and low jitter but also rapid following capability of multicast
   membership changes.

   The SP has to take care of the scalability impact about both
   bandwidth efficiency and number of receivers.

   This case is regarded as one-to-many streams.

4.1.2  Real-time / Unspecified receivers / Medium bandwidth

   Enterprise customers expect to build video conference environment on
   their exstiting VPNs.  Because you do not always know which receivers
   will join each conference, customer's multicast information might be
   dynamically added, removed, or changed.

   This fact will require that SP should control whether and how
   MDTunnel topologies are dynamically changed, and their bandwidth
   usage efficiency in SP core.

   Conference applications are often regarded as many-to-many streams.

4.1.3  Real-time / Unspecified receivers / Small bandwidth

   Enterprise customers, however, do not always require large bandwidth.
   For instance, applications like distributing stock market
   information, will strongly need good real-time QoS, but it does not
   require huge bandwidth.

   This case is not burdened with MDTunnel bandwidth efficiency issues,
   but it is still necessary to provide low delay, jitter, and high

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4.1.4  Real-time / Specified receivers

   Some customers may want to deploy a multicast VPN where the location
   of receivers if well known in advance.  One example would be a case
   of real-time programs to fixed locations, such as horse race live
   coverage to off-course betting shops.

   This kind of application is characterized by its static receivers,
   and by the fact their memberships are not modified so often.  In this
   case MDTunnels might not need rapid changes of their topology, and
   can be built in a relatively static way.

4.1.5  Non-real-time

   Content distributors might want to use a multicast VPN to more
   efficiently deliver their contents.  For example, when a central TV
   station delivers its recorded contents to lots of local stations, it
   uses one-to-many streams for transmitting files.

   If local stations begin exchanging their contents each other, the
   situation can be regarded as many-to-many streams.  Such file
   transfer scenario might need large bandwidth but does not require
   real-time following capability of multicast membership.

   Also it does not always need strict delay and guaranteed jitter.

4.1.6  Content broadcasting / Unspecified Receivers / Large Bandwidth

   A L3VPN architecture can be leveraged for video (or any content)
   broadcast distribution to broadband customers.

   In such a scenario, the location of receivers of a channel will be
   unknown, but a high level of aggregation could be expected (high-
   audience channels are likely to be requested by same sets of PEs).
   The number of channels will likely be high (hundreds), and the
   typical bandwidth would be the one of video codecs (somewhere between
   1 and 15 Mbps as of today).

   In this scenario, the multicast group join delay ([RFC2432], section
   3.4) will need to be very low.

   In this scenario, contrary to the Section 4.1.1 scenario, the delay
   and jitter do not need to be very low.

4.1.7  Symmetric Low Volume Traffic

   In this scenario, IP-Multicast is used to send heart beats and state
   information to a number of receivers being member of a single

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   multicast group.  Typical use case are management application
   monitoring and managing a number of distributed clients.  All nodes
   are senders and receivers at the same time building a many-to-many
   relationship.  If a node is not visible by sending packets to the
   multicast group it is considered as being down.  When IP-Multicast
   fails in general this is valid for all nodes and the management
   application fails to work even if unicast connectivity is working (no
   fallback to unicast available).

   Specifics of the scenario:

   o  One group

   o  Hundreds of receivers/senders

   o  Tens of PE devices

   o  Traffic volume : hundreds of Kb/s, with peaks at a few Mb/s

4.1.8  Mixed generic multicast VPN

   This is a general deployment scenario where IP-Multicast is used in
   every VPN : if a customer requests a VPN, then this VPN will support
   IP-Multicast per default.  In this case the number of mVPN equals the
   number of VPNs in the platform.  This implies a quite important
   scalability requirement (e.g. hundreds of PEs, hundreds of VPNs per
   PE, with a potential grow by one order of magnitude in the longer

   The per mVPN traffic behaviour is not predictable because it's
   completely up to the customer how the service is used.  This results
   in a traffic mix of the scenarios mentioned in section Scenarios.
   QoS requirements are similar to typical unicast scenarios, with the
   need for different classes.  Also in a such context, a reasonably
   large range of protocols should be made available to the customer for
   use at the PE-CE level.

   Also, in such a scenario, customers may want to deploy multicast
   connectivity between two or more mVPNs as well as access to internet

4.2  Scalability orders of magnitude

   This section proposes orders of magnitude for different scalability
   metrics relevant for multicast VPN issues.  It should be noted that
   the scalability figures proposed here relate to scalability
   expectations of future deployments of multicast VPN solutions, as the

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   author tried to no restrict the scope to the mere deployments known
   as of today.

   The figures proposed here are the result of an informal survey
   proposed to ISP in summer 2005.

   [ This section will be completed with the result of the "Multicast
   VPN Survey" posted to the L3VPN WG in July'05 ]

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5.  Requirements for supporting IP multicast within L3 PPVPNs

   Again, the aim of this document is not to specify solutions but to
   give requirements for supporting IP multicast within L3 PPVPNs.

   In order to list these requirements we have taken two different
   standpoints of two different important entities: the end user (the
   customer using the VPN) and the service provider.

   In the rest of the document, we mean by a "solution", a solution that
   allows to perform multicast in an L3 provider provisioned VPN, which
   addresses the requirements listed in this document.

5.1  End user/customer standpoint

5.1.1  Service definition

   As for unicast, the multicast service MUST be provider provisioned
   and SHALL NOT require the customer's devices (CE) to support any
   extra feature compared to those required for multicast in a non-VPN

5.1.2  CE-PE Multicast routing and management protocols

   Consequently to Section 3.1, the CEs and PEs SHOULD employ existing
   multicast protocols.

   Such protocols SHOULD include : PIM-SM [RFC2362] (including PIM-SSM
   [I-D.ietf-ssm-arch]), bidirectional PIM [I-D.ietf-pim-bidir], PIM-DM
   [RFC3973], and IGMP (v1 [RFC1112], v2 [RFC2236] and v3 [RFC3376]).

   Among those protocols, PIM-SM is considered a MUST.

   When IPv6 is supported by a VPN solution, relevant IPv6 corresponding
   protocols SHOULD also be supported, e.g.  Multicast Listener
   Discovery Protocol (MLD) (v1 [RFC2710]], v2 [RFC3810]]).

5.1.3  Quality of Service (QoS)

   First, general considerations about QoS in L3 VPNs as developed in
   section 5.5 of [RFC4031] are also relevant to this section.

   QoS is measured in terms of delay, jitter, packet loss, and
   availability.  These metrics are already defined for the current
   unicast PPVPN services, and are included in Service Level
   Agreements(SLA).  In some cases, provided SLA may be different
   between unicast and multicast, which will need service
   differentiation mechanisms as such.

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   The level of availability for the multicast service SHOULD be on par
   with what exists for unicast traffic.  For instance same traffic
   protection mechanisms SHOULD be available for customer multicast
   traffic when it is carried over the service provider's network.

   A multicast in VPN solution shall allow to define at least the same
   level of quality of service than what exists for unicast, and than
   what exist for multicast in a non-VPN context.  From this
   perspective, the deployment of multicast-based services within an L3
   PPVPN environment SHALL benefit from DiffServ [RFC2475] mechanisms
   that include multicast traffic identification, classification and
   marking capabilities, as well as multicast traffic policing,
   scheduling and conditioning capabilities.  Such capabilities MUST
   therefore be supported by any participating device in the
   establishment and the maintenance of the multicast distribution
   tunnel within the VPN.

   As multicast is often used to deliver high quality services such as
   TV broadcast, the solution should have additional features to support
   high QoS such as bandwidth reservation and admission control.

   Also, considering that multicast reception is receiver-triggered,
   group join delay (as defined in [RFC2432]) is also considered one
   important QoS parameter.  It is thus RECOMENDED that a multicast VPN
   solution be designed appropriately in this regard.

   The group leave delay (as defined in [RFC2432]) may also be important
   on the CE-PE link for some usage scenarios : in cases where the
   typical bandwidth of multicast streams is close to the bandwidth a
   PE-CE link, it will be important to have the ability to stop the
   emission of a stream on the PE-CE link as soon as it stops being
   requested by the CE, to allow for fast switching between two
   different high througput multicast streams.  This implies that it
   SHOULD be possible to tune the multicast routing or group protocol
   (e.g.  IGMP/MLD or PIM) used on the PE-CE adjacency to reduce the
   group leave delay to the minimum.

   Last, a multicast VPN solution SHOULD as much as possible ensure that
   client multicast traffic packets are neither lost nor duplicated,
   even when changes occur in the way a client multicast data stream is
   carried over the provider network.  Packet loss issues have also to
   be considered when a new source starts to send traffic to a group:
   any receiver interested in receiving such traffic SHOULD be serviced

5.1.4  SLA parameters measurement

   As SLA parameters are part of the service that is sold, they are

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   often monitored.  The monitoring is used for technical reasons by the
   service provider and is often sold to the customer for end-to-end
   service purposes.

   The solution MUST support (SLA) monitoring capabilities, which MAY
   possibly rely upon similar techniques (than those used by the unicast
   for the same monitoring purposes).

   Multicast specific characteristics that may be monitored are, for
   instance, multicast statistics per stream, end-to-end delay and group
   join delay (time to start receiving a multicast group traffic across
   the VPN, as defined in [RFC2432] section 3).

   A generic discussion of SLAs is provided in [RFC3809].

5.1.5  Security Requirements

   Security is a key point for a customer who uses subscribes to a VPN
   service.  The RFC2547bis [I-D.ietf-l3vpn-rfc2547bis] model offers
   some guarantees concerning the security level of data transmission
   within the VPN.

   A multicast VPN solution MUST provide an architecture that can
   provide the same level of security both for both the unicast and
   multicast traffics.

   Moreover, the activation of multicast features SHOULD be possible:

   o  with a VRF or VR granularity

   o  with a CE granularity (when multiple CE of a same VPN are
      connected to a common VRF)

   o  with a distinction between multicast reception and emission

   o  with a multicast group and/or channel granularity

   A multicast VPN solution may choose to make the optimality/
   scalability trade-off stated in Section 3.3 by sometimes distributing
   multicast traffic of a client group to a larger set of PE routers
   that may include PEs which are not part of the VPN.  From a security
   standpoint, this may be a problem for some VPN customers, thus a
   multicast VPN solution using such a scheme MAY offer ways to avoid
   this for specific customers (and/or specific customer multicast

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5.1.6  Monitoring and Troubleshooting

   A service provider and its customers MUST be able to manage the
   capabilities and characteristics of their multicast VPN services.
   Automated operations and interoperability with standard management
   platforms SHOULD be supported.

   Service management should also include the TMN 'FCAPS'
   functionalities, as follows: Fault, Configuration, Accounting,
   Provisioning, and Security.

   The monitoring of multicast specific parameters and statistics SHOULD
   include :

   o  multicast traffic statistics: total traffic conveyed, incoming,
      outgoing, dropped, etc., by period of time (as a MUST)

   o  IP Performance Metrics related information (IPPM, [RFC2330]) that
      is relevant to the multicast traffic usage: such information
      includes the one-way packet delay, the inter-packet delay
      variation, etc. (as a MAY)

   Apart from statistics on multicast traffic, customers of a multicast
   VPN will need information concerning the status of their multicast
   resource usage (state and bandwidth).  Indeed, as mentioned in
   Section 5.2.4, for scalability purposes, a service provider may limit
   the number (and/or throughput) of multicast streams that are received
   and produced at a client site, and so a multicast VPN solution SHOULD
   allow customers to find out their current resource usage (state and
   throughput), and to receive some kind of feedback if their usage
   exceed bounds.  Whether this issue will be better handled at the
   protocol level at the PE-CE interface or via the ISP customer
   support, needs further discussion.

5.1.7  Extranet

   In current PP L3VPN models, a customer site may be setup to be part
   of multiple VPNs and this should still be possible when a VPN is

   A multicast solution SHOULD offer means so that:

   o  receivers behind attached CEs can receive multicast traffic
      sourced in any of the VPNs (if security policy permits)

   o  sources behind attached CEs can reach multicast traffic receivers
      located in any of the VPNs

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   o  multicast can be independently enabled for the different VPNs (and
      multicast reception and emission can also be independently

   Proper support for this feature SHOULD not require replicating
   multicast traffic on a PE-CE link, whether it is a physical or
   logical link.

   For instance, an enterprise using a multicast-enabled VPN should have
   the ability to receive a multicast stream from, or originate a
   multicast stream towards, another VPN.

   In any case a solution not supporting such a feature MUST be
   compatible with setups where a VRF or VR is part of multiple VPNs and
   MUST document how it operates on multicast traffic in such a context.

5.1.8  Internet Multicast

   Connectivity with Internet Multicast (as a source or receiver)
   somehow fits in the context of the previous section.

   It should be considered OPTIONAL given additional considerations
   needed to fulfill requirements for Internet side, such as security

5.1.9  Carrier's carrier

   Many L3 PPVPN solutions, such as RFC2547bis [I-D.ietf-l3vpn-
   rfc2547bis] and VR [I-D.ietf-l3vpn-vpn-vr] define the "Carrier's
   Carrier" model, where a "carrier's carrier" service provider supports
   one or more customer ISP, or "sub-carriers".  A multicast VPN
   solution SHOULD support the carrier's carrier model in a scalable and
   efficient manner.

   Ideally the range of tunneling protocols available for the sub-
   carrier ISP should be the same as those available for the carrier's
   carrier ISP.  This implies that the protocols that may be used at the
   PE-CE level SHOULD NOT be restricted to protocols required as per
   Section 5.1.2 and SHOULD include some of the protocols listed in
   Section 5.2.3.

   In the context of MPLS-based L3VPN deployments, such as BGP/MPLS VPNs
   [I-D.ietf-l3vpn-rfc2547bis], this means that MPLS label distribution
   SHOULD happen at the PE-CE level, giving the ability to the sub-
   carrier to use multipoint LSPs as a tunneling mechanism.

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5.1.10  Multi-homing, load balancing and resiliency

   A multicast VPN solution should be compatible with current solutions
   that aim at improving the service robustness for customers such as
   multi-homing, CE-PE link load balancing and failover.  A multicast
   VPN solution SHOULD also be able to offer those same features for
   multicast traffic.  Any solution SHOULD support redundant topology of
   CE-PE links.  It SHOULD minimize multicast traffic disruption and

   On the other hand, it is also necessary to care about failover
   mechanisms that are unique to multicast routing control.  For
   instance, if the customer uses some control mechanism for RP
   redundancy on PIM-SM (e.g.  BSR), it SHOULD work transparently
   through that VPN.

5.1.11  RP Engineering

   When PIM-SM (or bidir-PIM) is used in ASM mode on the VPN customer
   side, the location of the RP has to be chosen.  In some cases this
   engineering problem is not trivial: for instance, if sources and
   receivers are located in VPN sites that are different than that of
   the RP, then traffic may flow twice through the SP network and the
   CE-PE link of the RP (from source to RP, and then from RP to
   receivers) ; this is obviously not ideal.  A multicast VPN solution
   SHOULD propose a way to help on solving this RP engineering issue.

   Moreover, some service providers offer to manage customer's multicast
   protocol operation on behalf of them.  This implies that it is needed
   to consider cases where the customer's RPs are outsourced (e.g., on

5.1.12  Addressing

   A multicast provider-provisioned L3VPN SHOULD NOT impose restrictions
   on multicast group addresses used by VPN customers.

   In particular, like unicast traffic, an overlap of multicast group
   address sets used by different VPN customers MUST be supported.

   The use of globally unique means of multicast-based service
   identification at the scale of the domain where such services are
   provided SHOULD be recommended.  If the ASM model is used, this
   implies the use of the multicast administratively scoped range,
   (239/8 as per [RFC2365]) for services which are to be used only
   inside the VPN, and of globally assigned group addresses for services
   for which traffic may be transmitted outside the VPN (e.g.  GLOP

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5.1.13  Minimum MTU

   For customers, it is often a serious issue whether transmitted
   packets will be fragmented or not.  In particular, some multicast
   applications might have different requirements than those that make
   use of unicast, and they may expect services that guarantee available
   packet length not to be fragmented.

   Therefore, a multicast VPN solution SHOULD let customers' devices be
   free of any fragmentation or reassembly activity.

   A committed minimum path MTU size SHOULD be provided to customers.
   Morover, since Ethernet LAN segments are often located at first and
   last hops, a minimum 1500 bytes IP MTU SHOULD be provided.

   It SHOULD also be compatible with Path MTU discovery mechanisms, such
   as those defined in [RFC1191] or [I-D.mathis-frag-harmful].

5.2  Service provider standpoint

   Note: please remember that, to avoid repetition and confusion with
   terms used in solution specifications, we introduced in Section 2.1
   the term MDTunnel (for Multicast Distribution Tunnel), which
   designates the data plane means used by the service provider to
   forward customer multicast traffic over the core network.

5.2.1  Scalability

   Some currently standardized and deployed L3VPN solutions have the
   major advantage of being scalable in the core regarding the number of
   customers and the number of customer routes.  For instance, in the
   RFC2547bis [I-D.ietf-l3vpn-rfc2547bis] and VR [I-D.ietf-l3vpn-vpn-vr]
   models, a P-router sees a number of MPLS tunnels that is only linked
   to the number of PEs and not to the number of VPNs, or customers'

   As far as possible, this independence in the core, with respect to
   the number of customers and to customer activity, is recommended.
   Yet, it is recognized that in our context scalability and resource
   usage optimality are competing goals, so this requirement may be
   reduced to giving the possibility of bounding the quantity of states
   that the service provider needs to maintain in the core for
   MDTunnels, with a bound being independent of the multicast activity
   of VPN customers.

   It is expected that multicast VPN solutions will use some kind of
   point point-to-multipoint technology to efficiently carry multicast

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   VPN traffic, and that such technologies require maintaining state
   information, and will use resources in the control plane (memory and
   processing, and possibly address space).

   Scalability is a key requirement for multicast VPN solutions.
   Solutions MUST be designed to scale well with an increase in the
   number of any of the following:

   o  the number of PEs

   o  the number of customers VPNs (total and per PE)

   o  the number of PEs and sites in any VPN

   o  the number of client multicast channels (groups or source-groups)

   Scalability of both performance and operation MUST be considered.

   Key considerations SHOULD include:

   o  the processing resources required by the control plane
      (neighborhood or session maintenance messages, keep-alives,
      timers, etc.)

   o  the memory resources needed for the control plane

   o  the amount of protocol information transmitted to manage a
      multicast VPN (e.g. signaling throughput)

   o  the amount of control plane processing required on PE and P to add
      remove a customer site (or a customer from a multicast session)

   o  the number of multicast IP addresses used (if IP multicast in ASM
      mode is proposed as a multicast distribution tunnel)

   o  other particular elements inherent to each solution that impacts
      scalability (e.g., if a solution uses some distribution tree
      inside the core, topology of the tree and number of leaf nodes may
      be some of them)

   It is expected that the applicability of each solution will be
   evaluated with regards to the aforementioned scalability criteria.

   These considerations naturally lead us to believe that proposed
   solutions SHOULD offer the possibility of sharing such resources
   between different multicast streams (between different VPNs, between
   different multicast streams of the same or of different VPNs).  This
   means for instance, if MDTunnels are trees, being able to share an

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   MDTunnel between several customers.

   Those scalability issues are expected to be more significant on
   P-routers, but a multicast in VPNs solution should address both P and
   PE routers as far as scalability is concerned.

5.2.2  Resource optimization  General goals

   One of the aims of the use of multicast instead of unicast is
   resource optimization in the network.

   The two obvious suboptimal behaviors that a multicast VPN solution
   would want to avoid are needless duplication (when same data travels
   twice or more on a same link, e.g. when doing ingress PE replication)
   and needless reception (e.g. a PE receiving traffic that it does not
   need because there are no downstream receivers).  Trade-off and tuning

   As previously stated in this document, designing a scalable solution
   that makes an optimal use of resources is considered difficult.  Thus
   what is expected from a multicast VPN solution is that it addresses
   the resource optimization issue while taking into account the fact
   that some trade-off has to be made.

   Moreover, it seems that a "one size fits all" trade-off probably does
   not exist either, and that the most sensible approach is a versatile
   solution offering the service providers appropriate configuration
   settings that let them tune the trade-off according to their peculiar
   constraints (network topology, platforms, customer applications,
   level of service offered etc.).

   As an illustration here are some example bounds of the trade-off

   Bandwidth optimization: setting up somehow optimal core MDTunnels
      whose topology (PIM or P2MP LSP trees, etc.) precisely follows
      customer's multicast routing changes.  This requires managing an
      important quantity of states in the core, and also quick reactions
      of the core to customer multicast routing changes.  This approach
      can be advantageous in terms of bandwidth, but it is bad in terms
      of state management.

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   State optimization: setting up MDTunnels that aggregate multiple
      customer multicast streams (all or some of them, across different
      VPNs or not).  This will have better scalability properties, but
      at the expense of bandwidth since some MDTunnel leaves will very
      likely receive traffic they don't need, and because increased
      constraints will make it harder to find optimal MDTunnels.  Traffic engineering

   If the VPN service provides traffic engineering features for the
   connection used between PEs for unicast traffic in the VPN service,
   the solution SHOULD provide equivalent features for multicast

   A solution should offer means to support key TE objectives as defined
   in [RFC3272], for the multicast service.

   A solution MAY also usefully support means to address multicast-
   specific traffic engineering issues: it is known that bandwidth
   resource optimization in the point-to-multipoint case is a NP-hard
   problem, and that techniques used for unicast TE may not be
   applicable to multicast traffic.

5.2.3  Tunneling Requirements  Tunneling technologies

   Following the principle of separation between the control plane and
   the forwarding plane, a multicast VPN solution SHOULD be designed so
   that control and forwarding planes are not inter-dependent: the
   control plane SHALL NOT depend on which forwarding plane is used (and
   vice versa), and the choice of forwarding plane SHOULD NOT be limited
   by the design of the solution.  The solution SHOULD also NOT be tied
   to a specific tunneling technology.

   In a multicast VPN solution extending a unicast L3 PPVPN solution,
   consistency in the tunneling technology has to be privileged: such a
   solution SHOULD allow the use of the same tunneling technology for
   multicast as for unicast.  Migration and operations ease are the main
   motivations behind this requirement.

   For MDTunnels (multicast distribution tunnels, the means used to
   carry VPNs' multicast traffic over the provider's network), a
   solution SHOULD be able to use a range of tunneling technologies,
   including point-to-point and point-to-multipoint, such as L2TP
   (including L2TP for multicast [RFC4045]), IPsec [RFC2401], GRE
   [RFC2784] (including GRE in multicast IP trees), IP-in-IP [RFC1853],

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   MPLS [RFC3031] (including MPLS P2MP extensions to RSVP [I-D.ietf-
   mpls-rsvp-te-p2mp] or LDP [I-D.leroux-mpls-mp-ldp-reqs][I-D.minei-
   mpls-ldp-p2mp][I-D.wijnands-mpls-ldp-mcast-ext]), etc.  Naturally,
   using the point-to-multipoint variants mentioned here may help
   improve bandwidth efficiency in our multicast VPN context.  MTU and Fragmentation

   A solution SHOULD support a method that provides minimum path MTU of
   the MDTunnel (e.g., to discover MTU, to tell MTU with signaling,
   etc.) so that :

   o  fragmentation inside the MDTunnel -even when allowed by the
      tunneling technology used- does not happen

   o  proper troubleshooting can be done if packets too big for the
      MDTunnel happen to be encapsulated in the MDTunnel

5.2.4  Control mechanisms

   The solution must provide some mechanisms to control the sources
   within a VPN.  This control includes the number of sources that are
   entitled to send traffic on the VPN, and/or the total bit rate of all
   the sources.

   At the reception level, the solution must also provide mechanisms to
   control the number of multicast groups or channels VPN users are
   entitled to subscribe to and/or the total bit rate represented by the
   corresponding multicast traffic.

   All these mechanisms must be configurable by the service provider in
   order to control the amount of multicast traffic and state within a

   Moreover it MAY be desirable to be able to impose some bound on the
   quantity of state used by a VPN in the core network for its multicast
   traffic, whether on each P or PE router, or globally.  The motivation
   is that it may be needed to avoid out-of-resources situations (e.g.
   out of memory to maintain PIM state if IP multicast is used in the
   core for multicast VPN traffic, or out of memory to maintain RSVP
   state if MPLS P2MP is used, etc.).

5.2.5  Quality of Service Differentiation

   A multicast VPN solution SHOULD give a VPN service provider the
   ability to offer, guarantee and enforce differentiated levels of QoS

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   to its differents customers.

5.2.6  Infrastructure security

   The solution shall provide the same level of security for the service
   provider as what currently exist for unicast VPNs.  For instance,
   that means that the intrinsic protection against DOS and DDOS attacks
   of the BGP/MPLS VPN solution must be equally supported by the
   multicast solution.

   Moreover, since multicast traffic and routing are intrinsically
   dynamic (receiver-initiated), some mechanism must be proposed so that
   the frequency of changes in the way client traffic is carried over
   the core is bounded and not tightly coupled to dynamic changes of
   multicast traffic in the customer network.  For example, multicast
   route dampening functions would be one possible mechanism.

   Network devices that participate in the deployment and the
   maintenance of a given L3 VPN MAY represent a superset of the
   participating devices that are also involved in the establishment and
   the maintenance of the multicast distribution tunnels.  As such the
   activation of IP multicast capabilities within a VPN SHOULD be
   device-specific, not only to make sure that only the relevant devices
   will be multicast-enabled, but also to make sure that multicast
   (routing) information will be disseminated to the multicast-enabled
   devices only, hence limiting the risk of multicast-inferred DOS

   Unwanted multicast traffic (e.g. multicast traffic that may be sent
   by a source located somewhere in the Internet and for which there is
   no interested receiver connected to a given VPN infrastructure) MUST
   NOT be propagated within a multicast-enabled VPN.

   Last, control mechanisms described in previous section are also to be
   considered from this infrastructure security point of view.

5.2.7  Robustness

   Resiliency is also crucial to infrastructure security, thus a
   multicast VPN solution shall whether avoid single points of failures
   or propose some technical solution making possible to implement a
   failover mechanism.

   As an illustration, one can consider the case of a solution that
   would use PIM-SM as a means to setup MDTunnels.  In such a case, the
   PIM RP might be a single point of failure.  Such a solution should
   thus be compatible with a solution implementing RP resiliency.

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5.2.8  Management tools, OAM

   The operation of a multicast VPN solution SHALL be as light as
   possible and providing automatic configuration and discovery SHOULD
   be prioritized.  Particularly the operational cost of setting up
   multicast on a PE should be as low as possible.

   Moreover, monitoring of multicast specific parameters and statistics
   SHOULD be offered to the service provider.

   Most notably the provider SHOULD have access to:

   o  Multicast traffic statistics (total traffic conveyed, incoming,
      outgoing, dropped, etc., by period of time) - Information about
      client multicast resource usage (state and throughput)

   o  The IPPM (IP Performance Metrics [RFC2330]) -related information
      that is relevant to the multicast traffic usage: such information
      includes the one-way packet delay, the inter-packet delay
      variation, etc.

   o  Alarms when limits are reached on such resources - Statistics on
      decisions related to how client traffic is carried on distribution
      tunnels (e.g. "traffic switched onto a multicast tree dedicated to
      such groups or channels")

   o  Statistics on parameters that could help the provider to evaluate
      its optimality/state trade-off

   All or part of this information SHOULD be made available through
   standardized SNMP ([RFC1157]) MIBs (Management Information Base).

5.2.9  Architectural Considerations

   As far as possible, the design of a solution should carefully
   consider the number of protocols within the core network.  If any
   additional protocols are introduced compared with unicast VPN, the
   balance between their advantage and operation burden should be
   examined thoroughly.

5.2.10  Compatibility and migration issues

   It is a requirement that unicast and multicast services MUST be able
   to co-exist within the same VPN.

   Likewise, the introduction of IP multicast capabilities in devices
   that participate to the deployment and the maintenance of a VPN
   SHOULD be as smooth as possible, i.e. without affecting the overall

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   quality provided with the services that are already supported by the
   underlying infrastructure.

   A multicast VPN solution SHOULD prevent compatibility and migration
   issues, for instance by prioritizing mechanisms facilitating forward
   compatibility.  Most notably a solution supporting only a subset of
   those requirements SHOULD be designed to be compatible with future
   enhanced revisions.

   It SHOULD be an aim of any multicast into VPN solution to offer as
   much backward compatibility as possible.  Ideally a solution would
   have be the ability to offer multicast VPN services across a network
   containing some legacy routers not supporting any multicast VPN
   specific features.

   In any case a solution SHOULD state a migration policy from possibly
   existing deployments.

5.2.11  Troubleshooting

   A multicast VPN solution that dynamically adapts the way some client
   multicast traffic is carried over the provider's network may incur
   the disadvantage of being hard to troubleshoot.  In such a case, to
   help diagnose multicast network issues, a multicast VPN solution
   SHOULD provide monitoring information describing how client traffic
   is carried over the network (e.g. if a solution uses multicast-based
   MDTunnels, which provider multicast group is used for such and such
   client multicast stream).  A solution MAY also provide configuration
   options to avoid any dynamic changes, for multicast traffic of a
   particular VPN or a particular multicast stream.

   Moreover, a solution MAY usefully provide some mechanism letting
   network operators check that all VPN sites that advertised interest
   in a particular customer multicast stream are properly associated
   with the corresponding MDTunnel.  Providing the operators with means
   to check the proper setup and operation of MDTunnels MAY also be
   provided (e.g. when MPLS is used for MDTunnels, integrating
   mechanisms such as LSPPing[I-D.ietf-mpls-lsp-ping][I-D.yasukawa-mpls-
   p2mp-lsp-ping] into the L3VPN troubleshooting functionalities will be
   desirable).  Depending on the implementation such verification could
   be initiated by source-PE or receiver-PE.

5.2.12  Inter-AS, inter-provider

   A multicast VPN solution SHOULD support inter-AS and inter inter-
   provider VPNs.  Considerations about coexistence with unicast
   inter-AS VPN Options A, B and C (as described in section 10 of

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   RFC2547bis [I-D.ietf-l3vpn-rfc2547bis]) are strongly encouraged.

   A multicast VPN solution SHOULD provide inter-AS mechanisms requiring
   the least possible coordination between providers, and keep the need
   for detailed knowledge of providers networks to a minimum - all this
   being in comparison with corresponding unicast VPN options.

   o  Within each service provider the service provider SHOULD be able
      on its own to pick the most appropriate tunneling mechanism to
      carry (multicast) traffic among PEs (just like what is done today
      for unicast)

   o  If a solution does require a single tunnel to span P routers in
      multiple ASs, the solution SHOULD provide mechanisms to ensure
      that the inter-provider co-ordination to setup such a tunnel is

   Moreover such support should be possible without compromising other
   requirements expressed in this requirement document, and should not
   incur penalty on scalability and bandwidth usage.

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6.  Security Considerations

   This document does not by itself raise any particular security issue.

   A set of security issues have been identified that MUST be addressed
   when considering the design and deployment of multicast-enabled VPN
   networks.  Such issues have been described in Section 5.1.5 and
   Section 5.2.6.

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7.  Acknowledgments

   The authors would like to thank, by rough chronological order,
   Vincent Parfait (Equant), Zubair Ahmad (Equant), Elodie Hemon-
   Larreur, Sebastien Loye (France Telecom), Rahul Aggarwal (Juniper),
   Hitoshi Fukuda (NTT Communications), Luyuan Fang (AT&T), Adrian
   Farrel, Daniel King, Yiqun Cai (Cisco), Ronald Bonica, Len Nieman,
   Satoru Matsushima (Japan Telecom), Netzahualcoyotl Ornelas (Renater),
   for their review, valuable input and feedback.

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8.  References

8.1  Normative references

   [RFC3978]  Bradner, S., "IETF Rights in Contributions", BCP 78,
              RFC 3978, March 2005.

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, October 1996.

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

   [RFC4031]  Carugi, M. and D. McDysan, "Service Requirements for Layer
              3 Provider Provisioned Virtual Private Networks (PPVPNs)",
              RFC 4031, April 2005.

   [RFC4026]  Andersson, L. and T. Madsen, "Provider Provisioned Virtual
              Private Network (VPN) Terminology", RFC 4026, March 2005.

   [RFC2362]  Estrin, D., Farinacci, D., Helmy, A., Thaler, D., Deering,
              S., Handley, M., and V. Jacobson, "Protocol Independent
              Multicast-Sparse Mode (PIM-SM): Protocol Specification",
              RFC 2362, June 1998.

   [RFC1112]  Deering, S., "Host extensions for IP multicasting", STD 5,
              RFC 1112, August 1989.

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

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

   [RFC3973]  Adams, A., Nicholas, J., and W. Siadak, "Protocol
              Independent Multicast - Dense Mode (PIM-DM): Protocol
              Specification (Revised)", RFC 3973, January 2005.

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

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

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8.2  Informative references

   [RFC2547]  Rosen, E. and Y. Rekhter, "BGP/MPLS VPNs", RFC 2547,
              March 1999.

              Rosen, E., "BGP/MPLS IP VPNs",
              draft-ietf-l3vpn-rfc2547bis-03 (work in progress),
              October 2004.

              Knight, P., Ould-Brahim, H., and B. Gleeson, "Network
              based IP VPN Architecture using Virtual Routers",
              draft-ietf-l3vpn-vpn-vr-02 (work in progress), April 2004.

              Holbrook, H. and B. Cain, "Source-Specific Multicast for
              IP", draft-ietf-ssm-arch-06 (work in progress),
              September 2004.

   [RFC2432]  Dubray, K., "Terminology for IP Multicast Benchmarking",
              RFC 2432, October 1998.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031, January 2001.

              Aggarwal, R., "Extensions to RSVP-TE for Point to
              Multipoint TE LSPs", draft-ietf-mpls-rsvp-te-p2mp-01 (work
              in progress), January 2005.

              Minei, I., "Label Distribution Protocol Extensions for
              Point-to-Multipoint Label  Switched Paths",
              draft-minei-mpls-ldp-p2mp-00 (work in progress),
              March 2005.

              Wijnands, I., "Multicast Extensions for LDP",
              draft-wijnands-mpls-ldp-mcast-ext-00 (work in progress),
              April 2005.

              Roux, J., "Requirements for multipoint extensions to the
              Label Distribution Protocol",
              draft-leroux-mpls-mp-ldp-reqs-00 (work in progress),
              July 2005.

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              Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
              "Bi-directional Protocol Independent Multicast (BIDIR-
              PIM)", draft-ietf-pim-bidir-07 (work in progress),
              March 2005.

   [RFC1853]  Simpson, W., "IP in IP Tunneling", RFC 1853, October 1995.

   [RFC3353]  Ooms, D., Sales, B., Livens, W., Acharya, A., Griffoul,
              F., and F. Ansari, "Overview of IP Multicast in a Multi-
              Protocol Label Switching (MPLS) Environment", RFC 3353,
              August 2002.

   [RFC3272]  Awduche, D., Chiu, A., Elwalid, A., Widjaja, I., and X.
              Xiao, "Overview and Principles of Internet Traffic
              Engineering", RFC 3272, May 2002.

   [RFC2784]  Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
              Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
              March 2000.

   [RFC4045]  Bourdon, G., "Extensions to Support Efficient Carrying of
              Multicast Traffic in Layer-2 Tunneling Protocol (L2TP)",
              RFC 4045, April 2005.

   [RFC3809]  Nagarajan, A., "Generic Requirements for Provider
              Provisioned Virtual Private Networks (PPVPN)", RFC 3809,
              June 2004.

   [RFC2401]  Kent, S. and R. Atkinson, "Security Architecture for the
              Internet Protocol", RFC 2401, November 1998.

   [RFC2365]  Meyer, D., "Administratively Scoped IP Multicast", BCP 23,
              RFC 2365, July 1998.

   [RFC2330]  Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
              "Framework for IP Performance Metrics", RFC 2330,
              May 1998.

   [RFC2475]  Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
              and W. Weiss, "An Architecture for Differentiated
              Services", RFC 2475, December 1998.

   [RFC3180]  Meyer, D. and P. Lothberg, "GLOP Addressing in 233/8",
              BCP 53, RFC 3180, September 2001.

   [RFC1157]  Case, J., Fedor, M., Schoffstall, M., and J. Davin,
              "Simple Network Management Protocol (SNMP)", STD 15,

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              RFC 1157, May 1990.

              Kompella, K. and G. Swallow, "Detecting MPLS Data Plane
              Failures", draft-ietf-mpls-lsp-ping-09 (work in progress),
              May 2005.

   [RFC1191]  Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
              November 1990.

              Yasukawa, S., "Detecting Data Plane Failures in Point-to-
              Multipoint MPLS Traffic  Engineering - Extensions to LSP
              Ping", draft-yasukawa-mpls-p2mp-lsp-ping-02 (work in
              progress), April 2005.

              Mathis, M., "Fragmentation Considered Very Harmful",
              draft-mathis-frag-harmful-00 (work in progress),
              July 2004.

   [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
              June 1999.

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   [3]  <mailto:y.kamite@ntt.com>

   [4]  <mailto:jeanlouis.leroux@francetelecom.com>

   [5]  <mailto:nicolai.leymann@t-systems.com>

   [6]  <mailto:renaud.moignard@francetelecom.com>

   [7]  <mailto:thomas.morin@francetelecom.com>

Author's Address

   Thomas Morin (editor)
   France Telecom R&D
   2, avenue Pierre Marzin
   Lannion  22307

   Email: thomas.morin@rd.francetelecom.com

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Appendix A.  Requirements summary

   [This section will contain a summary of all requirements of this
   document, that were expressed as MUST or SHOULD].

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Appendix B.  Changelog

   This section lists changes made to this document (minor or editorial
   changes excepted) between major revisions.

   It shall be removed before publication as an RFC.

B.1  Changes between -00 and -01

   o  integrated comments made on L3VPN WG mailing list after -00

   o  completed Carrier's carrier section (5.1.9)

   o  updates in sections 5.1 and 5.2 about minimum MTU

   o  added a section about "Quality of Service Differentiation" as ISP
      requirement (section 5.2.5)

   o  added P2MP LDP extensions as possible MDTunnels techniques

   o  started to build section 4 "Use Case"

   o  detailed section 5.1.3 "QoS", most notably about group join and
      leave delays

   o  additions to section 5.2.12 "Inter-AS, inter-provider"

   o  added MDTunnel verification requirement to section 5.2.11

   o  moved "Architectural Considerations" section

   o  moved contributors to top of document

   o  made draft content agnostic to unicast L3VPN solutions

   o  added two appendixes: "Changelog" and "Requirement summary"

   o  conversion to XML [RFC2629] with the help of some scripting and
      Bill Fenner's xml2rfc XMLMind plugin

   o  lot's of editorial changes

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