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Network Working Group                                           Shepherd
Internet-Draft                                                 Farinacci
Expires: December 11, 2006                                 Cisco Systems
                                                            June 9, 2006

             IPv4 unicast/multicast VPNs over an IPv6 core

Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2006).


   This document describes a method by which a Service Provider with an
   IPv6 backbone may provide VPNs (Virtual Private Networks) and MVPNs
   (Multicast Virtual Private Networks) for its IPv4 customers.  The
   IPv6 core network need only deploy native multicast services using
   Protocol Independent Multicast (PIM) .  All additional functionality

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   described is Customer Edge (CE) based and there are no additional
   Provider (P) or Provider Edge (PE) protocols.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

1.  Introduction

   Current PE based VPN solutions continue to overload functional and
   scaling requirements onto the PE nodes.  The next logical direction
   for VPN expansion is to move the functionality onto the CE nodes.  By
   doing so, we can remove the need for per-customer routetables inside
   any provider node.  The provider network need only implement a means
   to control traffic distribution to only those CE nodes participating
   in a particular VPN instance.

   This document describes a means by which an IPv6 provider network can
   use multicast to control traffic distribution between participating
   VPN CE nodes and how those CE nodes can auto discover all other VPN
   participating CE nodes without additional protocols nor overloaded
   extensions to existing protocols.

2.  Requirements

   o This is a CE-managed service.  That is the service provider PE and
   P routers only move native IPv6 packets and do not otherwise
   participate in the customer routing protocols.

   o The service provider infrastructure runs native multicast services
   as defined in [1] [RFC2362] so precise multicast replication can be
   performed among the VPN sites.

   o A unique IPv6 scoped multicast address is assigned to each VPN
   customer as defined in [2] [RFC4291].  The multicast group prefix of
   the VPN could be one of several possibilities: ff05, ff08, or could
   possibly have a new scope ID assignment.  The T flag may also be 1.

   o Each participating CE of a VPN joins the VPN assigned group
   creating a multipoint tunnel between the VPN sites so dynamic
   discovery of the CE devices can occur.  Broadcasting over the tunnel
   is realized by using the IPv6 multicast in the underlying provider
   network. o ARP protocol as in [3] [RFC0826] is used to discover the
   underlying tunnel endpoints.  The CE nodes ARP over the tunnel for a

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   VPN-based next-hop - on the tunnel's subnet - and the hardware
   address returned is an IPv6 address internal to the provider network.

   o Participating CEs within a VPN share a common routing protocol and
   neighbor adjacencies through the multipoint tunnel.

3.  Multicast VPNs

   o PIM runs with the Intergateway Protocol (IGP) at each customer site
   as well as over the multipoint tunnel through the provider network.

   o Sending PIM Hello messages are "broadcasted over the multipoint
   tunnel which ensures only the VPN member CE routers will get the

4.  Unicast VPNs

   Each VPN CE member router is configured with the core IPv6 VPN
   multicast group address, which is effectively a VPN ID.  Each CE
   member router joins this core IPv6 multicast group, creating a
   multipoint tunnel between each of the CE member routers.  The VPN
   customer IGP runs across this multipoint tunnel, establishing
   neighbor adjacencies and building a complete customer routing table.

   By using ARP across the multipoint tunnel to discover the next-hop of
   each of the CE member neighbors, the learned hardware address
   returned will be the core-facing IPv6 interface address of the
   multipoint neighbor.  Unicast packets coming from one CE destined to
   a remote CE VPN neighbor will be unicast encapsulated with the ARP-
   learned IPv6 next hop of the CE VPN neighbor.

5.  Packet Fowarding

5.1.  Unicast

   Unicast packets are forwarded at the customer site as IPv4 packets to
   the edge of the network following the IPv4 routed topology.  The CE
   router will encapsulate the IPv4 packets in IPv6 and send to the
   hardware address learned through the multipoint tunnel across the
   provider network.  The destination CE router will decapsulate and
   forward the internal IPv4 packet to the unicast destination.

5.2.  Multicast

   Multicast can run in any of Any Source Multicast (ASM), Source

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   Specific Multicast (SSM) or BiDirectional (BiDir) within each VPN.
   For ASM and Bidir the Rendezvous Point (RP) can be located at any of
   the VPN sites.  For joining SSM channels, the member in the receiver
   site will join a (S,G) which are IPv4 addresses.  The IGP routing
   within the VPN allows the PIM join to travel to the edge and over the
   multipoint tunnel.  The VPN internal multicast state is setup via
   IPv4 PIM.

   Multicast forwarding to receivers sites may be a subset of all
   participating VPN sites and precise replication/forwarding without
   unwanted traffic to non-receiver CEs may be desired.  To facilitate
   this, the CE router(s) in the receiver sites will take the IPv4 PIM
   (S,G) join, after sending it over the multipoint tunnel, and the IPv6
   VPN group address to build an IPv6 PIM (S,G) join where:

   S is the underlying IPv6 address of the CE router at the source site.

   G is a group address derived from the VPN IPv6 group address and the
   IPv4 (S,G) address.

   The complete group address G will be:
   ff18:vvvv:ssss:ssss:gggg:gggg::x where s and g are the nibbles of the
   IPv4 (S,G) address and vvvv is the unique 16-bit VPN ID value.  The
   IPv6 unique VPN multicast address SHOULD comprise only the higher
   order bits with trailing zeros to allow for at least 64 lower bits to
   be used for encoding the IPv4 (S,G) address.

6.  IANA Considerations

   A new ARP hardward type should be specified to identify the IP
   address of the interface joined to the multipoint tunnel.

7.  Security

   The VPN member CE routers could maintain secure communications
   through the use of Security Architecture for the Internet Protocol as
   described in [4] [RFC4301].

8.  Normative References

   [RFC0826]  Plummer, D., "Ethernet Address Resolution Protocol: Or
              converting network protocol addresses to 48.bit Ethernet
              address for transmission on Ethernet hardware", STD 37,
              RFC 826, November 1982.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate

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              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [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.

   [RFC4291]  Hinden, R. and S. Deering, "IP Version 6 Addressing
              Architecture", RFC 4291, February 2006.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

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Authors' Addresses

   Greg Shepherd
   Cisco Systems

   Email: shep@cisco.com

   Dino Farinacci
   Cisco Systems

   Email: dino@cisco.com

   Jianping Wu

   Email: jianping@cernet.edu.cn

   Xing Li

   Email: xing@cernet.edu.cn

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