Network Working Group Shepherd
Internet-Draft Farinacci
Expires: December 11, 2006 Cisco Systems
Wu
Li
Cernet
June 9, 2006
IPv4 unicast/multicast VPNs over an IPv6 core
draft-ietf-softwire-4over6vpns-00
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Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
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",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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
packets.
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
Cernet
Email: jianping@cernet.edu.cn
Xing Li
Cernet
Email: xing@cernet.edu.cn
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