VPN MPLS IPv6

BGP/MPLS virtual private networks based on Layer 3 network infrastructures (L3VPN) are now widely deployed by telecom operators. Introduced in the early 2000s, this technology has made a name for itself in a wide range of offerings. In particular, it is now widely used to provide corporate customers with solutions for interconnecting remote sites, and for setting up intranets or extranets. These virtual private networks are based on a shared IP/MPLS core infrastructure, and more specifically on IPv4 networks, the version of the IP protocol widely used when MPLS VPNs first appeared.

With the exhaustion of the Internet's available address space, a new version of the Internet protocol, IPv6, was specified and gradually deployed. The introduction of IPv6 to many access, service and content providers and their customers, poses technical problems for the coexistence of the two protocols in different areas before the generalization phase. To resolve these issues, the IETF Softwire working group is focusing on standardizing discovery, control and encapsulation mechanisms for communication between IPv4 islands across IPv6 networks, and vice versa, for communication between IPv6 islands across an IPv4 network.

Such mechanisms are needed in transition scenarios on topologies made up of heterogeneous nodes, some of which do not activate dual protocol stacks. In such cases, exchanges between IPv4 (respectively IPv6) islands are sometimes "tunneled" over an IPv6 (resp. IPv4) transport. The solutions defined in this group are suitable for :

• hub and spoke" architectures using point-to-point tunnels to a concentrator ;

• mesh architectures, in which islands are linked to islands of the same address family by "point-to-multipoint" softwire tunnels between so-called AFBR (Address Family Border Routers) edge routers.

As a result, the communication protocols used to build the MPLS VPN architecture have been adapted or replaced to integrate this issue and route IPv6 client traffic. This dossier presents BGP/MPLS VPN solutions for IPv6, also known as 6VPE, in which IPv6 virtual private networks are based on an IPv4 MPLS core network (standardized and implemented before the early work of the softwire group).

After a brief introduction to IPv4 BGP/MPLS VPN networks and the IPv6 protocol, this article describes the signaling and transfer plan protocol extensions required to implement the 6VPE infrastructure. It also discusses some of 6VPE's advanced features for inter-domain VPNs, as well as extensions of the IPv6 BGP/MPLS VPN solution to other, non-MPLS encapsulation methods.

Readers will find a table of acronyms and abbreviations...