Patent ID: 7733876

Claim:
A method of providing layer-2 virtual private network (L2-VPN) services in a multiple-autonomous-system network, comprising: (1) initially performing an auto-discovery process including: (i) in a first provider edge (PE) router of a first autonomous system (AS), sending a first internal routing Information (R-I) message to a first border router of the first AS, the first internal R-I message including network layer reachability information (NLRI) for a first L2-VPN forwarder operating within the first PE router, the NLRI including an identifier of a VPN and an identifier of the first L2-VPN forwarder; (ii) in the first border router in response to receiving the first internal R-I message, sending a first external R-I message along a path between the first AS and a second AS, the first external R-I message forwarding the NLRI of the first L2-VPN forwarder and identifying the first border router as a router through which the first L2-VPN forwarder can be reached; (iii) in a second border router of the second AS, receiving the first external R-I message, the first external R-I message including the NLRI of the first L2-VPN forwarder and identifying the first border router along the path between the first and second ASes as a router through which the first L2-VPN forwarder can be reached; and (iv) in the second border router in response to receiving the first external R-1 message, sending a second internal R-1 message to a second PE router of the second AS, the second internal R-1 message including the NLRI of the first L2-VPN forwarder and identifying the second border router as a router through which the first L2- VPN forwarder can be reached; and (2) subsequently performing a pseudowire establishment process including: (i) within each of the first and second ASes, establishing respective direct internal signaling connections and internal pseudo wires between the respective PE router and border router of the respective ASes; and (ii) at each of the first and second border routers, (a) establishing respective external signaling connections and external pseudowires along the path between the first and- second ASes and (b) stitching the respective external and internal pseudowires together to form at least part of an end-to-end connection between the first L2-VPN forwarder and a second L2-VPN forwarder in the second PE router over which communications of the VPN are to be carried, the first and second border routers stitching the respective external and internal pseudowires using endpoint identifiers learned from a border gateway protocol (BGP), wherein the first AS is different than the second AS.