Patent ID: 7599349

Claim:
A method for operating a first path computation element in a first autonomous system to participate in establishing an inter-autonomous system Multi-Protocol Label Switching (MPLS) Traffic Engineering Label Switched Path (LSP) between a head-end node and a tail-end node, said method comprising: receiving at said first path computation element, virtual shortest path tree information from a second path computation element in a second autonomous system, said virtual shortest path tree information identifying a virtual shortest path tree rooted at said tail-end node and extending to one or more border routers linking said first autonomous system and said second autonomous system; performing computations at said first path computation element, based on said received virtual shortest path tree information to determine a revised virtual shortest path tree, said revised virtual shortest path tree extending from said tail-end node to one or more border routers linking said first autonomous system and a third autonomous system; and sending information identifying said revised virtual shortest path tree from said first path computation element to a third path computation element in said third autonomous system; wherein said revised virtual shortest path tree is used to compute a path of said MPLS Traffic Engineering LSP between said head-end node and said tail-end node.