Patent ID: 8218447

Claim:
A method of identifying a path of travel for a packet in a multi-area domain operated according to a link state routing protocol, comprising the steps of: receiving topology information from a plurality of individual areas in a domain; identifying a plurality of intra-area least cost paths from the topology information; assembling a subset of the plurality of intra-area least cost paths into an end-to-end path between a starting address and a destination address; wherein the identifying step comprises: identifying at least one exit point from a first area through which the destination address is reachable; constructing at least one least cost path segment within the first area between the starting address and at least one of the exit points; selecting at least one of the least cost path segments to result in at least one selected first area least cost segment; for at least one of the exit points associated with at least one of the selected least cost path segments, identifying a second area within the domain to which said at least one exit point is connected; identifying at least one exit point from the second area through which the destination address is reachable; constructing at least one least cost path segment within the second area between the at least one exit point of the first area and at least one exit point of the second area; and selecting at least one of the least cost segments within the second area to result in at least one selected second area least cost segment; wherein the assembling step comprises connecting one of the selected first area least cost segments and one of the selected second area least cost segments.