Patent ID: 8014319

Claim:
A path management device that manages information about communication paths in a communication network, the communication network including a plurality of routers mutually connected by means of a communication line, link states between the plurality of routers being shared among each of the plurality of routers by means of link state advertisement messages that are announced from each of the plurality of routers, and routing tables being created in each of the plurality of routers based on shortest path trees, the path management device comprising: a receiving unit that receives the link state advertisement messages; a routing table creation unit that reproduces the shortest path trees and the routing tables of each of the plurality of routers based on the link state advertisement messages; a routing table recording unit that records the reproduced routing tables of each of the plurality of routers; a shortest path tree recording unit that records the reproduced shortest path trees from which the reproduced routing tables are created; a routing table re-creation unit that determines whether or not to rewrite a shortest path tree and a routing table based on a record of a shortest path tree relating to a changed-state link upon receiving a link state advertisement message announcing a change in a link state, wherein the routing table re-creation unit rewrites a shortest path tree and a routing table, and the routing table recording unit accumulates the reproduced routing tables and the rewritten routing table; a path change monitoring unit that compares the reproduced routing tables with the rewritten routing table, and creates path change data that is differential data between the reproduced routing tables and the rewritten routing table; and a path change recording unit that records the path change data for each of the plurality of routers.