Path management device and program storing medium

A non-transitory storing medium for storing a computer program that executes path management processing to manage 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 computer program, executed by a computer, comprising:

• a function of receiving the link state advertisement messages;
• a function of reproducing the shortest path trees and the routing tables of each of the plurality of routers based on the link state advertisement messages;
• a function of recording the reproduced routing tables of each of the plurality of routers;
• a function of recording the reproduced shortest path trees from which the reproduced routing tables are created;
• a routing table re-creation function 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 in the routing table re-creation function, a shortest path tree and a routing table are rewritten, and
• in the function of recording, the reproduced routing tables and the rewritten routing table are accumulated;
• a path change monitoring function of comparing the reproduced routing tables with the rewritten routing table, and creating path change data that is differential data between the reproduced routing tables and the rewritten routing table;
• and
• a function of recording the path change data for each of the plurality of routers.