Patent ID: 8892773

Claim:
A path control apparatus comprising: a status change detecting unit implemented at least in hardware and that detects a status change of a network; a path calculating unit implemented at least in hardware and that decides a path in accordance with the status of the network; a calculation execution node deciding unit implemented at least in hardware, the calculation execution node deciding unit selecting a first node connected to a next forwarding destination via a failure link in a path table before an occurrence of the status change, the calculation execution node selecting a second node in a path from the path control apparatus to the first node in a first shortest path tree, the calculation execution node deciding unit deciding that the second node is a node apparatus in the network which needs a path update, when the calculation execution node deciding unit determines that a second value is smaller than or equal to a first value, the first value being obtained by subtracting a cost for a path from the path control apparatus to the first node in a second shortest path tree, from a cost for a path from the path control apparatus to the first node in the first shortest path tree, the second value being a total of a cost for a path from the path control apparatus to the second node in the second shortest path tree and a cost for a path from the second node to the path control apparatus in a third shortest path tree, the first shortest path tree being a shortest path tree after the occurrence of the status change, the second shortest path tree being a shortest path tree before the occurrence of the status change, the third shortest path tree being a shortest path tree in an opposite direction before the occurrence of the status change; a message creating unit implemented at least in hardware and that creates a message showing the decided node apparatus which needs a path update; and a message transmitting unit implemented at least in hardware and that transmits the message to the decided node apparatus which needs a path update.