Network Design Apparatus and Network Design Method

1. A network design apparatus comprising: a memory; and a processor coupled to the memory, wherein the processor executes a process including: calculating an allocation pattern not requiring cancellation of a connection request from among a plurality of allocation candidates, when the connection request transmitted/received between nodes on a network is to be allocated to a slot that constructs a link on the network; determining a change procedure of the connection request in order to change an allocation pattern provided before the network is re-optimized to the allocation pattern calculated at the calculating; and outputting the allocation pattern calculated at the calculating as an allocation pattern after the network is re-optimized, along with the change procedure determined at the determining.

2. The network design apparatus according to claim 1 , wherein the calculating includes calculating an allocation pattern which results in the minimum number of cancellations of the connection request when the allocation pattern not requiring cancellation of the connection request does not exist.

3. The network design apparatus according to claim 1 , wherein the calculating includes determining which of links used before the re-optimization is diverted as a link used after the re-optimization when the connection request uses a different link before and after the network is re-optimized.

4. The network design apparatus according to claim 1 , further including performing control to ease a fixing constraint for a slot used by the connection request or a condition under which the connection request is cancelable, when the allocation pattern not requiring cancellation of the connection request does not exist.

5. The network design apparatus according to claim 4 , further including classifying a plurality of links corresponding to the same physical link into the same group prior to calculating the allocation pattern, wherein the performing includes adding the fixing constraint to a slot, which is used by the same connection request before and after the re-optimization, from among a plurality of slots constructing the plurality of links classified into the same group at the classifying.

6. A network design method comprising: in a network design apparatus, calculating an allocation pattern not requiring cancellation of a connection request from among a plurality of allocation candidates, when the connection request transmitted/received between nodes on a network is to be allocated to a slot that constructs a link on the network, using a processor; determining a change procedure of the connection request in order to change an allocation pattern provided before the network is re-optimized to the calculated allocation pattern, using the processor; and outputting the calculated allocation pattern as an allocation pattern after the network is re-optimized, along with the determined change procedure, using the processor.