Patent ID: 8493971

Claim:
A path calculation system comprising: a network management system (NMS) for maintaining topology information of a network allowing coexistence of Plesiochronous Digital Hierarchy (PDH) network and Synchronous Digital Hierarchy (SDH) network; and a path calculation device for calculating an optimum path in answer to a path calculation request from the network management system (NMS) on the basis of a topology data for path calculation generated therein, and transmitting a calculation result to the network management system (NMS), the network management system (NMS) generating the topology data for path calculation in the path calculation device in accordance with the topology information of the network after converting topology information of the PDH network into topology information of an SDH network, and reverting the SDH network topology information generated through conversion from the PDH network topology information among the SDH network topology information included in the calculation result received from the path calculation device to the PDH network topology information before the conversion.