Patent ID: 7961596

Claim:
A ring redundant communication path control method of causing, under a ring redundant communication path in which a plurality of transfer apparatuses are annularly connected by connecting two ports of a transfer apparatus to ports of transfer apparatuses adjacent thereto, respectively, and a frame transfer path for transferring frames in opposite directions is redundantly configured, a user to uniquely select the frame transfer path by setting at least one port among the ports, which annularly connect the transfer apparatuses, as a normally closed port that is closed even in a normal condition of the ring redundant communication path, the method comprising, for each of the transfer apparatuses: periodically transmitting an inspection frame for inspecting a communication path between the transfer apparatus and each of the adjacent transfer apparatuses to each of the adjacent transfer apparatuses from each of the ports connected to each of the adjacent transfer apparatuses; detecting, when the inspection frame transmitted from each of the adjacent transfer apparatuses is not received for a fixed time from a port connected to the adjacent transfer apparatus, a failure of the communication path in the port and transmitting a non-arrival notification frame, which notifies that the inspection frame has not arrived yet, from the port to the adjacent transfer apparatus; detecting, when the non-arrival notification frame transmitted from each of the adjacent transfer apparatuses is received from a port connected to the transfer apparatus, a failure of the communication path in the port; closing, when a failure is detected in any one of the ports connected to each of the adjacent transfer apparatuses, the port in which the failure is detected and transmitting an open command frame for commanding to open the normally closed port from another port other than the closed port; transferring, when the open command frame is received, the open command frame from another port configuring a ring redundant communication path same as that of the port in which the open command frame is received; and opening the normally closed port when the other port other than the closed port in which the failure is detected, the port in which the open command frame is received, or the other port configuring the ring redundant communication path same as that of the port in which the open command frame is received is the normally closed port.