Ring switching method and node apparatus using the same

A node apparatus for a ring network in which a plurality of nodes are arranged in a multi-ring formation, comprising:

• a routing table defining relationships between a receiving physical line identifier with port number and a sending physical line identifier with port number for virtual ring bypass routes, said relationships being individually provided for respective transmission lines connected to the node apparatus;
• and
• a detection unit detecting, at a time of detection of a failure, each of the relationships from the routing table to determine a transmission line to which a switching request is sent, the detection unit detecting, at a time of relaying, each of the relationships from the routing table to determine a transmission line to which one of a switching request and a switching response is sent, and the detection unit detecting, at a time of receiving of a switching response, each of the relationships from the routing table to determine a transmission line to which the switching response is sent.

A node apparatus for a wavelength-division-multiplexing ring network in which a plurality of nodes are arranged in a multi-ring formation, comprising:

• a routing table defining relationships between a receiving physical line identifier with wavelength data and a sending physical line identifier with wavelength data for virtual ring bypass routes, the relationships being individually provided for respective transmission lines connected to the node apparatus;
• and
• a detection unit detecting, at a time of detection of a failure, each of the relationships from the routing table to determine a transmission line to which a switching request is sent, the detection unit detecting, at a time of relaying, each of the relationships from the routing table to determine a transmission line to which one of a switching request and a switching response is sent, and the detection unit detecting, at a time of receiving of a switching request, each of the relationships from the routing table to determine a transmission line to which a switching response is sent.