Patent ID: 8320238

Claim:
A network system comprising multiple communication devices, the multiple communication devices comprising one start device, multiple end devices, and multiple relay devices for relaying data communication between the start device and the multiple end devices, wherein a point-to-point logical path is set to be used for unicast communication between the start device and each of the multiple end devices, wherein two point-to-multipoint logical paths are set to be used for multicast communication from the start node to the multiple end nodes, wherein the two point-to-multipoint logical paths comprise a first point-to-multipoint logical path, which passes through at least one of the multiple relay nodes, and a second point-to-multipoint logical path, which passes through at least another one of the multiple relay nodes different from the at least one of the multiple relay nodes along the first point-to-multipoint logical path, wherein the start device transmits, over the first point-to-multipoint logical path, data to be transmitted to the multiple end devices, wherein, when one of the multiple end devices detects a defect on the first point-to-multipoint logical path, the one of the multiple end devices that has detected the defect transmits management information containing a logical path switch request over the point-to-point logical path set between the one of the multiple end devices and the start device, wherein the start device receives the logical path switch request over the point-to-point logical path, and subsequently transmits, over the second point-to-multipoint logical path, the data to be transmitted to the multiple end devices, wherein the start device and the multiple end devices hold association information that associates point-to-point paths, the first point-to-multipoint path, and the second point-to-multipoint path with one another, wherein one of the end devices transmits management information containing a path switch request over a point-to-point path selected based on the association information, and wherein the start device transmits data to be transmitted to the multiple end devices over the second point-to-multipoint path selected based on the association information.