Patent ID: 8462617

Claim:
A method for relieving failure in a packet communication system, which comprises packet communication devices communicating mutually by using packets, each packet communication device comprising a packet transfer unit which transfers the packets and a path control unit which controls the packet transfer unit, and path communication devices which are provided on a transmission line between the packet communication devices, each path communication device comprising a lower layer transfer unit which transfers the packets and a lower layer path control unit which controls the lower layer transfer unit and sets or releases a path on the transmission line between the packet communication devices, when a packet communication device detects a failure on the transmission line or the path between itself and a correspondent packet communication device to restore the communication, the method comprising: transmitting packets from the packet transfer unit to the transmission line using a routing table, where a virtual interface includes address information of Layer 3 , is provided in the packet transfer unit, and specifies a path in the transmission line between the packet communication devices, and the routing table defines an interface for the packet transfer unit that is mapped to the virtual interface; a topology modification notice pending step of not reporting the fact that connection with the correspondent packet communication device has been disconnected to the other packet communication devices other than the correspondent packet communication device for a prescribed time; a path restoration step of, within the prescribed time, performing path setting signaling, triggering cooperation of the path communication device and the correspondent packet communication device, and setting a protection path; and a virtual interface setting modification step of, when the failure is detected, allocating a virtual interface associated with a working path to the protection path so that the other packet communication devices other than the correspondent packet communication device do not perform a modification process of a connection relationship within the prescribed time, wherein each physical interface is associated with one and only one virtual interface, and a plurality of physical interfaces are associated with a single virtual interface at the same time, and the path restoration step and the virtual interface setting modification step are performed within the prescribed time.