A node in a first ring stores therein connection information about connecting nodes between a second ring and a third ring. Upon receiving a route of a working path by a signaling, the node determines any one of nodes composing the second ring as a branch node. If the working path is not terminated on an end node that the working path ends in the second ring thereon, and also if no node composing the second ring stores therein connection information between the end node and any one of the connecting nodes in the third ring that is connected to the second ring, the node compares each condition of selectable routes of a backup path between the end node and the branch node, and selects any one of the selectable routes as the backup path based on a result of comparison.