A method includes the steps of a failure which occurs in a node or link, and b) identifying at most N (N is an integer equal to or greater than 2) nodes contained in each path affected by the occurrence of the failure. Each path is connected to a sender node which detects the failure, information is transferred to the sender node via the N nodes, and the sender node serves as a start point of each alternate path which is to be established. The method also includes the step of c) broadcasting a restoration message to links which outgo from the sender node, where the restoration message has an identifier of the sender node and identifiers of the N nodes specified for each path affected by the occurrence of the failure. The identifiers of the N nodes specified for each path being candidate nodes of an end point of each alternate path. The method als includes a step of d) determining whether or not a node being considered is one of the candidate nodes, where the node which is one of the candidate nodes is a destination node. Further, the method includes the steps of e) passing the restoration message through a repeater node which is a node other than the candidate nodes, and f) determining a route via which the restoration message has been transferred to the destination node to be an alternate path connected between the sender node and the destination node.