Bypass route changeover system and switch back system

PURPOSE:To change over routes without error by devising the system such that a node unable to be in direct relay contact with a relevant node due to the occurrence of a fault collects node information of sets of nodes consisting of entire start nodes using the relevant node as a passing node to a destination and of the relevant node. CONSTITUTION:Upon the detection of a route fault to a destination node D, a node A sends a route re-configuration start message to nodes A-C, E, K of D-A fragment to collect information of each node. Moreover, the node A receives reports link object nodes being adjacent nodes of the nodes of the D-A fragment and having an output path to the node D and generates a list. The node A selects a node L from the list to select a new route. When the fault is restored, a node M invites switch-back to the node A, node information of the D-A fragment is collected and a regular outgoing link is selected after the confirmation of no disadvantage. Thus, a bypass and a regular route are selected without error.