ATM NETWORK SYSTEM

An ATM network system of the present invention contains a clock synchronization source and a plurality of nodes. In this ATM network system, a plurality of clock supply routes are set, which are used in receiving clocks from the clock synchronization source by each of the nodes. When each of the nodes detects a failure occurred in the presently used route, each of the nodes supplies a failure signal to other nodes which receive the clock supplied from the own node through this route, and further changes a route under use into another route. When each of the nodes receive the failure signals from other nodes, each of these nodes changes the route under use into another route.