Network system

1. Field of the Invention A network system composed of a master network synchronization device and a slave network synchronization device. A master network synchronization device transmits hop count information. A slave network synchronization device receives the hop count information from an adjoining network synchronization device, determines a minimum hop count between the device itself and the master network synchronization device based on the hop count information, transmits the minimum hop count as the hop count information, and extracts a clock from the route from which the minimum hop count is received. Also, each of the network synchronization devices can be provided with the second master network synchronization device besides the first master network synchronization device, so that when a system failure occurs in the first master network synchronization device, the second master network synchronization device which detects the system failure performs the operation of a network synchronization master instead of the first master network synchronization device.