Patent ID: 7660237

Claim:
A synchronous clock supply system comprising: at least one relay node which is positioned in a clock supply route formed by coupling arbitrary virtual paths for a loop of nodes in a network; and a termination node which is positioned in a downstream side of the clock supply route farther than the relay node from a synchronous clock sending source used to synchronize the nodes in the network, and finally receives the synchronous clock via a predetermined port, the relay node having a clock supply line priority table representing a priority for port switching for supplying the synchronous clock is prepared at each node, wherein a priority is set for a port to be switched, fault detection means for, when no synchronous clock is supplied in a downstream direction from an upstream side of the clock supply route due to a fault in the virtual path, detecting that no synchronous clock is supplied, fault notification data transmission means for, when said fault detection means detects the fault, sending fault notification data representing occurrence of the fault to the downstream side of the clock supply route, first port switching means for, when switching instruction data designating switching to another port for supply of the synchronous clock is sent in the upstream side from the downstream side of the clock supply route, switching a port for receiving the synchronous clock to the port, a clock sending means which sends out a clock received from one of a connecting device or an internal clock supply source as the synchronous clock to said clock supply route, and the termination node having second port switching means for, when another port is connected to the sending source via another virtual path and the fault notification data is sent from the relay node, performing port switching for supplying the synchronous clock from the predetermined port to said another port, the first and second port switching means forming upstream and downstream switching ports, and port switching instruction means for, when said port switching means performs port switching by detection of the fault notification data, sending switching instruction data which instructs the upstream side of the clock supply route to switch the port to said another port for supply of the synchronous clock.