Synchronous transmission network system

A clock supply node, set in a network including a plurality of nodes, and supplying the plurality of nodes with a clock which the plurality of nodes operate in synchronization with, comprising:

• a transmission module for transmitting a quality request message for checking a quality of a clock supplied from a clock supply node itself toward the plurality of nodes;
• a receiving module for receiving a quality response message containing clock quality information representing the quality of the clock from each of the plurality of nodes;
• a quality determination module for determining the quality of the clock supplied by the clock supply node itself as clock supply quality information on the basis of the quality response message received by the receiving module;
• a notifying module for notifying, if the clock supply node itself is not a master for supplying the clock to the plurality of nodes in preference to other clock supply nodes of the clock supply node itself included in the plurality of nodes, the other clock supply node serving as the master of the clock supply quality information;
• and
• a node determination module for determining, if the clock supply node itself is the master, an optimum clock supply node supplying the best clock supply quality on the basis of the clock supply quality information which each of other clock supply nodes has notified of and the clock supply quality information of the clock supply node itself that is obtained by the quality determination module of the clock supply node itself.

A method of determining an optimum clock supply node in a synchronous transmission network system including a plurality of nodes including a plurality of clock supply nodes, and synchronizing all the plurality of nodes with a clock supplied from one of clock supply nodes as a master, the method making each of the clock supply nodes executing processes comprising:

• transmitting a quality request message for checking a quality of a clock supplied from a clock supply node itself toward all other nodes;
• receiving a quality response message containing clock quality information representing the quality of the clock from all the other nodes;
• determining the quality of the clock supplied by the clock supply node itself as clock supply quality information on the basis of the quality response message received by the receiving module;
• notifying, if the clock supply node itself is not a master, the other clock supply node serving as the master of the clock supply quality information;
• and
• determining, if the clock supply node itself is the master, an optimum clock supply node exhibiting the best clock supply quality on the basis of the clock supply quality information which each of other clock supply nodes has notified of and the clock supply quality information of the clock supply node itself that is obtained by the quality determination module of the clock supply node itself.