Patent ID: 8213455

Claim:
A communication node in a communication system in which a plurality of communication nodes are connected by Ethernet in a ring shape, the communication node comprising: a communication-right acquisition processor that, when receiving a token frame and acquiring a communication right, transmits a token-receipt completion notification frame addressed to a source communication node of the token frame, and releases the token frame when a data frame transmission is finished; a logical-ring-status control unit that switches between a transmission mode of disconnecting a logical connection within the own communication node upon acquisition of the communication right, and a repeat mode of finishing the disconnection of the logical connection within the own communication node upon reception of a token-receipt completion notification frame addressed to the own communication node; and a data-frame communication processor that transmits/receives a data frame, wherein the data-frame communication processor discards all received frames when the communication node is in the transmission mode, and forwards a received frame when the communication node is in the repeat mode, and wherein the logical-ring-status control unit switches the status of the own communication node to the repeat mode upon reception of a token-receipt completion notification frame addressed to other communication node, reception of the token-receipt completion notification frame addressed to other communication node indicating that the token-receipt completion notification frame addressed to the own communication node is lost.