Patent ID: 8351459
Filing Date: 2013-01-08
Classification: H04L

Abstract:
1. 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 data-frame communication processor that transmits/receives a data frame; 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, causes the data-frame communication processor to start transmitting the data frame, and releases the token frame when the data frame transmission by the data-frame communication processor 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; wherein the logical-ring-status control unit includes a function of switching the status of the own communication node to the repeat mode upon reception of a data frame issued and transmitted by another communication node without receiving the token-receipt completion notification frame addressed to the own communication node, and upon reception of the token frame without receiving the data frame issued and transmitted by the another communication node in the transmission mode or the token-receipt completion notification frame addressed to the own communication node, the communication-right acquisition processor again transmits the data frame, which has been transmitted by the own communication node before receiving the token frame transmitted by the another communication node, and thereafter releases the token frame, and 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.