Patent ID: 8700755

Claim:
A transmission device included in a communication network, the transmission device comprising: a link trace frame transfer unit that transfers a received first link trace frame and a second link trace frame from a first transferring port corresponding to an operation system route, and a second transferring port corresponding to a preliminary system route, respectively, when transferring ports of the transmission device have a route redundancy configuration, wherein the first link trace frame is destined to a target transmission device and the second link trace frame includes an identifier that distinguishes the second link trace frame from the first link trace frame; and a link trace response frame transmission unit that, in response to receiving the first link trace frame, determines whether a destination address of the received first link trace frame has been learned and transmits a first link trace response frame to an origin transmission device when determining that the destination address of the received first link trace frame has been learned, and transmits, in response to receiving the second link trace frame, a second link trace response frame to the origin transmission device regardless of whether a destination address of the second link trace frame has been learned, the second link trace response frame distinguishable from the first link trace response frame.