Patent ID: 7830808

Claim:
A path status monitoring method, comprising: cyclically generating frames serially connected for a number equivalent to an operation upper limit number of parallel physical paths, respectively for actually existing physical paths; shifting phases of the frames between the paths based on the number of the paths; collecting, when transmitting the frames through each path, statuses where a reception fault has occurred in each path to be stored in a frame predetermined per path among the frames; generating the frames to be transmitted to each path with the same phases before the cyclically generating; and delaying, after the generating, the frames sequentially generated in each path to be transmitted until a frame received from a destination of the frames indicates the occurrence of the reception fault, of obtaining a delay upon the occurrence of the reception fault as a transmission delay allowed for the path by the destination, and of obtaining transmission delays of the frames which occur between the paths by subtracting the respective allowable transmission delays from a maximum allowable transmission delay among the allowable transmission delays obtained in all of the paths, the shifting including shifting the phases of the frames generated at the cyclically generating between the paths by a time interval obtained by equally dividing a circulating cycle of the frames by the number of the paths in ascending order of the transmission delay, and then of restoring the shifts of the respective phases by the respective transmission delays.