Patent ID: 7269129

Claim:
A transmitting apparatus in a ring network in which a plurality of transmitting apparatuses are connected in ring form so as to be capable of transmitting in each of upstream and downstream directions, working and protection channels are assigned to each direction and, when failure occurs in a transmission path, a transmit signal is looped back using the protection channel to effect rescue, said apparatus comprising: rescue-impossible detection means for detecting that communication between an insert transmitting apparatus that incorporates a packet, which enters from a lower-order side, into a higher-order signal and transmits the signal to a transmission path, and a drop transmitting apparatus that extracts the packet from the higher-order signal and transmits the packet to another lower-order side, cannot be rescued because of transmission-path failure; packet-transmission halting means for halting transmission of the packet to the transmission path when communication has become unrescuable; and failure-occurrence detection means for detecting that multiple failures have occurred at multiple locations in a transmission path and obtaining a signal non-arrival range within which a signal does not arrive because of the multiple failures at the multiple locations; said rescue-impossible detection means of the insert transmitting apparatus determining that rescue is impossible when the drop transmitting apparatus resides in the signal non-arrival range.