Patent ID: 7630387

Claim:
A gateway apparatus which converts protocols among a first network which transmits IP packets and a second network which transmits time division multiplexed signals, comprising: a packet switch connected to the first network; IP conversion units which convert the time division multiplexed signals from the second network into the IP packets, and input the IP packets to the packet switch; a service system line concentrating unit which is provided on the packet switch and concentrates first controlling lines connected to the IP conversion units; a protection system line concentrating unit which is provided on the packet switch and concentrates the first controlling lines; a first monitoring module which monitors responses from the IP conversion units through the service system line concentrating unit and the protection system line concentrating unit via the first controlling lines; a second monitoring module which monitors the responses from the IP conversion units via second controlling lines differing from the first controlling lines; a failure determining module which determines whether a failure occurs or not in the service system line concentrating unit based on the presence or absence of each of the responses monitored by the first monitoring module and the second monitoring module; and a switching unit which causes the protection system line concentrating unit to be available and to operate as a new service system when the failure determining unit has determined that the failure occurs in the service system line concentrating unit.