Transmission device with data channel failure notification function during control channel failure

A transmission device in a transmission network system having a plurality of transmission devices and providing a data channel for transmitting data signals and a control channel for transmitting control signals individually between the transmission devices, said data signals being transmitted along a preset path, comprising:

• a reception unit for receiving information on a failure of a working data channel, said information on the failure being sent from a transmission device located at a downstream side on a working path set at its transmission device via a protection control channel for a working control channel of said transmission device located at the downstream side;
• a failure detecting unit for detecting a failure of the working data channel for transmitting data signals to be input along said working path;
• and
• a judgment unit for judging an occurrence location of the failure based on positional relationship between its transmission device and said transmission device positioned at the downstream side, and presence of failure detected by said failure detecting unit.

A transmission network system having a plurality of transmission devices and providing a data channel for transmitting data signals and a control channel for transmitting control signals individually between the transmission devices, said data signals being transmitted along a preset path, comprising:

• a first transmission device located at a downstream side of a working path being set;
• a second transmission device located at an upstream side of said working path being set;
• and
• a third transmission device for relaying information communicated between said first transmission device and said second transmission device,
• wherein said first transmission device comprises:
• a first failure detecting unit for detecting a failure of a working control channel which transmits control signals for controlling a first working data channel, said first working data channel transmitting data signals to be input from a transmission device adjacent to an upstream side on said working path along said working path;
• a second failure detecting unit for detecting a failure of said first working data channel;
• a route searching unit for searching a route of a protection control channel of the working control channel where a failure is detected by said first failure detecting unit between said first transmission device and said second transmission device;
• and
• a first transmission unit for transmitting information on the failure detected by said second failure detecting unit to said second transmission device by a protection control channel along the route searched by said route searching unit,
• said third transmission device comprises:
• a first reception unit for receiving said information transmitted by said first transmission unit via said protection control channel when said third transmission device positions on the route searched by said route searching unit;
• and
• a second transmission unit for transmitting said information via said protection control channel so that said information received by said reception unit is received by said second transmission device, and
• said second transmission device further comprises:
• a second reception unit for receiving said information transmitted from said first transmission device via said second transmission device;
• a third failure detecting unit for detecting a failure of a second working data channel for transmitting data signal to be input along said working path;
• and
• a judgment unit for judging said failure location based on positional relationship between said second transmission device and said first transmission device, and based on presence of the failure detected by said third failure detecting unit.