Transmission unit and failure recovery method

A transmission unit with failure recovery functions which restores communication over an optical network, comprising:

• label table management means for managing a label table which associates incoming labels related to incoming optical transmission data with outgoing labels related to outgoing optical transmission data, the incoming and outgoing labels being associated with optical wavelengths;
• transmission means for controlling switching of the incoming optical transmission data, based on the label table;
• optical path set-up means for establishing a loop-shaped protection optical path that includes a part or whole of transmission links of an existing working optical path and would allow transmission data to flow in the opposite direction to that of the working optical path;
• and
• failure recovery means for executing a failure recovery process when a failure occurs on the working optical path, by changing the association between the incoming and outgoing labels stored in the label table, so as to switch the failed part of the working optical path to the loop-shaped protection optical path.

A failure recovery method comprising the steps of:

• (a) managing a label table which associates incoming labels related to incoming transmission data with outgoing labels related to outgoing transmission data;
• (b) establishing a loop-shaped protection path that includes a part or whole of transmission links of an existing working path and would allow transmission data to flow in the opposite direction to that of the working path;
• and
• (c) executing a failure recovery process when a failure occurs on the working path, by modifying the association between the incoming and outgoing labels stored in the label table, so as to switch the failed part of the working path to the loop-shaped protection path.

A packet transmission unit with failure recovery functions, comprising:

• label table management means for managing a label table which associates incoming labels related to incoming packets with outgoing labels related to outgoing packets;
• transmission means for controlling label-switched routing of the incoming packets, based on the label table;
• path set-up means for establishing a loop-shaped protection path that includes a part or whole of transmission links of an existing working path and would allow packets to flow in the opposite direction to that of the working path;
• and
• failure recovery means for executing a failure recovery process when a failure occurs on the working path, by changing the association between the incoming and outgoing labels stored in the label table, so as to switch the failed part of the working path to the loop-shaped protection path.

A network system with failure recovery functions, comprising:

• a plurality of transmission units, each comprising:
• label table management means for managing a label table which associates incoming labels related to incoming transmission data with outgoing labels related to outgoing transmission data,
• transmission means for controlling label-switched routing of the incoming transmission data, based on the label table,
• path set-up means for establishing a loop-shaped protection path that includes a part or whole of transmission links of an existing working path and would allow transmission data to flow in the opposite direction to that of the working path, and
• failure recovery means for executing a failure recovery process when a failure occurs on the working path, by changing the association between the incoming and outgoing labels stored in the label table, so as to switch the failed part of the working path to the loop-shaped protection path;
• and
• a transmission medium which interconnects the plurality of transmission units to form a network.