Transmission apparatus and path establishing method

A transmission apparatus used as a start point node on a path between the start point node and an end point node in a network which is divided into at least a first area and a second area, wherein the start point node resides in the first area and the end point node resides in the second area, the transmission apparatus comprising:

• a determination unit configured to determine a boundary node, between the two areas, on a route having a minimum cost between the start point node and the end point node using a routing protocol that can advertise topology summary information between areas;
• a sending unit configured to send a path request message including designation of the boundary node to an adjacent node based on a signaling protocol for path establishment;
• a receiving unit configured to receive a message, from the adjacent node, that includes information related to a route of the path calculated by the boundary node and that is sent by the boundary node;
• and
• a path establishment processing unit configured to perform processes for establishing the path using the information related to the route included in the message.

A path establishing method for establishing a path between a start point node and an end point node in a network which is divided into at least a first area and a second area, wherein the start point node resides in the first area and the end point node resides in the second area, wherein:

• the start point node determines a boundary node, between the two areas, on a route having a minimum cost between the start point node and the end point node using a routing protocol that can advertise topology summary information between areas;
• the start point node sends a path request message including designation of the boundary node to an adjacent node based on a signaling protocol for path establishment;
• the boundary node receives the path request message, and calculate information related to a route between the start point node and the end point node using topology information of the first area and topology information of the second area;
• the boundary node sends a message including the calculated information related to the route to the start point node based on the signaling protocol;
• the start point node receives the message, sent by the boundary node, that includes the information related the route;
• and
• the start point node performs processes for establishing the path using the information related to the route included in the message.