Apparatus and method for establishing tunnels between nodes in a communication network

A method for establishing tunnels between nodes along a packet transfer route in a communication network including a plurality of relay nodes and a plurality of management servers, the plurality of relay nodes including first and second relay nodes and one or more intermediate relay nodes via which a packet is to be transferred along the packet transfer route, the first relay node receiving the first packet including a destination address, the second relay node being communicably coupled to a terminal identified by the destination address included in the first packet, the plurality of management servers including a first management server managing the first relay node and a second management server managing the second relay node, the method comprising:

• transmitting, by the first relay node, a request message including the destination address to the first management server so as to resolve relay-node addresses used for transferring the packet;
• transferring, by the plurality of management servers, the request message from the first management server to the second management server, based on transfer control information that is held in each of the plurality of management servers in association with the destination address, while storing, in the request message, a first list of relay-node addresses identifying relay nodes, included in the plurality of relay nodes, via which the packet is to be transferred;
• creating, by the second management apparatus, a reply message including a second list of relay-node addresses that respectively identify the first relay node, the one or more intermediate relay nodes via which the packet is to be transferred, and the second relay node, the second list being generated by adding, to the first list, at least one relay-node addresses held in the second management apparatus, the at least one relay-node address including a relay-node address identifying the second relay node;
• performing, by each of two or more relay nodes other than the second relay node whose relay-node addresses are stored in the second list of relay-node addresses, a procedure including:
• receiving the reply message,
• establishing, for the destination address, a tunnel used for transferring the packet between a pair of relay nodes included in the two or more relay nodes, in association with one of the second list of relay-node addresses included in the received reply message,
• updating the second list by removing, from the second list, at least one relay-node address including the one of the second list of relay-node address that is associated with the established tunnel, and
• transferring, when at least one relay-node address remains in the updated second list, the reply message including the updated second list to a relay node identified by one of the at least one relay-node addresses remaining in the updated second list;
• and
• when the packet is outputted from one of the two or more relay nodes via the established tunnel, encapsulating, by each of the two or more relay nodes, the packet with a header that stores, as a destination address, a relay-node address associated with the established tunnel.