Patent ID: 8099506

Claim:
A relay node device in a communication system, the communication system including a plurality of node devices, the plurality of node devices being connected to a network, wherein the plurality of the node devices include the relay node device, the relay node device being connected to the network, and the plurality of node devices include a first node device, the first node device being connected to the network through a relay device, the relay device preventing acceptance of session start from the network side, the relay node device comprising: a session retention unit that establishes and retains session with the first node device, the first node device being not able to accept session start through the relay device from the network side; a receiving unit that receives a message sent from any of the plurality of node devices; a first determining unit that determines whether a sending source of the message received by the receiving unit is the first node device; a converting unit that converts first network address information indicating a network address of the first node device into second network address information indicating a network address of the relay node device in response to determining that the sending source of the message is the first node device by the first determining unit, and the first address information is included in the message received by the receiving unit; a sending control unit that controls sending of the message converted by the converting unit to any of the plurality of node devices, and a second determining unit that determines whether the received message is to be sent to the first node device based on the relay information included in the received message, in response to receiving a message whose sending source is a node device of the plurality of node devices and is different from the first node device; wherein the sending control unit controls sending of the message to the first node device, in response to determining the received message is to be sent to the first node device, and wherein the converting unit converts the first network address information into the second network address information and adds relay information indicative of the first node device to the message converted by the converting unit, in response to receiving the message from the first node device by the receiving unit.