A communication network system including a connectionless type communication network and a connection type communication network, wherein a communication device forming the communication network comprises a unit which transfers in-band control information to be exchanged on an in-band of the connectionless type communication network to other communication device through a virtual control link generated on an IP control network for controlling the connection type communication network and exchanges the in-band control information with other communication device, a unit which determines whether to generate a new connection for the connection type communication network based on the in-band control information to be exchanged, and a unit which generates a new connection for the connection type communication network in response to an instruction from the determination unit.