A terminal on the first network, a gateway device connected between the first and second networks, and a network device on the second network enable the terminal to independently and seamlessly use a plurality of network devices and to seamlessly use a network device on the first network and the network device on the second network. The network device indirectly or directly provides the terminal and the gateway device with terminal behavior information and proxy processing behavior information in which a behavior required to use the device itself is described, or provides the gateway device with gateway functional module information including the terminal behavior information and the proxy processing behavior information.