A network system has: a communication device configured to perform frame transmission and reception; a network configured to transfer the frame; a gateway connected between the communication device and the network; and a controller configured to perform management of the communication device and the network. The frame is classified into a control frame for communicating control information necessary for communication and a data frame for communicating data between communication devices. The gateway determines whether a frame received from a source communication device is the control frame or the data frame, forwards the control frame to the controller, and forwards the data frame to the network. The controller performs the management based on the control frame received from the gateway. The network transfers the data frame received from the gateway to a destination communication device without through the controller.