NETWORK SYSTEM, SLAVE STATION COMMUNICATION DEVICE, MASTER STATION COMMUNICATION DEVICE, AND BAND CONTROL METHOD

PROBLEM TO BE SOLVED: To provide a network system implementing more flexible band control while efficiently utilizing a band of a network.SOLUTION: The invention relates to a network system having a plurality of slave station communication devices accommodating a plurality of subordinate low-order networks and a master station communication device connected to the slave station communication devices by using a transmission path. Each of the slave station communication devices is characterized in that the device calculates request bandwidth required for the low-order networks of the slave station communication device and transmits the bandwidth to the master station communication device; receives information of allocation bandwidth from the master station communication device; and performs control so that the bandwidth used for communication in the upward direction communication from the slave station communication device is not more than the allocation bandwidth. The master station communication device is characterized in that the device receives the request bandwidths from the slave station communication devices; calculates the allocation bandwidth to be allocated to each of the slave station communication devices by utilizing the received request bandwidths and the maximum bandwidth by which the communication is possible in the upward direction communication; and notifies each of the slave station communication devices of the calculated allocation bandwidth.