COMMUNICATION SYSTEM, COMMUNICATION DEVICE AND BAND CONTROL METHOD

PROBLEM TO BE SOLVED: To provide a communication system which suppresses function addition to a general-purpose node to decrease unfairness of throughput among nodes and executes band control based on a traffic volume of sending.SOLUTION: The communication system provided with a plurality of ring switches comprises switches 1 and 5 respectively provided with block ports. The switch 1 divides, regarding communication of a reception direction of the own device, available bands into a fixed allocation band and an allocation target band which is to be allocated based on a band requested by each communication device and sends a band allocation inquiry (S1), receives a band allocation request from the communication device in response to the band allocation inquiry (S2, S4, S6, and S8), and allocates the allocation target band based on a requested band included in the band allocation request and informs the communication device of the allocation result (S9).