Abstract: The band controller of the present invention comprises a band setting and storing part for setting a band for UDP traffic through own device, a band state table for managing information on band states of UDP traffic through own device, a frame generating and analyzing part for directing a transmitting-side device to decrease the transmission rate from the transmitting-side device by analyzing the transmission rate of UDP traffic over the network, calculating the buffer utilization rate in own device based on a setting band and information on band states, generating a source quench message, one of the ICMP messages, if the buffer utilization rate obtained by calculation is equal to or greater than the pre-determined buffer overflow critical utilization rate, and sending out the source quench message to the desired transmitting-side terminal, and a frame send-out timing controlling part for controlling timing of sending out a source quench message.