A first apparatus receives, at a first transmission rate, packets belonging to a target packet flow on which packet-shaping processing for controlling network traffic is to be performed, and stores the received packets in a first packet buffer. Then, the first apparatus performs first packet-shaping processing on the target packet flow by transmitting, at a second transmission rate, packets that belong to the target packet flow and read out from the first packet buffer. A second apparatus stores packets received from the first apparatus in a second packet buffer. When a shortage of buffer resource for storing packets belonging to the target packet flow occurs in the first packet buffer, the second apparatus performs second packet-shaping processing on the target packet flow by transmitting, at a third transmission rate, packets that belong to the target packet flow and are read out from the second packet buffer.