In a communication control system a reception-side terminal sends back transmission time information included in a transmission packet as an acknowledgment to a transmission-side terminal. The transmission-side terminal determines whether a response time, obtained from the transmission time information, is shorter than a threshold. When the response time is shorter, the transmission-side terminal controls so as to transmit to the reception-side terminal a larger number of packets than the number of packets upon transmission of the transmission packet, or to transmit the same number of packets as the number of packets upon transmission of the transmission packet.