A communication system includes a first information processing apparatus and a second information processing apparatus. The first information processing apparatus controls to determine an information amount to be used for a receipt acknowledgment response to packets to be transmitted to a second information processing apparatus on the basis of information relating to the packets and notifies the second information processing apparatus of that determined information amount. The second information processing apparatus controls to return the receipt acknowledgment response to the packets transmitted from the first information processing apparatus to the first information processing apparatus on the basis of the information amount notified from the first information processing apparatus.