To provide a communication apparatus which is capable of voluntarily controlling, according to its own reception capability, data transmission traffic, while reducing the burden for the control. The communication apparatus includes: a communication unit (35) which receives data; an ACK generating unit (45) which generates an ACK packet and transmit the ACK packet to a transmitting side apparatus (38), the ACK packet indicating a response to the transmitting side apparatus (38), the response corresponding to the data received by the communication unit (35); and a window updating notification generating unit (46) which generates a window updating notifying packet and transmit the window updating notifying packet to the transmitting side apparatus (38) irrespective of a result of the data reception by the communication unit (35), the window updating notifying packet requesting the transmitting side apparatus (38) to transmit data.