A communication apparatus which transmits data to a transmission destination, and receives, from the transmission destination, an acknowledgement indicating that the data has been received stores, in a memory, first specific data for specifying a plurality of transmission data, and transmission time data indicating transmission times of the plurality of transmission data. Based on second specific data contained in the acknowledgement, the communication apparatus searches the memory for first specific data for specifying transmission data corresponding to the acknowledgement, and calculates a round trip time based on the transmission time of the transmission data specified by the found first specific data, and a reception time at which the acknowledgement is received.