A communication terminal (3a, 3b, 3c) configured to receive a plurality of segments transmitted by a different terminal, comprising: a round trip time measuring unit configured to measure a round trip time, RTT, between the communication terminal (3a, 3b, 3c) and the different terminal; a retransmission timeout time calculator configured to calculate a retransmission timeout time, RTO, by using the round trip time, RTT, measured by the round trip time measuring unit, in order to estimate a retransmission timeout time which is set in the different terminal by using a round trip time measured by the different terminal; a timer configured to start a time counting operation of the retransmission timeout time, RTO, when a first segment of the plurality of segments is received from the different terminal; and a segment prompt transmitter (38a, 38b, 38c) configured to transmit, to the different terminal, a segment prompt signal for prompting the different terminal to transmit a second segment which should be transmitted after the first segment from the different terminal, after the second segment is not received from the different terminal during a time from the start of the time counting operation to the completion of the retransmission timeout time, RTO, wherein the retransmission timeout time, RTO, is calculated iteratively for each measured value of the round trip time, RTT, by using the following formulae: Err = M − A, A < − A + g * Err, D < − D + h * | Err | − D, and RTO = A + 4 D, wherein Err is the difference between the measured value M of the round trip time and a smoothed mean round trip time value A, D is a smoothed mean deviation, and g and h are predetermined coefficients. a round trip time measuring unit configured to measure a round trip time, RTT, between the communication terminal (3a, 3b, 3c) and the different terminal; a retransmission timeout time calculator configured to calculate a retransmission timeout time, RTO, by using the round trip time, RTT, measured by the round trip time measuring unit, in order to estimate a retransmission timeout time which is set in the different terminal by using a round trip time measured by the different terminal; a timer configured to start a time counting operation of the retransmission timeout time, RTO, when a first segment of the plurality of segments is received from the different terminal; and a segment prompt transmitter (38a, 38b, 38c) configured to transmit, to the different terminal, a segment prompt signal for prompting the different terminal to transmit a second segment which should be transmitted after the first segment from the different terminal, after the second segment is not received from the different terminal during a time from the start of the time counting operation to the completion of the retransmission timeout time, RTO, wherein the retransmission timeout time, RTO, is calculated iteratively for each measured value of the round trip time, RTT, by using the following formulae: Err = M − A, A < − A + g * Err, D < − D + h * | Err | − D, and RTO = A + 4 D, wherein Err is the difference between the measured value M of the round trip time and a smoothed mean round trip time value A, D is a smoothed mean deviation, and g and h are predetermined coefficients.