PURPOSE: To increase the through-put of communication, by decreasing the effect on the transmission control steps and the time required for error restortion, though the provision of time limit for retransmission and reception in an error restoring system for return reception.

CONSTITUTION: Through the return reception, the time limit is given to the transmission and reception waiting of the missing packet so that the error restoration is made quickly regardless of incompleteness in the range not affecting the processing of the transmission control steps. For example, if packets P1, P2 given with series number are transmitted and the P2 is missing on the way, it is detected at the transmission side through the return reception and retransmitted at time t7. The P2 and P3 are given to the transmission control processing by awaiting the reception of the packet P2 retransmitted at the reception side. If the retreansmission at time t13 for the missing P4 is not finished in the time of a timer TSI, the retransmission is given up and on the other hand, at the reception side, retransmission is awaited in the time of a timer TR, the waiting of the packet P4 is stopped by time-out and the P5 is given to the transmission control step for the restoration.