Abstract: A method for acknowledged transmission of data packets in a telecommunications system, comprising a convergence protocol layer for creating convergence protocol packets, and a link layer for transmitting convergence protocol packets and for acknowledging the transmission. A data packet number is defined for the convergence protocol packets by means of counters of the transmitter and the receiver which are synchronized with each other, in which case the transmitted convergence protocol packets are acknowledged by means of said counters. After reconfiguration of a radio bearer, the counters are synchronized by comparing the values of respective counters, and if the value of the transmitter's counter is smaller than the value of the receiver's counter, a temporary counter is started for the receiver. The value of the transmitter's counter is set as the value of the temporary counter, and the temporary counter is used until its value reaches a predetermined value.