There is provided a mechanism for controlling a transmission of data in a fragmentation transmission mode. When fragments are transmitted in a fragmentation transmission mode, it is determined whether the fragment frame is received successfully or whether an acknowledgment message for confirming a successful transmission of the fragment frame is received. In case the acknowledgment for the successful transmission of the one fragment frame is not received, or the fragment is frame is not successfully received, the fragmentation transmission mode is maintained and a retransmission of the fragment frame is initiated.