A method including generating a plurality of convergence layer protocol data units in a packet-switched telecommunications system protocol stack; ciphering the plurality of convergence layer protocol data units using a ciphering sequence number; transferring the plurality of ciphered convergence layer protocol data units to a link layer of the packet-switched telecommunications system; discarding at least one ciphered convergence layer protocol data unit at the link layer and generating a link layer protocol data unit from at least one of the ciphered convergence layer protocol data units that has not been discarded; and transmitting the link layer protocol data unit and information relating to the discarding for a peer link layer.