Sequence numbers for data packets to be transmitted using bearers having bearer identifiers in a communications system are generated, wherein the sequence numbers are generated independently for each of the bearers used for transmitting the data packets. Last generated sequence numbers for each of the bearers identifiers are stored and held in a memory. When a sequence number for a data packet to be transmitted using a bearer out of the bearers which has been used before is to be generated the memory is checked on a last generated sequence number for the bearer with a previously used bearer identifier and the sequence number is generated in accordance therewith.