An object of the present invention is to provide a mechanism for improving the performance of a radio access network. The object is achieved by a data packet (200) in a first network node (110). The first network node (110) is adapted to transmit the data packet (200) to a second network node (120), over a radio link (130). The first network node (110) and second network node (120) are comprised in a wireless communications network (100). The data packet (200) comprising a data packet header (210) and a data packet payload (220). The data packet header (210) comprising at least one length indicator (211, 212, 213, 214, 215). The data packet payload (220) comprising a number of consecutive packet data units (221, 222, 223), of the same specific size. The number of consecutive data units (221, 222, 223), of the same size is indicated in the data packet header (210) using a first length indicator of the at least one length indicators (211, 212, 213, 214, 215).