Methods and network devices for communicating data packets in a set of transmissions between a transmitter and a receiver of a communications network are described. The method includes prior exchanging transmitter-provided packet information and receiver-provided packet information between the transmitter and the receiver, generating an initial compression dictionary before the first transmission, based on the exchanged transmitter-provided packet information and the exchanged receiver-provided packet information. At the transmitter, the method further includes compressing the data packets of the first and subsequent transmissions of the set using the initial compression dictionary, and sending the compressed data packets over the communications network to the receiver. At the receiver, the method further includes receiving compressed data packets from the transmitter via the communications network, and decompressing the compressed data packets received in the first and subsequent transmissions of the set, using the initial compression dictionary. Improved compression of the first transmission is thus obtained.