A data transfer procedure for transferring data of a data sequence between a transmitting entity and a receiving entity

摘要

A data transfer procedure enables data of a data sequence to be transferred between a transmitting entity 13 and a receiving entity 19. The entities each comprise a higher data handling layer 11,17 and a lower data handling layer 12,18. The procedure comprises transferring down from the higher data handling layer 11 of the transmitting entity 13 to the lower data handling layer 12 of the transmitting entity a data unit of the data sequence, which data unit comprises one or more segments. The or each segment is transmitted from the lower data handling level 12 of the transmitting entity 13 to the lower data handling level 17 of the receiving entity 19 via a transmission link between the transmitting entity 13 and the receiving entity 19. An acknowledgement of receipt of the or each segment is sent from the lower data handling level 17 of the receiving entity to the lower data handling level 12 of the transmitting entity. The or each segment is transferred from the lower data handling layer 17 of the receiving entity to the higher data handling layer 18 of the receiving entity in data sequence order. The higher data handling layer of the transmitting entity 13 is arranged to retain a copy of the data unit until such time as an at least implied acknowledgement of receipt of earlier segments in the sequence is sent back from the receiving entity 19 to the lower data handling level of the transmitting entity. The procedure may further comprise determining that the transmission link is broken and re-establishing the link by purging (flushing) 27 the stores of data in the lower data handling layers of both the transmitting and receiving entities. The procedure may be used in a GRPS system, and the higher data handling layers may be subnetwork dependant convergence protocol (SNDCP) layers and the lower data handling layers may be Logical Link Control (LLC) layers.