Transmission method of SDU discard information between data link layers for a radio communications system

PURPOSE: A method for transferring a service data unit(SDU) discard information between data link layers in a wireless communication system is provided to play a role equal to the amount of a conventional method by sending a small amount of control signals when a radio link control layer(RLC) of a transmitting end needs not to send all information of discarded SDU to an RLC of a receiving end, thereby efficiently utilizing a restricted wireless resource. CONSTITUTION: A method for transferring an SDU discard information between data link layers in a wireless communication system includes the steps of: transferring all or a portion of SDU information discarded at a transmitting end; and being operated by dividing an A mode and a B mode. The A mode represents that an RLC is capable of transferring all the SDU discarded information generated in a transmitting end to a receiving end and the B mode represents that only the portion of SDU discarded information required to a moving of the receiving window is transferred.