The document describes the Radio Link Control (RLC) sub layer in 3GPP LTE, including its functions, modes of operation (unacknowledged, acknowledged, and transparent), state variables, procedures for transmitting and receiving data, and retransmission processes. The RLC sub layer provides transfer of upper layer PDUs, error correction, segmentation/reassembly, reordering, duplication detection, and supports both acknowledged and unacknowledged data transfer.