 sub-layer at the transmitting side. QoS setting. Configurable by Layer 3 to provide different levels of QoS. Notification of unrecoverable errors. Notifying the upper layer of errors that cannot be resolved by RLC" itself by normal exception handling procedures, e.g. by ad- justing the maximum number of retransmissions according to delay requirements. 3.8.3.4 RLC Functions Segmentation and reassembly. This function performs segmentation/reassembly of variable-length higher layer PDUs into/from smaller RLC Payload Units (PUs). The RLC PDU size is adjustable to the actual set of transport formats. Concatenation Padding. In the absence of concatenation and non-filled RLC PDUs of given size, the remainder of the data field gets filled with padding bits. Transfer of user data. Conveyance of data between users of RLC services. Error correction. Error correction by retransmission (e.g. Selective Repeat, Go Back N, or a Stop-and-Wait ARQ) in acknowledged data transfer mode. In-sequence delivery of higher layer PDUs. Preserves the order of higher layer PDUs when submitted for transfer by RLC using the acknowledged data transfer service. 11 There is a single RLC connection per radio bearer. The UMTS Network and Radio Access Technology Duplicate detection. Detects duplicated received RLC PDUs and ensures that the resultant higher layer PDU get delivered only once to the upper layer. Flow control. Allows an RLC receiver to control the rate at which the peer RLC transmitting entity may send information. Sequence number check (unacknowledged data transfer mode). Guarantees the integrity of reassembled PDUs and provides a mechanism for the detection of cor- rupted RLC SDUs through checking the sequence number in RLC PDUs when they are reassembled into a RLC SDU. Protocol error detection and recovery. Detects and recovers from errors in the operation of the RLC protocol. Ciphering. Prevents unauthorized acquisition of data. Ciphering occurs in the RLC layer for non-transparent RLC mode. Suspend/resume function. Suspension and r