The transfer delay QoS attribute for delay-sensitive applications is enforced in radio access networks by determining the ongoing validity of incomplete data packets based on a maximum data transfer delay constraint. According to one embodiment, upper-layer packet data units (PDUs) associated with an application having a maximum data transfer delay constraint are transferred by starting a timer responsive to initial transmission of an RLC data block associated with one or more of the upper-layer PDUs. The timer is initialized to a timer value that is based on the maximum data transfer delay constraint. The RLC data block is retransmitted responsive to a received message indicating reception of the RLC data block is unacknowledged so long as the timer has not expired. The RLC data block is deleted from memory responsive to the timer expiring or a received message indicating reception of the RLC data block is acknowledged.