Embodiments described herein provide an apparatus for transmitting data in an xDSL. In one example, the apparatus can include a transmitter configured to transmit data over the xDSL system in the form of data transmission units (DTUs), the transmitter having a physical media specific-transmission convergence (PMS-TC) communication sublayer and a retransmission unit that is implemented in the PMS-TC sublayer, the retransmission unit including a retransmission buffer configured to store transmitted DTUs and to index the transmitted DTUs using retransmit containers, each retransmit container being defined as a time slot corresponding to a respective sent DTU. A retransmit request specifies a DTU by a corresponding retransmit container and wherein the retransmission unit is configured to retransmit the specified DTU in response to the retransmit request.