A method includes sending a sequence number acknowledgement (SN-ACK) from a first device to a second device. The SN-ACK identifies a last consecutively correctly received data unit and includes a retry bit indicating whether at least one data unit of the plurality of data units was received by the first device subsequent to the last consecutively correctly received data unit. The method also includes, when the retry bit has a first value, sending a block acknowledgement (BA) after sending the SN-ACK. The BA includes a bitmap, where each particular bit of the bitmap indicates whether a corresponding data unit was correctly received. When the retry bit has a second value and one or more of the plurality of data units were incorrectly received by the first device, the first device receives a retransmission of one or more data units without sending the BA to the second device.