Abstract: The present invention is directed to a method of, and apparatus for, improving the efficiency of transferring data between a transmitting unit and a receiving unit in an end-to-end layer of a network which does not support full duplexed communication at the end-to-end layers. The method comprises the steps of determining a window size N, where N represents the number of frames which can be received by the receiving unit. The transmitting unit: sets a current window size equal to 2N minus one; accepting a frame of data for transmission; decrements the current window size; transmits the data if the current window size does not equal zero or, if the current window size equals zero, waits to receive a message from the receiving unit before transmitting the data; resets the current window size to the current window size plus N upon receipt of the message: and returns to the accepting data step if all data has not been sent.