On acknowledgement schemes of sliding window flow control

An investigation is conducted of two acknowledgment schemes for sliding window flow control in packet communications: the delayed acknowledgment (D-ACK) scheme and the window acknowledgment (W-ACK) scheme. It is shown that the acknowledgment scheme of the link layer of the X.25 protocol can be modeled by the D-ACK scheme and that of the packet layer by the W-ACK scheme. The efficiencies of these acknowledgment schemes are shown by the mean number of acknowledgment control frames generated for the transmission of a single information frame, the transmission blocking probability, and the mean transmission time of data frames. Numerical and simulation results showing that the D-ACK scheme with an appropriately selected value of predetermined waiting time is better than the W-ACK scheme are presented