Data-link control protocols are used to ensure reliable and efficient data transmission in computer networks by managing the flow of data between a sender and a receiver. Sliding-window data-link control protocols operate in two regimes: the large and small window. The efficiency is 100% in the large-window regime and decreases as the delay increases in the small-window case. The threshold is a function of the delay, link rate, frame (or packet) size and window size (in frames). This Demonstration showcases the threshold effect and how it changes with the adjustable parameters.