Calculate the link utilization (efficiency) for the stop-and-wait flow control…

Concept: In stop-and-wait flow control, the sender transmits one frame and then waits idle for its acknowledgement before sending the next. Link utilization (also called efficiency) is the fraction of time the link actually carries data, given by Tt / (Tt + 2Tp), where Tt is the transmission time and Tp is the one-way propagation time. The factor 2Tp accounts for the round trip the frame and its acknowledgement travel. This is a pure dimensionless ratio between 0 and 1 — it is not the throughput in bits per second.

Application: Substitute the given values step by step.

1. Transmission time Tt = frame size / bit rate = 4800 / 9600 = 0.5 s.

2. Propagation time Tp = distance / propagation speed = 2000 / 200000 = 0.01 s.

3. Efficiency = Tt / (Tt + 2Tp) = 0.5 / (0.5 + 2 × 0.01) = 0.5 / 0.52 = 0.9615.

Cross-check: Because the transmission time (0.5 s) is much larger than the round-trip propagation overhead (2 × 0.01 = 0.02 s), the sender stays busy almost the whole time, so the efficiency must be close to 1 — and 0.9615 ≈ 0.96 confirms this. (For reference, the actual data throughput would be 0.96 × 9600 ≈ 9231 bps; the utilization asked here is the ratio 0.96, not this bps value.)

Result: The link utilization is approximately 0.96.