A sender uses Stop and Wait protocol for transmission of 8000K bits size frames on a 1Gbps satellite channel with a propagation delay of $400ms$.What will be the link utilization(in percent),if probability of single frame error is 0.001.Assuming Ack from receiver have negligible transmission time.

My Work.

Though Stop and Wait has a window size of 1, I assume suppose I have 1000 frames to send.Now out of this 1 will be garbled(error rate is 0.001) and that would be retransmitted.

So, I calculated Link utilization as

$\frac{useful\,time}{total\,time} \times 100$

Now time to transmit 1 single 8000K bit frame over 1Gbps satellite channel would be $8ms.$

My Useful time would be $1000 \times 8(ms)$

Assuming $T_{ack}=0$, my total time for 1 frame would be $8+800=808ms$

So, my total time is $1001 \times 808\, ms$(1001 because 1 extra retransmission would be required).

So, efficiency=$\frac{8 \times 1000}{1001 \times 808} \times 100=0.98 \%$

Is my approach correct?


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