Consider a new TCP connection between a sender and a receiver. The receiver…
2026
Consider a new TCP connection between a sender and a receiver. The receiver advertised window is constant at 48 KB, the maximum segment size (MSS) is 2 KB, and the slow start threshold for TCP congestion control is 16 KB. Assume that there are no timeouts or duplicate acknowledgements. The number of rounds of transmission required for the congestion control algorithm of the TCP connection to reach the congestion avoidance phase is ___________. (answer in integer)
Attempted by 8 students.
Show answer & explanation
Correct answer: 4
Given:
MSS = 2 KB → initial cwnd = 1 MSS = 2 KB
ssthresh = 16 KB
Slow start growth (doubling each round):
Start: cwnd = 2 KB
After Round 1: cwnd = 4 KB
After Round 2: cwnd = 8 KB
After Round 3: cwnd = 16 KB
Now the key detail
TCP enters congestion avoidance after completing the round where cwnd reaches ssthresh.
So:
Round 1 → sending with 2 KB
Round 2 → sending with 4 KB
Round 3 → sending with 8 KB
Round 4 → sending with 16 KB (ssthresh)
Congestion avoidance starts after Round 4 begins transmission
Correct Answer:
4
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