Let the size of congestion window of a TCP connection be 32 KB when a timeout…
2014
Let the size of congestion window of a TCP connection be 32 KB when a timeout occurs. The round trip time of the connection is 100 msec and the maximum segment size used is 2 KB. The time taken (in msec) by the TCP connection to get back to 32 KB congestion window is _________.
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Correct answer: 1100
🔹 Given:
cwnd = 32 KB
MSS = 2 KB
RTT = 100 ms
👉 Convert cwnd to MSS units:
32 KB/2 KB=16 MSS
🔹 After Timeout:
ssthresh = 16 / 2 = 8 MSS
cwnd = 1 MSS
🚶 Growth Phases
1. Slow Start (exponential growth until ssthresh = 8 MSS)
RTT | cwnd (MSS) |
|---|---|
1 | 1 → 2 |
2 | 2 → 4 |
3 | 4 → 8 |
⏱ Time = 3 RTT = 3 × 100 = 300 ms
2. Congestion Avoidance (linear growth from 8 to 16 MSS)
Increase = +1 MSS per RTT
Needed increase = 16−8=8 MSS
⏱ Time = 8 RTT = 8 × 100 = 800 ms
🔹 Total Time:
300+800=1100 ms
✅ Final Answer:
1100 ms
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