Consider the following statements regarding the slow start phase of the TCP congestion control algorithm. Note that cwnd stands for the TCP congestion window and MSS denotes the Maximum Segment Size.

1. The cwnd increase by 2 MSS on every successful acknowledgement.
2. The cwnd approximately doubles on every successful acknowledgedment.
3. The cwnd increase by 1 MSS every round trip time.
4. The cwnd approximately doubles every round trip time.

Which one of the following is correct?

(A) Only (ii) and (iii) are true
(B) Only (i) and (iii) are true
(C) Only (iv) is true
(D) Only (i) and (iv) are true


Answer: (C)

Explanation: Slow-start begins initially with a congestion window size (cwnd) of 1, 2, 4 or 10 MSS. The value of the Congestion Window will be increased by one with each acknowledgement (ACK) received, effectively doubling the window size each round-trip time (approximately exponential).

The cwnd increase by 1 MSS on every successful acknowledgement.

Therefore, only statement (iv) is correct.
Option (C) is true.

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