Project ForgeConsider 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.
(i) The cwnd increases by 2 MSS on every successful acknowledgment. (ii) The cwnd approximately doubles on every successful acknowledgement. (iii) The cwnd increases by 1 MSS every round trip time. (iv) The cwnd approximately doubles every round trip time.
Which one of the following is correct?
- AOnly (ii) and (iii) are true
- BOnly (i) and (iii) are true
- Only (iv) is true
- DOnly (i) and (iv) are true
Explanation
In TCP slow start, cwnd increases by 1 MSS for EACH acknowledgment received (not 2, ruling out i and ii's per-ACK doubling claim), and since there are roughly cwnd/MSS segments acknowledged per round trip time, the cumulative effect is that cwnd approximately DOUBLES every RTT (not merely +1 MSS per RTT, ruling out iii). Only statement (iv) is correct.
Source: GATE CS 2018 (2018)
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