Threshold = congestion window/2 = 32/2 = 16 KB.
first approach...
MSS - 2 KB
4 KB
8 KB
16 KB THRESHOLD reached,now additive increase
18 KB
20 KB
22 KB
24 KB
26KB
28KB
30 KB
32 KB
total 12 RTT
12 RTT take 480 ms
so RTT = 40 ms
2 nd approach
MSS - 2 KB
4 KB
8 KB
16 KB THRESHOLD reached,now additive increase
17KB
18KB
19 KB
20 KB
21 KB
22 KB
23 KB
24 KB
25 KB
26 KB
27 KB
28 KB
29 KB
30 KB
31 KB
32 KB KB
20 RTT =480 ms
RTT= 24 ms.
I did it 2 way cause,some solution considers ,in the time of additive increase ,just add the the initial mss size,some solution consider it as strictly 1 mss.
REF:
1. https://gateoverflow.in/2156/gate2012_45
2. https://gateoverflow.in/1794/gate2014-1_27
one qs consider it 1 mss ,though initial size has given as 2 mss
and other consider it as 2 mss.