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Let the size of congestion window of a TCP connection be 32 KB. When the timeout occurs maximum segment size used is 2 KB. If the time taken by TCP connection to get 32 KB congestion window is 480 msec then the RTT of connection is _________ (in msec).
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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.

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MSS = 2KB

size of congestion window of a TCP connection is 32 KB. Threshold is 16KB = 8 MSS

1MSS | 2MSS | 4MSS | 8MSS | 9MSS | 10MSS | 11MSS | 12MSS | 13MSS | 14MSS | 15MSS | 16MSS

Number of RTT = 11

RTT = 480/11

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