pre ladder quiz

Question

Consider the TCP is using slow-start congestion control.After having 10th consecutive transmission failed due to Timeout,the current threshold value is set to 7KB .what was the congestion window size at the time of starting of these  transmissions ? assume MSS= 1kb

Comments

14kb

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How ?

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if you think carefully, you will know there is no way to find initial congestion window.

lets suppose initial congestion window size was x now you send the packets 1,2,4 which get lost so now new congestion window size is 4/2 = 2 , so where is x? in the picture

Answer 1

It's 10^th transmission just after Time out occur and Th = 7KB

It means Wc = 7*2 = 14 KB

By taking given information into account I think this should be the sequence :

1  2  4  8  9  10  11  12  13  14  (here TO occur notice It's 10^th transmission)

so congestion window size at this TO will be     Wc= 14 MSS = 14*1KB = 14 KB.