Question

Assume that host 1 has 7 segments with sequence numbers 8, 9, 10, 11, 12, 13, and 14 that needs to send to host 2. Make the assumption that GBN is used and the 3rd packet got dropped but all ACKs arrive correctly. How many transmissions does host 1 need to do until all segments are all sent? Assume N is 3.

Answer 1

Here N = 3 . That is window size is 3.

Sender or host1 will send 3 segments at once. And if any segment of a particular window is lost, it will resend all the segment of that frame again. This is called go back N.

Here 3rd packet gets dropped. Thus host 1 had to send the first frame containing 3rd packet all over again according to GoBackN.

So segments sent are

8 9 10 8 9 10 11 12 13 14

So total # of transmission are 10.

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