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Assume 2 computers are connected via a network. The network uses Go-Back 7 sliding window protocol for maintaining flow control. It is observed that every 5th packet that has been sent through the network is lost. What will be the number of extra packets that has to be resent for transmitting 10 such packet through the network? With explanation.
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1 2 3 4 5* 6 7

5 6 7* 8 9 10  (7 th will be lost we will count the previous 6,7 for the lost of 5 th packet. which is 7 here.)

7 8* 9 10

8 9 10*

10

 

Total 21 transmission: 

retransmission = total – actual = 21 – 10 = 11 

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8 re-transmitions 

1 2 3 4 | 5 6 7 8 9 10 | 6 packets are currently in window that will be discarded and retransmitted. note that we have already sent 10 packets now transmition will again start as –| 5(11) – 6(12)- 7(13)- 8(14)-9(15)-10(16) | now 9th packet is at 15th position so it is lost and then 9th along with 10 will be discarded and sent again, so more retransmitions

transmition will again start as – 9(17) ,  10(18)  and complete successfully

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