Question

Compare GBN, SR, and TCP (no delayed ACK). Assume that the timeout values for all three protocols are sufficiently long such that 5 consecutive data segments and their corresponding ACKs can be received (if not lost in the channel) by the receiving host (Host B) and the sending host (Host A) respectively. Suppose Host A sends 5 data segments to Host B, and the 2nd segment (sent from A) is lost. In the end, all 5 data segments have been correctly received by Host B.

Answer 1

Answer and Explanation:

a)

For Go-Back-N:

  Host A sent total number of segments is 9.The initial segment numbers are 1,2,3,4,5 and re-sent the segemnts 2,3,4 and 5 because 2nd segment was lost.

Host B sent the number of ACKs are 8.Host B sent ACKs 1 by four times because 2nd segment was lost and sent 4ACKs with sequence numbers 2,3,4 and 5

selective repeat:

 Host A sent total number of segments is 6.The initial segment numbers are 1,2,3,4,5 and re-sent the segemnts 2 because 2nd segment was lost.

Host B sent the number of ACKs are 5.Host B sent four ACKs with sequence numbers 1,3,4,5 and re-sent ACK2 with sequence number 2 because 2nd segment was lost.

TCP :

Host A sent total number of segments is 6.The initial segment numbers are 1,2,3,4,5 and re-sent the segemnts 2 because 2nd segment was lost.

Host B sent the number of ACKs are 5.Host B sent four ACKs with sequence number 2 and There is one ACK with sequence number 6.TCP always send an ACK with expected sequence number

b) If the timeout values for all three protocol are much longer than 5*RTT,then TCP protocol successfully delivers all five data segments in shortest time interval.