compare GBN,SR,and TCP (no delayed ACK) .Assume that the time out values for all
ID: 674604 • Letter: C
Question
compare GBN,SR,and TCP (no delayed ACK) .Assume that the time out values for all three protocols are sufficiently long such that 5 consecutive data segments and their corresponding ACKS can be recieved (if not lost in the channel) by the recieving host (Host B) and the sending host (Host A) respectively. Suppose host A sends 5 data segments to host B, and the second segment (sent from A) is lost. In the end, all 5 data segments have been correctly recieved by Host B.
a.) How many segments has host A sent in total and how many ACKs has Host B sent in total. What are their sequence numbers?Answet the question for all three protocols.
b.) If the timeout values for all three protocols are much longer than 5 RTT, then which protocol successfully delivers all five data segments in shortest time interval?
Explanation / Answer
Q)How many segments has Host A sent in total and how many ACKs has Host B sent in total? What are their sequence numbers?
Solution:
With GBN, Host A sent 9 segments in total and Host B has sent 8 ACKs in total. They are the segment 1,2,3,4,5 and after the timeout timer, the segment 2,3,4,5 have be retransmitted. The acknowledgment signals are 4 ACK1 and ACK 2,3,4,5 respectively.
With SR, Host A sent 6 segments in total Host B sent 5 ACKs in total. The segments are segment 1,2,3,4,5 and segment 2 again. The ACKs are 4 ACK1 and 1 ACK 5.
With TCP, Host A sent 6 segments in total Host B sent 5 ACKs in total. The segments are segments 1,2,3,4,5 and segment 2 again. The ACKs are 4 ACK 2 and 1 ACK 6.
Q) If the timeout values for all three protocol are much longer than 5 RTT, then which protocol success fully delivers all five data segments in shortest time interval?
Solution:
TCP, for with TCP, if the receiver has received triple duplicate ACKs, then the TCP would reckon it as packet loss and launch fast retransmission and don't wait the timeout counter to expire.
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