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4 votes
4 votes
During Congestion avoidance(Additive Increase) in tcp when 3 duplicate ACKs arrived then during that arrival phase by which algorithm did the  sender window adopt increment procedure?
a) Sender window uses additive increase
b)Sender window uses slow start
which option is correct?

4 Answers

5 votes
5 votes

From forouzan :: TCP/IP protocol suite:

If three duplicate ACKs are received, there is a weaker possibility of congestion; a segment may have been dropped but some segments after that have arrived safely since three duplicate ACKs are received. This is called fast transmission and fast recovery. In this case, TCP has a weaker reaction as shown below:
(A). It sets the value of the threshold to half of the current window size.
(B). It sets cwnd to the value of the threshold (some implementations add three segment sizes to the threshold).
(C). It starts the congestion avoidance phase.
 

0 votes
0 votes
Option a is correct .

Slow start mechanism occurs whenever time out occurs
0 votes
0 votes
3 duplicate ack means congestion is less so sender opts for additive increase rather than slow start which occurs when congestion is severe and time out happens.

Hence correct option is a.

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