0 votes 0 votes Consider instance of TCP AIMD protocol where the Window size at start is cwnd = 2, and the threshold is ssthresh = 16. Timeout occurs during the transmission of 7th packet. What is the value of cwnd at the end of 14RTT ? Computer Networks congestion-control algorithms computer-networks + – Na462 asked Sep 20, 2018 Na462 1.0k views answer comment Share Follow See all 6 Comments See all 6 6 Comments reply Na462 commented Sep 20, 2018 reply Follow Share My Approach:- TIME CWND SSTHRESH 0 1 16 1 2 16 2 4 16 Now during the transmmision of 7th packet the value of cwnd becomes = 6 and timeout occurs so cwnd = 1 and ssthresh = 3 3 1 3 4 2 3 5 3 3 6 4 3 7 5 3 8 6 3 9 7 3 10 8 3 11 9 3 12 10 3 13 11 3 14 12 3 Hence 12 is the answer 0 votes 0 votes Na462 commented Sep 20, 2018 reply Follow Share Is my approach valid ? 0 votes 0 votes nephron commented Sep 24, 2018 reply Follow Share This is wrong.... I am getting ssthresh = 9.5 0 votes 0 votes Na462 commented Sep 25, 2018 reply Follow Share PLEASE POINT MY MISTAKE :) 0 votes 0 votes nephron commented Sep 25, 2018 reply Follow Share see the answer. 0 votes 0 votes Magma commented Sep 25, 2018 reply Follow Share Na462 can you tell me that what's the answer given ??? 0 votes 0 votes Please log in or register to add a comment.
1 votes 1 votes this is the seq: trans started -> cwind 1 -> 2 2 ->4 3 ->8 4->16 5->17 6->18 7->19 new ssthresh = 9.5 => 9 new cwind = 1 8 -> 1 9->2 10->4 11->8 12->9 13->10 14->11 (14th transmission has started at cwind =11) so when 14th transmission has ended we have 14RTT and cwind increased from 11 to 12 nephron answered Sep 24, 2018 • edited Sep 24, 2018 by nephron nephron comment Share Follow See all 10 Comments See all 10 10 Comments reply Show 7 previous comments Smishra95 commented Sep 25, 2018 i edited by Smishra95 Sep 25, 2018 reply Follow Share source :- Forouzan >>>when there Time out occurs then TCP acts strongly : A:- It sets the valuee of threshold to one half the current window size. B:- it sets cwnd the size of one segment . C: it strats slow -start phase again. >>> when detection is by ACK's i.e. three ACK's received then : A:- - It sets the valuee of threshold to one half the current window size. B: sets CWND to threshold. C: congestion avoidance phase starts. In This question starting window size is two . That's why it must be two , four, eight ... 0 votes 0 votes nephron commented Sep 25, 2018 reply Follow Share Answer in the above Forozoun is B ?? isn't it B option mentions that cwind = 1 segment so it is repeating from 1,2, 4... after timeout 0 votes 0 votes Magma commented Sep 25, 2018 reply Follow Share nephron Hmm I was wrong...thank you 0 votes 0 votes Please log in or register to add a comment.