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 981 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.