25 votes 25 votes The maximum window size for data transmission using the selective reject protocol with $n\text{-bit}$ frame sequence numbers is: $2^n$ $2^{n-1}$ $2^n-1$ $2^{n-2}$ Computer Networks gatecse-2005 computer-networks sliding-window easy + – Kathleen asked Sep 22, 2014 edited Dec 30, 2018 by Subarna Das Kathleen 38.5k views answer comment Share Follow See all 7 Comments See all 7 7 Comments reply Show 4 previous comments endurance1 commented Oct 26, 2020 reply Follow Share Selective Repeat is sometimes calles as Select Reject. Source : Forouzan, 4th Edition. 6 votes 6 votes sayan chowdhury commented Apr 3, 2022 reply Follow Share Are selective repeat and selective reject the same thing? 0 votes 0 votes GO Classes Support commented Dec 16, 2023 i edited by GO Classes Support Dec 16, 2023 reply Follow Share GO to the Root of Concept: Video Explanation with timestamp Efficiency,Throughput| Relation Between WindowSize & Sequence No. Sliding Window | With NOTES 0 votes 0 votes Please log in or register to add a comment.
Best answer 54 votes 54 votes Answer is b) In $\text{selective reject protocol},$ the maximum window size must be half the Sequence number space $=\dfrac{2^n}{2}=2^{n-1}$. For Go-back n, the maximum window size can be $2^n-1$. http://webmuseum.mi.fh-offenburg.de/index.php?view=exh&src=73 or archive Aditi Dan answered Dec 23, 2014 edited Apr 6, 2022 by Arjun Aditi Dan comment Share Follow See all 9 Comments See all 9 9 Comments reply Show 6 previous comments raja11sep commented Apr 6, 2022 reply Follow Share @rfzahid 😂 0 votes 0 votes Arjun commented Apr 6, 2022 reply Follow Share @rfzahid Clicking on edit history can tell you why :) https://gateoverflow.in/revisions/5654 4 votes 4 votes Pranavpurkar commented Apr 14, 2022 reply Follow Share Arjun sir 😂🤣 0 votes 0 votes Please log in or register to add a comment.
20 votes 20 votes NUMBER OF SEQUENCE NUMBERS AVAILABLE >= SENDER WINDOW SIZE+RECEIVER WINDOW SIZE. Thus with n bits 2^n sequence numbers are available. In SR protocol SENDER WINDOW SIZE = RECEIVER WINDOW SIZE.. thus window size= 2^n/2= 2^n-1 sushmita answered Dec 4, 2017 sushmita comment Share Follow See all 2 Comments See all 2 2 Comments reply Abhisek Tiwari 4 commented Dec 28, 2018 reply Follow Share @sushmita plz verify this Ws+Wr=2*N for SR and Ws +Wr =N+1 for gobackN 2x=2^n so x=2^(n-1) sender and receiver side have unique sequence no? why so? 1 votes 1 votes Arpit Patel commented Jan 11, 2022 reply Follow Share Sender and Receiver should always have unique(different) sequence no. for prevention of acceptance of duplicate packets as a next window of packets. Total available seq no. = 4 Lets say SWS=4 and RWS=4 Sender having sequence no.( 0,1,2,3) Receiver seq no also (0,1,2,3) Say after sending first windows, all the acks are lost. Now sender thinks all packets are lost(how it will know that acks are lost) and receiver thinks all acks are sent and received. Now sender will again retransmit all the 4 packets thinking all were lost but receiver will accept them thinking that all are from next set of windows. So here duplicate packets are received. Same is the case for any common seq. no. between Sender and Receiver. Now lets take total Seq. no. =8 SWS = RWS = 4 First window is sent of (0,1,2,3) and all acks are send but not received by sender. But now Receiver shifts its window to (4,5,6,7) after acknowledging the previous window. Now if any duplicate packets comes it will discard( but will send acks to confirm sender) 0 votes 0 votes Please log in or register to add a comment.
5 votes 5 votes Here n bit has been used for sequence no.. so total possible sequence no is = 2^n As we know sender window size= receiver window size (Selective repeat / Reject protocol).. So window size= (2^n)/2 => 2^(n-1) Manis answered Nov 5, 2017 Manis comment Share Follow See 1 comment See all 1 1 comment reply ShivangiChauhan commented Nov 2, 2020 i reshown by ShivangiChauhan Nov 2, 2020 reply Follow Share In selective repeat or selective reject Sender window size = receiver window size = x (let) and we know that available sequence number $\leq$ sender window size + receiver window size ${\color{Red} \rightarrow }$ 1 for n bits sequence number available sequence number = $2^{n}$ put in equation 1 $2^{n}$ = x + x (since sender window size= receiver window size = x (let)) $2^{n}$ = 2x then, x= $2^{n}$ /2 x= $2^{n-1}$ therefore maximum window size is $2^{n-1}$ therefore answer is B correct me if i am wrong anywhere 1 votes 1 votes Please log in or register to add a comment.
3 votes 3 votes n bits in sequence no means 2^n sequence numbers are there we know that in SR ,sender and reciever's window size are same...so divide these 2^n sequence no's equally.. so sender can have maximum 2^(n-1) sequence nos...so maximum possible window size is 2^(n-1)... sudsho answered Dec 13, 2016 edited Dec 13, 2016 by sudsho sudsho comment Share Follow See all 4 Comments See all 4 4 Comments reply focus _GATE commented Dec 13, 2016 reply Follow Share @sudsho i hav edoubt that in general SWS+RWS<=N SWS: sender window size=2n-1 RWS: receiver window size=2n-1 so 2n-1+ 2n-1<=N 2n <=N and my question is that it is not asking about the sender window size but it asks about window size ?? correct me 0 votes 0 votes sudsho commented Dec 13, 2016 reply Follow Share sequence nos are greater than or equal to sender window size+reciever window size here N is sequence no bits...so sequence nos are 2^N..means 2^N >= sender+reciever... 0 votes 0 votes sudsho commented Dec 13, 2016 reply Follow Share why is this so is important...to avoid duplicate packets with same sequence nos...if total u have 100 sequence nos than it depends on you what u wanna use..say u want to use all..then in SR u have to give 50 to sender and 50 to reciever...if u want to use only 80..no problem..give 40 to sender and 40 to reciever... in GBN if u have 100 sequence nos..then u can give 99 to sender and 1 different to reciever,...so on 0 votes 0 votes sudsho commented Dec 13, 2016 reply Follow Share question is saying maximum window size for data tranmission....if u have 100 sequence nos and u divided them 50-50 to sender and reciver..than at any time u can transfer atmost 50 bytes data only..so 2^(n-1) 0 votes 0 votes Please log in or register to add a comment.