The Gateway to Computer Science Excellence
First time here? Checkout the FAQ!
x
0 votes
41 views
Consider the GBN protocol with sender and receiver window size as 5.Suppose client sends data 0,1,2,3,4 and only data packet 2 is lost and all ACKs are lost. What will be the content of receiver and sender window. Before Senders timeout value expires ?

 

A. Sender: 01234  ,  Receiver : 01234

B. Sender: 23456  ,  Receiver : 01234

C. Sender: 23456  ,  Receiver : 23456

D. Sender: 01234  ,  Receiver : 23456
asked ago in Computer Networks by Loyal (5.6k points) | 41 views
0
all ACK's lost ==> sender have 0,1,2,3,4 in it's window.

packet 2 is lost ==> actually Receiver waiting for 2 ===> Receiver window is 2

note that in GBN, Receiver have only window size = 1
0
B is the answer ???
0
i didn't get the question properly ...given that data packet 2 is lost that means only packet 2 ACK is lost right ??

why they write "All ack is lost before the time out ??"

and if data packet 2 lost it means that 0 and 1 is acknowledge and receiver wait for a packet 2 due to the packet lost

senders again send the packet 2 3 4 5 6 and before the time out of '2' senders have 2 3 4 5 6 in his window
0
Hmmm A is the correct answer
0

Made easy answer is D 

When 0,1,2,3,4 will be sent the packet 0,1 is accepted and its acknowledgement is sent at that time window is moved to 2,3,4,5,6 it will not get 2 and will get 3 and 4 it will send 3,4 ack which will be lost and do nothing for 2 as eventually its timeout will be done and will be sent by sender again

0
@ Shaik , brother there are two cases of GBN one with windows size of reciever as 1 (which is mostly asked) and other with above shown question :)
0

@Na462

if those are have same size, it will called as SELECT REPEAT.

in GB-N, receiver window size should be 1, otherwise it doesn't call as GB-N ( think why this name came to this procedure. )

0
OOh know I understand properly

 

ist  senders send 0 1 2 3 4 ,

0 and 1 successfully transfer to receiver and now receiver waits for packet '2' but packet 2 is lost

all acknowledgement will be lost means (data packet 0 and 1 ACK is lost )

now after time out timer of 0 packet senders again sends  all the packets 0 1 2 3 4 but now receiver reject all the duplicates packets (0 and 1 and send the ACK to senders that I'm waiting for packet no 2

then from senders packet '2' is send.

but here they ask what  will be the content of receiver and sender window before TOT

therefore  Sender: 01234  ,  Receiver : 23456
0

@Brother,

In go back n the situation why the receiver window size is 1 is that the receiver will strictly accept those packets which should be next in sequence thats why if say 2,3,4 are sent and 2 is lost it wont accept other packets.

But it doesnt mean that the receiver window size cant be greater then 1 , if its greater then 1 (See below its from tanenbaum)

 

0
I have a doubt in made easy solution why the sequence number in sender and receiver WS upto 31
0

which question ??  Na462

0
The solution of made easy above?
0
shouldn't the sequence number run from = 0 to 9
Available sequence no = sender + receiver = 5 + 5 = 10 ??
0

Na462  those are not sequence number..In this question no role of sequence number

this are data packets only which is numbered  0 1 2  3 4

because in this question total sequence number  =  5 +1 = 6

0 to 5 sequences we use

but answer given  Sender: 01234  ,  Receiver : 23456

it means 6 is the data packet number

0
WHy total sequence number is 5 + 1 ?? receiver WS is not 1 here na.

And data packet number ???? Packet is represented by a sequence number na
0
ouuuh sorry sorry  I read it wrong
0
So... what should it be ?
0
the question is wrong probably
0

@Na462

shouldn't the sequence number run from = 0 to 9
Available sequence no = sender + receiver = 5 + 5 = 10 ??

there is no restriction on usage of sequence no.

generally 5+5=10 ==> 4 bits for representating sequence number is sufficient, it doesn't mean we should use 4 bits only

in the above solution, they take no.of bits for sequence no is 5. ( in directly we are wasting the sequence numbers. )


In go back n the situation why the receiver window size is 1 is that the receiver will strictly accept those packets which should be next in sequence thats why if say 2,3,4 are sent and 2 is lost it wont accept other packets.

But it doesnt mean that the receiver window size cant be greater then 1 , if its greater then 1 (See below its from tanenbaum)

if you continue the reading the last para to the next page, you will understand it is Selective Repeat.

Please log in or register to answer this question.



Quick search syntax
tags tag:apple
author user:martin
title title:apple
content content:apple
exclude -tag:apple
force match +apple
views views:100
score score:10
answers answers:2
is accepted isaccepted:true
is closed isclosed:true

39,529 questions
46,674 answers
139,828 comments
57,596 users