The Gateway to Computer Science Excellence
First time here? Checkout the FAQ!
x
+3 votes
110 views

Assume that X and Y are the only two stations on an Ethernet. Each has a steady queue of frames to send. Both X and Y attempt to transmit a frame, they wait to get the control of channel using binary exponential algorithm. The probability that both were successfully allowed to send the frame on fifth round of the algorithm (assuming every time both X and Y will collide in back-off race till 4th round) is ________.

asked in Computer Networks by Loyal (8.5k points) | 110 views
0
I think it will be 15/16.

After four collisions (Since it is given to assume four collision have happened I think we need not consider that probability), each host will choose a number between (0,$2^{4-1}$).

Probability of collision is 1/16 (Both choosing the same number).

Hence probability of success=15/16.
0
i think 31/32 will be the ans
0
Thanks for noticing, Updated it.

1 Answer

+2 votes

Here they are asking about the fifth iteration. That means we have to find the probability of success in 5th iteration not in 4th iteration. 

For K=5, i.e. (0 to 25-1) = (0,31)PT. 

So the probability of collision is 1/32 and hence the probability of success will be (1-1/32) = 31/32. 

answered by Active (1.5k points)
0
Answer should be 15/16 not 31/32
0

@Mayank 

successfully allowed to send the frame on fifth round of the algorithm 

Means the value of k will go up to 5 na, if value goes up to 5 i.e. (0 to (2^5)-1). Please suggest what I did wrong here.

0
5th round successful means 4 times collision has occurred. K=4.
0
Collision occurred 4 times but successful in only 5th time na
0
When first collision occurred k=1 is used for second round

When  second collision occurred k=2 used for resolving the third round

When third collision occurred k=3 is used for resolving the 4th round

When 4th collision occurred k=4 is used for resolving the 5th round.

I think so.
0

probability that both were successfully allowed to send the frame on fifth round of the algorithm 

Isn't this means to find the success in 5th round. Please explain. 

Related questions

0 votes
0 answers
3
+2 votes
2 answers
7
asked Mar 14, 2017 in Computer Networks by Arnabi Loyal (8.1k points) | 562 views


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

44,071 questions
49,594 answers
162,954 comments
65,786 users