Token Bucket

Question

A computer on a 10­Mbps network is regulated by a token bucket. The token bucket is filled at a rate of 4 Mbps. It is initially filled to capacity with 15 Megabits. How long can the computer transmit at the full 8 Mbps (in seconds) upto two decimal places?

a.  3.75 sec

b. 3.55 sec

c. 4.20 sec

d. 3.46 sec

Comments

the question should be AT A FULL RATE OF 10 Mbps NOT AT 8Mbps the question is wrong the question should be at what time we REACH 8Mbps then the below  answer is correct

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Please update the question. It should be

A computer on a 8Mbps network is regulated by a token bucket.

Answer 1

Input Rate =4Mbps

Output Rate Required=8 Mbps

Net effect=4Mbps drain rate of the bucket

Initial capacity =15Mb

Now to drain 15Mb at rate of 4Mb/sec,we need

4Mb drained in => 1 sec

1Mb drained in =>1/4 sec

15Mb drained in=>15/4 sec =3.75 sec

So, we can have full 8Mbps for 3.75 seconds

a is correct answer

Comments

why you have not consider op rate as 10Mbps?

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Question says 8Mbps required 

How long can the computer transmit at the full 8 Mbps (in seconds) upto two decimal places?
 

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then what does 10Mbps means in this question. is its maximum supported BW??

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Actually the place where it is 8Mbps,it should be 10Mbps.I have solved all questions which has 10Mbps in place where your question says 8Mbps.

Here you can say like we have a bucket at 10Mbps but we are operating it at 8Mbps.

Answer 2

t=15/(8-4)=3.75