Computer Networking Exercise 3. Suppose users share a 2 Mbps link. Also suppose

Question

Computer Networking

Exercise 3. Suppose users share a 2 Mbps link. Also suppose each user transmits continuously at 1 Mbps when transmitting, but each user transmits only 20 percent of the time. a. When circuit switching is used, how many users can be supported? b. For the remainder of this problem suppose packet switching is used. Explain why there will be almost no queuing delay if two or fewer users transmit at the same time. Why will there be a queuing delay if three users transmit at the same time? c. Find the probability that a given user is transmitting. d. Suppose now there are three users. Find the probability that at any given time, all three users are transmitting simultaneously. Find the fraction of time during which the queue grows

Explanation / Answer

As per given,
a) Total trasmission rate between users = 2Mbps
Minimum transmission for each user = 1 Mbps.

Then number of users = 2/1 = 2 users.

b) If two users trasmit at the same time, there will be no queuing delay by using packet switcing. We know that each user requires 1 Mbps and they will share a maximum of 2 Mbps link. So that there will be no delay.

Suppose if three users transmit at the same time using packet switching,eachj user requires 1 Mbps and for three users it requires 3Mbps. But as per given users can share 2 Mbps only. So that there will be queuing delay.

c) Given that each user transmits 20 percent of time.
20 percent means, there will be 5 parts.
The probability = 1/5

d)Probability that three users transmitting simultaneously = ncr pr (1-p)n-r
= 3c3 p3 (1-p)0
= 1* (0.2)3 1
= 0.008
The probability will be = 0.008
If three users are transmitting simultaneously as usual queue grows.
SO that, fraction of time during queue grows = 0.008

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.