Suppose that a 5 Mbps link is being shared by a number of users. Each user alternates between period of activity during which the user transmits at rate 1 Mbps and periods of silence, when the user does not transmit. Assume that each user is in the active state only 15% of the time.
a) If circuit switching is used, what is the maximum number, Nc, of users that can be supported on the link?
b) With circuit switching, suppose it takes 500 ms to set up the circuit. If the length of the link is 100 km, how long would it take for a user to transfer a 320 Kbit file across the link from one end to the other (assume that the signal propagation speed along the link is 2.8*108 m/s)?
c) Now suppose that packet switching is being used. In order for the average queueing delay to be acceptable, the probability that the aggregate transmission rate of the users exceeds the link rate must be less that 10-4. In this case, what is the maximum number of users, Np, that can be supported on the link?