Suppose users share a 2Mbps link. Also suppose each user requires 0.5Mbps when t

Question

Suppose users share a 2Mbps link. Also suppose each user requires 0.5Mbps when transmitting, but each user transmits only 15% of the time. (See the discussion of statistical multiplexing in Section 1.3)

a.When circuit switching is used, how many users can be supported?  

b.For the remainder of this problem, suppose packet switching is use. Why will there be essentially no queuing delay before the link if four or fewer users transmit at the same time? Why will there be a queuing delay if five users transmit at the same time?

Explanation / Answer

a.)When circuit switching is used, how many users can be supported?

Answer:

4 users can be supported because each user requires 0.5 of the link bandwidth.

b).For the remainder of this problem, suppose packet switching is use. Why will there be essentially no queuing delay before the link if four or fewer users transmit at the same time? Why will there be a queuing delay if five users transmit at the same time?

Answer:

Since each user requires 0.5Mbps when transmitting, if four or fewer users transmit simultaneously, a maximum of 2Mbps will be required. Since the available bandwidth of the shared link is 2Mbps, there will be no queuing delay before the link. Whereas, if five users transmit simultaneously, the bandwidth required will be 2.5Mbps which is more than the available bandwidth of the shared link. In this case, there will be queuing delay before the link.

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