A data link is shared by 20 data sources. Each source is active only 10% of the time and produces 1Mbps data rate when active. The sources start their transmissions at random.

a)  What is the data rate R of the link required to support the 20 data sources in circuit-switching mode of operation?  

b)  How many sources could be supported by the link of data rate R as calculated in (a) above if packet switched mode of operation is used and there is a buffer at the entrance to the link of sufficient capacity to smooth out the short term variation in the total data rate produced by the sources?

c)  If the sources produce packets of length L=1000 bytes each and there are 190 sources connected to the link of rate R as above, what will be the average packet delay if packet switched mode of operation is used and the buffer at the entrance to the link is of sufficient capacity to always accommodate newly arriving packets? Note: model the average delay as T = (L/R) / 1-I where L is packet length, R is the link data rate, and I is the traffic intensity.