When an error is detected during a data exchange, what are the options available for recovery? Explain each and elaborate which one you would use under what circumstances. What are the methods to implement WANs? Explain each category together with use cases for each.

Assume that an end-to-end communications system is made up of three networks with date rate in Mbps 1, 2, and 3, respectively. Ignoring the other delay components, what is the total end-to-end delay to transmit a packet size of ?

A data channel at 5 Gbps is shared by two users. Assume that each user is trans- mitting at 2.5Gbps data rate continuously. Each user only transmits only 30% of the time. (a) If circuit switching is used, how many users can be supported? (b) If packet switching is used, would there be queuing delay to accommodate these two users? If a third identical user is added will there be a queuing delay? (c) What is the probability that a user is sending data? (d) Now assume three users under packet switching. Compute the probability that at any given time all three are transmitting at the same time. What is the fraction of time when the queue is growing?