1. Consider sending a file of F bits over a path of Q links. Each link transmits at R bits per second (bps). The network is lightly loaded so that there are no queueing delays. When a form of packet switching is used, the F bits are broken up into packets, each packet with L bits, of which h bits of it are header. Propagation delay is negligible. Let F = 5×104, Q = 20, R = 1 Mbps, L = 1000, and h = 10.

a. Suppose that the network is a circuit-switched network. Further, suppose that the transmission rate of the circuit between the source and destination is R bps. Assuming ts = 10 milliseconds set-up time and h bits of header appended to the entire file, how long does it take to send the file? (5 pts)

b. Suppose the network is a packet-switched datagram network and a connectionless service is used. How long does it take to send the file? (5 pts)

c. Suppose the network is a packet-switched virtual circuit network. Denote the VC set-up time by ts = 250 milliseconds. How long does it take to send the file from source to destination? (5 pts)

2. Consider sending a large file of F bits from Host A to Host B. There are four links (and three switches) between A and B, and the links are not congested (that is, no queueing delays). Host A segments the file into segments of S bits each and adds 20 bits of header to each segment, forming packets of L = 20 + S bits. Each link has a transmission rate of R bps. Find the value of S that minimizes the delay of moving the file from Host A to Host B. Neglect propagation delay. (10 pts)

3. List the three layers a router must implement to operate. (3 pts)

4. What is the title of RFC 1882? (1 pt)

5. List the connection-oriented and connectionless transport protocols used in the Internet. Identify at least two differences between them. (4 pts)

6. Suppose two hosts, A and B, are separated by 5,000 kilometers and are connected by a direct link of R = 1 Gbps. Assume the propagation speed over the link is 2.0×108 meters/second.

a. Calculate the propagation delay tprop. (2 pts.)

b. How many bits are in transit between hosts A and B? (2 pts.)

7. Suppose users share a 2-Gbps link. Also, suppose each user requires 200 Mbps when transmitting, but each user only transmits 40 percent of the time.

a. When circuit switching is used, how many users can be supported? (5 pts)

b. For the remainder of this problem, suppose packet switching is used. What is the maximum number of users that can be supported if the required blocking probability is strictly less than 0.05? (5 pts)



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