Compute Networks

Computer Networks - CS132/EECS148 - Spring 2013
Instructor: Karim El Defrawy Assignment 1 Deadline : April 18th – 9:30pm (hard and soft copies required) Each problem has 10 points.

-------------------------------------------------------------------------Problem 1 - Consider a packet switching architecture. a. What are the main components of delay when we use packet switching? Processing delay, queuing delay, transmission delay and propagation delay b. What is the difference between transmission delay and propagation delay? Transmission delay is the time needed to put the entire packet on the link and is dependent on the length of the packet, while the propagation delay is needed time for one bit to reach to the other end of the link. c. How is propagation delay affected if the length of the packet is increased? This delay is just a function of link length and its physical characteristics, so it is NOT affected. Problem 2 - Consider an application that transmits data at a steady rate (for example the sender generates an N-bit unit of data every K time units, where K is small and fixed). Also, when such an application starts, it will continue running for a relatively long period of time. Answer the following questions, briefly justifying your answers. a. Would a packet-switched network or a circuit-switched network be more appropriate for this application? Why? A circuit-switched network would be well suited to the application, because the application involves long sessions with predictable smooth bandwidth requirements. Since the transmission rate is known and not bursty, bandwidth can be reserved for each application session without significant waste. In addition, the overhead costs of setting up and tearing down

connections are amortized over the lengthy duration of a typical application session. b. Suppose a packet-switched network is used and the only traffic in this network comes from this application as described above. Furthermore, assume that the sum of...