Chap.1

1. Imagine that you have trained your St. Bernard, Bernie, to carry a box of

three 8mm tapes instead of a flask of brandy. (When your disk fills up, you

consider that an emergency.) These tapes each contain 7 gigabytes. The dog

can travel to your side, wherever you may be, at 18 km/hour. For what range

of distances does Bernie have a higher data rate than a transmission line

whose data rate (excluding overhead) is 150 Mbps?

2. An alternative to a LAN is simply a big timesharing system with terminals

for all users. Give two advantages of a client-server system using a LAN.

3. The performance of a client-server system is influenced by two network

factors: the bandwidth of the network (how many bits/sec it can transport)

and the latency (how many seconds it takes for the first bit to get from the

client to the server). Give an example of a network that exhibits high

bandwidth and high latency. Then give an example of one with low bandwidth

and low latency.

4. Besides bandwidth and latency, what other parameter is needed to give a good

characterization of the quality of service offered by a network used for

digitized voice traffic?

5. A factor in the delay of a store-and-forward packet-switching system is how

long it takes to store and forward a packet through a switch. If switching

time is 10 µsec, is this likely to be a major factor in the response of a

client-server system where the client is in New York and the server is in

California? Assume the propagation speed in copper and fiber to be 2/3 the

speed of light in vacuum.

6. A client-server system uses a satellite network, with the satellite at a

height of 40,000 km. What is the best-case delay in response to a request?

7. In the future, when everyone has a home terminal connected to a comput