Computer Networks

Tutorial #10

1. What are some of the characteristics of multi-access LANs which distinguish them from the point-to-point data links of last lecture?

2. What does CSMA/CD mean?

3. In the lecture, it was stated that an Ethernet collision occurs when two stations start to transmit at the same time. Discuss the meaning of the term at the same time as used in this context.

4. In slide 6 of today's lecture, it is stated that the key difference between Ethernet and IEEE 802.3 LANs is the meaning of the 16 bit "type" field (used as a "length" field in 802.3). In many LANS, Ethernet and 802.3 frames co-exist perfectly happily. How can a receiving station know whether to treat the field as a length or as a type?

5. In many installations, Ethernet LANs are operated over fibre optic cabling, particularly when interconnecting buildings. Now, the main characteristics of optical fibres are that they are strictly point-to-point, and data can only travel in one direction. How do you think a fibre interconnect for Ethernet might be configured?

6. List and discuss the advantages and disadvantages of bridges relative to a repeater.

7. The 10baseT configuration has captured the Ethernet market from thin wire. Discuss reasons why network planners and managers might prefer this technology.

8. Even though 10baseT Ethernet LANs are physically cabled as point-to-point networks, they are different to the point-to-point links of last lecture in a fundamental way. What is this?

9. Research question: What is the historical origin of the difference between Ethernet and IEEE 802.3?

10. Research Question: At Bendigo, most of the student labs are cabled using "thin wire" Ethernet. This implies that there must also be something called "thick wire". What is it, and why isn't it used?