Below are some observations from the marking of the NCT4 assessed exercises for 2001/2002 with some guidance as to how the sites were actually graded.
The exercise was generally well done. Marks were awarded for technical accuracy and (reasonable) completeness (see list below) as well as good use of web features to grade exposure to technical material. Some submissions did not drill down far enough, failing to explain, for example, the fundamental relationship between the minimum frame size, transmission rate and diameter of a collision domain, which is vital to an understanding of why high-speed non-switched Ethernets have to be so small.
When there is a nominal word limit (as in this exercise) it is important to balance your coverage so that you focus most attention on the most relevant aspects of the subject. Nowadays, for example, switched, fast and gigabit Ethernet are important, 10Base5 and 10Base 2 much less so. Some submissions sacrificed the former in favour of the latter.
Diagrams are powerful aids to technical explanation and their intelligent use is essential in this kind of exercise That doesn't just mean nabbing diagrams from other sources but designing and drawing your own as well where appropriate. No credit for diagrams just added for decoration however— they must serve a technical purpose in a site like this.
Any serious web information site must not only attribute its sources appropriately but also provide links to further, more detailed or related information. Marks were awarded for the extent to which this was done.
Site navigation is important. There were many different types of site design submitted, some including suggested (or even guided) traversal routes, others not. However, a technical site should always provide an easy means to navigate to any particular page should a reader wish to do so and some kind of reasonably detailed site map is therefore strongly advisable.
A well-designed comprehensive glossary in a technical website can be a uniquely powerful tool because hyperlinks make it so accessible from anywhere.
The course text (my own book), published in early 1998, has a reasonable amount of detail on the fundamental operation of Ethernet, but its treatment of Fast and Gigabit, for example, is limited by the fact that, at the time, Fast was relatively new and development work on Gigabit was only partially completed. There is plenty of more complete information easily available now that these are fully mature technologies. Marks were awarded for up-to-date treatment of these areas (an indication of thorough research) such as the observation that Gigabit Ethernet is actually now nearly always used in switched implementations. I have recently added a page about Fast and Gigabit Ethernet to the NCT4 Web site to augment the material in the book
N.B. This assessed exercise covers an important part of NCT4. Be aware that, as such, the material IS examinable.
The headings below list the main areas a thorough examination of Ethernet at the honours level might be expected to tackle. The list is merely a guide and not a design for a solution to the NCT4 2001/2002 exercise.
This is not a critical area but provides a useful context.
What are they? How do they affect guaranteed delivery? ALOHA?
Describe carrier sense and persistence strategies. Why collisions still happen.
Importance of network RTT for size of collision window
Effect of collision detection. Criticality of minimum packet size.
Basic frame structure. Ethernet addresses.
Differences in frame format. Type/length field. LLC and SNAP
Brief description of Ethernet physical layer
Brief details of the CSMA/CD variant. Binary exponential backoff etc.
Brief. No need to say much about these as they are of decreasing importance
Description of role and operation of hub as collapsed bus. UTP connections. Advantages etc.
Difference between switches and hubs. Absence of collisions. Relaxation of size constraints and possibility of FDX operation. FDSE and 802.3x.
Brief introduction to bridging (802.1D). How do they differ from switches?
Importance of broadcast domains in switched Ethernets. Distinguish between broadcast and collision domains
Effect of increased speed and same collision window on network size.
Brief survey of TX, T4 etc
Fast Ethernet has a different sub-MAC stack. MII interface etc
Severe effect of increased speed on size of a collision domain. Discussion of extension and bursting techniques. Dominance of switches.
Fibre, copper solutions (brief).
GMII etc
Brief survey of aims, intended roles and current status.