6.4.2 Describe the features of communications needed for networking.
Teaching Notes:
Ethernet, public and private telephone lines, ISDN, ADSL, fiber optic and wireless methods should all be familiar and strudents should be able to select the most suitable method of communication in a given situation, and to state the advantages of each method. Technical details will not be required.
JSR Notes:
Check out page 342 of the textbook; there’s lots of good material to address this assessment statement. And at this point, you’ll note that a lot of what preceded this page in the 6.4.2 section was more general stuff – but it can all help you address what the Teaching note above gets you to focus on.
So, there are basically 6 kinds of networking listed, and you need to be able to give advantages and disadvantages, and select the most suitable of them for a given situation. I’ll let you come up with your own Adv. Disadv. chart, but here are some miscellaneous points that you may have missed.
- Ethernet transmits at what is referred to as 10 base-T, or 100 base-T or 1000 base-T. But all these values really are is Mbits/sec. So in the school lab, most of the computers are connected with 100 Mb connections, though as it so happens, 4 of them are bumped up to 1000 Mb connections (i.e. Gigabit connections). And the backbone connections between the four groups of switches in the school’s LAN are all fiber-optic Gigabit connections.
- Ethernet cables have RJ-45 jacks that are bigger than their telephone RJ-11 jack cousins. The contain “twisted-pair” wires, which are twisted for a variety of reasons, including the fact that it’s harder for them go kink up when the wires are twisted, and it cuts down on electro-magnetic interference.
- ISDN is an older technology than ADSL, but both use phone lines. What makes ADSL able to have faster connections is that the A in ADSL stands for Asymmetric, and that means that the upload and download rates can indeed be asymmetrical, i.e. they don’t have to be the same. So most Internet Service Providers will gear the download to be much faster than the upload, since downloading is more often what users want speed for.
- Not only is fiber optic expensive, but it is dangerous to work with. But because it is light, and not electrical pulses going through it, it is much more secure; it cannot be “tapped” as other wires can be.
- And in terms of wireless, you should be equipped with your own latest tidbit of information on the latest wireless trend.
Meantime, when and where to use each of these? Points to make or reinforce include the following. For places that don’t have a lot of resources, financial or otherwise, using existing telephone lines will be slow, but that’s better than nothing. And for dirt-poor regions without even reliable telephone systems, wireless is great since all you need are a few microwave towers installed, and your in business; this versus digging up or wiring up a full brand new conventional wired system. Meantime, if you already have a certain wired system to begin with, why not take advantage of that. Basically, any cable that can carry electricity can carry digital data. And for those businesses or indeed regions and countries the financial resources to do so, the highest capacity wires possible, even fiber optic for as much as the system as is possible, is the way to go, though you’ll note in these situations it is often “the last 10 meters” that ends up the bottleneck.