6.4.1 Outline the role of the computers used in the separate type of networks: WAN, LAN and the Internet.
Teaching Notes:
The roles of providers, servers, and clients should be understood for each of these networks. Students should be able to select the appropriate type of network for a given situation. They must understand the rold of gateways.
Sample Question:
A small company has a LAN connecting its various desk-top computers and
peripheral devices.
(a) Explain, with an example, how handshaking might be used during data
transmission over this LAN. [2 marks]
The company is going to provide Internet access to its LAN.
(b) State the name of an additional hardware device that would be required to permit
Internet access. [1 mark]
(c) Explain how a firewall would help to provide security for the LAN. [3 marks]
(d) Suggest, with reasons, two further measures that the company should take to
safeguard its data from unlawful access via the Internet. [4 marks]
JSR Notes:
So, it’s one thing to take a look at all of the very good stuff written in the text book, but this is one of those assessment statements wants you to be able to go beyond the facts, and draw connections. The teaching note above is most salient in this regard. In fact the three things mentioned in it are three different things. So here are answers to each:
The roles of provider, servers and clients in:
WAN-
Provider – the “main” server which enables the component LANs to connect, and gain access to some sort of common database. So in a University system WAN, for example, a huge library database could be provided across the WAN.
Servers – in the example, the mainframes of each university, which pass on the services of the provider, along with their own services, like printing and Internet access.
Clients – the end-users, who connect to a local server, and in turn connect to the provider via a local server.
LAN-
Basically this is just a subset of what was written above. The idea is that within a LAN you do not necessarily have access to “the outside world”, though usually now-a-days, all LANs will be at least connected to an Internet Service Provider, though not often to any other WAN provider.
The Internet
The first thing to point out here is that the Internet is indeed a WAN; it’s just that it’s a very big one. And there is no one particular provider that provides all the other providers; they all work together. Each client gains access to the Internet network either via a server on their LAN, which connects them to a provider, or they are directly connected to their ISP, like you are with your home computer, unless you have a LAN there.
In terms of what type of network is appropriate when and where, it’s pretty straight-forward, if you understand how each is structured. To implement a Local Area Network, you generally need to be able to physically connect all of the devices on your network. The Ethernet network is the most common structural set up, and for it, you run Cat-5 “Ethernet” cables from each computer/printer etc. to a switch. So if it’s not a limited geographic area you won’t be able to do this. Generally, therefore, you think of a LAN being in your house, or in any given building like a school, or perhaps multiple buildings, which are close to each other as in a hospital or university campus.
For all other “wider” physical setups, like a university campus that is spread all around a city, or a certain bank spread all around a country, you will need to take the structural and financial step up to a WAN. In that case that equipment needed goes way beyond wires collected in a central switch, and so the costs go up as well. Cost in fact may be a determining factor of whether or not a certain situation could accommodate a WAN.
The role of a gateway is to filter access to a LAN. That’s basically it. But what form that filtering takes is a little more complex.