Describe the roles that a computer can take in a networked world.


Teaching Note:

Roles include client, server, email server, DNS server, router and firewall.


JSR Notes

Firstly, note that Topic 3 is Networks, so there is lots more to follow later on. (JSR: So maybe wait before going over too much here.)


The Client-Server model

Client - any computer/device which receives services from another computer.

Server - the computer which serves data and/or other resources to a client.

Servers that Mr Rayworth runs from the Windows 8 server in the server room across from the US boys bathroom:

And around the school, for example, any and everything that can be shared is done within the context of a client-server model. At ISP, the various servers include:

Router - a device that routes a file or a other data from one place to another. A router can be as simple as the one that you have as part of your modem that connects to the internet and distributes the signal either in a wired or a wireless way or both to other devices in your house. And a router can be a more robust and route to many more devices than that, as within an office building.

Firewall - a special router which prevents certain IP addresses from going through (similar to a DNS in the way that it has a list of the IP addresses which are not allowed to get through)



Sample Question:

A small company has a LAN connecting its various desk-top computers and
peripheral devices.

(a) (Doesn't apply to the new curriculum.)

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 FORMER CURRICULUM - 6.4.1 Outline the role of the computers used in the separate type of networks: WAN, LAN and the Internet.:

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:
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.

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. 




See 3.1.1 and on (Networking Topic)


CompSci2014.wikispaces.com **


Jaime: server: sending and receiving?

League of Legends, Battle.net Starcraft etc. are all good examples of client-server with central server.

Minecraft and many Steam games you can host your own server.

Deep web and DNS - things not listed on public DNS servers ----??? www???

(not the Dark net....)


DNS Table: (http://media02.hongkiat.com/dns-propogation-check/ceipam.jpg)

dns table

Jose: Dedicated game servers have resoponsibilities to that gaming community - ridiculous to be taking a couple of minutes to change servers.