|Candidates should be able to:
A Computer Network is a system of connected computers, peripherals and
communication devices that can exchange information and share resources.
- The connections could be cable, fibre-optic, or
wireless (infra-red, microwave or
radio) and may be between computers
in one building or between computers in different parts of the world. They
either link computers directly or more commonly link them through a hub or
- The hardware includes the network interface card
fitted inside the computers and hubs or switches with some
Often the computers in a network are linked to a server,
this is a powerful computer
which holds the software to run the network. It also stores and
manages the shared
resources of the network like the users’ files, software packages and printer
queues. It usually has a much higher specification
than the other computers on the network, with a very large hard disk drive.
Common Network Environments:
- The Internet:
This is a wide area network (WAN) which
connects millions of small computer networks all over the world.
- An Intranet: This is a small-scale
Internet on a local area network (LAN).
It is constructed and managed using standard Internet technology and
applications such as internal e-mail systems, message boards and local web
sites can be accessed using a standard web browser. An Intranet
can be set up to be accessed from the Internet via a secure log on.
- Network software: This may be part of the operating
system, or it can be software designed specifically to manage a
Methods of communication:
- radio signals exchanged via satellite.
- electronic signals exchanged
via telephone line or LAN cable.
- light signals exchanged via optical fibre.
- Network Interface Card (NIC): This is
needed to connect a computer to the network. The network card looks like a small circuit board
and slots into one of the connectors on the main circuit board (called the mother
board) inside the computer. Network cards have connectors
on them for network cables.
- Communication Hardware:
- A switch provides a central connection
point for all the cables and the server in a
star network topology.
- A hub is a low-cost substitute for a
switch in a network which has low network traffic.
- A wireless access point allows
laptops and PDA's to connect to a network using radio signals.
- A bridge is used to connect separate LANs of the
- A router connects
different types of LAN and
connects a LAN to a
WAN such as the Internet.
Network management - servers:
Networks are often arranged in a hierarchical
way. This means that one or more server computers
are more powerful than the other client
computers. This is known as a client-server
relationship. Servers manage all the printing, file maintenance and access
The clients computers may have little no disk storage or processing power of their own
as these functions can be provided by the server.
Advantage - Client computers can be very low specification and therefore cheap.
Disadvantage - The client computers can be totally dependant on the server.
Network management - encryption and
Because data is being transferred between computers it can be intercepted
more easily than on a non-networked computer. To intercept data
transmitted over a wireless network a hacker does not even have to be physically
in the same building as the network.
There are two ways to reduce these security risks:
- Encryption - scrambling the
data so that it cannot be understood without the number key that was used to
- Authentication techniques
- such as using unique User ID's to
control access to files and computer settings and
passwords to protect unauthorised used of the user ID's.