1. Networks

2. What is a computer network?
A network is two or more computers that are linked together so that they are able to share resources.

3. Shared resources include
Hardware – printers, scanners, storage, etc.
Software – need only be installed on one computer.
Data (e.g. database files).
An Internet connection.

4. Advantages & Disadvantages
Data can be shared making it easier to work together.
Computers can share hardware like printers – no need to buy more than one, so it is cheaper.
It is quicker to update software – it is stored in one place on a server.
Viruses can be easily spread through networks.
If data and software is all in one place, all computers will not work if the network experiences problems.
Networks require regular maintenance – this is expensive.

5. Internet, Intranet, Extranet
Service/
Hardware
Explanation
Internet
The Internet is a WAN which is made up of many other smaller networks.
Extranet
An extranet is an external network which can be viewed by many different people at an organisation such as employees, customers, suppliers and shareholders.
Intranet
This internal network is private to one organisation, viewable to employees only.

6. LANs and WANs Local area networks: Confined to a small area.
Usually located in a single building.
Use cable, wireless, infrared and microwave links that are usually owned by the organization.
Cheap to build.
Cheap to run.
Wide area networks:
Cover a wide geographical area (i.e., between cities, countries and even continents).
In lots of different buildings and cities, countries, etc.
Use more expensive telecommunication links that are supplied by telecom companies.
Expensive to build.
Expensive to run.

7. Network Topologies
Ring
Bus
Star

8. An ICT network consists of
Hardware/communication devices
Network software
Data transfer media

9. Communication devices
A network interface card:
prepares data for sending over the network
sends the data
controls the flow of data.

10. Communication devices
A hub:
is used to join computers in a network
allows the connection of cables
allows the sharing of files and Internet access

11. Communication devices
A switch:
is similar to a hub but more intelligent
can look at a packet of data to decide where it should go
reduces the number of packets of data on a network, which speeds it up

12. Communication devices
A router:
can be wired or wireless
is used to join several networks together
is often used to connect several computers in the home to the Internet

13. Gateways, Bridges, Packet Switches
Service/
Hardware
Explanation
Gateways
These allow two different networks to speak to one another by translating data.
Bridges
These are used to join – or bridge – two LANs together to form one larger network.
Packet switching
Switches can speed up networks by only sending packets of data to the computers which need the data. This means that less data is travelling unnecessarily around the entire network.

14. Network software Network software consists of:
Network operating systems – specialist operating systems designed specifically for networks.
Network management software – used to help a network manager run a network by keeping track of software, keeping software up-to-date, installing software security patches, helping to manage the help-desk, etc.

15. Data transfer media The medium/method by which the data is
transferred in a
network can be:
metal wire
fibre optic cable
wireless.