1. © Vera Castleman Networks Grade 10

2. The Network System A network links components electronically. Each component is a NODE. A node could be: A PC A printer A modem etc. The essential components of a network are Network devices (e.g. computers, printers) Communication channels (e.g. cables) Network interface cards Network software.

3. Types of Networks Networks can be: Simple  two computers at home could be linked directly. If both have the same control  called a peer-to-peer network. Complex  server based  the server controls the components linked together in the network.

4. Advantages of a network Share Resources Centralise and update data in one place Centralise programs on server  Upgrades can be done in one place Files transfer is easy. Contact maintained by using e-mail which can also update Inter-Office appointments. Security is maintained  sensitive material is restricted from general use. Networks save time and resources. They improve productivity and also save money.

5. Disadvantages of a network are always a concern in a network. A well managed network will restrict unauthorised users Each user will have a profile protected by a password. Rules for creating a password Don’t use things that a user can guess like a pet’s name, a boy or girl friend’s name, your birth date etc. Change your password regularly especially if you think it has been guessed. Never use a sequence of letters or numbers (e.g. 12345 or abcde) Use an alphanumeric code Make some of the letters uppercase Substitute numbers for some of the letters  Sabelo  8Ab310 DO NOT write it down!

6. Black, Grey and White Hats Black Hats  gain access to try to steal or destroy information They will leave a message so that people will know that they have been in. Grey Hats  ½ a White and ½ a Black Hat. They enjoy the challenge of breaking in – will usually inform the company and suggest payment for providing a fix for the security breach. White Hats  will do it for a challenge and will let the company know how to fix it.

7. Examples of networks PAN  (Personal Area Network)  e.g. pictures taken with your cell phone can be sent to your printer. HAN  (Home Area Network)  2 or more PC’s in a home are connected to share resources, OAN  (Office Area Network)  a small office connecting as above LAN  (Local Area Network)  exists in a company within a small geographical space e.g. one office complex. WAN  (Wide Area Networks)  cover a vast geographical span e.g. between offices and the head office, various colleges of a university etc. GAN  (Global Area Networks)  refers to the internet or a company with ties to a company in another country usually via satellite.

8. Communication Channels Telephone lines Coaxial Cables UTP cabling Microwave Transmission Fibre Optic cables Infrared Transmission Cellular Radio Systems

9. Telephone Cables The telephone line is designed for transmitting voices. It operates at a slow analog speed. If computers use telephone lines for communications operate via a digital signal A MODEM convert the signal Telephone lines are suitable for transmitting data over variable distances as it is cheap. communication is slow and corruption of data may occur ADSL lines are popular as they are dedicated phone lines which rapidly transports data. Transmission rate is faster. Less data corruption occurs.

10. Coaxial Cables These are made up of groups of insulated wires with a central core. Data is transmitted much faster Usually used when the distance to be covered is short, for example within an office building.

11. UTP cabling UTP stands for Unshielded Twisted Pair Connects computers in a simple network environment. It consists of pairs of twisted wires inside a plastic “tube”. If used over distances greater than 100m the data can be lost It is cheap

12. Microwave Transmission Works in a similar way to radio waves. It is fast The microwave saucer-shaped antennae must be within “sight” of each other. Data can be transmitted from one microwave station to another until the end has been reached. The signals are amplified before being sent to the next station.

13. Fibre Optic cables These thin fibres of glass or plastic use light to transmit the data. The fibres are contained by a protective outer covering. One fibre is able, in one second, to transmit data across the country that would take a conventional telephone line many hours. There is virtually no chance of corruption of data occurring but it is relatively expensive.

14. Infra-red transmission When the stations are in the same room, infrared transmission can be used. Signals are picked up from line of sight or are reflected off a surface. The transmission distance is usually less than 10m. PDA’s and some input devices could use infrared transmission.

15. Cellular Radio System Cells are usually a few kilometres apart. The cells are connected via fibre optic cable to a switching office … …which in turn is connected to a public telephone exchange which sends the signal via satellite or microwave links.

16. Communications Interfaces An interface is a piece of hardware that helps various devices to communicate. There are many ways that different communication components can be linked: Modem Switch Router

17. MODEM (MOdulator-DEModulator) A modem is needed when telephone communication is used. From computer  MODULATION From Phone line  DEMODULATION

18. Switch Manages the network. An older way to connect a network is via a hub. A switch: Works faster than a hub. Congestion on the network is reduced. Is more expensive than a hub.

19. Router It chooses a fast and cheap route for data to travel from one network to another. A wireless router is also be used to connect a computer (often a laptop) to the Internet. The internet needs routers to manage the correct transference of data to the right place.