1. UNIT 4
NETWORK ENVIRONMENTS

2. Networks
A computer network consists of two or more computers linked together.

3. Advantages of a Network Environment
Hardware resources (printers, etc) can be shared – saves money.
Software can be shared rather than every user having their own copy.
Communication between network stations is possible.
Access to software and files can be controlled. Different users can have different privileges.
Software need only be installed once and it will be available to all users.
Security and backup can be controlled centrally

4. Advantages of a Stand Alone Environment
Less hardware and software needed – Do not need network cards, cables and network software.
Less IT knowledge needed. The efficiency of a network requires skills of a systems manager. A badly managed network will be less efficient than a stand alone.
Fewer problems with viruses being passed from one machine to another.
Not as hardware dependant. If the server crashes on a network – the whole system is down.

5. LANS And WANS LAN stands for LOCAL AREA NETWORK WAN stands for
WIDE AREA NETWORK

6. Network Topologies
There are many ways in which networks can be arranged. The most popular 4 are:
Ring Topology
Bus Topology
Mesh Topology
Star Topology

7. SERVER BASED Vs PEER TO PEER
There are two types of LAN networks:
Server based – where more than 4 computers are to be linked together.
Peer to Peer – where computers are linked directly to each other.

8. Comparing the Two Set Ups
Central store is available to all users
Storage facilities are distributed throughout the network
Software is centrally held and shared
Copies of the software are held on each machine
User IDs,passwords and access levels are controlled by the central computer
Security is not centrally controlled.
Backup facilities are centralised
Backup is the responsibility of individual computer users
All users are reliant on the service provided by the central facility. If it goes down, all users are affected.
No reliance on a central computer.
Computers on the network may be of different types.
Individual computers on the network must have the same software to control communication with each other.

9. Mr Doves` Work Is Never Done!
Any network requires maintenance. Someone must ensure that:
Response time is adequate
Hardware is upgraded when necessary
The required software is loaded
Software is upgraded when necessary
A system of regular backups is adhered to
Network security is maintained

10. Communications Media
In a wide area network where computers are linked over a very large area, even different continents, communication between them is carried out with:
Twisted pair (Copper cable) used in much of the telephone network.
Coaxial cable – High quality, well insulated cable tat can transmit data at high speeds.
Fibre optic cable – pulses of light rather than electricity can be sent in digital form.
Microwave – similar to radio waves. (used by mobile phone networks.
Communication Satellite – using a satellite in geosynchronous orbit above the earth.

11. Geek Alert !!

12. Factors Affecting the Rate of Data Transmission
The speed of the modem – most transmit data at 56 bps (bits per second)
Nature of the transmission line – an ISDN line has a much higher transmission speed than an analogue line.
The type of cable used – twisted pair cable has a transfer rate of about 10Mbps whereas fibre optic cable is about 100Mbps
The type of transmission – asynchronous (one character at a time is sent with a start bit and a stop bit and a check digit) or synchronous (no need for a start bit and a stop bit)

13. To Put It Another Way……. The speed of data transmission depends on:
What type of cable is used
The speed the modem sends it
How it is sent
Bandwidth

14. Important Parts of Networks
Network Card
Cabling
Repeater – An electronic device that receives a signal and outputs it in boasted form
Hub – A hub is a switching cabinet that will connect to the server and to several computers.
Bridge – Allows two LAN to be linked
Network gateway – enables a LAN to connect to a WAN such as the internet.

15. And Finally….Protocol
In order for equipment from different suppliers to be networked, a strict set of rules (protocols) has been created. These standards cover:
Physical connections
cabling
mode of transmission
speed
data format
error detection and correction
Any equipment which uses the same communication protocol can be linked together.

16. Questions

17. A local surgery uses a number of stand-alone computer systems to manage patient records, appointments, staff pay and all financial accounts. The surgery manager is considering changing to a LAN network.
Compare the relative advantages of stand-alone and LAN network systems (6 Marks)
At the central office of a landscape gardening company there are six employees. Each employee has a stand – alone computer and a printer. The company director has commissioned a business survey which indicated that it would be more efficient if the six pcs were formed into a peer to peer network.
State three benefits that the company would gain from networking their computers as a peer to peer system rather than a server based system (3 Marks)

18. 3. In a solicitors practice there are ten employees working in three offices. Each employee has a stand alone computer system and there is a shared printer in each office. The head of the practice has been advised that it would be more efficient if the ten computers were formed into a server based network.
a) State three benefits that the practice would gain from networking their computer systems (3)
b) Give two reasons for choosing a server based system rather than a peer to peer system. (2)
c) State two items of hardware that will be needed to connect these ten computers as a server based network. State why each item is required. (4)

19. 4. A school is investing in 16 computers
4. A school is investing in 16 computers. They need to choose between a network or 16 stand alone machines.
Describe the advantages and disadvantages of each
(8 marks)