INTRODUCTION TO COMPUTER NETWORKS

Presenter: Simwaka P.

What is a Computer network?

‘Lets Discuss’

DEFINITION:

a

network consists of two or more connected

computers or it can be defined as a group of two

or more computer systems linked together.

NETWORK

T

he figure above illustrates the major hardware,

software, and transmission components used in a

simple network: computers, network interfaces, a connection medium, network operating system software, and either a hub or a switch.

IMPORTANCE OF NETWORKS

Networks allow people to share computer hardware, reducing costs and access more powerful hardware resourcesNetworks allow people to share data and software

programs increasing efficiency and productivityNetworks allow people to work together in ways

otherwise would be difficult and impossible for example video conferencing

‘LETS DISCUSS’ DO YOU KNOW ANY TYPES

OF NETWORKS

TYPES OF NETWORKS

T

here are many different kinds of

networks and ways of classifying them.

O

ne way of looking at networks is in

terms of their geographic scope

TYPES OF NETWORKS

• LAN: it covers a small geographical area e.g. in the same building, in a home. • MAN: it covers a broad geographical

area e.g Buildings, a city• WAN: it covers a wide geographical

area e.g. the internet

WIDE AREA NETWORKS

ADVANTAGES OF NETWORKS

Sharing resources e.g. printers, Reducing costs Information and

communication is made easier

NETWORK TOPOLOGY

A

topology is the arrangement

of its modes or devices.

NETWORK TOPOLOGIES

NETWORK TOPOLOGIES

S

tar Topologies. Connect end user computers to a central node(e.g

switch). Used for centralizing processing. Since the network is reliant on

the performance of the central node, this topology is less reliable than

either ring or bus. If the central computer fails, the network fails. May be

used in WANs and LANs.

R

ing Topologies. Connect end user computers together in a ring on a

more equal basis. It is more reliable and has no single point of failure.

Used mostly in LANs.

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NETWORK TOPOLOGIES

B

us Topologies. Connect end user computers on a common channel.

Used commonly in business LANs. It also has no single point of

failure. It is cheaper than ring networks, but sometimes less reliable.

M

esh Networks. A variation of a ring network that uses a direct

communication line to connect some or all of the computers in the

ring to each other.

STAR TOPOLOGY

I

n a star topology, all devices on the network connect to a

single hub.

F

igure 8-8 illustrates a simple star network in which all network

components connect to a single hub.

A

ll network traffic flows through the hub. In an extended star,

multiple layers or hubs are organized into a hierarchy.

BUS TOPOLOGY

I

n a bus topology, one station transmits signals, which travel in both directions along

single transmission segment.

All of the signals are broadcast in both directions to the entire network.

A

ll machines on the network receive the same signals, and software installed on the

clients enables each client to listen for messages addressed specifically it.

B

us networks are the most common Ethernet topology.

RING TOPOLOGY

A

ring topology connects network components in a closed loop.

Messages pass from computer to computer in only one

direction around the loop, and only one station at a time may

transmit.

R

ing networks are used primarily in older LANs using Token

Ring networking software.

SOME DEVICES USED IN NETWORKSS

witches. A communication processor that makes connections between

telecommunications circuits in a network so a message can reach its intended

destination.

R

outers. A processor used to interconnect networks with different protocols. Used for

routing messages to their destination.

H

ubs. It enables temporary connections to be made to different devices, e.g. printers,

servers, workstations etc., on the network. Thus, it allows network resources to be

shared.

G

ateways. Allow networks with different architectures, e.g. mainframes and

client/servers, to be interconnected.

F

ire walls. Security devices used to protect networks from intrusions by screening all

network traffic.

N

etwork Operating System. Software that controls telecommunications and the use of

shared resources. eg UNIX

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QUESTIONS?

TASK

1) What is a Computer Network?

2) List 2 advantages of computer networks.

3) What is a topology?

4) List three types of computer topologies with the aid of

diagram.

5) Mention 3 devices used in a network.

END OF LESSON

Thank You