Network Topologies - JSS 2

NETWORK TOPOLOGIES

SUBJECT	Digital Technologies
CLASS	JSS 2 (Basic 8)
TERM	First Term
WEEK	4
TOPIC	Network Topologies
SUBTOPICS	Meaning and types: Bus, Star and Ring; Advantages and disadvantages
DURATION	80 Minutes (Double Period)

INTRODUCTION

In a computer network, computers and other devices need to be connected in an organized manner so that they can communicate and share resources. The arrangement of these devices and their connections is known as network topology.

Different network topologies have different structures, advantages and limitations. In this lesson, we will study three common network topologies: bus, star and ring topology.

MEANING OF NETWORK TOPOLOGY

Network topology is the physical or logical arrangement of computers, network devices and communication links in a computer network.

In simple terms, network topology describes how devices in a network are connected to one another.

The way devices are arranged can affect the cost, performance, reliability and maintenance of a network.

1. BUS TOPOLOGY

Definition: Bus topology is a network arrangement in which all connected devices share a single main communication cable called the backbone.

In a bus topology, computers and other devices are connected along one main cable. Data travels along the shared communication line and devices receive the data intended for them.

Characteristics of Bus Topology

It uses one main backbone cable.
Several devices are connected to the backbone.
It does not require a central switch for the basic arrangement.
It is relatively simple for small network installations.

Advantages of Bus Topology

It can require less cable than some other topologies.
It can be relatively simple to install for a small network.
It does not require a central connecting device for the basic design.
It can be useful for simple network arrangements.

Disadvantages of Bus Topology

A failure of the main backbone cable can affect the entire network.
Performance can decrease as more devices are added.
Finding faults can be difficult.
The length of the main cable limits the network.

Remember: The most important feature of bus topology is the single main backbone cable shared by the connected devices.

2. STAR TOPOLOGY

Definition: Star topology is a network arrangement in which each device is connected to a central device, such as a switch.

In a star topology, the central device acts as the point through which connected devices communicate. Modern Ethernet local area networks commonly use switches in a star-like arrangement.

Characteristics of Star Topology

It has a central connecting device.
Each computer or device has its own connection to the central device.
It is commonly used in modern local area networks.
Individual devices can usually be added or removed without affecting the other connections.

Advantages of Star Topology

It is relatively easy to install and manage.
A failure of one cable usually affects only the connected device.
Faults can be easier to identify.
New devices can be added relatively easily.
It can provide good network performance when properly designed.

Disadvantages of Star Topology

It requires more cable than a basic bus topology.
It depends heavily on the central device.
If the central switch or connecting device fails, communication through that device can be disrupted.
It can cost more to install than a simple bus arrangement.

Remember: The key feature of star topology is the central device to which the other devices are connected.

3. RING TOPOLOGY

Definition: Ring topology is a network arrangement in which devices are connected in a circular or ring-like structure.

Each device is connected to neighbouring devices, forming a closed communication path.

Characteristics of Ring Topology

Devices are arranged in a circular structure.
Each device is connected to one or two neighbouring devices, depending on the design.
The network forms a closed loop.
Data can travel around the ring according to the network's communication method.

Advantages of Ring Topology

Each device has a defined connection to neighbouring devices.
Data transmission can follow an organized path.
It can provide predictable communication in certain network designs.
It does not require every device to connect directly to one central device.

Disadvantages of Ring Topology

A break in the ring can disrupt communication in some ring designs.
Adding or removing devices can be more difficult.
Finding faults may be difficult.
A problem affecting a connection can affect communication around the network.

Remember: The main feature of ring topology is its circular arrangement of connected devices.

COMPARISON OF BUS, STAR AND RING TOPOLOGIES

Feature	Bus	Star	Ring
Arrangement	Devices share one main backbone cable.	Devices connect to a central device.	Devices form a circular arrangement.
Central Device	Not required for the basic arrangement.	Required.	Not required for the basic arrangement.
Cable Requirement	Generally uses one main backbone cable with connections to devices.	Usually requires a separate connection from each device to the central device.	Connections link devices around the ring.
Fault Effect	A backbone failure can affect the whole network.	A single cable failure usually affects one device, but central-device failure can affect the network.	A connection failure can disrupt communication depending on the ring design.
Management	Can become difficult as the network grows.	Relatively easy to manage.	Can be more difficult to manage.

DIFFERENCE BETWEEN THE THREE TOPOLOGIES

The major difference between the three topologies is the way network devices are arranged and connected.

Bus topology: Devices share one main backbone cable.
Star topology: Devices connect to a central device.
Ring topology: Devices are connected in a circular arrangement.

IMPORTANCE OF NETWORK TOPOLOGY

Network topology is important because the arrangement of devices affects how a network is installed, operated, maintained and expanded.

A suitable topology can help to:

Organize network connections.
Make network management easier.
Determine the amount of cable and equipment required.
Influence network performance.
Make it easier to identify possible connection problems.
Determine how easily new devices can be added.

CLASS ACTIVITY

Study the three network topologies discussed in this lesson. Draw and label each of the following:

Bus topology
Star topology
Ring topology

For each drawing, identify the major feature that makes it different from the other topologies.

SUMMARY

Network topology refers to the arrangement of devices and connections in a computer network.

The three topologies studied in this lesson are bus, star and ring topology.

In bus topology, devices share a main backbone cable. In star topology, each device connects to a central device such as a switch. In ring topology, devices are connected in a circular arrangement.

Each topology has its own advantages and disadvantages, and the choice of topology depends on the requirements of the network.

EVALUATION

What is network topology?
State three types of network topology.
Describe bus topology.
State two advantages of bus topology.
State two disadvantages of bus topology.
What is star topology?
State two advantages of star topology.
State two disadvantages of star topology.
What is ring topology?
State two advantages of ring topology.
State two disadvantages of ring topology.
Give two differences between bus and star topology.

ASSIGNMENT

Draw and label the following network topologies in your notebook:

Bus topology
Star topology
Ring topology

Under each diagram, write two advantages and two disadvantages of the topology.

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