3. Network Topologies

Network Topologies

A network topology is the way devices are arranged and connected within a network. This layout affects how data travels between devices and how easy it is to manage or expand the network. Different topologies are chosen depending on the size of the network, the cost, how reliable the connection needs to be, and how much data the network has to handle.

There are several common types of topologies: star, bus, and ring.

Learning Objectives

Define the term network topology and identify the main types.
Describe how star, bus, and ring topologies are structured.
Compare the advantages and disadvantages of each.
Understand how topologies affect network performance and reliability.

Key Terms

Topology: The physical or logical layout of a network.
Node: Any device connected to a network (e.g. computer, printer, phone).
Star topology: A layout where all devices connect to a central hub or switch.
Bus topology: A layout with all devices connected to a single main cable (the backbone).
Ring topology: A layout where each device is connected to exactly two others in a loop.
Hub/Switch: A central device that manages and directs data traffic in a star network.
Backbone: The main central cable used to carry signals in a bus network.
Data collision: When two devices send data at the same time and their signals crash into each other, causing errors.
Hybrid topology: A network layout that combines two or more different topologies.
Mesh topology: A layout where devices are interconnected with many redundant connections (mentioned when talking about modern networks).
Relay: A passing method where data moves device to device in order (used in ring topologies).

Star Topology

In a star topology, every device (called a node) is connected to a central hub or switch. This hub acts like a traffic controller, making sure that data goes to the right destination.

Real life example:
Imagine a teacher (the hub) standing in the middle of a classroom giving instructions to students (the nodes). Each student can only talk to the teacher, and the teacher passes on messages to other students if needed. If one student leaves the room, the others can continue working without any problem.

Why it’s popular:
Star topologies are common in schools, offices, and even in your home Wi-Fi network, because they are very reliable. If one cable or computer fails, the rest of the network keeps working. However, they do need more cable and a central device like a hub or switch, which can make them more expensive to set up.

Quick Anecdote:
In one school, a technician accidentally unplugged one student's computer from the hub while trying to fix a chair. The student lost connection — but the rest of the network stayed perfectly fine. That’s the power of a star topology!

Bus Topology

A bus topology uses a single central cable, known as the backbone, to which all devices are connected.

How it works:
When one device sends data, the signal travels along the backbone, and all connected devices see it, but only the intended recipient accepts and processes the message.

Real life example:
Think of a group chat where everyone sees every message, but you might only read the ones meant for you.

Advantages and problems:
Bus networks are cheaper to build because they use less cable and no expensive central device. However, if the main cable breaks, the entire network fails. Also, as more devices join the network, it can become slower because of data collisions — when two devices send data at the same time and their signals crash into each other.

Quick Anecdote:
At a gaming party, a group of friends set up a quick bus network with one long cable. It worked great for a few hours — until someone tripped over the main cable. Suddenly, no one could play. That’s a typical bus network problem!

Ring Topology

In a ring topology, devices are connected in a circle. Data travels in one direction around the ring, passing from one device to the next until it reaches the right one.

How it works:
Each device has exactly two connections — one to the device on its left, and one to the device on its right.

Real life example:
Think of a relay race. Each runner (device) passes the baton (data) to the next runner until it gets to the finish line (the destination device).

Advantages and problems:
Ring networks can handle lots of data better than bus networks and are very predictable — data always flows in the same direction. However, if one link breaks, the entire network can crash, unless special technology like a "dual ring" is used to create a backup path.

Quick Anecdote:
A university once had an old ring network connecting its library computers. One night, a janitor accidentally unplugged just one computer to clean underneath. The next morning, none of the library computers worked — all because of a single broken connection!

Hybrid Topologies

Modern networks often use hybrid topologies, which combine features of different types. For example, a large organisation might use a star layout within each office floor, and connect the floors together using a ring or even a mesh system (where every device connects to many others).

Real life example:
Think of a shopping mall: each shop has its own small network (like a star), and the shops are all connected together around the mall (like a ring). This way, if one shop has an issue, it doesn't crash the whole mall’s Wi-Fi.

Why Topologies Matter

Choosing the right topology is about balancing cost, speed, reliability, and future growth.
A cheap network might save money at first, but cause big problems later if it can't handle more users or data. A more expensive network might last longer and perform better.

If you were setting up a school network, would you go for the cheap option that could crash easily, or a reliable but pricier one that could handle hundreds of students streaming videos and handing in homework at the same time?

Revision Focus

A star topology is reliable but uses more cable and hardware.
A bus topology is cheap but fragile – one broken cable can stop everything.
A ring topology moves data in a loop but fails if one link breaks.
Choosing a topology involves balancing cost, speed, and reliability.

Lesson Flashcards

RED TASKS (do not use AI to answer these)

Comprehension Questions

Copy them into your WBK and then answer in complete sentences.

What is a network topology? (Define it in your own words.)
What name is given to any device connected to a network?
In a star topology, where do all devices connect?
What is the main cable in a bus topology called?
How is data passed between devices in a ring topology?
Why might a star topology be considered more reliable than a bus topology?
What happens when two devices send data at the same time on a bus network?
What is a hybrid topology? Give one reason why it might be used.
What does a mesh topology look like, and why is it very reliable?
Give an example of a real-life situation where a ring topology might cause problems.

WBK Tasks

Use a seperate slide for each task. Title it appropriately.

Task 1: Topology Diagrams

Draw your own simple diagrams for the following network topologies:

Star topology
Bus topology
Ring topology
Mesh topology

Rules for this task:

You must label important parts (e.g., backbone, hub, nodes).
You must add one sentence under each diagram explaining how data moves in that layout. You can use ideas that you wrote for the Comprehension Questions.
Do not copy any diagrams from the lesson — create your own versions based on what you understood.

Task 2: Lesson Summary

In your WBK, create a summary poster using these sections:

A definition of "network topology" in your own words - you can use the definition from Comprehension Q1
Three bullet points each about star, bus, and ring topologies (one advantage, one disadvantage, one fact about how data moves).
A simple explanation of hybrid and mesh topologies (no more than two sentences each).
One real-life example for any one topology.

Rules for this task:

You must use your own sentences — not copy the lesson notes but you can use ideas that you wrote for the Comprehension Questions.
Try to use colour or simple sketches to organise your ideas clearly.
Keep it simple: aim for one page maximum.

Exam-style Questions

(2 marks) Compare the structure of a star network with a ring network.
(3 marks) Explain one advantage and one disadvantage of using a bus topology.
(2 marks) State what would happen if a device is removed from a ring network and why.

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