Network Topologies: Star, Mesh, and Bus

This lesson covers the three network topologies you need to know for OCR J277 Section 1.3.1: star, mesh, and bus. A topology describes the physical or logical arrangement of devices in a network.

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What Is a Network Topology?

A network topology is the layout or structure describing how devices (nodes) in a network are arranged and connected. The topology affects the network's performance, reliability, cost, and ease of maintenance.

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Star Topology

Description

In a star topology, all devices are connected to a central device (usually a switch or hub). Devices do not connect directly to each other — all communication passes through the central device.

    [PC1]
      |
[PC2]--[SWITCH]--[PC3]
      |
    [PC4]

How It Works

1. Device A wants to send data to Device B.
2. Device A sends the data to the central switch.
3. The switch reads the destination address and forwards the data only to Device B.

Advantages of Star Topology

Advantage	Explanation
Easy to add/remove devices	New devices can be connected without disrupting the network
Fault isolation	If one cable or device fails, only that device is affected; the rest of the network continues working
Good performance	The switch sends data only to the intended recipient, reducing unnecessary traffic
Easy to troubleshoot	Faults can be identified and fixed quickly

Disadvantages of Star Topology

Disadvantage	Explanation
Central point of failure	If the switch/hub fails, the entire network goes down
More cabling	Each device needs its own cable to the central device, increasing cost
Cost	The central switch/hub adds to the cost

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Mesh Topology

Description

In a mesh topology, devices are connected to multiple other devices. There are two types:

Type	Description
Full mesh	Every device is connected directly to every other device
Partial mesh	Some devices are connected to all others, but some are only connected to a few

Full Mesh (4 devices):
[PC1]---[PC2]
 | \   / |
 |  \ /  |
 |   X   |
 |  / \  |
 | /   \ |
[PC3]---[PC4]

How It Works

• Data can travel from one device to another via multiple paths.
• If one connection fails, data can be rerouted through an alternative path.
• This makes mesh networks highly resilient.

Advantages of Mesh Topology

Advantage	Explanation
No single point of failure	If one connection fails, alternative paths exist
High reliability	Multiple routes mean the network can tolerate faults
Data can be transmitted simultaneously	Multiple paths allow parallel data transmission
Good for critical systems	Used where downtime is unacceptable

Disadvantages of Mesh Topology

Disadvantage	Explanation
Expensive	Requires many cables and network interfaces
Complex	Difficult to set up and manage
Impractical for large networks	The number of connections grows rapidly as devices are added
Maintenance	More connections mean more to maintain and troubleshoot