Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Define and differentiate between bus, star, ring, and mesh topologies.
• Describe the advantages and disadvantages of each topology.
• Identify and explain different types of wired communication media.
• Compare the characteristics of different communication media.

Lesson summary

This week, we delve into the fundamental building blocks of networks: network topologies and communication media. In today's interconnected world, understanding how networks are structured and how data travels through them is crucial. From accessing online educational resources to conducting business transactions, networks are essential for modern life in South Africa. A solid grasp of these concepts will empower you to troubleshoot network issues, make informed decisions about network design, and ultimately, thrive in a technology-driven environment.

Lesson notes

2.1 Network Topologies A network topology refers to the physical or logical arrangement of devices (computers, servers, printers, etc.) in a network. It defines how data flows between these devices. Understanding different topologies is essential for designing efficient and reliable networks.

Bus Topology: In a bus topology, all devices are connected to a single cable, called the bus. Data travels along the bus, and each device checks the destination address to see if the data is intended for it.

Advantages: Simple to install and relatively inexpensive.

Disadvantages: If the bus cable breaks, the entire network goes down. It can also suffer from performance degradation as more devices are added due to collisions (when two devices try to transmit data simultaneously). Not very scalable.

Example: Imagine a single power cord with multiple plug points along its length. Each device plugs into one of these points. If the cord is cut, everything loses power.

Star Topology: In a star topology, all devices are connected to a central device, such as a hub or switch. Data is sent from one device to the central device, which then forwards it to the intended recipient.

Advantages: Easy to troubleshoot. If one device fails, it doesn't affect the rest of the network. More scalable than bus topology. Easier to manage and monitor from the central point.

Disadvantages: Requires more cabling than a bus topology. The central device is a single point of failure; if it fails, the entire network goes down.

Example: Think of a spoked bicycle wheel. The hub is the central device, and each spoke connects to a device (the rim).

Ring Topology: In a ring topology, devices are connected in a closed loop. Data travels around the ring in one direction until it reaches the destination device. Each device acts as a repeater, forwarding the data to the next device in the ring.

Advantages: Relatively simple to implement. Can handle high bandwidth.

Disadvantages: If one device fails, the entire network can be disrupted. Difficult to troubleshoot. Adding or removing devices can be complex.

Example: Visualize a bicycle chain. Each link in the chain represents a device. The chain (data) moves in one direction.

Mesh Topology: In a mesh topology, each device is connected to multiple other devices. This provides redundancy and fault tolerance.

Advantages: Very reliable. If one path fails, data can be routed through another path. High bandwidth.

Disadvantages: Complex to implement and manage. Very expensive due to the large amount of cabling required.

Example: Envision a spider web. Each strand connects to multiple other strands, providing alternative routes if one is broken. Think about the power grid; multiple paths exist for electricity to flow. 2.2 Communication Media Communication media refers to the physical channels through which data is transmitted between devices in a network. Different types of media have different characteristics in terms of bandwidth (data carrying capacity), cost, security, and distance limitations.

Twisted-Pair Cable: Consists of two or more pairs of insulated copper wires twisted together to reduce electromagnetic interference (EMI).

Unshielded Twisted Pair (UTP): Most common type. Inexpensive and easy to install. Used for Ethernet networks. Vulnerable to EM

I. Distance limitation of around 100 meters.

Shielded Twisted Pair (STP): Contains a shield to protect the wires from EMI. More expensive than UTP. Used in environments with high levels of EMI.