Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Describe and compare network topologies: Bus, Star, Ring, Mesh, Tree.
• Identify different communication media: Twisted Pair, Coaxial, Fibre Optic, Wireless.
• Explain factors for choosing a topology and media.
• Understand the basics of network addressing.
• Identify common network devices and their roles.

Lesson summary

In today's interconnected world, understanding computer networks is no longer just for IT professionals. From accessing online educational resources to communicating with family via WhatsApp or using mobile banking, our daily lives are heavily reliant on networks. This lesson focuses on the backbone of these networks: how computers are connected (network topologies) and the physical cables or wireless signals (communication media) that allow them to communicate. Imagine a school network – how are the computers in the lab connected? What type of cables are used to connect them to the internet?

Lesson notes

2.1 Network Topologies A network topology describes the physical or logical arrangement of devices (computers, servers, printers, etc.) in a network. The topology influences the network's performance, reliability, and cost.

Bus Topology: All devices are connected to a single cable (the bus) using connectors and terminators.

Advantages: Simple to install and inexpensive for small networks.

Disadvantages: If the bus cable breaks, the entire network goes down. Difficult to troubleshoot. Performance degrades as more devices are added. Less secure as all data travels along the same cable.

Example: older Ethernet networks.

South African Relevance: You might find a bus topology in very old installations in some schools or small businesses, but it's largely obsolete now.

Star Topology: All devices are connected to a central hub or switch.

Advantages: Easy to install and troubleshoot. A break in one cable only affects one device. Scalable – easy to add new devices. More secure than bus topology.

Disadvantages: Requires more cable than bus topology. The central hub/switch is a single point of failure. More expensive than bus topology due to the cost of the hub/switch.

South African Relevance: The most common topology in homes, schools, and businesses in South Africa. Think of the computers in a school lab connecting to a central switch that provides internet access.

Ring Topology: Devices are connected in a circular fashion, with each device connected to two other devices. Data travels in one direction around the ring.

Advantages: Relatively simple to implement. Data flows in an orderly manner.

Disadvantages: A break in the ring cable brings down the entire network. Difficult to troubleshoot. Adding or removing devices can disrupt the network.

South African Relevance: Less common. Might be used in specific industrial control systems but generally not prevalent in typical office or home networks.

Mesh Topology: Each device is connected to multiple other devices.

Advantages: Highly redundant and reliable. If one link fails, data can be routed through another path. Very secure.

Disadvantages: Very expensive and complex to implement, due to the high amount of cabling required. Difficult to manage.

South African Relevance: Used in critical infrastructure or backbone networks of large telecommunications companies in South Africa, where reliability is paramount.

Example: key parts of the Eskom grid.

Tree Topology: A hierarchical topology, combining elements of bus and star topologies.

Advantages: Scalable and flexible. Easy to manage and expand.

Disadvantages: Failure of the central "root" node can affect large parts of the network. More complex to install and configure than star topology.

South African Relevance: Common in larger organizations with multiple departments or branches. Think of a school district where each school has a star topology, but the schools are connected in a tree structure to the district's central server.