Lesson 6: Common Network Topologies: Star, Bus, Ring, and Mesh

Network topology describes the physical or logical arrangement of connections within a network. The topology chosen affects performance, cost, and reliability.

1. Star Topology

• Description: All devices are connected to a single central device, typically a switch or a hub.
• Pros: Easy to install, failure of one device does not affect others. Easy to troubleshoot.
• Cons: If the central device fails, the entire network segment goes down. Requires more cable than Bus topology.

2. Bus Topology

• Description: All devices are connected to a single central cable, called the backbone or segment.
• Pros: Requires the least amount of cable. Simple and inexpensive for small networks.
• Cons: Very hard to troubleshoot. A break in the central cable brings the entire network down. Data collisions are common.

3. Ring Topology

• Description: Each device is connected directly to exactly two other devices, forming a circular structure. Data travels in one direction (unidirectional).
• Pros: High-performing under heavy load (due to token passing mechanisms).
• Cons: A failure in a single cable or device can break the entire ring. Difficult to add or remove devices.

4. Mesh Topology

• Description: Every device is connected directly to every other device in the network (Full Mesh).
• Pros: Extremely reliable and fault-tolerant (if one path fails, there are many others). High redundancy.
• Cons: Extremely expensive and complex to install and maintain due to the vast number of cables required (N * (N-1) / 2 connections).

Modern Networks: The Star topology is overwhelmingly the most common physical layout used in modern LANs, often combined with a hierarchical structure.