What do you understand by Topology? Explain various topologies in detail with a diagram.

Network topology means the physical or logical arrangement of computers, cables and devices in a network — how nodes are connected and how data flows. Choosing the right topology affects cost, speed, reliability and ease of repair. It is the “map” of the network.

Types of topologies:

1. Bus Topology: All computers connect to one single central cable (backbone) with terminators at both ends.

• Advantage: Cheap, easy to install for small labs.
• Disadvantage: If main cable breaks, whole network fails; slow when many users.
• Diagram: PC — PC — PC all on one line ====backbone====.
• Use: Old small labs.

2. Star Topology: Every computer connects separately to a central device (hub/switch). Most common today.

• Advantage: If one cable fails, only that PC affected; easy to add/remove; fast with switch.
• Disadvantage: If central switch fails, all fail; needs more cable.
• Diagram: Switch in centre, PCs like star points around it.
• Use: Schools, banks, Nepal government offices with UTP + switch.

3. Ring Topology: Each computer connects to exactly two neighbours forming a circle. Data travels in one (or both) direction(s) passing through each node.

• Advantage: Equal access, no central failure point; good for predictable traffic.
• Disadvantage: One break can disturb ring (unless dual ring); adding node is difficult.
• Diagram: PCs in a circle ○.
• Use: Old Token Ring, some fibre networks.

4. Mesh Topology: Every device connects to every other device (full mesh) or to several devices (partial mesh). Maximum redundancy.

• Advantage: Very reliable — if one path fails, another path works; best for critical systems.
• Disadvantage: Most expensive, complex cabling.
• Use: Army, ISP backbone, bank data centres.

5. Tree / Hybrid Topology: Combination of star + bus in layers (like departments → central switch → main server). Scalable for large campuses.

Topology	Cost	Reliability	Best for
Bus	Low	Low	Tiny lab
Star	Medium	Good	Office LAN
Ring	Medium	Medium	Fibre loop
Mesh	High	Highest	Critical backbone

Exam tip: Draw simple diagrams with boxes + lines, write 2 advantages + 1 disadvantage each, and conclude: star is best for offices, mesh for critical backbone.