Mesh Topology

Every device has a dedicated point-to-point link to every other device ($n(n-1)/2$ links).

Advantages

• Dedicated links: no traffic problems
• Very robust: one link failure does not affect others
• Good privacy and security; easy fault identification

Disadvantages

• Very high cabling and port cost ($n-1$ ports per device)
• Difficult installation and reconfiguration
• Does not scale well

Star Topology

All devices connect to a central hub/switch.

Advantages

• Cheap, easy to install and extend
• Failure of one node/link does not affect others
• Easy fault detection and management

Disadvantages

• Central hub is a single point of failure
• Hub capacity limits network size; more cable than bus

Ring Topology

Each device connects to exactly two neighbours, forming a closed loop; data travels in one direction (often with token passing).

Advantages

• Simple, needs only two connections per device
• Easy to install; orderly access (no collisions with token passing)
• Equal access for all stations

Disadvantages

• Failure of one node or link can break the whole ring (unless dual ring)
• Adding or removing nodes disrupts the network
• Unidirectional traffic can add delay

Summary

Basis	Mesh	Star	Ring
Links (n nodes)	n(n-1)/2	n	n
Cost	Very high	Low	Low
Reliability	Very high	Depends on hub	Low (single ring)
Fault finding	Easy	Easy	Moderate
Scalability	Poor	Good	Moderate