Network Topologies: Bus, Star, Ring, Tree, Mesh, and Hybrid

What is a Network Topology? (In Simple Words)

In simple words, Network Topology is the geometric arrangement or layout of computers, cables, and other devices in a network. It tells you how computers are physically connected to each other with wires.

1. Physical vs. Logical Topology

• Physical Topology: How the actual wires and computers look in the room (e.g., all cables plugged into a central switch box on the wall looks like a Star).
• Logical Topology: The actual path that electronic signals take between computers (e.g., whether signals move in a circle or broadcast to everyone).

2. Bus Topology

In a Bus Topology, all computers are connected to a single continuous central transmission cable called the Backbone Cable.

Working & Key Points:

• When PC 1 sends a message, it travels down the backbone in both directions. Every PC reads the address. Only the matching PC accepts it; others ignore it.
• Terminators: Placed at both ends of the cable to absorb signals and prevent signal reflection (bouncing waves that corrupt data).
• Advantage: Requires the least amount of cable; cheapest to install.
• Disadvantage: If the main backbone cable breaks anywhere, the entire network goes down!

3. Star Topology (Most Popular)

In a Star Topology, every computer is connected via its own separate cable to a central device—usually a Switch or Hub.

Working & Key Points:

• Real-Life Example: Your college lab! All computers have blue LAN cables going into a central switch box.
• Advantage: High fault tolerance. If PC 2’s cable is cut, only PC 2 goes offline; all other 39 PCs work perfectly.
• Disadvantage: If the central switch loses power or burns out, the whole lab stops working.

4. Ring Topology

In a Ring Topology, every computer is connected to exactly two neighboring computers, forming a closed circular loop.

Working & Key Points:

• Data travels in one single direction (unidirectional) around the circle.
• Token Passing: To prevent collisions, an electronic “token” circulates around the ring. Only the computer that currently holds the token is allowed to transmit data (like passing the parcel!).
• Disadvantage: If a single cable breaks or one computer is turned off, the entire ring breaks.

5. Mesh Topology (Full Mesh)

In a Full Mesh Topology, every single computer is directly connected to every other computer by a dedicated point-to-point cable.

• Formula for Number of Cables: For N computers, the number of cables required is:

  Formula: Number of Links = (N(N - 1)) / (2)

  • Example: For 6 computers: (6 × 5 / 2) = 15 cables.
• Advantage: Maximum reliability and security. If cable 1-2 breaks, data can travel via 1-3-2. Zero traffic congestion.
• Disadvantage: Extremely expensive and complicated to install due to the massive number of wires.

6. Tree and Hybrid Topologies

• Tree Topology: Combines characteristics of Star and Bus topologies. Multiple star networks are connected to a central bus backbone cable (like branches of a tree). Used in large multi-story college campuses.
• Hybrid Topology: A combination of two or more different topologies (e.g., Star-Ring or Star-Bus).

💡 DAVV Exam Tip

Question (10 Marks): “Explain different network topologies with diagrams. Differentiate between Star, Bus, and Ring topologies.”

• Draw neat diagrams for Bus, Star, and Ring.
• Give the Mesh formula: N(N-1)/2.
• Mention why Star is the most popular topology in modern offices.