Lecture on Topology

Introduction

• Topology: The arrangement of devices in a network.
• Types of Topologies: Mesh, Star, Bus, Ring, Hybrid.
• Importance: Simple topic but frequently featured in UGC NET exam questions.

Mesh Topology

• Definition: All devices are connected to each other.

• Diagram Explanation: Four devices connected to each other, five devices example.

• Key Questions: Number of Cables and Ports

  • For 'n' devices:
    • Cables: nC2 = n * (n-1) / 2
    • Ports per Device: n - 1
    • Total Ports: n * (n-1)

• Reliability:

  • High reliability due to multiple paths for a message; system continues to work even if one cable fails.

• Cost:

  • High cost due to a large number of cables needed (e.g., 10 devices require 45 cables).

• Security:

  • High security since messages sent between devices are not visible to others.

• Disadvantages:

  • High maintenance due to a large number of cables.

• Point-to-Point Communication:

  • Supports dedicated communication between devices, not multi-casting.

Star Topology (Hub Topology)

• Definition: Devices are connected through a centralized hub.

• Key Elements: Number of Cables and Ports

  • Cables: n (for 'n' devices)
  • Ports per Device: 1
  • Total Ports: n

• Reliability:

  • Low reliability due to single point of failure at the hub.

• Cost:

  • Lower cost compared to mesh topology.
  • Higher cost for the hub itself but overall less expensive than mesh.

• Security:

  • Moderate security since a hub broadcasts messages to all devices.
  • Although security measures can be implemented, by default it is low.

• Point-to-Point Communication:

  • Supports point-to-point communication but not multipoint.

Conclusion

• Covered basics of mesh and star topologies.
• Other topologies (Bus, Ring, Hybrid) and more details to be covered in next videos.

Note

• Refer to the shared video link for in-depth hub functionality information.

Thank You!