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Network Topologies

Topology refers to: how the devices are connected. This includes - Physical connection - Logical connection - Hybrid (Both physical and logical)

Bus Topology

Bus.png

  • When a message is sent, all the intermediate nodes receives the message but will discard it.
  • At the ends of the bus, there will be a terminator node which prevents the bounce back of signals

Advantages

  • Easy to implement
  • Cost efficient for small networks

Disadvantages

  • Collisions
  • If the bus fails, entire network goes down
  • Troubleshooting is difficult

Star Topology

Star.png

  • The device in the center would be a hub or a switch
  • The hub acts as a controller

Advantages

  • When one device fails, network remains intact
  • Easy to install and manage
  • Easy to add and remove devices

Disadvantages

  • When the central hub fails, the entire network fails
  • Require more cables compared to bus

Ring Topology

Ring.png

  • Each device is connected to exactly two others, forming a circle
  • Data travels in one direction(unidirectional) or both(bidirectional)

Advantages

  • Simple and easy to implement

Disadvantages

  • If one device fails, the entire network fails
  • Adding or removing a device disrupts the network
  • Troubleshooting is hard

Token Ring

Token Ring.png

  • A token (control frame) circulates around the ring
  • Only device holding the token can transmit
  • If a device receives a message with token, it checks the address and forwards.
  • When the message receives the address, it attaches a flag and forwards
  • When the message comes back to the sender with the flag, it removes the flag and the message and forwards the token, which the next device can use.

Advantages

  • No collisions
  • Predictable performance under heavy load also

Disadvantages

  • More complex
  • Slower compared to modern Ethernet
  • Token loss or duplication can cause issues

Mesh Topology

Mesh.png

  • Every machine is connected to every other machine
  • For n nodes, $\frac{n(n-1)}{2}$ connections are needed

Advantages

  • Very reliable
  • High fault tolerance
  • Supports high traffic (multiple paths)

Disadvantages

  • Expensive
  • Complex installation and maintenance
  • Not scalable for a very large network

P2P Topology

P2P.png

  • Point to Point topology
  • Direct connection between two nodes only
  • Can be wired or wireless

Advantages

  • Very simple, minimal configuration
  • Maximum bandwidth dedicated to the link
  • Very reliable for two-device communication

Disadvantages

  • Only connected two nodes (not scalable)

NSL is physically STAR topology But logically its Bus or Ring (inside the switch) => Its Hybrid

Note

Hybrids are of 2 types

  • STAR + Bus
  • STAR + Ring