Network Topology

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Definition

• Topology is the way in which computer network is connected.
• Interconnection configuration to provide efficient communication.
• Arrangement of nodes, cables and connecting devices.

Types

1) Ring topology

• Each node connected to each other forming a ring like structure.
• Data packets travels from node to node as there is single path.
• Packet travels until it finds the final destination from node to node.
• Physically it is star topology but logically its a ring topology.
• Advantages:
  • Does not require a server.
  • Cable failure affects limited users.
  • Acts better in heavy network load.
  • Each node has access to token and opportunity to transmit.
• Disadvantages:
  • Failure of one node can affect the entire network.
  • Adding, removing or moving nodes affects the network.
  • Wiring is costly and network adapter cards are required.

2) Bus topology:

• All devices such as server, node, printer are connected to common shared cable called as a bus.
• T-connectors are used to connect each device.
• Buses are bidirectional hence all devices are capable to send and receive signals simultaneously.
• But some buses are unidirectional.
• Messages passes to each node, if it matches to its address it takes it, else it transmits to the next node.
• Bus cable is terminated at each end of node by placing terminators to prevent signal reflecting back.
• Advantages:
  • Failure of one node does not affect the network.
  • Good for smaller network in LAN.
  • Less expensive than star topology.
  • Easy to add devices or peripherals.
• Disadvantages:
  • Finite over speed and size.
  • Failure of main cable can shutdown the entire network.
  • Terminators are required at both ends.
  • Finding an error in network is difficult.

3) Star topology

• All nodes are connected to central hub.
• Hub routes the messages from source to destination.
• It acts like repeater for data flow
• Advantages:
  • Easy for installing, wiring and adding or removing nodes.
  • Node failure doesn't affect the network.
  • Simple to detect errors and faults.
  • Good for big network.
• Disadvantages:
  • Hub failure can shutdown whole network.
  • Expensive cabling is required.

4) Tree topology

• Central hub or root node is connected to other lower end nodes.
• Central hub manages and functions each node.
• Root node act as a server.
• Lower level nodes can be connected to next lower level.
• Point-to-point configuration wiring for each node.
• Advantages:
  • Easy to add or remove node.
  • Can be use for large networks.
• Disadvantages:
  • Central root or node failure can shut down entire network.
  • Hard for installing and configuring, compare to other topologies.

5) Mesh Topology

• Dedicated point-to-point link is established between nodes.
• It requires n(n-1)/2 links to connect n nodes.
• Advantages:
  • Any node failure doesn't affect the network.
  • Traffic load is very less because of dedicated link.
  • Privacy and security is maintained.
  • Fault detection and isolation is easy.
• Disadvantages:
  • Lot of cabling and i/o ports are required.
  • Installation and reconfiguring is harder.

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