Network Topology

Network topology determines how devices are connected and which components are used inside topology. Topology classified into two types- Physical and Logical

Physical Topology : – Defines how devices are physically connected

Logical Topology : – Defines how data is move inside physical topology

  • Below are the fives types of topology
    • Star Topology
    • Mesh Topology
    • Bus Topology
    • Ring Topology
    • Hybrid Topology

Star Topology

  • In star topology all devices are connected to a central device
  • This central device is known as hub or switch
  • There is no direct communication between devices. All communication between devices always passes through central device

Advantages

  • Only single IO port require on a device to connect to a central device
  • Easy to install
  • As compared to Mesh topology, less amount of cables are require to implement star topology
  • Easy to detect fault or troubleshoot
  • Star is a robust topology. If a link between single device and hub fails, it doesn’t impact entire network. Only that devices is placed out of network. Remaining devices are able to communicate with each other

Disadvantages

  • If central devices goes down then entire network is impacted
  • It requires maintenance of central device

Mesh Topology

  • In mesh topology, each node is directly connected to every other node in the network.
  • There is no use of central device in the network.
  • In the above network diagram, there are four nodes. Each node in the network has connection to all nodes. Node 1 has connections to all 3 nodes(node 2, node 3 and node 4).
  • We can use formula (N-1) to calculate number of cables and IO port require on each node. N is the number of nodes
  • In the above network, there are 4 nodes so using formula N-1 (4-1) will provide result 3. 3 is the number of cables and IO ports require on each node to connect all nodes in the network.
  • Mesh Topology is classified into two types
    • Full Mesh
    • Partial Mesh

Advantages

  • It is a robust network
  • It provides security due to direct communication between nodes
  • Easy to troubleshoot

Disadvantages

  • Configuration and installation is difficult
  • Cost increases as the number of nodes in the network increases
  • Require multiple NIC card on nodes

BUS Topology

  • Bus topology also referred to as line topology
  • All devices are connected to a single cable
  • This single cable where all devices are connected also known as backbone or main cable
  • Communication always flow in one direction and bidirectional communication not supported
  • Type of cable using as a backbone cable depends on the type of network card attached on device
  • Backbone cable consists of terminator at both end of the cable

Advantage

  • Easy to add and remove devices
  • Cost is less as compared to other topologies such as Mesh or Star
  • Failure of one device does not have effect on communication of other devices
  • Easy to expand by connecting two cables

Disadvantage

  • Performance decreases as the number of devices increases in the network
  • If main or backbone cable fails then the entire network goes down
  • Collision occurs if traffic increases. CSMA/CD protocol is use to prevent collision on the network
  • Terminator is require to prevent bouncing of signal

Ring Topology

  • Ring topology also known as ring network
  • Each node in connected to its neighboring nodes forming a shape of ring
  • It make use of token for forwarding data over the network
  • Data flow on this topology can be arranged either in clockwise or anti-clockwise direction

Advantages

  • Packet collision is minimize due to data flow is in one direction
  • There is no need of server to control communication on the topology
  • Less expansive as compared to other topologies such as mesh or star

Disadvantages

  • Single break in the cable can make entire network down
  • Difficult to add and remove device
  • Difficult to troubleshoot

Hybrid Topology

  • Hybrid topology is the combination of two or more topologies
  • Examples
    • Star and Mesh topology
    • Bus and Star topology

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