Network Topologies

Network topologies refer to the arrangement and connection patterns of computers in the network. It is the physical layout of the terminals, links, and computers in the network. Network topology can be defined as the cabling structure or geographical arrangement of computers in the network. It is the physical layout of the terminals, links, and computers in the network. Network topology can be defined as the cabling structure of the geographical arrangement of computers in a Local Area is known as Network Topology or LAN Topology. Network topologies are of several types. Some topologies used in LAN are as follows:
  1. Bus or Linear topology
  2. Star Topology
  3. Ring Topology
  4. Tree Topology
  5. Mesh Topology

a. Bus or linear topology

Bus Topology is the simplest of the network topologies. In this type of topology, all the nodes (computers as well as servers) are connected to a single cable with the help of interface connectors. This central cable is called the backbone of the network and is known as Bus. Every workstation communicates with the other devices through this Bus. It’s every end has a terminator and the terminator stops the flow of data out of the bus. In this network, if the cable breaks, it affects the whole network. There is a maximum chance of collision of data.
bus topology diagram hand drawn

Advantages of Bus Topology

  • It is easy to set up and extend.
  • Bus topology is comparatively cheaper.
  • The cable length is required for this topology is the least compared to other networks.
  • Linear Bus network is mostly used in small networks.

Disadvantages of Bus Topology

  • If the main cable (i.e. bus) encounters any problem, the whole network breaks down.
  • There is a maximum chance of collision of data.
  • It is difficult to detect and troubleshoot fault at the individual stations.

b. Star Topology

This is the most commonly used and popular topologies in LAN. In this topology, all the components of the network are connected to the central device (which may be a hub, a router, or a switch). unlike Bus topology, where nodes are connected to a central cable, here all the workstations are connected to a central device with a point-to-point connection. So it can be said that every computer is indirectly connected to every node with the help of a hub or switch.
All the data on the star topology passes through the central controlling device before reaching the intended destination. Hub acts as a junction to connect different nodes in a star topology. It also manages and controls the entire network system. Central device can also communicate with other hubs of different networks. Unshielded Twisted Pair (UTP), Ethernet cable, is used to connect workstations to the central nodes. In this network, if the central point (server) fails, the whole network fails but the failure of one computer doesn’t affect the rest of the network. There is no chance of data collision.
star topology diagram hand drawn

Advantages of Star Topology

  • Star topology provides much better performance in comparison to bus topology.
  • In this topology, new nodes can be added easily without affecting the rest of the network.
  • Centralized management helps in monitoring the network.
  • Failure of one node or link doesn’t affect the rest of the network.

Disadvantages of Star Topology

  • If the central device (hub) fails, the entire network will break down.
  • The use of a hub, a router, or a switch as the central device increases the overall cost of the network.
  • Performance, as well as the number of nodes that can be added in such topology, is dependent on the capacity of the central device.

c. Ring Topology

In-Ring Topology, all the nodes are connected to each other in such a way that they make a closed circular loop. In this topology, one computer is connected to other components on either side and it communicates with these two adjacent neighbors. There is no master computer to control data communication in a ring topology. This network provides equal access for all computers so, if one of the computers fails, it impacts all the computers in the network. There is no chance of data collision because data are traveled in one direction only that is clockwise or anti-clockwise. It is an example of peer to peer network mode.
In-ring topology, sending and receiving of data takes place with the help of TOKEN. The token contains a piece of information along with data that is sent by the source computer. This token then passes to the next node, which checks if the signal is intended for it. If yes, it receives it and passes the empty to into the network, otherwise passes the token along with the data to the next node. This process continues until the signal reaches its intended destination.
ring topology diagram hand drawn

Advantages of Ring Topology

  • This type of network topology is very organized so, it helps to reduce the chances of data collision.
  • There is no need for a network server to control the connectivity between workstations.
  • Additional components do not affect the performance of the network.
  • Each computer has equal access to resources.

Disadvantages of Ring Topology

  • Each packet of data must pass through all the computers between source and destination. So, makes it slower than Start topology.
  • If one workstation or port goes down, the entire network gets affected.
  • The network is highly dependent on the wire which connects different components.

d. Tree Topology

This is one of the hybrid topologies. Tree topologies integrate multiple star topologies together onto a bus. In the simplest form, only hub devices connect directly to the tree bus, and each hub functions as the “root” of a tree of devices. This bus/ star hybrid approach supports future expandability of the network much better than a bus (limited in the number of devices due to the broadcast traffic it generates) or a star (limited by the number of hub connection points) alone.
tree topology diagram hand drawn

Advantages of Tree Topology

  • In this topology, there is point-to-point writing for individual segments.
  • It is supported by several hardware and software vendors.
  • It is easy to add new branches.
  • A large number of computers can be connected.
  • There is no disruption to the network while connecting and removing devices.

Disadvantages of Tree Topology

  • The overall length of each segment is limited by the type of cabling used.
  • If the backbone line breaks, the entire segment goes down.
  • More difficult to configure and wire than other topologies.

e. Mesh Topology

Mesh topologies involve the concept of routes. unlike each of the previous topologies, messages sent on a mesh network can take several possible paths from source to destination. Some WANs, most notably the Internet, employ mesh network routing. In a mesh network, every device connects to every other by a communication cable. The control is distributed with each node deciding its communication priorities.
mesh topology diagram hand drawn

Advantages of Mesh Topology

  • It is reliable because any link failure will affect only direct communication between the nodes connected by that link.
  • Each node of the network need not have individual routing capabilities.
  • Communication is very fast between two nodes.
  • Failure of the device does not affect the data transmission to the destination device.

Disadvantages of Mesh Topology

  • It is the most expensive network from the point of view of link cost.
  • Difficult to install/set up.
  • Difficult to reconfiguration.

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