Topology in Computer Network

 Topology

Topology defines the structure of the network of how all components are interconnected to each other.There are two types of topology: Physical and Logical. Physical topology is the geometric representation of all the node in a network.

Types of Topology

There are various type of topology which are given below :

1. Bus Topology

The bus topology is designed in such a way that tell the stations are connected through a single cable known as a backbone cable.Each node is either connected to the backbone cable by drop cable or directly connected to the backbone cable.

In case of Bus topology, all devices share single communication line or cable.Bus topology may have problem while multiple hosts sending data at the same time.

It is one of the simple forms of networking where a failure of a device does not affect the other devices. But failure of the shared communication line can make all other devices stop functioning. 

The configuration of a bus topology is quite simpler as compared to other typologies. The backbone cable is considered as a "single lane" through which the message is broadcast to all the stations.

2. Ring Topology 

In ring topology, each host machine connects to exactly two other machines, creating a circular network structure. When one host tries to communicate or send message to a host which is not adjacent to it, the data travels through all intermediate hosts. To connect one more host in the existing structure, the administrator may need only one more extra cable.

The data flow is one direction means it is unidirectional.The data flow in a clockwise direction. The most conman access method of ring topology is token passing.

Failure of any host results in failure of the whole ring.Thus, every connection in the ring is a point of failure. There are methods which employ one more backup ring.

3. Star Topology 

Star topology is an arrangement of the network in which every node is connected to the central device like hub, switch or router or a central computer.

The central computer is known as a server as a server, and the peripheral devices attached to the server are known as clients.Coaxial cable or RJ-45 cables are used to connect the computer.

As in Bus topology, hub acts as single point of failure. If hub fails, connectivity of all hosts to all other hosts fails. Every communication between hosts, takes place through only the hub.Star topology is not expensive as to connect one more host, only one cable is required and configuration is simple.

4. Tree Topology 

Tree topology combines the characteristics of bus topology and star topology.A tree topology is a type of structure in which all the computers are connected with each other in hierarchical fashion so it is also know as Hierarchical Topology.

The top most node in tree topology is know as root node, and all the other nodes are the descendants of the root node. There is only one path exist between two nodes for the data transmission. Thus it forms a parent-child hierarchy.

This topology divides the network in to multiple levels/layers of network. Mainly in LAN's, a network is bifurcated into three types of network devices. The lowermost is access-layer where computers are attached. The middle layer is known as distribution layer, which works as mediator between upper layer and lower layer. The highest layer is known as core layer, and is central point of the network, i.e. root of the tree from which all nodes fork.

All neighboring hosts have point-to-point connection between them.Similar to the Bus topology, if the root goes down, then the entire network suffers even.though it is not the single point of failure. Every connection serves as point of failure, failing of which divides the network into unreachable segment.

5. Mesh Topology

Mesh topology is an arrangement of the network in which computers are interconnected with each other through various redundant connections. there are multiple paths from one computer to another computer. It does not contain the switch, hub or any central computer which act as a central point of communication.The internet is the example of Mesh topology.

Hosts in Mesh topology also work as relay for other hosts which do not have direct point-to-point links. Mesh technology comes into two types:

Full Mesh: All hosts have a point-to-point connection to every other host in the network. Thus for every new host n(n-1)/2 connections are required. It provides the most reliable network structure among all network topologies.

Partially Mesh: Not all hosts have point-to-point connection to every other host. Hosts connect to each other in some arbitrarily fashion. This topology exists where we need to provide reliability to some hosts out of all.

6. Hybrid Topology

A network structure whose design contains more than one topology is said to be hybrid topology. Hybrid topology inherits merits and demerits of all the incorporating topologies.

When two or more different topologies are combined together is termed as Hybrid topology.The above picture represents an arbitrarily hybrid topology. The combining topologies may contain attributes of Star, Ring,and Bus topologies. Internet is the best example of largest Hybrid topology.