Topology in Computer Networks

Network Topology
The arrangement in which elements like links, nodes of common network are connected is known as network topology. Example of Network topology is found in local area network.

We have five types of topologies:
1.) Mesh Topology
2.) Bus Topology
3.) Ring Topology
4.) Star Topology
5.) Hybrid Topology

1.) Mesh Topology: In mesh topology every device is connected with another device via a particular channel.

2.) Bus Topology: The bus topology is used when a network installation is small, simple and temporary.
On a typical bus network cable is just one or more wires with no active electronics to amplify the signal or pass it along from computer to computer. This makes the bus a passive topology. Only one computer can send data at one time therefore the number of computers attached to a bus network can significantly affect the speed of the network a computer must wait until the bus is free before it can transmitted.

Advantages of bus topology:

• Easy to install
• Backbone cable can be laid along the most efficient path 
• Less cable length required then match, rain, star entry except. 
• It is easy to expand the bus

Disadvantages of Bus Topology:

• Difficult reconfiguration 
• Adding and deleting requires redesigning of backbone.
•  New devices can not easily added. 
• Difficult fault isolation.
•  In case of bus fault the areas such signals back to origin creating noise.
•  Signal reflection at-taps can degrade equality or service.

Ring topology:

In a ring topology each computer is connected to the next computer with the last one connected to the first one. Every computer is connected to the next computer in the ring and retransmits what it receives from the previous computer. The message flow around the ring in one direction.

Advantages of ring topology:

• Because every computer is given equal access to the token no 1 computer can monopolize the network.
•  The fair sharing of network allows the network to degrade gracefully as more users are added.
•  Fault isolation is easy.

Disadvantages of ring topology:

• It is difficult to troubleshoot a ring network.
•  Adding and removing computers disrupts the network.
• Failure of one computer on the name can affect the whole network.
•  Uni-directional traffic can be disadvantage.
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Star Topology:

Star topology consists of a Central node to which all other nodes are connected by a single path. It is the topology used in most existing information networks involving data processing or voice communications. The most common example of star topology is IBM 370 installations.

Advantages of star topology:

• Ease of service.
•  One device per connection.
•  Centralised control problem diagnosis.
•  Simple access protocols.

Disadvantages of star topology:

• Long cable length.
•  Difficult to expand.
•  Central node dependency.

Hybrid topology:

Hybrid topology is a topology that uses two or more different network topologies.

Advantages of hybrid topology:

• It is extremely flexible.Ii
• Its very reliable. 
• It is easily scalable.

Disadvantages of hybrid topology:

• It is expensive.
•  The design of hybrid topology is very complex.
• Hardware changes are required in order to connect topology to another topology