What is Topology ? What are types of topology ? What is advantages and disadvantages of various Topology ?

                               Topology refers to the way in which the network of computers is connected. Each topology is suited to specific tasks and has its own advantages and disadvantages. The choice of topology is dependent upon type and number of equipment being used, planned
applications and rate of data transfer required, response time, and cost. Topology can also be defined as the geometrically interconnection pattern by which the stations (nodes/computers) are connected using suitable transmission media (which can be point-to-point and broadcast).
 Various commonly used topologies are as follows:

1.Mesh Topology :-

In this topology each node or station is connected to every other station .

The key characteristics of this topology are as follows:
o Fully connected
o Robust – Highly reliable
o Not flexible
o Poor expandability
In MeshTopology two nodes are connected by dedicated point-point links between them. So the total number of links to connect n nodes = n(n-1)/2; which is proportional to n2 .

Media used :-
for the connection (links) can be twisted pair, co-axial cable or optical fiber.

With this topology there is no need to provide any additional information, that is from where the packet is coming, along with the packet because two nodes have a point-point dedicated link between them. And each node knows which link is connected to which node on the
other end.
Mesh Topology is not flexible and has a
poor expandability as to add a new node n
links have to be laid because that new node
has to be connected to each of the existing
nodes .

Advantages:-
- if any device failed in network not affecting network.
- A fault is diagnosed easily.
- Good in privacy and security.
- it is relatively power.

 Disadvantages :-
 - it is costlier.
- it is complex.

2.BUS Topology :-

            A bus topology is a topology for a Local Area Network in which all the nodes are connected to a single cable. The cable to which the nodes connect is called a "backbone". 

* Advantages :-

- easy to connect.

- low cost

- require less cable

- best in small organisation.

*Disadvantages :-

- if backbone cable fail then entire network will shut down.

- difficult to identify failure problem

- can't used in large network.


3. STAR  Topology :-

Star topology is a network topology where each individual piece of a network is attached to a central node (often called a hub or switch). The attachment of these network pieces to the central component is visually represented in a form similar to a star. Star topology is also known as a star network.

Advantages :-

- If one node or its connection breaks, it doesn’t  affect the other computers nor their connections

- Devices can be added or removed without disturbing the network

- They work well under heavy loading

- It is possible to create very large network.

Disadvantages :-

- An expensive network layout to install because of the number and length of cables needed to wire each host to the central hub


- The central hub is a single point of failure or the network

4. Ring Topolology :-

     ln ring topology all  devices are connected in a ring and pass information to or from each other according to their adjacent proximity in the ring structure. This type of topology is highly efficient and handles heavier loads better than bus topology.

Advantages :-
-Very orderly network where every device has access to the token and the opportunity to transmit

-Performs better than a bus topology under heavy network load

-Does not require a central node to manage the connectivity between the computers

-Due to the point to point line configuration of devices with a device on either side (each device is connected to its immediate neighbor), it is quite easy to install and reconfigure since adding or removing a device requires moving just two connections.

-Point to point line configuration makes it easy to identify and isolate faults.


-Reconfiguration for line faults of bidirectional rings can be very fast, as switching happens at a high level, and thus the traffic does not require individual rerouting.

Disadvantages :- 

-One malfunctioning workstation can create problems for the entire network. This can be solved by using a dual ring or a switch that closes off the break.

-Moving, adding and changing the devices can affect the network

-Communication delay is directly proportional to number of nodes in the network

-Bandwidth is shared on all links between devices


-More difficult to configure than a Star: node adjunction = Ring shutdown and reconfiguration

5. Hybrid Topology :-

Hybrid topology is an interconnection of two or more basic network topologies, each of which contains its own nodes.

The resulting interconnection allows the nodes in a given basic topology to communicate with other nodes in the same basic topology as well as those in other basic topologies within the hybrid topology.

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