What is computer network? Explain network topology with its advantages and disadvantages

Computer Network

A computer network is a telecommunication media through which connected computers are allowed to exchange data. Each computer in a network is known as node, and each node is connected through a medium using either connected or wireless media.

Internet is the best computer network in present.

Network Topology

The arrangement of nodes in a specific geometrical representation is known as topology.

There are 5 network topology, they are:

1. Star topology
2. Bus topology
3. Ring topology
4. Mesh topology
5. Tree topology

Star topology

In star topology, all the nodes are connected to the central hub. A wired/wireless connection is made through the central hub to the nodes. The hub to be used in the star topology network can be active or passive. Each node sends the data to the central hub from where it is resent to the destination node.

Advantages

1. If one node fails, it doesn't effects the whole system.
2. Installation of a new node is easy.
3. Adding new nodes does not effects the transmission time.

Disadvantage

1. If the central hub fails, the whole system collapse.
2. More cabling cost.

Bus topology

In bus topology, all the nodes are connected to one another linearly, one after the other. When one computer send the data, all of the computers on the network receives it, but the destination computer encodes and accepts the data while the others rejects.

Advantages

1. Easy installation.
2. Simple and ideal for small networks.
3. Cabling cost is low.
4. Easy to add new node by joining two cables with a BNC barrel connector.

Disadvantages

1. If one node fails, the entire system collapse.
2. Heavy network traffic means slow bus speed.
3. Only one computer can transmit data at a time while others have to wait, and there is no time-coordination between computers for transmitting time.

Ring topology

In ring topology, each node is connected as the representation of a ring, there is no terminal node. Each computer is connected to its next and last one. The data transmission in the ring topology is only in one direction. If a token (small message) is passed through the system, it is received by all the computers in the sequence until it reach the destination node.

Advantage

1. Every node is given equal preference.
2. Easy installation.

Disadvantage

1. If one node fails, the entire system collapse.
2. Difficultly in troubleshoot.
3. Adding /removing nodes disturbs the whole network.

Mesh topology

In mesh topology, every node is connected to each and every computer in the network system. It has n(n-1)/2 links, where n is the number of computers in the system.

Advantages

1. Every node is connected to each node in the system hence there is no network traffic.
2. If node fails, it does not affects the whole system.
3. Diagnosis of fault is easy due to point to point connection.

Disadvantages

1. More cabling cost.
2. Difficulty in installation process.
3. Expensive.

Tree topology

In tree topology, nodes of each branch are connected to the central hub as in star topology. Not every computer is connected to the central hub whereas some of them are connected to the secondary hub which is connected to the central hub.. The secondary hub may be active or passive. 

Advantages

1. It allows nodes to isolate their priorities from the whole network system.
2. It allows more devices to be connected to the hub as the hub provides a physical connection between the nodes

Disadvantages

1. More cabling cost.
2. Expensive.
3. If central hub fails, the whole system collapse.