Basic Newtwork

What is Network

 A network is defined as a group of computer systems linked together. Devices, they are connected in network are called Networking devices. 

Example.

The Internet is excellent example of network. The Internet is networks of network, which connects millions of user over world.

Note: As per the report released by “Internet World State” more than 1/3 of the world population now has access to the internet. The internet plays very important role in our daily lives and its impact will continue to grow. The current internet architecture designed 40 year ago is facing unprecedented challenges in many aspects, especially in the commercial context.

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Network devices

• Desktop computers, Webcams, laptops, mainframes, thin clients, Smartphones and tablets and servers

• Firewalls, Consoles, Repeaters, Bridges, Network Interface cards, Switches, hubs, modems, and routers etc.

Topology 

How to design a network that is topology. Topology is a layout of network. How to arrange network devices in network, So it's only describe the structure of network.

Types of topology

BUS Topology

In Bus topology, every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called Linear Bus topology.

Features of Bus Topology

• One directional Data transmission.
• Every device is connected to a single cable

Advantages:

• cost effective.
• Used in small networks.
• It is easy to understand.
• Easy to expand joining two cables together.

Disadvantages:

• Cables fails then whole network fails.
• If network traffic is heavy or nodes are more the performance of the network decreases.
• Cable has a limited length.
• It is slower than the ring topology.

RING Topology

In this topology, each computer is connected to another computer in the form of ring or closed loop, with the last one connected to the first. Exactly each devices have two neighbours.

Data communication : Token used for data communication in Ring topology. Token contains a piece of information which along with data is sent by the source node . This token then passes to next node, which checks if the data is intended to it. If yes, it receives it and passes the empty to into the network, otherwise passes token along with the data to next node. This process continues until the data reaches its intended destination.
The nodes with token are the ones only allowed to send data. Other nodes have to wait for an empty token to reach them.

The transmission is unidirectional, but it can be made bidirectional by having 2 connections between each Network Node, it is called Dual Ring Topology. In Dual Ring Topology, two ring networks are formed, and data flow is in opposite direction in them. Also, if one ring fails, the second ring can act as a backup, to keep the network up. Data is transferred in a sequential manner that is bit by bit. Data transmitted, has to pass through each node of the network, till the destination node.

This network is usually found in offices, schools and small buildings.

Advantages :

1.     Ring topology all the traffic flows in only one  direction at very high speed.

2.     Its performance is better than that of Bus topology, when the load on the network increases

3.      Additional components do not affect the performance of network.

4.      Each computer has equal access to resources.

5.     Cheap to install and expand

Disadvantages :

1.     Network is highly dependent on the wire which connects different components.

2.     Add or delete nodes from network, disturbs the whole network.

3.     Failure of one node, entire network get affected.

STAR Topology:

In this topology all the computers or nodes are connected to a single central device through a cable. This hub/Switch/Router is the central node. All computer or nodes are connected to the central device.

All the in Star topology passes through central device before reaching the destination. This central device or hub can communicate with other hubs in different network.

Advantages :

1.     Fast performance with few nodes and low network traffic.

2.     Centralized management

3.     Easy to connect new nodes.

4.     Hub can be upgraded easily.

5.     Easy to troubleshoot.

6.     Easy to setup and modify.

7.     If any node fail that will never affect to other.

Disadvantages :

1.     Central device has its own drawback. If central device fail, whole network goes down.

2.     Expensive to use.

3.     Performance is based on the capacity of the hub.