Introduction

 

NETWORK-

A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network.

 Computer network mean a collection of autonomous computers interconnected by a single technology. Two computers are said to be interconnected if they are able to exchange information.

 The connection need not be via a copper wire; fiber optics, microwaves, infrared, and communication satellites can also be used.

USES OF COMPUTER NETWORKS

Business Applications 

1.      To distribute information throughout the company (resource sharing). sharing physical resources such as printers, and tape backup systems, is sharing information

2.      Client-server model. It is widely used and forms the basis of much network usage. 

3.      Communication medium -among employees. Email (electronic mail), which employees generally use for a great deal of daily communication.  Telephone calls between employees may be carried by the computer network instead of by the phone company. This technology is called IP telephony or Voice over IP (VoIP) when Internet technology is used. 

4.      Desktop sharing lets remote workers see and interact with a graphical computer screen

5.      Doing business electronically, especially with customers and suppliers. This new model is called e-commerce (electronic commerce) and it has grown rapidly in recent years.

 

 Home Applications 

Peer-to-peer communication

 Person-to-person communication

Electronic commerce

entertainment.(game playing,)

 

Characteristics of a data communications system -depends on four fundamental: delivery, accuracy, timeliness, and jitter.


1.   Delivery. The system must deliver data to the correct destination. Data must be received by the intended device or user and only by that device or user.


2.       Accuracy. The system must deliver the data accurately. Data that have been altered in transmission and left uncorrected are unusable.


3.      Timeliness. The system must deliver data in a timely manner. Data delivered late are useless. In the case of video and audio, timely delivery means delivering data as they are produced, in the same order that they are produced, and without significant delay. This kind of delivery  is called real-time transmission.


4.      Jitter. Jitter refers to the variation in the packet arrival time. It is the uneven delay in the delivery of audio or video packets. For example, let us assume that video packets are sent every 30 ms. If some of the packets arrive with 30-ms delay and others with 40-ms delay, an uneven quality in the video is the result.

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