The key elements of the communication model are as follows

The key elements of the communication model are as follows:

·         Source:

This device generates the data to the transmitted; examples are telephones and personal computers.

·         Transmitter:

usually, the data generated by a source system are not transmit directly in the form in which they were generated. Rather, a transmitter transforms and encodes the information in such a way as to produce electromagnetic signal that can transmitted across some sort some sort ol transmission system. For example, a modem takes a digital bit stream from an attached device such as a personal computer and transforms that hit stream into an analog signal that can he handled by the telephone network.

·         Transmission system:

This can be a single transmission line or a complex work connecting source and destination.

·         Receiver:

 The receiver accepts the signal from the transmission system and converts it into a form that can he handled by the destination device. For exampIe, a modem will accept an analog signal coming from a network or through transmission line and convert it into a digital hit stream.

·         Destination:

Takes the incoming data from the receiver

   Another example is the exchange of voice signals between two telephones over the

   same network. 

STANDARD AND ARCHITECTURE

A Communication model

We begin our study with a simple model of communications. Illustrated by the block diagram in Figure below

General block diagram

The fundamental purpose of a communication system is the exchange of data between two parties. Figure below b presents one particular example. Which is communnication between a workstation and a server over a public telephone network.

COMMUNICATION SYSTEMS AND STANDARD

One effect of these trends has been a growing overlap of the computer and communications industries, from component fabrication to system integration. Another result is the development of integrated systems that transmit and process all types of data and information. Both the technology and the technical standards or organizations are driving toward integrated public systems that make virtually all data and information sources around the world easily and uniformly accessible.

This topic aims to provide a unified view of the broad field of data and computer communications. The organization of the hook reflects an attempt to break this massive subject into comprehensible parts and to build Piece by piece. A survey of the state of the art. This introductory chapter begins with a general model of communications.

MOVING DATA THROUGH NETWORK

INTRODUCTION

Data communications deals with the transmission of signals in a reliable and efficient  manner. Topics covered include signal transmission, transmission media, interfacing, data link control, and multiplexing.

Networking deals with the technology and architecture of the comniunications networks used to interconnect communicating devices. This field is generally divided into the topics of local area networks (LANs) and wide area networks (WANs).

VPN

The Virtual Private Network - VPN - has attracted the attention of many organizations looking to both expand their networking capabilities and reduce their costs.

The VPN can be found in workplaces and homes, where they allow employees to safely log into company networks. Telecommuters and those who travel often find a VPN a more convenient way to stay "plugged in" to the corporate intranet

What Exactly Is A VPN?

A VPN supplies network connectivity over a possibly long physical distance. In this respect, a VPN is a form of Wide Area Network (WAN).

The key feature of a VPN, however, is its ability to use public networks like the Internet rather than rely on private leased lines. VPN technologies implement restricted-access networks that utilize the same cabling and routers as a public network, and they do so without sacrificing features or basic security.

A VPN supports at least three different modes of use:

·         Remote access client connections

·         LAN-to-LAN internetworking

·         Controlled access within an intranet perspective.