INTRODUCTION TO COMPUTER NETWORK

What is Computer Network ?

1.         “A Computer network refers to the collection of two or more computers connected to each other so that they can exchange information, such as messages or documents, and share resources, such as disk storage or printers.” In other way, “when two or more computers are interconnected for sharing information and resources then that arrangement is called a Network.”

2.         Today, computer networks are the core of modern communication. The scope of communication has increased significantly in the past decade, and this boom in communications would not have been possible without the progressively advancing computer network. The Internet or World Wide Web has reached to the core level of our personal, occupational and educational spheres of life. A day with the internet in present corporate world can be only possible in a nightmare, not in real life. And, the internet is nothing but just a outcome of networking.

Types of Computer network

3.         Networking is so vast a thing that, it can be classified in multi dimensional ways. But, most of the time the classification of networks is described as per physical or organizational extent or scale. As per that concept, network types are as follows :

a.         Local Area Network (LAN)  A local area network (LAN) is a network that connects computers and devices in a limited geographical area such as home, school, computer laboratory, office building, or closely positioned group of buildings. Note that the term LAN doesn’t mean that the network is small with fewer PCs. A LAN can, in fact, contain hundreds of computers but only located within close proximity to each other. Usually a LAN is contained within a single building, but can extend to several buildings on a campus. A LAN can be subdivided in to many classes like:

           

            a.         Personal area network.

            b.         Home network.          

            c.         Small office network

            d.         Lab network

            e.         Campus network etc

b.         Metropolitan Area Network (MAN) This type of network is larger than a LAN. Typically, a MAN connects two or more LANs within a few adjacent campuses, buildings, cities or small area. A MAN can be in various forms, such as:

            (1)        Enterprise private network.                

            (2)        Business Network

            (3)        Internet service provider etc

c.         Wide Area Network (WAN).  A wide area     network (WAN) is a computer network that covers a large geographic area such as a city, country, or spans even  intercontinental  distances, using a communications channel that combines many types of media such as telephone lines, cables, and air waves.WAN often uses  transmission facilities provided by common carriers, such as telephone companies.

d.    Global Area Network (GAN). A GAN refers to a network composed of different interconnected networks that cover an unlimited geographical area. The term is loosely    synonymous with Internet, which is considered a global area network. A GAN is composed of satellite, mobile network, submarine cable and other public communication channels which are  brought together by different methods of interfacing and collaboration.

4.         Network Architecture.  Each elements of a network (e.g. computer, printer, servers) have got particular relationship. This relationship is otherwise called as network architectures. There are essentially two types of network architectures, such as:

           

 a.         Client Server Network. A network architecture in which each computer or process on the     network is either a client or a server. Servers are powerful computers or processes  dedicated to managing disk drives (file servers), printers (print servers), or network traffic (network server).Clients are PCs or workstations on which users run applications. Clients rely on servers for resources, such as files, devices, and even processing power.

Fig: Client-Server Network b.         Peer to peer network (P2P). P2P networking is a distributed network architecture that divides tasks or workloads among peers. Peers are equally privileged and responsible in the network. Peers make a portion of their resources, such as processing power, disk storage or network bandwidth, directly available to other network participants, without the need for central coordination by servers. Peers are both suppliers and consumers of resources, whereas, in client–server architecture, servers supply (send), and clients consume (receive). Fig: Peer to peer network (P2P)

5.         Purposes of Networking. Purpose of bringing computers and devices into a networks are all about sharing. Specifically, networks are about sharing three things: information, resources, and applications.

            a.  Sharing information.  Networks allow users to share information in several  different ways. The most common way of sharing information is to share individual files. For  example, two or more people can work together on a single spreadsheet file or word-processing document. In addition to sharing files, networks allow users to communicate with each other by messaging applications, emails, online meetings and video conferences over the network.

           

            b.         Sharing resources.   Certain computer resources, such as printers or hard drives, can be set up so that network users can share them. Sharing these resources can result in significant cost savings. An internet connection sharing network shares a single internet connection over the network backbone.

            c.         Sharing applications.           One of the most common reasons for networking in many businesses is so that several users can work together on a single business application. For      example, an accounting department may have accounting software that can be used from several computers at the same time. Likewise, Database or other multi-user applications can           also be shared within a network.

           

6.         Organizational Scope of Network.             Networks are typically managed by organizations which own them. According to the owner's point of view, networks are seen as intranets or extranets. A special case of network is the Internet, which has no single owner but a distinct status when seen by an organizational entity – that of permitting virtually unlimited global connectivity for a great multitude of purposes. Here is the pen picture of these scopes.

            a.         Intranets.        An intranet is a set of networks that is under the control of a single administrative authority. That administrative entity closes the intranet to all but specific,    authorized       users. Most commonly, an intranet is the internal network of an organization. A large intranet will typically have at least one web server to provide users with organizational        information. Intranets are parts or extensions of a computer network, usually a LAN.

            b.         Extranets.      An extranet is a network that is limited in scope to a single organization or entity and also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities—a company's customers may be given access to           some part of its intranet—while at the same time the customers may not be considered trusted           from a security standpoint. An extranet cannot consist of a single LAN; it must have at least one             connection with an external network.

7.         The Internet.              The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite (TCP/IP) to serve billions of users worldwide. It is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless and optical networking technologies. The Internet carries a vast range of information resources and services, such as the inter-linked hypertext documents of the World Wide Web (WWW) and the infrastructure to support email.