What is a Network?
A network is a group of computers or computer like devices connected together to share the resources like file, printer, services etc. A typical network contains users working at workstations (also known as client), running clientt operating systems like Windows XP and store their files on a central server. The server computer has more resources like memory, disk space and more processing power compared with client computers. The server machine also run an Operating System, which has more precessing capabilities compared with the client machine. The server may be installed with special software, which is helps it so function as a server. The special software allows file and print services, serve web pages, transfer emails etc.
LAN, MAN and WAN Local Area Network (LAN) is a network, which is limited to a single building, college campus etc. A Wide Area Network (WAN) spans over multiple geographic locations, which is composed of multiple LANs. A Metropolitan Area Network (MAN) refers to a network, which is located in a city or metropolitan area. If an organization has multiple offices in a city, the term that refers the network is called MAN.
Internet, Intranet, Extranet
• Internet. The Internet is a worldwide, publicly accessible network of interconnected computer networks that transmit data using the standard Internet Protocol (IP). The terms World Wide Web (WWW) and Internet are not the same. The Internet is a collection of interconnected computer networks, linked by copper wires, fiber-optic cables, wireless connections, etc. Web is a collection of interconnected documents and other resources, linked by hyperlinks and URLs. The World Wide Web is one of the services accessible via the Internet, along with various others including e-mail, file sharing, online gaming etc.
• Intranet. An intranet is a private network that is contained within an enterprise. It may consist of many interlinked local area networks and also use leased lines in the wide area network. The main purpose of an intranet is to share company information and computing resources among employees.
• Extranet. An extranet can be viewed as part of a company’s intranet that is extended to users outside the company like suppliers, vendors, partners, customers, or other businesses.
Logical Classification of Network
A network can be divided into two categories. 1) Peer-to-Peer 2) Client-Server
1) Peer-to-Peer. A Peer-to-Peer network has no dedicated servers. Here a number of workstations are connected together for the purpose of sharing information or devices. All the workstations are considered as equal. Any one computer can act as client or server at any instance. This network is ideal for small networks where there is no need for dedicated servers, like home network or small business establishments or shops. The Microsoft term for peer-to-peer network is “Workgroup”. Typically a workgroup contain less than 10 workstations. Normal workstation operating systems are Windows 95/98, ME, XP, NT Workstation, 2000 professional, Vista, RHEL Workstation etc.
2) Client-Server. The client/server model consists of high-end servers serving clients continuously on a network, by providing them with specific services upon request. The classifications for servers are
a) File server, can be used to store the client documents and files centrally. An ideal file server should have large amount of memory, fast hard-disks, multiple processors, fast network adapters, redundant power supplies etc.
b) Print server, which redirects print jobs from clients to specific printers.
c) Application server, which allows clients to run certain programs on the server, and enables multiple users to common applications across the network. Typically Application Servers run business logic. Which means, every business is different and the Application Server is the Server Software which controls the business process. Examples for Application Servers are SAP BASIS, WebLogic, WebSphere etc.
d) Database server, which allows authorized clients to view, modify and/or delete data in a common database. Examples of Database Management Systems are Oracle 8i/9i/10g, MS SQL Server 2000/2005/2008, DB2, MySQL etc.
e) Directory Servers, which allows the central administration of users and resources. Examples of Directory Servers are Active Directory, NDS (Novell Directory Services), Fedora Directory Server, openLDAP etc.
Server needs a Network Operating System to function. The most popular NOSs are Windows NT, Windows 2000, Windows 2003, Unix, GNU/Linux, Novell Netware etc. These Server Operating Systems will provide the services, which are requested by the client computers.