When computers and other devices such as printer are connected to each other through a medium then this arrangement is called network. A network provides the facility for communicating data and information between different departments in an organization. Computerization of banks is an example of this. Another important advantage of networking is that it allows resources such as a printer, scanner, modem etc. to be shared among all the systems connected to the network.
Computer networks provide many services besides travel reservations and financial transactions, but these applications show two important features of computer networks:
- They provide shared access to information, such as account balances or airline flight status.
- They allow the movement of data, such as flight status updates, or financial transfers.
Advantages of Networking: Networking serves four important purposes:
1. Resource Sharing: It allows departments to share hardware e.g. if there is only one laser printer in a company then networking allows each department’s computer to use this laser printer.
2. Reliability: A file can have copies on two or three different machines, so if one of them is unavailable (hardware crash), the other copies could be used.
3. Cost factor: A computer network saves time.
4. Communication Medium: Using a network, it is possible for 3 managers, working far apart, to prepare a financial report of the company.
Functions of a Computer Network: A networked computer can do many things which a standalone computer cannot do:
1. Share a single copy of a file among all the users, even simultaneously.
2. Transfer files from computer to computer or from one computer to the shared hard-disk on the server.
3. Share computer resources like printer, all types of disks and drives, modems, fax machines, scanners etc.
4. Share applications even of the entire network, thus, reducing the cost of purchasing. A multi-user license costs much less than buying a standalone license for each user.
5. Use e-mail for internal communications, inter-office notes etc., creating an almost paperless office.
Components used in a Computer Network: A network is a combination of different components. The most essential components of a single network are:
1. Servers: Servers are the faster computers to run different software/ programs, store and process information and to provide a human interface of the users to be able to use the networked computers.
2. Nodes: Nodes are the computers on the Network which are provided to the users to carry out their tasks using the network.
3. LAN Cable: This is the medium over which the information travels from computer to computer
4. Network Operating System: It is used to control the movement of information on the network.
5. Network Interface Card: This is used to connect the cables to the computers.
Types of Networks: Networks can be classified as follows:
(1) Local Area Network (LAN): A LAN is a system of interlinked personal computers in a localized area, typically under 1 km across. LANs normally operate within a compact area such as an office building or a campus owned by the using organization. The configuration of a LAN can be a star, a ring or; simple devices attached along a length of cable. In LAN, transmission channels used are coaxial or fibre optic cable and special interface units rather than telephone lines and modems. Thus, the transmission speed is very high. The attached computers may be of different types and performing a variety of functions such as data processing, word processing and electronic mail.
There are two main advantages of LAN: One is resource sharing and another is communication.
Characteristics of LAN: Following are the characteristics of LAN Nodes are located in a relatively limited geographic area (less than 15 miles).
1. Owned by a single organization.
2. Usually decentralized control.
3. High data rate.
4. Low error rate.
5. Inexpensive transmission medium (e.g., coaxial).
6. Maintenance is easy.
(2) Wide Area Network (WAN): When the network of computers is spread throughout the country or in the entire world then such a network is called Wide Area Network. Several LANs are connected to form a WAN. WAN provides communication services to a large geographic area (100’s to 1000’s of km). Communication on a WAN takes place via telephone lines, satellite or microwave links, rather than through a physical cable.
ARPANET of the Advanced Research Project Agency of the U.S. Department of Defence is an example of WAN.
Characteristics of WAN:
Following are the characteristics of WAN:
1. Nodes are found over a much wider area.
2. Usually used by several different organizations.
3. Often access regulated public or private communication systems.
4. Frequently used for large database access by users over telephone lines
5. Example – INFONET (Computer Science Corporation).
(3) Metropolitan Area Network (MAN): In between LAN and WAN is the Metropolitan Area Network (MAN). A MAN is a network that covers an entire city but uses LAN technology. Cable television networks are an example of MANs distributing television signals. The MANs we are interested in, any information in the form of computer signals from one computer to another. Characteristics of MAN: Following are the characteristics of MAN
1. Nodes are located in wider areas (generally connects the cities).
2. Owned by big organizations (Government, semi-government or big private organizations).
3. The data rate is slow as compared to LAN.
4. The error rate is high as compared to LAN.
5. Expensive.
6. Maintenance is not easy.
