Briefly describe Local Area Network (LAN) and Wide Area Network (WAN).

Ans.

Local Area Network (LAN)

A local area network (LAN) is digital communication system capable of interconnecting a large number of computers, terminals and other peripheral devices within a limited geographical area, typically under 1 km across. LANS normally operate within a compact area such as an office building or a campus and is owned by the using organization. The configuration of an LAN can be star, a ring, or simply devices attached along length of a cable. In LAN, transmission channels generally use coaxial or fiber optic cables 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 be performing a variety of functions such as data processing, word processing, and electronic mail. The two main purposes of the local area network are to link computers within an organization or campus so that they may share expensive peripheral devices, e.g., high speed printers or magnetic disks holding the data base, and to allow these computers to communicate with each other.

For necessary operation, a LAN has to provide for the following specifications:

1. A medium through when the data flows-twisted-pair wire, co-axial cable, etc.

2. Network Interface Card (NIC) which connect the computer and the communicating medium.

3. A topology, defining the configuration of physically inter connecting the stand alone machines-how these are connected to form the network system is a whole.

4. A set of programs, collectively called Network Operating System to ensure error-free operation of the system with full security and protection.

5. A transmission from any one of the stations is received by all other stations but used by the destination station only.

6. A local area network operating system must provide a layer of compatibility at the software level so that software can be easily written and widely distributed.

7. All computers are prone to system lockups, power failures and other catastrophies. If a centralized processing system goes down, all users connected to it are left without a machine to work on. A LAN operating system should be powerful enough to withstand accidents.

8. Bridging of different LANS together is one of the most important requirements of any LAN. Users should be able to access resources from all workstations on the bridge network in a transparent way, no special commands should be required to cross the bridge.

The advantages for using LAN includes:

(1) Security for programs and data can be achieved using servers that are locked through software and physical means. Diskless nodes also offer security by not allowing users to download important data on floppies or upload unwanted software or virus.

(2) Organizational benefits like reduced costs in computer hardware. software and peripherals, and a drastic reduction in the time and cost of training or re-training manpower to use the systems.

(3) flexibility in the system is possible as the network system can be expanded to cover additional units or it may even be inter-connected with other networks. This arrangement considerably saves investment cost involved in procuring various computer facilities.

(4) Software cost and upgradation are much easter as any given package can be stored centrally on the server.

(5) Electronic mail and Message broadcasting allows users to communicate more easily among themselves. Each user can be assigned a mail-box on the server. Messages to other users can then be dropped into the mail-box and read by them when they log into the network.

(6) Provides improved and more economic communication facilities in general, including voice communication.

(7) LANs enable users to share files with each other, e.g., corporate data bases, important policy or procedure statements, and even local classified advertisements can all be stored on shared computer files.

Application Areas of Local Area Networks:

1. In an office environment where exchange of textual information and sharing of data bases are of primary importance, a LAN can prove to be very useful. It can provide messaging facilities to enable various users to communicate among themselves. Common data bases can be developed over LAN which can be accessed by LAN users from their computers. The common data bases can be updated by different divisions in the office and the updated information can readily be accessed by various users. Adequate security measures can be incorporated to prevent unauthorized access to the confidential information.

2. Academic and Research institutions can take lots of advantages of a LAN. Individual students can be provided with low cost terminals which can be interfaced with a network to enable them to access different computers in the campus.

3. In a factory environment where lots of intelligent devices could be operative to perform complicated machine control functions, a Local Area Network can provide a very effective way of inter-connecting them for the purpose of synchronization and better results. Also, the status of all such devices can easily be monitored by connecting an appropriate monitoring devices to the LAN.

4. A hospital is another potential place for LAN application. Modern medical equipment utilizing microprocessors and advanced computer technology extensively can easily be connected to a LAN and provide ready information to the specialist doctors. Medical professional can access medical reference library through a LAN.

5. Other relevant applications of local area network include file transfer and access, word and text processing, electronic message handling, personal filing and information handling, graphical information, remote database access, personal computing, digital voice transmission and storage, etc.

Wide Area Network (WAN)

A wide area network (WAN) is a digital communication system which inter-connects different sites, computer installations and user terminals, and may also enable LANs to communicate with each other. This type of communication network may be developed to operate nationwide or worldwide. In a WAN, the transmission medium used is normally public systems such as telephone lines, microwave and satellite links. Organization often leases communication lines from companies like AT & T to make wide area network. Thus wide area network includes all the networks that are involved in transporting information from one geographic location to another. The basic components in a common wide area distributed processing network include a host computer which is linked by various interconnected communication lines to subordinate computer is comparable to any public service computer that provides users with electronic mail, computers, the host on-line data bases, or other services.

The goal of a wide area network is to allow users to send electronic messages, data, graphics, programs, documents and even video information rapidly and economically. Wide area network also known as global networks make judicious use of data communications common carriers throughout the world and/or private microwave links to connects its computers. The network’s computers accept transmissions, route them to their destination via the other computer, and alert addressees to waiting messages and other transmission. WAN also enables file exchange, remote database access, electronic mail, telecommuting, etc. Business organizations use WAN for electronic data interchange (EDI), a procedure by which companies can exchange standard documents, such as purchase orders, invoices, transfer of funds, etc.