WAN (Wide Area Network)
Communications
You have already seen in the module on Local Area Networks how computers can be linked together to form networks, enabling them to communicate, share information and resources. While information requirements within a limited area (like an office building or university campus) can be handled by Local Area Networks (LANs), communication requirements beyond that need Metropolitan Area Networks (MANs) or Wide Area Networks (WANs).
In this session, you will see how the services available on Wide Area Networks help in expanding the usage of a PC. The rapid increase of such networks has been responsible for transforming the PC from an information-processing machine into a communications center.
Wide Area Networks may be commercial networks which anyone can subscribe or they may be run privately by companies for their internal use only. There are international networks with thousands of users as well as smaller ones run by local computer clubs. Computer equipment manufacturers have networks to give their customers the latest information on their products. Customers can also report problems or place orders through them.
Networks like CompuServe offer their users (subscribers) many useful facilities like:
- Communication with other users through E-Mail (Electronic Mail) or FAX (Facsimile).
- Transfer of files from one computer to another. You may want to send a file to a particular user, or you may want to share a game or utility that you have developed with other users. In such a case, you can upload (send) it to the network, from where other users can download it for their use.
- Access to centralized databases. These are like libraries on computers containing business, technical or academic information. They have complete text of publications or abstracts that you can browse through, as in a library. Some well known centralized databases are:
- Dow Jones & Co's Dow Jones News/Retrieval Service.
- Lockheed's Dialog Information Service. It has 518 separate databases covering science, engineering, business and economics.
- Mead Data Central's NEXIS/LEXIS. It offers full text from 15 newspapers like New York Times and 31 magazines like Byte, Newsweek and Business Week, etc.
- West Publishing Co's Westlaw. It allows lawyers to browse through court cases and federal regulations.
- Special Interest Groups (SIGs) or forums where you can ask questions, get responses and exchange information about your specific areas of interest, that could be medicine, cricket or computers.
- On-line services offered by various banks, airlines and shopping centers allow you to transact with them through the network.
- Support forums maintained by various hardware and software companies provide technical expertise and solutions to problems to their customers.
- Computing Time, i.e. allowing you to link to mainframes and utilize their processing capacity.
Wide Area Networks that offer such services are called Bulletin Board Services (BBSs).
Requirements to Connect your PC to a Network
Unlike a Local Area Network, where the workstations are normally connected through cables, connection to a Wide Area Network is done through telephone lines, and so a telephone connection is a pre-requisite.
To connect to a WAN, you need a device called a modem, and a communication software for dialing and establishing a connection with another PC. ProComm, ProComm Plus, pcANYWHERE, Telix and Crosstalk are some well-known communication packages.
Lastly, you must subscribe and get an account to become a user of a WAN or BBS that you want to use.
The general features provided by a communication package are:
- Operation in host and remote modes: If the communication software is running in the host mode on your computer, other computers can connect themselves to it and utilize its services. Your machine is called the host as it provides its resources to the others. When you connect to another host and utilize its services, you are said to be a remote user. In host mode, the communication software can handle the task of providing services while the host computer can be left unmanned.
- Sending and receiving of files: This could be used to send a file to one or multiple destinations. Files are normally compressed and then transferred to save time on the network.
- Automatic logging of incoming data to printer or disk: You may want to use this when you want messages/files that are received to be saved on disk or printed without prompting and disturbing your other activities on the PC.
- Recording and playback of sessions and calls: This helps you keep track of all the calls made, duration and amount of data transfer for each one of them. You can also re-run a call. This is useful if the transfer of the same data has to be repeated.
- Providing a Process Control Language: This helps you to program repetitive functions such as unattended file transfer to multiple destinations after business hours.
Wide Area Network (WAN)
As the advantages of networking became known, business saw the need to expand the networks. LANs could not adequately support the network needs of a large business, with offices and operations spread over a wide area. This led to the development of Wide Area Networks.
When a network is spread over wide areas, such as across cities, states or countries, it is called a Wide Area Network (WAN). Communication on a WAN takes place via telephone lines, satellites or microwave links, rather than through a physical cable.