ETKjide Area Networks. Telecommunications networks covering a large geographic area are called remote networks, long-distance networks, or, more popularly, wide area networks (WANs).
Networks that cover a large city or metropolitan area (metropolitan area networks) can also be included in this category. Such large networks have become a necessity for carrying out the day-to-day activities of many business and government organizations and their end users.
Thus, WANs are used by manufacturing firms, banks, retailers, distributors, transportation companies, and government agencies to transmit and receive information among their employees, customers, suppliers, and other organizations across cities, regions, countries, or the world.
Local Area Networks. Local area networks (LANs) connect computers and other information processing devices within a limited physical area, such as an office, a building, manufacturing plant, or other work site.
LANs have become commonplace in many organizations for providing telecommunications network capabilities that link end users in offices, departments, and other work groups.
LANs use a variety of telecommunications media, such as ordinary telephone wiring, coaxial cable, or even wireless radio systems to interconnect microcomputer workstations and computer peripherals. To communicate over the network, each PC must have a circuit board installed called a network interface card.
Most LANs use a powerful microcomputer having a large hard disk capacity, called a file server or network server that contains a network operating system program that controls telecommunications and the use of network resources.
LANs allow end users in a work group to communicate electronically; share hardware, software, and data resources; and pool their efforts when working on group projects.
For example, a project team of end users whose microcomputer workstations are interconnected by a LAN can send each other electronic mail messages and share the use of laser printers and hard magnetic disk units, copies of electronic spreadsheets or word processing documents, and project databases.
LANs have thus become a more popular alternative for end user and work group computing than the use of terminals connected to larger computers.
Internetworks. Most local area networks are eventually connected to other LANs or wide area networks. That’s because end users need to communicate with the workstations of colleagues on other LAN’s, or to access the computing resources and databases at other company locations or at other organizations.
This frequently takes the form of client-server networks, where end user microcomputer workstations (clients are connected to LAN servers and interconnected to other LANs and their servers, or to WANs and their mainframe super servers).
Local area networks rely on internetwork processors, such as bridges, routers, hubs, or gateways, to make internetworking connections to other LANs and wide area networks.
The goal of such internetwork architectures is to create a seamless “network of networks” within each organization and between organizations that have business relationships.
such networks are designed to be open systems, whose connectivity provides easy access and interoperability among its interconnected workstations, computers, computer-based devices databases, and other networks.
The Internet. The Internet is the largest “network of networks” today. The Internet (the Net) is a rapidly growing global web of thousands of business, educational, and research networks connecting millions of computers and their users in over 100 countries to each other.
The Internet evolved from a research and development network (ARPANET) established in 1969 by the U. S. Defense Department to enable corporate, academic, and government researchers to communicate with E-mail and share data and computing resources.
The Net doesn’t have a central computer system or telecommunications center. Instead each message sent has an address code so any computer in the network can forward it to its destination.
The Internet doesn’t have a headquarters or governing body. The Internet society in Reston, Virginia, is a volunteer group of individual and corporate members who promote use of the Internet and the development of new communications standards or protocols.
These common standards are the key to the free flow of messages among the widely different computers and networks in the system.
The most popular Internet application is E-mail. Internet E-mail is fast, faster than many public networks. Messages usually arrive in seconds or a few minutes, anywhere in the world. And Internet E-mail messages can take the form of data, text, fax, and video files.
The Internet also supports bulletin board systems formed by thousands of special interest groups. Anyone can post messages on thousands of topics for interested users to read. Other popular applications include accessing files and databases from libraries and thousands of organizations, logging on to other computers in the network, and holding real-time conversations with other Internet users.
