Introduction to Wide Area Network(WAN)

What is a WAN?

A WAN is a data communications network that operates beyond the geographic scope of a LAN.

WANs are different from LANs in several ways. While a LAN connects computers, peripherals, and other devices in a single building or other small geographic area, a WAN allows the transmission of data across greater geographic distances. In addition, an enterprise must subscribe to a WAN service provider to use WAN carrier network services. LANs are typically owned by the company or organization that uses them.

WANs use facilities provided by a service provider, or carrier, such as a telephone or cable company, to connect the locations of an organization to each other, to locations of other organizations, to external services, and to remote users. WANs generally carry a variety of traffic types, such as voice, data, and video.
Here are the three major characteristics of WANs:

WANs generally connect devices that are separated by a broader geographical area than can be served by a LAN.
WANs use the services of carriers, such as telephone companies, cable companies, satellite systems, and network providers.
WANs use serial connections of various types to provide access to bandwidth over large geographic areas.
Why Are WANs Necessary?

LAN technologies provide both speed and cost-efficiency for the transmission of data in organizations over relatively small geographic areas. However, there are other business needs that require communication among remote sites, including the following:

People in the regional or branch offices of an organization need to be able to communicate and share data with the central site.
Organizations often want to share information with other organizations across large distances. For example, software manufacturers routinely communicate product and promotion information to distributors that sell their products to end users.
Employees who travel on company business frequently need to access information that resides on their corporate networks.

In addition, home computer users need to send and receive data across increasingly larger distances. Here are some examples:

It is now common in many households for consumers to communicate with banks, stores, and a variety of providers of goods and services via computers.
Students do research for classes by accessing library indexes and publications located in other parts of their country and in other parts of the world.

Since it is obviously not feasible to connect computers across a country or around the world in the same way that computers are connected in a LAN with cables, different technologies have evolved to support this need. Increasingly, the Internet is being used as an inexpensive alternative to using an enterprise WAN for some applications. New technologies are available to businesses to provide security and privacy for their Internet communications and transactions. WANs used by themselves, or in concert with the Internet, allow organizations and individuals to meet their wide-area communication needs.
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