• Computer can communicate with another computer down the street, across town, across the country and across the world, thanks to a vast array of networks.

• The World Wide Web is a system of interconnected information sources, however, it would be meaningless without networks that allow computers to access information and communicate with each other.

LAN

• A local area network, or LAN, is a connection of computers within a small area, such as an office, a building or multiple buildings located close together.

• Local area networks can be as broad as connecting computers within a college campus, or as simple as linking two computers in a household.

• A LAN is relatively inexpensive compared to other types of network applications, and can be built with wired or wireless connections.

• Local area networks operate within a modest geographical area, but by connecting to other larger networks, a LAN's reach is greatly expanded.

MAN

• When two or more local area networks are connected together it is known as metropolitan area network, or MAN.

• Many LANs within a city are often linked to a MAN through very high speed connections, such as fiber optic cable. In many cases metropolitan area networks are operated by a government entity, or a large company, such as a cable TV provider, that make services available to a city and suburbs. In many instances, metropolitan area networks are important links between the smaller, localized LAN, and the vast coverage of a wide area network.

WAN

• A wide area network, known as a WAN, covers broad geographical areas, like a state, a region or entire country.

• A WAN can be self-contained, but almost always connects with other local and metropolitan area networks.

• Wide area networks utilize networking equipment that is very costly and are mainly operated by large corporations or communications companies that need to share data over a vast area.

• As an example, a large retail drugstore chain would use a WAN for customer prescription information.

• A customer can then fill a prescription at one location, and through a wide area network, that information can be accessed for a refill at any location the retailer has worldwide.

SAN

• Storage area networks, called a SAN, are a variation of a LAN. The main purpose of a SAN is the storage of large amounts of data that can be retrieved at a high rate of speed.

• Storage area networks are commonly used by businesses that maintain broad databases.

• Media companies that perform large amounts of video editing benefit by using storage area networks because of their high data transfer rates.

Applications:

• Business Applications

• Home Applications

• Mobile Users

• Social Issues.