Wide Area Networks- WAN


Wide area networks are networks designed to facilitate communications between users and applications over large distances—between the various corporate offices of an international organization that are located in cities all over the world.

There are two primary compelling reasons for designing and building wide area network capabilities:

■ An organization requires data communication links between widely spread facilities and between an organization and its business partners, customers, and suppliers.

■ An organization requires fast access to the Internet, either as a consumer or as a provider of Internet services, or both.

These two requirements, may, of course, overlap substantially. For example, an extranet is a connection between a business and its business partners, used for the exchange of information and services, and for collaboration, coordination and planning. The Internet is generally preferred as the medium for extranet activities.

The main distinguishing feature that characterizes the wide area network concept is the extensive reliance on service providers to supply the required connectivity between the various locations of the network nodes. The distances are too large to connect directly with a network owner’s own resources and it is impractical to obtain rights of access to all of the intervening property, public or private. Plus, it just isn’t practical for a company to lay its own cable across the Pacific Ocean! Wide area networks require the use of resources that are within the sphere of public switched telephone networks (PSTNs).

Most wide area networks are classified topologically as partial mesh networks, but occasionally you may see examples of full mesh topology and star topology at the visible and logically connected top level of a wide area network. Figure 12.29 shows two examples of wide area network configurations. Figure 12.29(a) shows an example of a star-configured wide area network. In this example, all of the logical connections within the carrier network connect between individual regional research and educational centers and the main center in Amsterdam. There are no direct connections between the branches. Figure 12.29(b) shows a more typical partial-mesh configuration.




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