LANs, WANs, and Other Area Networks

Remy_3D

Computer networks come in many different shapes and sizes. Over the years, the networking industry has coined terms like "LAN" and "WAN" attempting to define sensible categories for the major types of network designs. The precise meaning of this terminology remains lost on the average person, however.

Area Networks

For historical reasons, the industry refers to nearly every type of network as an "area network." The most commonly-discussed categories of computer networks include the following -

    * Local Area Network (LAN)
    * Wide Area Network (WAN)
    * Metropolitan Area Network (MAN)
    * Storage Area Network (SAN)
    * System Area Network (SAN)
    * Server Area Network (SAN)
    * Small Area Network (SAN)
    * Personal Area Network (PAN)
    * Desk Area Network (DAN)
    * Controller Area Network (CAN)
    * Cluster Area Network (CAN)

LANs and WANs were the original flavors of network design. The concept of "area" made good sense at this time, because a key distinction between a LAN and a WAN involves the physical distance that the network spans. A third category, the MAN, also fit into this scheme as it too is centered on a distance-based concept.

As technology improved, new types of networks appeared on the scene. These, too, became known as various types of "area networks" for consistency's sake, although distance no longer proved a useful differentiator.

LAN Basics

A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs, and occasionally a LAN will span a group of nearby buildings. In IP networking, one can conceive of a LAN as a single IP subnet (though this is not necessarily true in practice).

Besides operating in a limited space, LANs include several other distinctive features. LANs are typically owned, controlled, and managed by a single person or organization. They also use certain specific connectivity technologies, primarily Ethernet and Token Ring.

WAN Basics

As the term implies, a wide-area network spans a large physical distance. A WAN like the Internet spans most of the world!

A WAN is a geographically-dispered collection of LANs. A network device called a router connects LANs to a WAN. In IP networking, the router maintains both a LAN address and a WAN address.

WANs differ from LANs in several important ways. Like the Internet, most WANs are not owned by any one organization but rather exist under collective or distributed ownership and management. WANs use technology like ATM, Frame Relay and X.25 for connectivity.

LANs and WANs at Home

Home networkers with cable modem or DSL service already have encountered LANs and WANs in practice, though they may not have noticed. A cable/DSL router like those in the Linksys family join the home LAN to the WAN link maintained by one's ISP. The ISP provides a WAN IP address used by the router, and all of the computers on the home network use private LAN addresses. On a home network, like many LANs, all computers can communicate directly with each other, but they must go through a central gateway location to reach devices outside of their local area.

What About MAN, SAN, PAN, DAN, and CAN?

Future articles will describe the many other types of area networks in more detail. After LANs and WANs, one will most commonly encounter the following three network designs:

A Metropolitan Area Network connects an area larger than a LAN but smaller than a WAN, such as a city, with dedicated or high-performance hardware.

A Storage Area Network connects servers to data storage devices through a technology like Fibre Channel.

A System Area Network connects high-performance computers with high-speed connections in a cluster configuration.

Conclusion

To the uninitiated, LANs, WANs, and the other area network acroymns appear to be just more alphabet soup in a technology industry already drowning in terminology. The names of these networks are not nearly as important as the technologies used to construct them, however. A person can use the categorizations as a learning tool to better understand concepts like subnets, gateways, and routers.