Wide Area Network

Wide Area Network:

Chances are you are an experienced wide area network (WAN) user and don’t even know it. If you have ever connected to the Internet, you have used the largest WAN on the planet. A WAN is any network that crosses metropolitan, regional, or national boundaries. Most networking professionals define a WAN as any network that uses routers and public network links. The Internet fits both definitions.

       WANs differ from LANs in the following ways:

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                WANs cover greater distances.

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                WAN speeds are slower.

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                WANs can be connected on demand or permanently connected; LANs have permanent

                connections between stations.

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                WANs can use public or private network transports; LANs primarily use private network

                transports.

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                WANs can use either full- or half-duplex 

communications. LANs have typically used halfduplex

                communications, although many local area networks today use full-duplex communications

                (see the sidebar “Full-Duplex vs. Half-Duplex Communications”).

The Internet is actually a specific type of WAN. The Internet is a collection of networks that

are interconnected and, therefore, is technically an internetwork

( Internet is short for the word internetwork ).

                A WAN can be centralized or distributed. A centralized WAN consists of a central computer (at

a central site) to which other computers and dumb terminals connect. The Internet, on the other

hand, consists of many interconnected computers in many locations. Thus, it is a distributed WAN.

Full-Duplex vs. Half-Duplex Communications :

All network communications (including LAN and WAN communications) can be categorized as half-duplex or full-duplex. With half-duplex, communications happen in both directions, but in only one direction at a time. When two computers communicate using half-duplex, one computer sends a signal and the other receives; then, at some point, they switch sending and receiving roles. Chances are that you are familiar with half-duplex communications. If you have ever used a push-to-talk technology, such as a CB radio or walkie-talkie, you were communicating via half-duplex: One person talks, and then the other person talks. Full-duplex, on the other hand, allows communication in both directions simultaneously. Both stations can send and receive signals at the same time. Full-duplex communications are similar

to a telephone call, in which both people can talk simultaneously.

Example: