CHARACTERIZATION OF NETWORKS:
There are three kinds of characterization of networks.
LOCAL AREA NETWORK (LAN):
It is needed for a single building.
METROPOLOTAN AREA NETWORK (MAN):
It is needed for a single city.
WIDE AREA NETWORK (WAN):
It is needed for a country level networking and even for continents.
DIFFERENCE BETWEEN LAN AND WAN:
Although LAN is for a local area but satellite bridge can extend LAN across longer distances. But it still could not accommodate arbitrarily several computers.
On the other hand WAN has to be scalable to long distances and several computers.