A wide area network or WAN is a computer network covering a broad geographical area.
Contrast with personal area networks (PANs), local area networks (LANs) or metropolitan area networks
(MANs) that are usually limited to a room, building or campus respect
ively. The largest and most
known example of a WAN is the Internet.
WANs are used to connect local area networks (LANs) together, so that users and computers in
one location can communicate with users and computers in other locations. Many WANs are b
uilt for one
particular organization and are private. Others, built by Internet service providers, provide connections
from an organization's LAN to the Internet. WANs are most often built using leased lines. At each end of
the leased line, a router connec
ts to the LAN on one side and a hub within the WAN on the other. Leased
lines can be very expensive. Instead of using leased lines, WANs can also be built using less costly
circuit switching or packet switching methods. Network protocols including TCP/IP d
eliver transport and
addressing functions. Protocols including Packet over SONET/SDH, MPLS, ATM and Frame relay are
often used by service providers to deliver the links that are used in WANs. X.25 was an important early
WAN protocol, and is often considere
d to be the "grandfather" of Frame Relay as many of the underlying
protocols and functions of X.25 are still in use today (with upgrades) by Frame Relay.
Academic research into wide area networks can be broken down into three areas: Mathematical models,
twork emulation and network simulation.
Such a network generally requires the crossing of public right
ways, and rely at least in part on
circuits provided by a common carrier, Typically, a WAN consists of a number of interconnected switching
transmission from any one device is routed through these internal nodes to the specified
destination device. These nodes (including the boundary nodes) are not concerned with the contents of
data; rather their purpose is to provide a switching facility tha
t will move the data from node to node until
they reach their destination. Performance improvements are sometimes delivered via WAFS or WAN