A Wide Area Network (WAN) is a network that
covers a broad area (i.e., any telecommunications network that links across
metropolitan, regional, or national boundaries) using private
or public
network transports. Business and government entities utilize WANs to relay
data among employees, clients, buyers, and suppliers from various geographical
locations. In essence, this mode of telecommunication allows a business to
effectively carry out its daily function regardless of location. The Internet
can be considered a WAN as well, and is used by businesses, governments,
organizations, and individuals for almost any purpose imaginable.
Related terms for other types of networks are personal
area networks (PANs), local
area networks (LANs),
campus area networks (CANs), or metropolitan
area networks (MANs)
which are usually limited to a room, building, campus or specific metropolitan
area (e.g., a city) respectively.
The textbook definition of a WAN is a computer
network spanning regions, countries, or even the world. However, in terms of
the application of computer networking protocols and concepts, it may be best
to view WANs as computer networking technologies used to transmit data over
long distances, and between different LANs,
MANs
and other localised
computer networking architectures. This distinction stems from the fact
that common LAN
technologies operating at Layer 1/2 (such as the forms of Ethernet or Wifi) are
often geared towards physically localised
networks, and thus cannot transmit data over tens, hundreds or even
thousands of miles or kilometres.
WANs necessarily do not just connect physically
disparate LANs.
A CAN, for example, may have a localised backbone of a WAN technology, which
connects different LANs
within a campus. This could be to facilitate higher bandwidth applications, or
provide better functionality for users in the CAN.
WANs are used to connect LANs
and other types of networks together, so that users and computers in one
location can communicate with users and computers in other locations. Many WANs
are built 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 often built using leased lines. At each end of the leased line, a router
connects the LAN
on one side with a second router within the LAN
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
deliver 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 considered 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.
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