Wide area network

(communications) A system consisting of a set of nodes that are interconnected by a set of links, and generally covers a large geographic area, usually on the order of hundreds of miles. Abbreviated WAN.

System linking an organization's individual computer workstations throughout a state, a country, or the world using telecommunications for the purpose of simultaneously sharing files and organizational information. See also Local Area Network (LAN).

A wide area network (WAN) is a telecommunications network, usually used for connecting computers, that spans a wide geographical area. WANs can by used to connect cities, states, or even countries. WANs are often used by larger corporations or organizations to facilitate the exchange of data, and in a wide variety of industries, corporations with facilities at multiple locations have embraced WANs. Increasingly, however, even small businesses are utilizing WANs as a way of increasing their communications capabilities.

Although WANs serve a purpose similar to that of local area networks (LANs), WANs are structured and operated quite differently. The user of a WAN usually does not own the communications lines that connect the remote computer systems; instead, the user subscribes to a service through a telecommunications provider. Unlike LANs, WANs typically do not link individual computers, but rather are used to link LANs. WANs also transmit data at slower speeds than LANs. WANs are also structurally similar to metropolitan area networks (MANs), but provide communications links for distances greater than 50 kilometers.

WANs have existed for decades, but new technologies, services, and applications have developed over the years to dramatically increase their efficacy for business. WANs were originally developed for digital leased-line services carrying only voice, rather than data. As such, they connected the private branch exchanges (PBXs) of remote offices of the same company. WANs are still used for voice services, but today they are used more frequently for data and image transmission (such as video conferencing). These added applications have spurred significant growth in WAN usage, primarily because of the surge in LAN connections to the wider networks.

How Wans Work

WANs are either point-to-point, involving a direct connection between two sites, or operate across packet-switched networks, in which data is transmitted in packets over shared circuits. Point-to-point WAN service may involve either analog dial-up lines, in which a modem is used to connect the computer to the telephone line, or dedicated leased digital telephone lines, also known as "private lines." Analog lines, which may be either part of a public-switched telephone network or leased lines, are suitable for batch data transmissions, such as nonurgent order entry and point-of-sale transactions. Dedicated digital phone lines permit uninterrupted, secure data transmission at fixed costs.

Point-to-point WAN service providers include both local telephone companies and long distance carriers. Packet-switched network services are typically chosen by organizations which have low volumes of data or numerous sites, for which multiple dedicated lines would be too expensive.

Depending on the service, WANs can be used for almost any data sharing purpose for which LANs can be used. Slower transmission speeds, however, may make some applications less practical for WANs. The most basic uses of WANs are for electronic mail and file transfer, but WANs can also permit users at remote sites to access and enter data on a central site's database, such as instantaneously updating accounting records. New types of network-based software that facilitate productivity and production tracking, such as groupware and work-flow automation software, can also be used over WANs. Using groupware, workers at dispersed locations can more easily collaborate on projects. WANs also give remote offices access to a central office's other data communications services, including the Internet.

Further Reading:

Chappell, Laura A., and Roger L. Spicer. Novell's Guide to Multiprotocol Internetworking. Novell Press, 1994.

Pecar, Joseph A., Roger J. O'Connor, and David A. Garbin. The McGraw-Hill Telecommunications Factbook. McGraw-Hill, 1993.

Sharp, Duane E. "Wide Area Networks: The Key to Enterprise Productivity." Canadian Manager. Summer 1996.

See also: Local Area Networks

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A wide area network (WAN) is a computer network that covers a broad area (i.e., any network whose communications links cross metropolitan, regional, or national boundaries ^[1]). This is in contrast with 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.

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 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 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.

Academic research into wide area networks can be broken down into three areas: Mathematical models, network emulation and network simulation.

Performance improvements are sometimes delivered via WAFS or WAN optimization.

Several options are available for WAN connectivity: ^[2]

Option:	Description	Advantages	Disadvantages	Bandwidth range	Sample protocols used
Leased line	Point-to-Point connection between two computers or Local Area Networks (LANs)	Most secure	Expensive		PPP, HDLC, SDLC, HNAS
Circuit switching	A dedicated circuit path is created between end points. Best example is dialup connections	Less Expensive	Call Setup	28 - 144 kbps	PPP, ISDN
Packet switching	Devices transport packets via a shared single point-to-point or point-to-multipoint link across a carrier internetwork. Variable length packets are transmitted over Permanent Virtual Circuits (PVC) or Switched Virtual Circuits (SVC)		Shared media across link		X.25 Frame-Relay
Cell relay	Similar to packet switching, but uses fixed length cells instead of variable length packets. Data is divided into fixed-length cells and then transported across virtual circuits	Best for simultaneous use of voice and data	Overhead can be considerable		ATM

Transmission rate usually range from 1200 bps to 6 Mbps, although some connections such as ATM and Leased lines can reach speeds greater than 156 Mbps. Typical communication links used in WANs are telephone lines, microwave links & satellite channels.

Recently with the proliferation of low cost of Internet connectivity many companies and organizations have turned to VPN to interconnect their networks, creating a WAN in that way. Companies such as Cisco, New Edge Networks and Check Point offer solutions to create VPN networks.

References

1. ^ Groth, David; Toby Skandier (2005). 'Network+ Study Guide, Fourth Edition'. Sybex, Inc.. ISBN 0-7821-4406-3. 
2. ^ McQuerry, Steve (November 19, 2003). 'CCNA Self-Study: Interconnecting Cisco Network Devices (ICND), Second Edition'. Cisco Press. ISBN 1-58705-142-7. 

See also

Computer network Personal area network (PAN) Local area network (LAN) Storage area network (SAN) Campus area network (CAN) Metropolitan area network (MAN) Internet Leased Line Circuit Switching Packet Switching

Cell Switching Label Switching X.25 Frame Relay ATM SONET/SDH MPLS Wireless Wide Area Network (WWAN) Wide Area File Services (WAFS) Wide Area Application Services (WAAS)

External links

• Cisco - Introduction to WAN Technologies

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