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A wide area network (WAN) is a network that exists over a large-scale geographical area, as compared to other network types, such as a local area network (LAN).
A WAN connects different smaller networks, including local area networks (LANs) and metro area networks (MANs), so that computers and users in one location can communicate with computers and users in other locations. WAN implementation can be done through either a public transmission system or a private network.
In many ways, a WAN works in a similar fashion to a LAN, just on a larger scale. Typically, TCP/IP is the protocol used for a WAN, in combination with devices such as routers, switches, firewalls and modems.
One of the most basic ways to think about a wide area network involves understanding how and why it connects smaller local area networks. Again, the local area network is defined within a small geographical area. Typically, it's within a single family home, or an individual office building. The LAN often uses a single modem or router as its “gateway” or connection point to the Internet, or directly to other LANs.
A wide area network takes these individual LANs as nodes and “clusters” them together through broader connectivity that spans a larger geographical area. This architecture serves various purposes; for example, to connect different LANs representing individual branches of a multi-national organization, to build on a greater network “umbrella.”
To date, many wide area networks have been composed of switched networking infrastructures. Circuit-switched WAN is often built on a model of PSTN or ISDN, another kind of circuit-switched networking capability that uses traditional telephony switching.
Other technology options include the use of radio wave networks or optical fiber to create the wide area network.
However, new types of wide area networks are changing what's possible in this interesting field.
First, there's the software-defined wide area network or SD-WAN. By utilizing smart network functionality, an SD-WAN creates more functionality in the wide area network space. It in some ways automates some of the processes that used to be done by discrete hardware in a traditional circuit-switching environment.
Another key innovation is voice over Internet Protocol (VoIP) where this type of new IP connectivity can be used as an alternative to traditional circuit-switched WAN over telephony.
Experts are talking about using SD-WAN setups to create more distributed VoIP networks. Some talk about “host your own VoIP” as an emerging model, where creative companies are hosting their own services and building networks based on VoIP structure and controlled by an SD-WAN.
Another innovation is the use of wide area networks that connect virtual LANs or “VLANs.” In a virtual local area network, individual hardware nodes or pieces handle traffic for more than one LAN, with LANs being configured virtually instead of physically. The WAN can administrate these setups just like it would a traditional LAN.
In general, the WAN provides the functionality for remote work connections and everything else that goes into geographically distributed networking systems. WANs have their own interfaces with the global Internet as a whole, working with addressing and other conventions to make geographically dispersed LAN clusters consistently universal.