What Is a Wide Area Network (WAN)?

A wide area network spans a large geographic area such as a city, state, or country. It can be private to connect parts of a business, or it can be public to connect smaller networks.

How a WAN Works

The easiest way to understand a WAN is to think of the internet, the world's largest WAN. The internet is a WAN because, using ISPs, it connects many smaller local area networks or metro area networks.

On a smaller scale, a business may have a WAN comprised of cloud services, its headquarters, and branch offices. The WAN, in this case, connects those sections of the business.

No matter what the WAN joins together or how far apart the networks are, the result allows smaller networks from separate locations to communicate.

How WANs Are Connected

Since WANs, by definition, cover a larger distance than LANs, it makes sense to connect the various parts of the WAN using a virtual private network. This framework protects communications between sites.

Although VPNs provide reasonable levels of security for business uses, a public internet connection does not always provide the predictable levels of performance that a dedicated WAN link provides. Therefore, fiber optic cables are sometimes used to facilitate communication between the WAN links.

X.25, Frame Relay, and MPLS

Since the 1970s, many WANs were built using a technology standard called X.25. These networks supported automated teller machines, credit card transaction systems, and some early online information services such as CompuServe. Older X.25 networks used 56 Kbps dial-up modem connections.

Frame Relay technology simplifies X.25 protocols and provides a less expensive solution for wide area networks that needed to run at higher speeds. Frame Relay became a popular choice for telecommunications companies in the United States during the 1990s, notably AT&T.

Multiprotocol Label Switching replaced Frame Relay by improving protocol support for handling voice and video traffic in addition to normal data traffic. The Quality of Service feature of MPLS was key to its success. Triple-play network services built on MPLS increased in popularity during the 2000s and eventually replaced Frame Relay.

Leased Lines and Metro Ethernet

Many businesses started using leased line WANs in the mid-1990s as the web and internet exploded in popularity. T1 and T3 lines often support MPLS or internet VPN communications.

Long-distance, point-to-point Ethernet links can also be used to build dedicated wide area networks. While more expensive than internet VPNs or MPLS solutions, private Ethernet WANs offer high performance, with links typically rated at 1 Gbps compared to the 1.544 Mbps of a T1.

If a WAN combines two or more connection types—for example, if it uses MPLS circuits and T3 lines—it is considered a hybrid WAN. These configurations are a cost-effective method to connect network branches and have a faster method of transferring important data if needed.

Problems With Wide Area Networks

WANs are more expensive than home or corporate intranets.

WANs that cross international and other territorial boundaries fall under different legal jurisdictions. Disputes can arise between governments over ownership rights and network usage restrictions.

Global WANs require the use of undersea network cables to communicate across continents. Undersea cables are subject to sabotage and unintentional breaks from ships and weather conditions. Compared to underground landlines, undersea cables tend to take longer and cost more to repair.