What Is a Wide Area Network (WAN)?

WAN Definition and an Explanation on How WANs Work

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A WAN (wide area network) is a communications network that spans a large geographic area such as across cities, states, or countries. They can be private to connect parts of a business or they can be more public to connect smaller networks together.

The easiest way to understand what a WAN is to think of the internet as a whole, which is the world's largest WAN. The internet is a WAN because through the use of ISPs, it connects lots of smaller local area networks (LANs) or metro area networks (MANs).

On a smaller scale, a business may have a WAN that's comprised of cloud services, its headquarters, and smaller branch offices. The WAN in this case would be used to connect all of those sections of the business together.

No matter what the WAN joins together or how far apart the networks are, the end result is always intended to allow different smaller networks from different locations to communicate with one another.

Note: The acronym WAN is sometimes used to describe a wireless area network, though it's most often abbreviated as WLAN.

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 (VPN). This provides protected communications between sites, which is necessary given that the data transfers are happening over the internet.

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 can.

This is why fiber optic cables are sometimes used to facilitate communicate 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 types of networks supported automated teller machines, credit card transaction systems, and some of the early online information services such as CompuServe.

Older X.25 networks ran using 56 Kbps dial-up modem connections.

Frame Relay technology was created to simplify X.25 protocols and provide 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, particularly AT&T.

Multiprotocol Label Switching (MPLS) was built to replace Frame Relay by improving protocol support for handling voice and video traffic in addition to normal data traffic. The Quality of Service (QoS) features of MPLS were key to its success. So-called "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 are often used to support MPLS or internet VPN communications.

Long-distance, point-to-point Ethernet links can also be used to build dedicated wide area networks. While much more expensive than internet VPNs or MPLS solutions, private Ethernet WANs offer very high performance, with links typically rated at 1 Gbps compared to the 45 Mbps of a traditional T1.

If a WAN combines two or more connection types, like if it uses MPLS circuits as well as T3 lines, it can be considered a hybrid WAN. These are useful if the organization wants to provide a cost-effective method to connect their branches together but also have a faster method of transferring important data if needed.

Problems With Wide Area Networks

WAN networks are much 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 also unintentional breaks from ships and weather conditions. Compared to underground land lines, undersea cables tend to take much longer and cost much more to repair.