What Is a Wide Area Network (WAN)? How WANs Are Connected?

A wide area network (WAN) is a computer network that spans a relatively large geographical area and consists of two or more interconnected local area networks (LANs).

A LAN is a network that connects computers and other devices in a relatively small area, typically a single building or a group of adjacent buildings.

Many WANs are built for one particular organization and are private. They are commonly implemented in enterprise networking environments to link offices in different cities, states, countries and even continents. WANs are also built by Internet service providers (ISPs) to provide connections from the LANs of their customers to the Internet. The Internet, which is a world-wide network of interconnected computer networks, is a WAN, and thus it is the largest WAN in existence.

WANs are commonly constructed using leased lines (i.e., dedicated telephone connections between two points that are set up for a company or other organization by a telecommunications common carrier), but they can also use conventional telephone lines and satellite links. At each end of the leased line a router connects to the LAN on one side and to a hub within the WAN on the other. A router is an electronic device and/or software that connects at least two networks and forwards packets (i.e., the fundamental unit of information transport in all modern computer networks) among them based on their IP addresses, network conditions, etc. A hub is a common connection point for multiple twisted pair copper wire cables or optical fiber cables in a LAN.

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 communication between the WAN links.

Types of WAN connections

WAN connections can include wired and wireless technologies. Wired WAN services can include multiprotocol label switching, T1s, Carrier Ethernet and commercial broadband internet links. Wireless WAN technologies can include cellular data networks like 4G LTE, as well as public Wi-Fi or satellite networks.

WANs over wired network connections remain the preferred medium for most enterprises, but wireless WAN technologies, based on the 4G LTE standard, are gaining traction.

WAN infrastructure may be privately owned or leased as a service from a third-party service provider, such as a telecommunications carrier, internet service provider, private IP network operator or cable company. The service itself may operate over a dedicated, private connection -- often backed by a service-level agreement -- or over a shared, public medium like the internet. Hybrid WANs employ a combination of private and public network services.