What is a Wide Area Network, WAN

Wide area networks or WANs are widely used within data communications to link devices over a wide area, often globally via leased lines.


Data Networking Fundamentals Includes:
Networking fundamentals     Local area networks     Wide area networks    

See also: Software defined networks     Network functions virtualisation     SD-WAN    


Wide Area Networks, or WANs are a common feature of data communications technology being found in many large corporations, businesses, academic institutions, government organisations and many more.

A wide area network is essentially a large data communications network that is not on a single location, but it is a data network that is spread further afield.

As such WANs can enable the communication of data over large distances and over many locations, and not tied to a single location as in the case of a local area network.

One of the best known examples of a wide area network is the Internet. This consists of a huge network that is linked to an enormous number of local area networks and other items.

Wide area network, WAN definition

As with many computer entities, the terms can be used, often without a compete understanding of what the item or entity is, so a definition can be helpful.

There is no official definition and different organisations and people tend to define a wide area network, WAN in slightly different ways.

The definition below aims to provide a summary of what people think a wide area network actually is.

Wide Area Network, WAN, definition:

A wide area network or WAN is a form of network that contains a number of other networks such as local area networks, LANs and the data communications often includes links that are carried over leased lines or those of telecommunications providers, and they often cover many countries.

This definition of a WAN serves to give a useful basis for any description and investigation of WANs and their technology.

Wide area network, WAN basics

Wide area networks also tend not to be confined by physical location and can exist globally through the use of leased lines, and as such its confines are generally not limited. Local area networks are confined to a general location and will generally not used leased lines because, by their very nature, they are local.

In view of this, wide area networks, WANs are not necessarily constrained by geography. Often large multinational organisations set up their own WANs and use these for communication within the organisation at different locations around the country or around the globe.

A wide area network, WAN consists of many network entities. The main ones are noted below.

  • Local area networks:   WANs normally link to a large number of small local area networks, each one being in a widely different location. A router, layer-3 switch or even a modem may be used to connect a local area network to the WAN.

  • Edge devices:   Edge devices for WANs include routers, switches and modems and similar devices.

  • Connecting media:   It is important to consider the media that connect the various elements oft he wide area network. These can be any form of data link including fibre, wireless communications links, microwave links and satellite links. They might use Ethernet as the transport mechanism, or they can use other mechanisms to ensure the data is transported in a manageable fashion.

  • Customer premises equipment, CPE:   The WAN will need to interface to many customer sites. Items called customer premises equipment provide the interface between the customer equipment and the WAN itself. A customer premises equipment is normally installed at the customer site of the user to provide the last-mile interface for WAN connection.

    Large enterprises will use enterprise-grade routers or layer-3 switches as CPEs. These will be able to handle vast amounts of data and will be able to provide very high levels of reliability and speed.

    Although there is little difference between a LAN router and a customer premises equipment, the CPE term tends to indicate it is a large router that is used to interface a commercial LAN tot he WAN whereas a router is the term used for the item that interfaces a small business or home LAN to the WAN.

Large public WANs may link to hundreds, thousands, or more smaller LANs. The data from these LANs is then routed to their destinations by the routers installed on the edge of each LAN. These routers use the routing algorithms to enable the data to be sent over the WAN to its final destination as packets of data.

WAN types

When talking about wide area networks, WANs, it will soon be discovered that there are several types that can be used for different types of usage. The terms may be appear at different times when looking at WAN technology.

To help provide some clarity amidst all the jargon of the different types of wide area network, here are soem terms explained about the different types of WAN that may be encountered.

  • Private WAN:   A private WAN is essentially what it says. It is a wide area network that is set up for the private use of the individuals within that organisation. It is kept private as general external users are not permitted on the WAN. This type of WAN may be used by organisations for their employees, etc.

    The private WAN will be set up using leased data lines which will be operated by a telecommunications provider. These lines create a system that has the same upload and download speeds and it reserves specific infrastructure for the private WAN.

    In view of the fact that lines are reserved, this is a very expensive option for a wide area network.

  • Cloud WAN:   Cloud techniques are becoming ever more popualr because they are scaleable and require less management by a company - it is undertaken by the Cloud provider in many instances. A cloud based wide area network utilises a mesh of networks and provides a very high degree of redundancy and connectivity anywhere around the globe.

    For example a cloud provider may offer a managed service that organisations can use to build and manage a global wide area network that connects resources running across the cloud as well as with on-premises environments.

  • MPLS WAN:   An MPLS network gains its name from the the MultiProtocol Label Switching routing technique used. This is a routing technique that directs data from one node to the next based on labels rather than network addresses.

    An MPLS network is managed from end to end by a single provider and it uses an existing set of physical networks to create a virtual path through them. As with many other networks, TCP/IP is used to break the data stream into small packets which can be routed accordingly.

    Data packets on an MPLS network are labeled and routed based on a pre-defined path that gives fast transport speeds across the network.

  • SD-WAN:   As wide area network technology has gained more widespread usage, so the technologies and techniques required to ensure their performance meet their requirements.

    With WANs carrying huge amounts of data and requiring very high levels of performance as well as making the optimum use of the available hardware a number of technologies or techniques have been developed to ensure that the operate to their maximum efficiency for as much as possible of the time.

    One approach which has been developed is known as SD-WAN or software defined WAN. This is an approach for making wide area network architectures far more effective. It utilises virtualization, application-level policies and overlay networks, as well as onsite SD-WAN devices and software platforms. Although this may sound far more complicated, the SD-WAN approach brings huge dividends to the network operators.

    SD-WAN techniques significantly improve the efficiency of data transfers across the network by moving traffic to lower cost network links reduce the load on the more expensive leased or MPLS lines.

    The SD-WAN architecture enables the network to dynamically change according to the overall conditions.



Wide area networks, WANs are an essential element of today's data communications centric society. With the use of the Internet, probably the largest WAN, increasing steadily, the use of WAN technology is only set to increase.


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