A WAN, or Wide Area Network, is a computer network in which the computers connected may be far apart, as opposed to a Local Area Network, where they are all close together (usually within a radius of a half a mile). This enables businesses to connect branch offices to their headquarters, to allow retail locations to communicate with each other on the same network, sharing resources such as customer databases and price lookup tables.

In a traditional WAN, all of the hardware and software must exist on the same network. If your company adds a new location, you must bring in the same Internet service, provision and configure a new piece of hardware, and setup the firmware to identify and integrate the new location devices. This often requires multiple disciplines, manpower, and specializations to work in tandem to simply add a location to your existing WAN.
How is an SD-WAN Different From a Traditional WAN
With a Software-Defined WAN, sometimes known as a WAN Virtualization, changes this formula by allowing any Internet service to link the varied locations together via cloud-based software, rather than on-premise firmware. Now, new locations can be turned up and added to an existing WAN with minimal effort, remotely.
By essentially carving out your own network using secure connections over the larger Internet, you give your enterprise its own private Internet.
How is an SD-WAN Deployed
Typical SD-WAN deployments use an appliance that is provided to the customer and links two or more inexpensive broadband Internet connections to enhance or replace traditional network technologies. The different locations can aggregate their bandwidth across available connections to provide bandwidth when and where it is needed.
Different ISPs Can Work Together
You might have a location in a city like Dallas, with access to high speed FIOS connections, but your remote location in Odessa can barely muster a 40MB Cable connection. Then, the distribution center in Atlanta has higher speed Cable, boosting to 500MB. SD-WAN, using the Internet to connect the locations, is fine with this, and you can share files, printers, and other resources as if you were on the same network all along.
Imagine the headache of setting up a WAN with an offshore location. SD-WAN makes this problem only as big as time zone differences when trying to set up an all-hands meeting.
Failsafes and Redundancies Make For a More Reliable Connection
The SD-WAN appliance will have connections for multiple Internet services. So, you can have a backup cellular cradle point, or a cable connection in addition to your FIOS connection and the software will seamlessly move from one to the other depending on traffic and uptime, as defined by your own administrator.
What Do You Mean, Administrator?
With application aware QoS, your SD-WAN can continually monitor performance on your broadband connection to optimize quality of service for VoIP traffic. An administrator can access an easy to use interface to visualize the network in real-time. Your admin can make changes to access points, quality of service, and other application data.
In short, SD-WAN allows you to deliver superior performance even over low-cost broadband all while using existing network topologies. With SD-WAN, you can build your own private Internet.