SD-WAN
A software-defined wide area network (SD-WAN) is a wide area network that uses software-defined networking technology, such as communicating over the Internet using overlay tunnels which are encrypted when destined for internal organization locations.
If standard tunnel setup and configuration messages are supported by all of the network hardware vendors, SD-WAN simplifies the management and operation of a WAN by decoupling the networking hardware from its control mechanism. This concept is similar to how software-defined networking implements virtualization technology to improve data center management and operation. In practice, proprietary protocols are used to set up and manage an SD-WAN, meaning there is no decoupling of the hardware and its control mechanism.
A key application of SD-WAN is to allow companies to build higher-performance WANs using lower-cost and commercially available Internet access, enabling businesses to partially or wholly replace more expensive private WAN connection technologies such as MPLS.
When SD-WAN traffic is carried over the Internet, there are no end-to-end performance guarantees. Carrier MPLS VPN WAN services are not carried as Internet traffic, but rather over carefully-controlled carrier capacity, and do come with an end-to-end performance guarantee.