The diagram below illustrates all of the definitive components that together help define a standard MEF 3.0 SD-WAN service. One of the key elements is the SD-WAN Edge, which is a function existing at the subscriber site, e.g. an enterprise customer premises, that connects the SD-WAN user-to-network interface (UNI) to the underlay connectivity service (UCS) UNI. This function applies policies to the IP packets entering the SD-WAN service, determining how they are classified into application flows and forwarded across the underlay connectivity services according to the policy configuration.
Much like MEF’s service standards for underlay connectivity, an SD-WAN service consists of SD-WAN end points, specifically SD-WAN Virtual Connection End Points that together form the SD-WAN Virtual Connection. These end points represent the demarcation between the responsibility of the SD-WAN service provider and the subscriber. As an overlay service, SD-WAN involves multiple underlay connectivity services. In the sample below, there are two such services, which can leverage either MEF 3.0 underlay connectivity services, like Carrier Ethernet or other services, for example, an Internet broadband service. Furthermore, a unique element of SD-WAN services is the ability to forward traffic directly to the Internet from an SD-WAN UNI, which is termed Internet Breakout.