You can use software-defined WAN (SD-WAN) services to unify underlay and overlay services under a single player, simplify the SD-WAN elements of your businesswide network fabric, and provide skills that are missing within your customer organization. But to realize these benefits, you'll first have to select from a diverse set of vendors that vary by size, functionality, geography, and vertical market focus. Infrastructure and operations (I&O) professionals should use this report to understand the value they can expect from an SD-WAN services provider and to select one based on size and functionality.