I was curious, having spent a couple decades doing network config automation, and it appears there is quite a bit of overlap with what they are calling SDN-WAN

I was curious, having spent a couple decades doing network config automation, and it appears there is quite a bit of overlap with what they are calling SDN-WAN now. It is my understanding that software defined networks in a data center local area network have controllers that set up a switching path for each new packet flow. When a new flow is detected the edge device, perhaps a switch, asks the controller what to do with it. The switches are dumb, it is the controller that is programmed with all of the rules for the network. A single (redundant) set of controllers has the rules to direct traffic through all the network devices in a data center. The article seems to describe software defined networking over a wide area network as having a centralized configuration management server that maintains the configurations for all wide area networking devices - the configurations for tunnel endpoints, security access lists, and queueing. Software is put in charge of the device configs, but they are the same configs that a human might otherwise manipulate. Decisions on packet routing are handled by the end point devices, not by the controller. This makes sense, given that outages on a wide area network might affect access to the centralized controller. You wouldn't want all the sites on your network to be unable to route traffic just because the site with the controller is no longer accessible over the wide area network. Network config automation brings a lot of value, removing the element of human error, and allowing a set amount of network engineers to accomplish much more than they could otherwise.