The underlying concept of software-defined WAN is that a router’s management and control planes are abstracted from the hardware and reside in the cloud. That router abstraction allows a company to join multiple physical locations into a single network over redundant, low-cost, telecommunication links. The idea is that a router chassis is drawn apart and distributed across a distance — the I/O modules remain physically on-premises while the switch fabric is stretched over long distance media (via TCP/IP, MPLS, 4G/LTE, etc.) and the backplane is virtualized on cloud servers.

The software of a router can be viewed as having three component systems: 

1) The Data Plane refers to all the functions and processes that forward packets and frames from one interface to another — routed data. In SD-WAN, the data plane is tunneled between on-premises edge-routers. Cisco calls them vEdges (named for Viptella, an SD-WAN company that Cisco bought) or cEdges. 

2) The Control Plane refers to all the functions and processes that determine which path to use — routing data. in SD-WAN, the control plane is shared between edge-routers via cloud-based controllers. Cisco’s controllers are called vSmart, and Cisco SD-WAN also requires another cloud-based server called vBond for network discovery. 

3) The Management Plane refers to the configuration used to control and monitor devices. In SD-WAN, the management plane also resides in the cloud. Cisco’s management server is called vManage.