Which control-plane protocol do Cisco SD-WAN routers use to communicate with vSmart controllers?

Cisco SD-WAN routers use Overlay Management Protocol (OMP) to communicate with vSmart controllers. OMP is a proprietary control-plane protocol that runs over DTLS or TLS and is responsible for advertising routes, policies, and services within the SD-WAN fabric. It enables the vSmart controllers to build a centralized view of the network topology and enforce policies. TCP and UDP are transport layer protocols, not control-plane protocols specific to SD-WAN. While OMP uses TCP for its underlying transport, OMP itself is the control-plane protocol. BGP is a routing protocol used in traditional IP networks and can be integrated into SD-WAN for external routing, but it is not the primary control-plane protocol between SD-WAN routers and vSmart controllers.