Which control plane protocol is used between Cisco SD-WAN routers and vSmart controllers?

OTCP is not a recognized control plane protocol in the Cisco SD-WAN architecture.

OMP (Overlay Management Protocol) is a TCP-based control plane protocol specific to Cisco SD-WAN. It handles the advertisement of network prefixes (vRoutes), service routes, and VPN topology information between vEdge/cEdge devices and vSmart controllers, forming the core of the SD-WAN's routing and policy distribution.

UDP is a transport layer protocol, not an application-layer control plane protocol like OMP, although OMP does run over a transport layer.

BGP is a common routing protocol, but in Cisco SD-WAN, OMP is the proprietary control plane protocol used for router-to-vSmart controller communication, not BGP.