In the Cisco SD-WAN architecture, the Overlay Management Protocol (OMP) is used to exchange routing, policy, and management information between the vSmart controllers and the WAN Edge routers. The vSmart controller acts as a central orchestrator that communicates with each WAN Edge router to distribute policies and maintain a cohesive network state. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) - Official Certification Guide