Which protocol runs between the vSmart controllers and between the vSmart controllers and the vEdge routers, and unifies all control plane functions under a single protocol umbrella?

OMP (Overlay Management Protocol) is a proprietary Cisco SD-WAN protocol that runs between vSmart controllers and vEdge routers. It functions as the control plane for the SD-WAN fabric, distributing routing information, policy information, and service data securely within the overlay network.

OSPF (Open Shortest Path First) is an interior gateway protocol used for routing within an autonomous system and is not the control plane protocol for Cisco SD-WAN overlay networks.

IKE (Internet Key Exchange) is used for establishing security associations (SAs) and keys for IPsec, which provides data plane security, not control plane communication in Cisco SD-WAN.

VRRP (Virtual Router Redundancy Protocol) provides default gateway redundancy for hosts on a LAN, and it is not involved in the SD-WAN control plane communication between controllers and routers.

BGP (Border Gateway Protocol) is an exterior gateway protocol used for routing between autonomous systems, and while used in some SD-WAN deployments for underlay routing, it is not the unified control plane protocol for the overlay.