In Cisco SD-WAN, what protocol is used for control connections between SD-WAN devices?

DTLS (Datagram Transport Layer Security) is the secure tunnel encapsulation protocol that secures the control connections, but OMP is the actual routing protocol that runs over these connections.

OMP (Overlay Management Protocol) is the proprietary routing protocol integral to Cisco SD-WAN, operating over the secure DTLS or TLS control connections established between vSmart controllers and WAN Edge routers. It is responsible for advertising routing information, service routes, TLOC routes, and security policies across the entire overlay network, forming the control plane backbone.

BGP (Border Gateway Protocol) can be used for routing within the SD-WAN overlay in specific scenarios, but it is not the primary control connection protocol between core SD-WAN devices.

OSPF (Open Shortest Path First) is an Interior Gateway Protocol (IGP) used in traditional LAN environments and may be used on the service side of a WAN Edge router, but not for control connections within the SD-WAN fabric.