In the Cisco SD-WAN architecture, Datagram Transport Layer Security (DTLS) is used to encrypt the control plane traffic between the SD-WAN controllers and the SD-WAN endpoints. DTLS is a communications protocol that provides security for datagram-based applications by allowing them to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery. References: Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR) v1.1