For SC-7(4), what is defined as control plane traffic?

Control plane traffic in the context of external telecommunications systems are the exchanges with the telecommunication providers that allow for the use of data and voice services and include (e.g., management protocols, Domain Name Services (DNS) and Border Gateway Protocol (BGP)). The term management plane is not a NIST term and not mentioned in this control but in this context it would be the plane where device management and monitoring takes place inside the authorization boundary. While there would not be a prescribed implementation detecting changes the protocols that defined network level changes do have safeguards built. How the CSP chooses to monitor for changes will be dependent on the implementation.