Which protocol secures signaling between Cisco Unified Communications Manager (CUCM) and endpoints?

• A. UDP
• B. RTP
• C. TLS (SIP over TLS)
• D. TCP

Answer: (C)

Securing signaling between CUCM and endpoints means protecting the SIP control messages that set up and manage calls. Using TLS wraps SIP signaling in encryption, providing confidentiality, integrity, and server/client authentication through certificates. This is typically implemented as SIP over TLS (often called SIP over TLS or SIPS), running with certificates issued by a trusted CA and configured on both CUCM and endpoints. This ensures signaling cannot be eavesdropped or tampered with during call setup.

UDP and TCP are transport methods, not encryption by themselves—UDP offers no security and unreliability; TCP provides reliable transport but not encryption unless paired with TLS. RTP carries the media stream, not the signaling. So the secure signaling choice is TLS.