RTP

Real-time Transport Protocol (RTP) is the standard protocol for delivering audio and video over IP networks. While SIP handles call signaling (setup, teardown), RTP carries the actual voice and video media between endpoints.

Standard RTP sends media unencrypted. SRTP (Secure RTP) adds encryption and authentication, protecting the media stream from eavesdropping. For sensitive communications, SRTP is essential — and most modern softphones support it by default.