Which protocol is known for facilitating secure video conferencing?

The answer identifies RTMP (Real-Time Messaging Protocol) as the protocol known for facilitating secure video conferencing. RTMP is designed specifically for transmitting audio, video, and data over the internet in real-time, making it particularly effective for live streaming and video communication applications. It establishes a persistent connection, which allows for low-latency transmission, a crucial requirement for effective video conferencing.

In contrast, other listed protocols serve different primary purposes. HTTP (Hypertext Transfer Protocol) is used for transmitting web page content and is not optimized for real-time communication. FTP (File Transfer Protocol) is primarily used for transferring files over the internet and does not support video conferencing needs effectively. SMTP (Simple Mail Transfer Protocol) is designed for email transmission and thus is not relevant to the requirements of video conferencing. Each of these alternatives lacks the specific features necessary for the efficient and secure transmission of real-time video and audio that RTMP provides.