Why does Flash Media Server use RTMP and not Real Time Streaming Protocol (RTSP)?
RTMP enables multidirectional communication from Flash Player to Flash Media Server. This protocol allows the client to control the stream delivery quality and security. RTMP has different modes that include two real-time encryption modes: SSL (RTMPS) and RTMPE. It also allows multiway interactive applications to send data back and forth. Real Time Streaming Protocol (RTSP) is an insecure, one-way protocol. With RTSP, alternate solutions and workflows are needed to protect your content (such as DRM). In addition, multidirectional communication is not possible with RTSP.