The Real Time Streaming Protocol, or RTSP, is an application-level protocol for excising a control over the delivery of data, with real-time properties. RTSP provides an extensible framework to enable controlled, on-demand delivery of real-time data, such as audio and video. Sources of data can include both live data feeds and stored clips. This protocol is intended to control multiple data delivery sessions,to provide a means for choosing delivery channels such as UDP, multicast UDP and TCP, and to provide a means for choosing delivery mechanisms based upon RTP (RFC 1889). It is designed to leverage existing web infrastructure and works well both for large audiences as well as single-viewer media-on-demand.
H.323 and RTSP are complementary in function. H.323 is useful for setting up audio/video conferences in moderately sized peer-to-peer groups, whereas RTSP is useful for large-scale broadcasts and audio/video-on-demand streaming. One could think of H.323 as offering services equivalent to a telephone with three-way calling, while RTSP offers services like a video store with delivery services, a VCR or cable television. RTSP provides “VCR-style” control functionality such as pause, fast forward, reverse, and absolute positioning, which is beyond the scope of H.323 and RTP.
The RTSP re-direction feature allows Caching Proxy to redirect requests for any streaming media sessions controlled by RTSP. The RTSP redirector does not cache or directly proxy media presentations. The RTSP redirector must be used in conjunction with a third-party streaming media server ,to provide either or both of those functions.
