1.4 Relationship to Other Protocols
RTSP relies on TCP [RFC793] for controlling the streaming media session. Although the User Datagram Protocol (UDP) [RFC768] is also allowed, it is rarely used for this purpose.
RTSP uses Session Description Protocol (SDP) [RFC4566] syntax to specify the properties of content.
RTSP uses Real-Time Transport Protocol (RTP) [RFC3550] for the delivery of multimedia data and Real-Time Transport Control Protocol (RTCP) [RFC3556] for RTP feedback and statistics. RTP and RTCP packets are transmitted over either UDP or TCP. It is possible to transmit some RTP streams over UDP and other RTP streams over TCP.
RTSP with Windows Media extensions depends on Advanced Systems Format (ASF) [ASF], which is used in both the SDP syntax and the payload of RTP packets. This is similar in functionality to the Windows Media HTTP Streaming Protocol [MS-WMSP]. However, in that protocol, the delivery of ASF packets is limited to TCP only.
RTSP is similar in functionality to the Microsoft Media Server (MMS) protocol [MS-MMSP]. However, RTSP with Windows Media extensions provides additional functionality that is not available in MMS.