Real Time Transport Protocol, or RTP for short, is a data transfer protocol designed specifically to exchange real-time sensitive, audio-visual data on IP-based networks. RTP is often used in Voice-over-IP telephony (VoIP telephony). IP-capable telephone systems therefore also feature the Real Time Transport Protocol. The first standardization was already recorded in 1996 in RFC 1889. Since 2003 RTP is a specification in RFC 3550.
The Real Time Transport Protocol is able to code multimedia data streams such as audio or video, divide them into packets and transmit them over an IP network. At transport level, Real Time Transport Protocol typically uses connectionless UDP (User Datagram Protocol). RTP allows data to be exchanged in Unicast as well as Multicast communication. In order to handle and meet the necessary Quality of Service parameters (QoS parameters) during the transfer, RTP partners with the Real Time Control Protocol (RTCP).
RTP has been established as the communication link standard for transmitting audio or video streams for the IP telephony protocols SIP and H.323.