Real-time Transfer Protocol (RTP) is the Internet-standard protocol for the transport of real-time data, including audio and video. It can be used for media-on-demand as well as interactive services such as Internet telephony. RTP consists of a data and a control part. The latter is called RTCP.
The data part of RTP is a thin protocol providing support for applications with real-time properties such as continuous media (e.g., audio and video), including timing reconstruction, loss detection, security and content identification.
RTCP provides support for real-time conferencing of groups of any size within an internet. This support includes source identification and support for gateways like audio and video bridges as well as multicast-to-unicast translators. It offers quality-of-service feedback from receivers to the multicast group as well as support for the synchronization of different media streams.
While UDP/IP is its initial target networking environment, efforts have been made to make RTP transport-independent so that it could be used, say, over CLNP, IPX or other protocols. RTP is currently also in experimental use directly over AAL5/ATM. RTP does not address the issue of resource reservation or quality of service control; instead, it relies on resource reservation protocols such as RSVP .
Other applications, such as real-time control and distributed simulation, are also targets.
RTP was developed by the Audio-Video Transport Working Group of the IETF and first published in 1996 as RFC 1889 . It was originally designed as a multicast protocol, but has since been applied in many unicast applications. It is frequently used in streaming media systems (in conjunction with RTSP ) as well as videoconferencing and push to talk systems (in conjunction with H.323 or SIP ), making it the technical foundation of the Voice over IP industry. It goes along with the RTP Control Protocol ( RTCP ) and it's built on top of the User Datagram Protocol ( UDP ) (in OSI model ).
According to RFC 1889 , the services provided by RTP include: