I have created this hub today so that students studying voice over IP services can learn about real time transport protocol. This is also for communication engineering students who are into VoIP training and have assignments and VoIP projects.

Real time transport protocol (RTP) or transport protocol in real time is a protocol, which as its name implies is used for transmission of real-time info such as video or voice data. RTP is a much higher-level protocol, which works on user datagram protocol or UDP using the multiplexing or checksum services in order to provide some programs that generate data such as managing real time transmissions through multicast or unicast broadcasts.

However, RTP or Real time transport protocol is not reliable enough by itself, but it provides applications of lower layers and resources provided by routers and switches in order to ensure reliability. Real time protocol packets contain no length field because when it runs over user datagram protocol, RTP is the one, which encases the compressed voice real-time datagrams.

RTCP or RTP Control Protocol is a tool, which uses Real time protocol or RTP to achieve real time transmission of data and this is the one which provides feedback to the backup system about quality of distribution and network congestion. In simple words with RTCP the VoIP service providers can easily monitor the quality of the service rendered and can diagnose various network congestion problems that may be present in the network.

Besides this, RTCP sync video and audio also knows about number of users that are present at a conference and it also calculates and monitors the rate at which data packets should be sent. It is important to note that all the above options become mandatory when real time protocols are used in IP multicast environments. There is also another optional application, which is known as session management, which is required in situations where there is widespread or considerable use of users that come and go constantly such as in call centers.

Real time protocol is able to run on high-speed wide area network protocols such as Asynchronous Transfer Mode Protocol with no problem. Real time protocol is able to run on asymmetric networks such as cable modems, asymmetric digital subscriber lines, or satellite links but complies with certain characteristics of bandwidth in each direction and is used exclusively to implement real time protocol or RTP.

Transmission control protocol or TCP is a heavy information transport protocol and carries video and voice data but TCP and other protocols like XTP (Xpress Transfer Protocol) become inappropriate for 3 basic reasons:

1. First drawback of TCP is that it does not support multicast and leads to loss of packets using broadcast packages.
2. Second drawback of TCP is that the TCP congestion control reduces the transmission window when it detects audio and video data packet loss whereas the alternative applications for TCP do not allow such reductions in transmission window.
3. Third drawback of TCP is that the header of these protocols is longer than RTPs.