Real-time Transport protocol
What is RTP  ?
Defined by Audio Video Transport (AVT) working group of
the Internet Engineering Task Force (IETF) .
It is a transport protocol for streaming media.  Such a
protocol requires 
Ø low latency ( less overhead TCP unsuitable)
Ø Sequencing ( UDP insufficient)
Ø Timing information.
Ø Field to identify payload type ( format of the media transported)
RTP packets are typically carried by UDP datagrams.
RTCP ( RTP Control Protocol )
Ø a companion protocol to monitor the quality of data delivery
offered by the RTP.