RFC 1889 (rfc1889) - Page 3 of 75

RTP: A Transport Protocol for Real-Time Applications

RFC 1889                          RTP                       January 1996


   A.8        Estimating the Interarrival Jitter ..................   71
   B.         Security Considerations .............................   72
   C.         Addresses of Authors ................................   72
   D.         Bibliography ........................................   73

1.  Introduction

   This memorandum specifies the real-time transport protocol (RTP),
   which provides end-to-end delivery services for data with real-time
   characteristics, such as interactive audio and video. Those services
   include payload type identification, sequence numbering, timestamping
   and delivery monitoring. Applications typically run RTP on top of UDP
   to make use of its multiplexing and checksum services; both protocols
   contribute parts of the transport protocol functionality. However,
   RTP may be used with other suitable underlying network or transport
   protocols (see Section 10). RTP supports data transfer to multiple
   destinations using multicast distribution if provided by the
   underlying network.

   Note that RTP itself does not provide any mechanism to ensure timely
   delivery or provide other quality-of-service guarantees, but relies
   on lower-layer services to do so. It does not guarantee delivery or
   prevent out-of-order delivery, nor does it assume that the underlying
   network is reliable and delivers packets in sequence. The sequence
   numbers included in RTP allow the receiver to reconstruct the
   sender's packet sequence, but sequence numbers might also be used to
   determine the proper location of a packet, for example in video
   decoding, without necessarily decoding packets in sequence.

   While RTP is primarily designed to satisfy the needs of multi-
   participant multimedia conferences, it is not limited to that
   particular application. Storage of continuous data, interactive
   distributed simulation, active badge, and control and measurement
   applications may also find RTP applicable.

   This document defines RTP, consisting of two closely-linked parts:

        o the real-time transport protocol (RTP), to carry data that has
         real-time properties.

        o the RTP control protocol (RTCP), to monitor the quality of
         service and to convey information about the participants in an
         on-going session. The latter aspect of RTCP may be sufficient
         for "loosely controlled" sessions, i.e., where there is no
         explicit membership control and set-up, but it is not
         necessarily intended to support all of an application's control
         communication requirements.  This functionality may be fully or
         partially subsumed by a separate session control protocol,



Schulzrinne, et al          Standards Track