RTP: A Transport Protocol for Real-Time Applications
RFC 1889

 
Document Type RFC - Proposed Standard (January 1996; No errata)
Obsoleted by RFC 3550
Last updated 2013-03-02
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Network Working Group                Audio-Video Transport Working Group
Request for Comments: 1889                                H. Schulzrinne
Category: Standards Track                                      GMD Fokus
                                                               S. Casner
                                                  Precept Software, Inc.
                                                            R. Frederick
                                         Xerox Palo Alto Research Center
                                                             V. Jacobson
                                   Lawrence Berkeley National Laboratory
                                                            January 1996

          RTP: A Transport Protocol for Real-Time Applications

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   This memorandum describes RTP, the real-time transport protocol. RTP
   provides end-to-end network transport functions suitable for
   applications transmitting real-time data, such as audio, video or
   simulation data, over multicast or unicast network services. RTP does
   not address resource reservation and does not guarantee quality-of-
   service for real-time services. The data transport is augmented by a
   control protocol (RTCP) to allow monitoring of the data delivery in a
   manner scalable to large multicast networks, and to provide minimal
   control and identification functionality. RTP and RTCP are designed
   to be independent of the underlying transport and network layers. The
   protocol supports the use of RTP-level translators and mixers.

Table of Contents

   1.         Introduction ........................................    3
   2.         RTP Use Scenarios ...................................    5
   2.1        Simple Multicast Audio Conference ...................    5
   2.2        Audio and Video Conference ..........................    6
   2.3        Mixers and Translators ..............................    6
   3.         Definitions .........................................    7
   4.         Byte Order, Alignment, and Time Format ..............    9
   5.         RTP Data Transfer Protocol ..........................   10
   5.1        RTP Fixed Header Fields .............................   10
   5.2        Multiplexing RTP Sessions ...........................   13

Schulzrinne, et al          Standards Track                     [Page 1]
RFC 1889                          RTP                       January 1996

   5.3        Profile-Specific Modifications to the RTP Header.....   14
   5.3.1      RTP Header Extension ................................   14
   6.         RTP Control Protocol -- RTCP ........................   15
   6.1        RTCP Packet Format ..................................   17
   6.2        RTCP Transmission Interval ..........................   19
   6.2.1      Maintaining the number of session members ...........   21
   6.2.2      Allocation of source description bandwidth ..........   21
   6.3        Sender and Receiver Reports .........................   22
   6.3.1      SR: Sender report RTCP packet .......................   23
   6.3.2      RR: Receiver report RTCP packet .....................   28
   6.3.3      Extending the sender and receiver reports ...........   29
   6.3.4      Analyzing sender and receiver reports ...............   29
   6.4        SDES: Source description RTCP packet ................   31
   6.4.1      CNAME: Canonical end-point identifier SDES item .....   32
   6.4.2      NAME: User name SDES item ...........................   34
   6.4.3      EMAIL: Electronic mail address SDES item ............   34
   6.4.4      PHONE: Phone number SDES item .......................   34
   6.4.5      LOC: Geographic user location SDES item .............   35
   6.4.6      TOOL: Application or tool name SDES item ............   35
   6.4.7      NOTE: Notice/status SDES item .......................   35
   6.4.8      PRIV: Private extensions SDES item ..................   36
   6.5        BYE: Goodbye RTCP packet ............................   37
   6.6        APP: Application-defined RTCP packet ................   38
   7.         RTP Translators and Mixers ..........................   39
   7.1        General Description .................................   39
   7.2        RTCP Processing in Translators ......................   41
   7.3        RTCP Processing in Mixers ...........................   43
   7.4        Cascaded Mixers .....................................   44
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