rfc3550-RTP-RTSP协议（英文原版）

Network Working Group H. Schulzrinne

Request for Comments: 3550 Columbia University

Obsoletes: 1889 S. Casner

Category: Standards Track Packet Design

R. Frederick

Blue Coat Systems Inc.

V. Jacobson

Packet Design

Official Protocol Standards" (STD 1) for the standardization state

and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2003). All Rights Reserved.

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

translators and mixers.

Most of the text in this memorandum is identical to RFC 1889 which it

obsoletes. There are no changes in the packet formats on the wire,

only changes to the rules and algorithms governing how the protocol

is used. The biggest change is an enhancement to the scalable timer

algorithm for calculating when to send RTCP packets in order to

minimize transmission in excess of the intended rate when many

participants join a session simultaneously.

Schulzrinne, et al. Standards Track [Page 1]

RFC 3550 RTP July 2003

Table of Contents

1. Introduction ................................................ 4

1.1 Terminology ............................................ 5

2.1 Simple Multicast Audio Conference ...................... 6

2.2 Audio and Video Conference ............................. 7

5.3 Profile-Specific Modifications to the RTP Header ....... 18

5.3.1 RTP Header Extension ............................ 18

6.1 RTCP Packet Format ..................................... 21

6.2.1 Maintaining the Number of Session Members ....... 28

6.3.1 Computing the RTCP Transmission Interval ........ 29

6.3.3 Receiving an RTP or Non-BYE RTCP Packet ......... 31

6.3.4 Receiving an RTCP BYE Packet .................... 31

6.3.5 Timing Out an SSRC .............................. 32

6.3.6 Expiration of Transmission Timer ................ 32

6.3.7 Transmitting a BYE Packet ....................... 33

6.4.4 Analyzing Sender and Receiver Reports ........... 43

6.5 SDES: Source Description RTCP Packet ................... 45

6.5.1 CNAME: Canonical End-Point Identifier SDES Item . 46

6.5.2 NAME: User Name SDES Item ....................... 48

6.5.3 EMAIL: Electronic Mail Address SDES Item ........ 48

6.5.4 PHONE: Phone Number SDES Item ................... 49

6.5.5 LOC: Geographic User Location SDES Item ......... 49

6.5.6 TOOL: Application or Tool Name SDES Item ........ 49

6.5.7 NOTE: Notice/Status SDES Item ................... 50

6.5.8 PRIV: Private Extensions SDES Item .............. 50

6.6 BYE: Goodbye RTCP Packet ............................... 51

6.7 APP: Application-Defined RTCP Packet ................... 52

7. RTP Translators and Mixers .................................. 53

7.1 General Description .................................... 53

Schulzrinne, et al. Standards Track [Page 2]

RFC 3550 RTP July 2003

7.2 RTCP Processing in Translators ......................... 55

7.3 RTCP Processing in Mixers .............................. 57

7.4 Cascaded Mixers ........................................ 58

8. SSRC Identifier Allocation and Use .......................... 59

8.2 Collision Resolution and Loop Detection ................ 60

8.3 Use with Layered Encodings ............................. 64

12.2 SDES Types ............................................. 70

13. RTP Profiles and Payload Format Specifications .............. 71

15. IANA Considerations ......................................... 73

17. Acknowledgments ............................................. 74

Appendix A.1 RTP Data Header Validity Checks ................... 78

Appendix A.3 Determining Number of Packets Expected and Lost ... 83

Appendix A.4 Generating RTCP SDES Packets ...................... 84

Appendix A.5 Parsing RTCP SDES Packets ......................... 85

Appendix A.6 Generating a Random 32-bit Identifier ............. 85

Appendix A.7 Computing the RTCP Transmission Interval .......... 87

Full Copyright Statement ........................................ 104