Network Working Group J. Rey
Request for Comments: 4588 Panasonic
Category: Standards Track D. Leon
Consultant
A. Miyazaki
Panasonic
V. Varsa
Nokia
R. Hakenberg
Panasonic
July 2006
RTP Retransmission Payload Format
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.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
RTP retransmission is an effective packet loss recovery technique for
real-time applications with relaxed delay bounds. This document
describes an RTP payload format for performing retransmissions.
Retransmitted RTP packets are sent in a separate stream from the
original RTP stream. It is assumed that feedback from receivers to
senders is available. In particular, it is assumed that Real-time
Transport Control Protocol (RTCP) feedback as defined in the extended
RTP profile for RTCP-based feedback (denoted RTP/AVPF) is available
in this memo.
Rey, et al. Standards Track [Page 1]RFC 4588 RTP Retransmission Payload Format July 2006Table of Contents
1. Introduction ....................................................3
2. Terminology .....................................................3
3. Requirements and Design Rationale for a Retransmission Scheme ...4
3.1. Multiplexing Scheme Choice .................................6
4. Retransmission Payload Format ...................................7
5. Association of Retransmission and Original Streams ..............9
5.1. Retransmission Session Sharing .............................9
5.2. CNAME Use ..................................................9
5.3. Association at the Receiver ................................9
6. Use with the Extended RTP Profile for RTCP-based Feedback ......11
6.1. RTCP at the Sender ........................................11
6.2. RTCP Receiver Reports .....................................11
6.3. Retransmission Requests ...................................12
6.4. Timing Rules ..............................................13
7. Congestion Control .............................................13
8. Retransmission Payload Format MIME Type Registration ...........15
8.1. Introduction ..............................................15
8.2. Registration of audio/rtx .................................16
8.3. Registration of video/rtx .................................17
8.4. Registration of text/rtx ..................................18
8.5. Registration of application/rtx ...........................19
8.6. Mapping to SDP ............................................20
8.7. SDP Description with Session-Multiplexing .................20
8.8. SDP Description with SSRC-Multiplexing ....................21
9. RTSP Considerations ............................................22
9.1. RTSP Control with SSRC-Multiplexing .......................22
9.2. RTSP Control with Session-Multiplexing ....................22
9.3. RTSP Control of the Retransmission Stream .................23
9.4. Cache Control .............................................23
10. Implementation Examples .......................................23
10.1. A Minimal Receiver Implementation Example ................24
10.2. Retransmission of Layered Encoded Media in Multicast .....25
11. IANA Considerations ...........................................26
12. Security Considerations .......................................26
13. Acknowledgements ..............................................27
14. References ....................................................27
14.1. Normative References .....................................27
14.2. Informative References ...................................28
Appendix A. How to Control the Number of Rtxs. per Packet .........29
datatracker.ietf.org