Duplicating RTP Streams
RFC 7198

Internet Engineering Task Force (IETF)                          A. Begen
Request for Comments: 7198                                         Cisco
Category: Standards Track                                     C. Perkins
ISSN: 2070-1721                                    University of Glasgow
                                                              April 2014

                        Duplicating RTP Streams

Abstract

   Packet loss is undesirable for real-time multimedia sessions but can
   occur due to a variety of reasons including unplanned network
   outages.  In unicast transmissions, recovering from such an outage
   can be difficult depending on the outage duration, due to the
   potentially large number of missing packets.  In multicast
   transmissions, recovery is even more challenging as many receivers
   could be impacted by the outage.  For this challenge, one solution
   that does not incur unbounded delay is to duplicate the packets and
   send them in separate redundant streams, provided that the underlying
   network satisfies certain requirements.  This document explains how
   Real-time Transport Protocol (RTP) streams can be duplicated without
   breaking RTP or RTP Control Protocol (RTCP) rules.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7198.

Begen & Perkins              Standards Track                    [Page 1]
RFC 7198                     RTP Duplication                  April 2014

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology and Requirements Notation . . . . . . . . . . . .   4
   3.  Use Cases for Dual Streaming  . . . . . . . . . . . . . . . .   4
     3.1.  Temporal Redundancy . . . . . . . . . . . . . . . . . . .   4
     3.2.  Spatial Redundancy  . . . . . . . . . . . . . . . . . . .   5
     3.3.  Dual Streaming over a Single Path or Multiple Paths . . .   5
     3.4.  Requirements  . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Use of RTP and RTCP with Temporal Redundancy  . . . . . . . .   7
     4.1.  RTCP Considerations . . . . . . . . . . . . . . . . . . .   7
     4.2.  Signaling Considerations  . . . . . . . . . . . . . . . .   7
   5.  Use of RTP and RTCP with Spatial Redundancy . . . . . . . . .   8
     5.1.  RTCP Considerations . . . . . . . . . . . . . . . . . . .   9
     5.2.  Signaling Considerations  . . . . . . . . . . . . . . . .   9
   6.  Use of RTP and RTCP with Temporal and Spatial Redundancy  . .  10
   7.  Congestion Control Considerations . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  11
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  12
     10.2.  Informative References . . . . . . . . . . . . . . . . .  12

Begen & Perkins              Standards Track                    [Page 2]
RFC 7198                     RTP Duplication                  April 2014

1.  Introduction

   The Real-time Transport Protocol (RTP) [RFC3550] is widely used today
   for delivering IPTV traffic and other real-time multimedia sessions.
   Many of these applications support very large numbers of receivers
   and rely on intra-domain UDP/IP multicast for efficient distribution
   of traffic within the network.

   While this combination has proved successful, there does exist a
   weakness.  As [RFC2354] noted, packet loss is not avoidable.  This