Multiplexing RTP Data and Control Packets on a Single Port
RFC 5761

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Internet Engineering Task Force (IETF)                        C. Perkins
Request for Comments: 5761                         University of Glasgow
Updates: 3550, 3551                                        M. Westerlund
Category: Standards Track                                       Ericsson
ISSN: 2070-1721                                               April 2010

       Multiplexing RTP Data and Control Packets on a Single Port

Abstract

   This memo discusses issues that arise when multiplexing RTP data
   packets and RTP Control Protocol (RTCP) packets on a single UDP port.
   It updates RFC 3550 and RFC 3551 to describe when such multiplexing
   is and is not appropriate, and it explains how the Session
   Description Protocol (SDP) can be used to signal multiplexed
   sessions.

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/rfc5761.

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   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Perkins & Westerlund         Standards Track                    [Page 1]
RFC 5761                Multiplexing RTP and RTCP             April 2010

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1. Introduction ....................................................3
   2. Background ......................................................3
   3. Terminology .....................................................4
   4. Distinguishable RTP and RTCP Packets ............................4
   5. Multiplexing RTP and RTCP on a Single Port ......................6
      5.1. Unicast Sessions ...........................................6
           5.1.1. SDP Signalling ......................................6
           5.1.2. Interactions with SIP Forking .......................7
           5.1.3. Interactions with ICE ...............................7
           5.1.4. Interactions with Header Compression ................8
      5.2. Any Source Multicast Sessions ..............................9
      5.3. Source-Specific Multicast Sessions .........................9
   6. Multiplexing, Bandwidth, and Quality of Service ................10
   7. Security Considerations ........................................10
   8. IANA Considerations ............................................11
   9. Acknowledgements ...............................................11
   10. References ....................................................11
      10.1. Normative References .....................................11
      10.2. Informative References ...................................12

Perkins & Westerlund         Standards Track                    [Page 2]
RFC 5761                Multiplexing RTP and RTCP             April 2010

1.  Introduction

   The Real-time Transport Protocol (RTP) [1] comprises two components:
   a data transfer protocol and an associated control protocol (RTCP).
   Historically, RTP and RTCP have been run on separate UDP ports.  With
   increased use of Network Address Port Translation (NAPT) [14], this
   has become problematic, since maintaining multiple NAT bindings can
   be costly.  It also complicates firewall administration, since
   multiple ports must be opened to allow RTP traffic.  This memo