rfc5761.Multiplexing RTP Data and Control Packets on a Singl

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Internet Engineering Task Force (IETF) C. PerkinsRequest for Comments: 5761 University of GlasgowUpdates: 3550, 3551 M. WesterlundCategory: Standards Track EricssonISSN: 2070-1721 April 2010 Multiplexing RTP Data and Control Packets on a Single PortAbstract

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://doc.guandang.net/info/rfc5761.

Copyright Notice

Copyright (c) 2010 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 Provisions Relating to IETF Documents

(http://doc.guandang.net/license-info) in effect on the date of publication of this document. Please review these documents

carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

Perkins & Westerlund Standards Track [Page 1]

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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 ...................................12Perkins & Westerlund Standards Track [Page 2]

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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

discusses how the RTP and RTCP flows for a single media type can be run on a single port, to ease NAT traversal and simplify firewall administration, and considers when such multiplexing is appropriate. The multiplexing of several types of media (e.g., audio and video) onto a single port is not considered here (but see Section 5.2 of

[1]).

This memo is structured as follows: in Section 2 we discuss the

design choices that led to the use of separate ports and comment on the applicability of those choices to current network environments. We discuss terminology in Section 3 and how to distinguish

multiplexed packets in Section 4; we then specify when and how RTP and RTCP should be multiplexed, and how to signal multiplexed

sessions, in Section 5. Quality of service and bandwidth issues are discussed in Section 6. We conclude with security considerations in Section 7 and IANA considerations in Section 8.

This memo updates Section 11 of [1].

2. Background