datatracker.ietf.org
Sign in
Version 5.6.2.p2, 2014-07-24
Report a bug

Application Mechanism for Keeping Alive the NAT Mappings Associated with RTP / RTP Control Protocol (RTCP) Flows
RFC 6263

Internet Engineering Task Force (IETF)                         X. Marjou
Request for Comments: 6263                                    A. Sollaud
Category: Standards Track                          France Telecom Orange
ISSN: 2070-1721                                                June 2011

        Application Mechanism for Keeping Alive the NAT Mappings
        Associated with RTP / RTP Control Protocol (RTCP) Flows

Abstract

   This document lists the different mechanisms that enable applications
   using the Real-time Transport Protocol (RTP) and the RTP Control
   Protocol (RTCP) to keep their RTP Network Address Translator (NAT)
   mappings alive.  It also makes a recommendation for a preferred
   mechanism.  This document is not applicable to Interactive
   Connectivity Establishment (ICE) agents.

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/rfc6263.

Copyright Notice

   Copyright (c) 2011 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://trustee.ietf.org/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.

Marjou & Sollaud             Standards Track                    [Page 1]
RFC 6263                      RTP Keepalive                    June 2011

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................4
   3. Requirements ....................................................4
   4. List of Alternatives for Performing RTP Keepalive ...............4
      4.1. Empty (0-Byte) Transport Packet ............................4
      4.2. RTP Packet with Comfort Noise Payload ......................5
      4.3. RTCP Packets Multiplexed with RTP Packets ..................5
      4.4. STUN Indication Packet .....................................6
      4.5. RTP Packet with Incorrect Version Number ...................6
      4.6. RTP Packet with Unknown Payload Type .......................6
   5. Recommended Solution for Keepalive Mechanism ....................7
   6. Media Format Exceptions .........................................7
   7. Timing and Transport Considerations .............................7
   8. RTCP Flow Keepalive .............................................8
   9. Security Considerations .........................................9
   10. Acknowledgements ...............................................9
   11. References ....................................................10
      11.1. Normative References .....................................10
      11.2. Informative References ...................................10

1.  Introduction

   [RFC4787] and [RFC5382] describe Network Address Translator (NAT)
   behaviors and point out that two key aspects of NAT are mappings
   (a.k.a. bindings) and keeping them refreshed.  This introduces a
   derived requirement for applications engaged in a multimedia session
   involving NAT traversal: they need to generate a minimum of flow
   activity in order to create NAT mappings and maintain them.

   When applied to applications using the Real-time Transport Protocol
   (RTP) [RFC3550], the RTP media stream packets themselves normally
   fulfill this requirement.  However, there exist some cases where RTP
   does not generate the minimum required flow activity.

   The examples are:

   o  In some RTP usages, such as the Session Initiation Protocol (SIP)
      [RFC3261], agents can negotiate a unidirectional media stream by
      using the Session Description Protocol (SDP) [RFC4566] "recvonly"
      attribute on one agent and "sendonly" on the peer, as defined in
      [RFC3264].  [RFC3264] directs implementations not to transmit
      media on the receiving agent.  If the agent receiving the media is

[include full document text]