Guidelines for End-to-End Support of the RTP Control Protocol (RTCP) in Back-to-Back User Agents (B2BUAs)
RFC 8079

Document Type RFC - Proposed Standard (February 2017; No errata)
Last updated 2017-02-22
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IESG IESG state RFC 8079 (Proposed Standard)
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Internet Engineering Task Force (IETF)                        L. Miniero
Request for Comments: 8079                                      Meetecho
Category: Standards Track                              S. Garcia Murillo
ISSN: 2070-1721                                                  Medooze
                                                              V. Pascual
                                                                  Oracle
                                                           February 2017

Guidelines for End-to-End Support of the RTP Control Protocol (RTCP) in
                   Back-to-Back User Agents (B2BUAs)

Abstract

   SIP Back-to-Back User Agents (B2BUAs) are often designed to also be
   on the media path, rather than just to intercept signalling.  This
   means that B2BUAs often implement an RTP or RTP Control Protocol
   (RTCP) stack as well, thus leading to separate multimedia sessions
   that the B2BUA correlates and bridges together.  If not disciplined,
   this behaviour can severely impact the communication experience,
   especially when statistics and feedback information contained in RTCP
   messages get lost because of mismatches in the reported data.

   This document defines the proper behaviour B2BUAs should follow when
   acting on both the signalling plane and media plane in order to
   preserve the end-to-end functionality of RTCP.

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 7841.

   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/rfc8079.

Miniero, et al.              Standards Track                    [Page 1]
RFC 8079               RTCP Translation in B2BUAs          February 2017

Copyright Notice

   Copyright (c) 2017 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
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   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Signalling/Media Plane B2BUAs . . . . . . . . . . . . . . . .   4
     3.1.  Media Relay . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Media-Aware Relay . . . . . . . . . . . . . . . . . . . .   6
     3.3.  Media Terminator  . . . . . . . . . . . . . . . . . . . .  11
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   Session Initiation Protocol (SIP) [RFC3261] Back-to-Back User Agents
   (B2BUAs) are SIP entities that can act as a logical combination of
   both a User Agent Server (UAS) and a User Agent Client (UAC).  As
   such, their behaviour is not always completely adherent to standards
   and can lead to unexpected situations.  [RFC7092] presents a taxonomy
   of the most commonly deployed B2BUA implementations and describes how
   they differ in terms of the functionality and features they provide.

   Such components often do not only act on the signalling plane
   (intercepting and possibly modifying SIP messages), but also on the
   media plane.  This means that, in order to receive and manage all RTP
   and RTCP [RFC3550] packets in a session, these components also
   manipulate the session descriptions [RFC4566] in the related offer/
   answer exchanges [RFC3264].  The reasons for such behaviour can be
   different.  The B2BUA may want, for instance, to provide transcoding

Miniero, et al.              Standards Track                    [Page 2]
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