Guidelines for End-to-End Support of the RTP Control Protocol (RTCP) in Back-to-Back User Agents (B2BUAs)
RFC 8079
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Type |
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RFC - Proposed Standard
(February 2017; No errata)
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Last updated |
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2018-12-20
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IETF
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Submitted to IESG for Publication
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Document shepherd |
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Christer Holmberg
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(last changed 2015-05-12)
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RFC 8079 (Proposed Standard)
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Ben Campbell
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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
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.
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]
RFC 8079 RTCP Translation in B2BUAs February 2017
functionality for participants with incompatible codecs, or it may
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