Guidelines for Extending the RTP Control Protocol (RTCP)
RFC 5968

Document Type RFC - Informational (September 2010; No errata)
Last updated 2015-10-14
Replaces draft-ott-avt-rtcp-guidelines
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Internet Engineering Task Force (IETF)                            J. Ott
Request for Comments: 5968                              Aalto University
Category: Informational                                       C. Perkins
ISSN: 2070-1721                                    University of Glasgow
                                                          September 2010

        Guidelines for Extending the RTP Control Protocol (RTCP)

Abstract

   The RTP Control Protocol (RTCP) is used along with the Real-time
   Transport Protocol (RTP) to provide a control channel between media
   senders and receivers.  This allows constructing a feedback loop to
   enable application adaptation and monitoring, among other uses.  The
   basic reporting mechanisms offered by RTCP are generic, yet quite
   powerful and suffice to cover a range of uses.  This document
   provides guidelines on extending RTCP if those basic mechanisms prove
   insufficient.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see 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/rfc5968.

Ott & Perkins                 Informational                     [Page 1]
RFC 5968             Guidelines for RTCP Extensions       September 2010

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://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 ....................................................3
   2. Terminology .....................................................4
   3. RTP and RTCP Operation Overview .................................4
      3.1. RTCP Capabilities ..........................................5
      3.2. RTCP Limitations ...........................................7
      3.3. Interactions with Network- and Transport-Layer Mechanisms ..8
   4. Issues with RTCP Extensions .....................................9
   5. Guidelines .....................................................10
   6. Security Considerations ........................................14
   7. Acknowledgements ...............................................15
   8. References .....................................................15
      8.1. Normative References ......................................15
      8.2. Informative References ....................................16

Ott & Perkins                 Informational                     [Page 2]
RFC 5968             Guidelines for RTCP Extensions       September 2010

1.  Introduction

   The Real-time Transport Protocol (RTP) [RFC3550] is used to carry
   time-dependent (often continuous) media such as audio or video across
   a packet network in an RTP session.  RTP usually runs on top of an
   unreliable transport such as UDP, Datagram Transport Layer Security
   (DTLS), or the Datagram Congestion Control Protocol (DCCP), so that
   RTP packets are susceptible to loss, re-ordering, or duplication.
   Associated with RTP is the RTP Control Protocol (RTCP), which
   provides a control channel for each session: media senders provide
   information about their current sending activities ("feed forward"),
   and media receivers report on their reception statistics ("feedback")
   in terms of received packets, losses, and jitter.  Senders and
   receivers provide self-descriptions allowing them to disambiguate all
   entities in an RTP session and correlate synchronisation source
   (SSRC) identifiers with specific application instances.  RTCP is
   carried over the same transport as RTP and is inherently best-effort;
   hence the RTCP reports are designed for such an unreliable
   environment, e.g., by making them "for information only".
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