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Explicit Congestion Notification (ECN) for RTP over UDP
RFC 6679

Internet Engineering Task Force (IETF)                     M. Westerlund
Request for Comments: 6679                                  I. Johansson
Category: Standards Track                                       Ericsson
ISSN: 2070-1721                                               C. Perkins
                                                   University of Glasgow
                                                             P. O'Hanlon
                                                    University of Oxford
                                                             K. Carlberg
                                                                     G11
                                                             August 2012

        Explicit Congestion Notification (ECN) for RTP over UDP

Abstract

   This memo specifies how Explicit Congestion Notification (ECN) can be
   used with the Real-time Transport Protocol (RTP) running over UDP,
   using the RTP Control Protocol (RTCP) as a feedback mechanism.  It
   defines a new RTCP Extended Report (XR) block for periodic ECN
   feedback, a new RTCP transport feedback message for timely reporting
   of congestion events, and a Session Traversal Utilities for NAT
   (STUN) extension used in the optional initialisation method using
   Interactive Connectivity Establishment (ICE).  Signalling and
   procedures for negotiation of capabilities and initialisation methods
   are also defined.

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/rfc6679.

Westerlund, et al.           Standards Track                    [Page 1]
RFC 6679                 ECN for RTP over UDP/IP             August 2012

Copyright Notice

   Copyright (c) 2012 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.

Westerlund, et al.           Standards Track                    [Page 2]
RFC 6679                 ECN for RTP over UDP/IP             August 2012

Table of Contents

   1. Introduction ....................................................4
   2. Conventions, Definitions, and Acronyms ..........................5
   3. Discussion, Requirements, and Design Rationale ..................6
      3.1. Requirements ...............................................8
      3.2. Applicability ..............................................8
      3.3. Interoperability ..........................................12
   4. Overview of Use of ECN with RTP/UDP/IP .........................13
   5. RTCP Extensions for ECN Feedback ...............................16
      5.1. RTP/AVPF Transport-Layer ECN Feedback Packet ..............16
      5.2. RTCP XR Report Block for ECN Summary Information ..........19
   6. SDP Signalling Extensions for ECN ..............................21
      6.1. Signalling ECN Capability Using SDP .......................21
      6.2. RTCP ECN Feedback SDP Parameter ...........................26
      6.3. XR Block ECN SDP Parameter ................................26
      6.4. ICE Parameter to Signal ECN Capability ....................27
   7. Use of ECN with RTP/UDP/IP .....................................27
      7.1. Negotiation of ECN Capability .............................27
      7.2. Initiation of ECN Use in an RTP Session ...................28
      7.3. Ongoing Use of ECN within an RTP Session ..................35
      7.4. Detecting Failures ........................................38
   8. Processing ECN in RTP Translators and Mixers ...................42
      8.1. Transport Translators .....................................42
      8.2. Fragmentation and Reassembly in Translators ...............43
      8.3. Generating RTCP ECN Feedback in Media Transcoders .........45

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