Re: [AVTCORE] I-D Action: draft-ietf-avtcore-ecn-for-rtp-02.txt

Magnus Westerlund <> Tue, 07 June 2011 11:35 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 55B9411E80D2 for <>; Tue, 7 Jun 2011 04:35:30 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -106.599
X-Spam-Status: No, score=-106.599 tagged_above=-999 required=5 tests=[BAYES_00=-2.599, RCVD_IN_DNSWL_MED=-4, USER_IN_WHITELIST=-100]
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id uDBllpQpcKFF for <>; Tue, 7 Jun 2011 04:35:29 -0700 (PDT)
Received: from ( []) by (Postfix) with ESMTP id 26DAA21F847C for <>; Tue, 7 Jun 2011 04:34:48 -0700 (PDT)
X-AuditID: c1b4fb39-b7bfdae000005125-a7-4dee0cd718b3
Received: from (Unknown_Domain []) by (Symantec Mail Security) with SMTP id E9.EF.20773.7DC0EED4; Tue, 7 Jun 2011 13:34:47 +0200 (CEST)
Received: from [] ( by ( with Microsoft SMTP Server id; Tue, 7 Jun 2011 13:34:23 +0200
Message-ID: <>
Date: Tue, 07 Jun 2011 13:34:22 +0200
From: Magnus Westerlund <>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv: Gecko/20110414 Thunderbird/3.1.10
MIME-Version: 1.0
References: <>
In-Reply-To: <>
X-Enigmail-Version: 1.1.1
Content-Type: text/plain; charset="ISO-8859-1"
Content-Transfer-Encoding: 8bit
X-Brightmail-Tracker: AAAAAA==
Subject: Re: [AVTCORE] I-D Action: draft-ietf-avtcore-ecn-for-rtp-02.txt
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Audio/Video Transport Core Maintenance <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Tue, 07 Jun 2011 11:35:30 -0000


We finally managed to get ready to submit this update. It is quite a lot
of changes in this version is both attempts to address the open issues
we have discussed in the meeting and a complete editorial pass.

The diff to previous version:

However, I would recommend that people read through the whole document
due to the amount of changes.

The really major change in this version is the change of the data
formats to address the counter wrap issue that was discussed.

A list of the other substantial changes are (not 100% complete):

1. Changed the applicability statement for Topo-Translators to remove
normative ECN treatment behavior from this section and move it into
section 8.
   - Added a new subsection in 8 for transport translator
   - Added in the applicability statement that additional rules applies
for ICE initiation with transport translators.

2. Added a SHALL NOT instead of "cannot" in the Topo-Video-switch-MCU
applicability statement.

3. Changed back the text regarding media level attribute in Section 6.1:

4. changed a "will" to "SHALL" in the Generating ECN Probe Packets text
in Section 7.2.1

5. Section 7.2.1, Generating RTCP ECN Feedback, making clear that XR
summary blocks MUST be sent independently if any ECT or ECN-CE marked
packets are received.

6. Implemented an CNAME based optimization. I will respond to mailing
list on how my considerations for trade-off looks.

7. Added text in 7.2.2 about ICE init and Translators.

8. Section 7.3.2, changed a SHOULD send RR/SR to "will send RR/SR unless
reduced size RTCP is used."

9. Removed a note in 7.3.2 talking about possible optimizations.

10. Section 7.3.3: Changed the formulation of the must statement based
on feedback from Thomas Belling:

The default reaction on the reception of these ECN-CE marked packets
MUST be to provide the congestion control algorithm with a congestion
notification, that triggers the algorithm to react as when packet loss
would be encountered.

11. Section 7.3.3. last paragraph, additional sentence:
 As it is possible to detect flows that are non-responsive to CE and
punish such flow it appears best if the application is well behaved.

12. Updated text in Section 8.2 (Fragmentation/assembling translators)

13. Added reduced size RTCP to the O/A SDP example.

14. Added a clarification in Section 3 on that RTCP feedback is in
packets, thus byte counting is difficult.

15. Added clarification on the usage of non symmetric init methods that
they can be done when mixers or translators are part of the picture.

16. Removed the limitation to not try ICE init over TURN. This would be
an artificial limitation as TURN can support ECN.

17. Added an applicability statement on ICE init method.

So please review and comment to the list.



On 2011-05-31 09:50, wrote:
> A New Internet-Draft is available from the on-line Internet-Drafts directories. This draft is a work item of the Audio/Video Transport Core Maintenance Working Group of the IETF.
> 	Title           : Explicit Congestion Notification (ECN) for RTP over UDP
> 	Author(s)       : Magnus Westerlund
>                           Ingemar Johansson
>                           Colin Perkins
>                           Piers O&#39;Hanlon
>                           Ken Carlberg
> 	Filename        : draft-ietf-avtcore-ecn-for-rtp-02.txt
> 	Pages           : 56
> 	Date            : 2011-05-31
>    This memo specifies how Explicit Congestion Notification (ECN) can be
>    used with Real-time Transport Protocol (RTP) running over UDP, using
>    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 initilization method using Interactive
>    Connectivity Establishment (ICE).  Signalling and procedures for
>    negotiation of capabilities and initilization methods are also
>    defined.
> A URL for this Internet-Draft is:
> Internet-Drafts are also available by anonymous FTP at:
> This Internet-Draft can be retrieved at:
> _______________________________________________
> Audio/Video Transport Core Maintenance


Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVM
Ericsson AB                | Phone  +46 10 7148287
Färögatan 6                | Mobile +46 73 0949079
SE-164 80 Stockholm, Sweden| mailto: