Subject: Re: [rmcat] I-D Action: draft-ietf-rmcat-coupled-cc-00.txt

From: Karen Elisabeth Egede Nielsen <[email-masked]>
Date: Fri, 30 Oct 2015 21:04:14 +0100

Hi,

Please accept the following comments to the new draft:

General comments:

* Active versus Passive: The document describes both passive and active, but
passive is put into appendix as
"extremely experimental" of something like this :-). I think the text in
section 4 should relate to this.

* Should the document not relate to the applicability to coupling also with
other flows that RTP flows - vis-à-vis the following requirement for the
rmcat req doc ?
        A.  The algorithm should also share information and adaptation
            with other non-RTP flows between the same endpoints, such as
            a WebRTC DataChannel [I-D.ietf-rtcweb-data-channel], when
            possible

* The document should (should it not ?) be extended to be generic and not
relate to Nada only (but this point has been addressed in other
communications).

Detailed comments:

* Section 4- Paragraph below Figure 1:

In the discussions of multiple applications, multiple flows and
applicability of coupled CC, the coupling with non RTP flows and e.g. the
RTCWEB datachannel seems relevant to discuss ?

Section 5.2:

"  In the FSE, each FG contains one static variable S_CR which is meant
   to be the sum of the calculated rates of all flows in the same FG
   (including the flow itself).  This value is used to calculate the
   sending rate."

Suggest to remove the (..). The variable is per FG there is no "flow
itself".

Section 5.2.3:

(3) and (a): The text nor the pseudo code explains well how the timer for
2RTTS is used exactly. What happens when it is set and what happens when it
expires ?

Section 6.1:

"   When applying the FSE to NADA, the UPDATE function call described in
   Section 5.3 gives the FSE NADA's reference rate R_n.  The recommended
   algorithm for NADA is the Active FSE in Section 5.3.1.  In step 3
   (c), when the FSE_R(i) is "sent" to the flow i, this means updating

                  ^^^^^^^^^^^^^^^^^^
   R_v and R_s of flow i with the value of FSE_R(i)."^
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Does this mean "with the value FSE_R(i) in place of R_n" ?
Suggest to clarify this.

"R_n" BTW now is "r_n".

BR, Karen

> -----Original Message-----
> From: rmcat [mailto:[email-masked]] On Behalf Of internet-
> [email-masked]
> Sent: 14. september 2015 14:14
> To: [email-masked]
> Cc: [email-masked]
> Subject: [rmcat] I-D Action: draft-ietf-rmcat-coupled-cc-00.txt
>
>
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
>  This draft is a work item of the RTP Media Congestion Avoidance
> Techniques
> Working Group of the IETF.
>
>         Title           : Coupled congestion control for RTP media
>         Authors         : Safiqul Islam
>                           Michael Welzl
>                           Stein Gjessing
> 	Filename        : draft-ietf-rmcat-coupled-cc-00.txt
> 	Pages           : 20
> 	Date            : 2015-09-14
>
> Abstract:
>    When multiple congestion controlled RTP sessions traverse the same
>    network bottleneck, it can be beneficial to combine their controls
>    such that the total on-the-wire behavior is improved.  This document
>    describes such a method for flows that have the same sender, in a way
>    that is as flexible and simple as possible while minimizing the
>    amount of changes needed to existing RTP applications.  It specifies
>    how to apply the method for the NADA congestion control algorithm.
>
>
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-rmcat-coupled-cc/
>
> There's also a htmlized version available at:
> https://tools.ietf.org/html/draft-ietf-rmcat-coupled-cc-00
>
>
> Please note that it may take a couple of minutes from the time of
> submission
> until the htmlized version and diff are available at tools.ietf.org.
>
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/