Re: [tsvwg] Comments on draft-ietf-tsvwg-ecn-l4s-id-05

[Bob Briscoe <[e-mail]>]

Ingemar,

On 11/11/2018 20:28, Ingemar Johansson S wrote:
>
> Q3. When you say the following:
>
>     RFC8298 (SCReAM) currently only specifies classic ECN handling,
>     but running code of SCReAM found at
>     https://github.com/EricssonResearch/scream has a working L4S
>     implementation.
>
> are you saying RFC8298 only specifies classic ECN feedback? Or are you 
> now talking about the L4S sender setting ECT(1) and using scalable 
> (L4S) congestion control? Or both?
>
> [IJ] RFC8298 does only specify the behavior assuming classic ECN 
> feedback (ECT(0) set). The running code has an additional L4S mode 
> that implements a scalable reaction to congestion. It is possible that 
> this can added to an updated RFC8298 when/if it is updated from 
> experimental to standards track.
>
>
> If you are solely talking about the sender behaviour here, I would 
> rather move this to where we talk about setting the codepoint or the 
> congestion control.
>

[BB] Your answer still seems to mix feedback (receiver and sender) with 
congestion response (sender).

Here's my question written more clearly:

If both ends already support avtcore-cc-feedback-message, can one end 
unilaterally implement the L4S congestion response (and therefore set 
ECT(1) on outgoing packets)?
Or did you have to enhance the avtcore-cc-feedback-message code (for 
writing feedback at one end and reading it at the other), before one end 
(or both) could add the L4S congestion response?

The stated goal of avtcore-cc-feedback-message is:

    To enable algorithm evolution as well as
    interoperability across designs (e.g., different rate adaptation
    algorithms), it is highly desirable to have generic congestion
    control feedback format.

If you had to enhance the feedback format for L4S, that would imply the 
feedback message is still not generic enough.


Bob

-- 
________________________________________________________________
Bob Briscoe                               http://bobbriscoe.net/