[Ecn-sane] osx ecn

[Sebastian Moeller]

Hi Jonathan,


> On Aug 27, 2019, at 09:05, Jonathan Morton <chromatix99 at gmail.com> wrote:
> 
>> On 27 Aug, 2019, at 9:58 am, Sebastian Moeller <moeller0 at gmx.de> wrote:
>> 
>>> 0 connection fell back to non-ECN due to excessive CE-markings
>> 
>> I wonder whether macosx would be able to gracefully survive a misclassification into a L4S/NQB queue at a dual queue AQM? What is the threshold here?
> 
> No, I don't think so.  L4S assumes the DCTCP response function which stabilises at 2 CE marks per RTT, which is still a fairly low percentage if the cwnd is high.  I doubt that would be detected as "excessive" in this context.  Also, because the RFC-3168 response to CE is much sharper, the actual marking rate will be lower, as the flow won't stay in the saturating regime where marking occurs.
> 
> - Jonathan Morton


thanks for the detailed answer.

Best Regards
	Sebastian