[Ecn-sane] [tsvwg] Fwd: my backlogged comments on the ECT(1) interim call

[Sebastian Moeller]

Hi Bob,

> On Apr 29, 2020, at 15:37, Bob Briscoe <ietf at bobbriscoe.net> wrote:
> 
> [...]
> 3. I should add that I know you personally have tried to address the asymmetric capacity problem with the ACK thinning in CAKE.

ACK thinning in cake happened because Ryan Mounce on a rather unsavory asymmetric DOCSIS link (120/2.5 or 48:1) wanted to free some upstream capacity for data (with cake in the path his DOCSIS-Modem stopped ACK filtering, since it never saw the queue necessary to collect the ACKs to "merge"). Also ACK compression was eating into the downstream rates as well (turns out ACK "clocking" is a rather optimistic concept to rely on once bandwidth get tight and jitter gets high). 
The root cause here was the arguably misconfigured asymmetry of his link by his ISP, and that can unfortunately not be addressed by cake's ACK-filter, just worked-around. 

That said, in your case with the first mover being CableLabs/DOCSIS, I would have assumed that you (or cablelabs) would simply have grandfathered in the ACK filter into the design of the upstream shaper instance. Did you not?

Best Regards
	Sebastian