Re: [LOOPS] How important is congestion detection

[Carsten Bormann <[e-mail]>]

Sorry for typing a message from a heated BOF where I was representing a WG that needs a specific outcome…

>>  Bob pointed out that some end host implementations today interpret CE as definite congestion events, while applying congestion detection to loss signals, so this conversion might be counterproductive.
> 
> The last sentence - I don't understand it (“interpret CE as definite… while applying detection to loss” - huh?). What does it mean? Or, maybe: what’s the issue here?

What I think Bob meant: An end-host noticing a loss might make its own determination (a.k.a. congestion detection) whether that is a reason to slow down or not.
An end-host getting a CE might simply assume this is indeed congestion, and always slow down.  So, CE > loss, and a simple replacement of loss by CE worsens throughput.

>  I thought the whole point is to signal CE *as a replacement* for the loss that LOOPS repairs. So, then… ?

If CE > loss, replacing loss by CE is not enough, we need to vet the losses via a LOOPS-side congestion detection that is as good as the one as the end-host would do, or (preferably) better.

Grüße, Carsten