[Bloat] [aqm] [iccrg] AQM deployment status?

Mikael Abrahamsson swmike at swm.pp.se
Sun Sep 29 05:37:56 EDT 2013

On Sun, 29 Sep 2013, Bob Briscoe wrote:

> The shallow marking threshold certainly keeps standing queuing delay 
> low. However, that's only under long-running constant conditions. During 
> dynamics, not waiting a few hundred msec to respond to a change in the 
> queue is what keeps the queuing delay predictably low. Dynamics are the 
> norm, not constant conditions.

Well, my original question was in the context of a 3-5ms tail drop queue 
(such as are frequently available in lower end switches). My understanding 
from earlier experience is that TCP will severely saw-tooth under these 
conditions and only way I could see marking as being valuable was if the 
RTT was less than buffer depth (or at least very low).

There was a discussion earlier on bloat-l regarding what the impact of a 
10ms CoDel queuing scheme will have on 200ms RTT existing non-ECN TCP 
performance. Deep queues were invented to handle this specific use-case.

One way would absolutely be for TCP to not send a lot of packets 
back-to-back but instead pace them out at the rate that actually makes the 
TCP rate be exact in a millisecond resolution instead of as it is today, 
perhaps tens or hundreds of milliseconds. I believe some implementations 
already do this.

Mikael Abrahamsson    email: swmike at swm.pp.se

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