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

[Mikael Abrahamsson <swmike@swm.pp.se>]

On Fri, 27 Sep 2013, Scheffenegger, Richard wrote:

> Hi Mikael,
>
> the papers around DCTCP have probably the information you are looking 
> for (map/reduce type workloads, leading to incast issues - momentary 
> filling of queues; loosing the final segments of a TCP session [1], 
> which is likely with drop tail queue management policy, is well known to 
> result in timely retransmission timeout-type recoveries. Tweaking OS 
> time granularities down to recover in few milliseconds on paths that 
> usually have a few dozen microseconds delay is often not good enough, 
> but even that is not for cautious.

Ok, so this makes sense within a data center with ECN, but I fail to see 
any substantial upside deploying this in an environment where RTT is in 
the tens of ms because TCP won't have time to react.

I seem to remember reading about enhancement to TCP where packets are 
actually sent out with spacing between packets instead of in line-rate 
bursts. If everybody started doing that then I would imagine there would 
be less tail-drop in large RTT environments with large TCP windows?

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se