Re: [aqm] AQM schemes: Queue length vs. delay based

[Preethi Natarajan <[e-mail]>]

From:  Anoop Ghanwani <[e-mail]>
Date:  Sunday, November 17, 2013 10:53 AM
To:  Preethi Natarajan <[e-mail]>
Cc:  Naeem Khademi <[e-mail]>, curtis
<[e-mail]>, Michael Welzl <[e-mail]>, "[e-mail]"
<[e-mail]>
Subject:  Re: [aqm] AQM schemes: Queue length vs. delay based

> 
> 
> 
> On Thu, Nov 14, 2013 at 5:33 PM, Preethi Natarajan <[e-mail]>
> wrote:
>> 
>> Just pointing out the evidence here --
>> http://www.ietf.org/proceedings/86/slides/slides-86-iccrg-5.pdf
>> 
>> The slides contain preliminary results from DC scenarios, showing PIE's
>> parameters and adaptability to DC scenarios. Thank god for the IETF archives
>> :)
>> 
> Hi Preethi,
> 
> In these simulations what was the buffer size used?  From my read, it looks
> like the setup had ~400 KB per port before any marking/discarding would take
> place.  This is significantly more than what is available in top-of-the-rack
> switches used in many data centers.
> 
> This should give you an idea of the kind of buffering that is actually
> available.  As port-counts go up, the amount of buffering per port goes down.
> http://people.ucsc.edu/~warner/buffer.html
> 
> For the simulations to be relevant for such switches, they would have to be
> done with significantly smaller buffer sizes.  The sizing gets even worse when
> we consider there may be multiple priorities and some of those may be lossless
> (requiring dedicated buffers be set aside for them).
> 

Hi Anoop,

Thanks for the pointer regarding small buffers.

We haven't run simulations with small buffers in DC environments. However,
from our experience, PIE's control law usually adapts well to small buffers
for a given network condition. Maybe you can help us refine the DC
simulation parameters and we can give this a try.

We'll follow-up offline if that makes sense.

Thanks,
Preethi