R: [e2e] [Fwd: RED-->ECN]

[Atiquzzaman, Mohammed]

> -----Original Message-----
> From: Saverio Mascolo [mailto:mascolo at poliba.it]
> Sent: Tuesday, February 06, 2001 10:54 AM
> To: Kathleen Nichols
> Cc: end2end-interest at postel.org
> Subject: R: R: [e2e] [Fwd: RED-->ECN]
> 
> 
> I have no reasons to believe that results reported in the 
> paper below are
> not correct.
> Robust tuning of RED parameter is of course a great issue.
> Regarding Random Early Discard my question is: since the goal 
> is to produce
> an early congestion indication through early dropping, why 
> should we relate
> dropping to average queue instead of instantaneous queue?
> Average introduces delay and this is against the goal of having early
> congestion indication.

Averaging would tend to filter out transient congestion (due to data bursts)
but will take into account perstistent congestion.  During transient
congestion data will be discarded not by RED but by tail drop.

Thanks
Mohammed Atiquzzaman           Tel:   (405) 325 8077
School of Computer Science     Fax:   (520) 962 8422, 
University of Oklahoma                (405) 325 4044
200 Felgar St., Room EL-154    Email: atiq at ou.edu
Norman, OK 73019-6151                 atiq at ieee.org
www.cs.ou.edu/~atiq                     

> 
> Saverio Mascolo, Ph.D
> 
> Associate Professor
> Dipartimento di Elettrotecnica ed Elettronica
> Politecnico di Bari
> Via Orabona 4
> 70125 Italy
> email: mascolo at poliba.it
> tel. +39 080 5963621
> fax. +39 080 5963410
> http://www-dee.poliba.it/dee-web/Personale/mascolo.html
> 
> > Saverio Mascolo wrote:
> > >
> > > What Hollot says is right. Averaging the queue makes much 
> more difficult
> to
> > > control the queue level. In control terms is like to add 
> another pole in
> the
> > > feedback loop.
> > > An interesting paper is also "Reasons not to deploy RED" 
> by J. Bolot et.
> al.
> > > ( at http://citeseer.nj.nec.com/337634.html).
> > > This paper experiments average vs. instantaneous queue 
> RED dropping.
> > >
> > ...
> >
> > There are a lot of interesting things to look at in 
> RED-type work and
> > one of them is to closely examine the quality of the experiments
> > that are done and cited in papers. Unless the above cited paper has
> > changed since someone at Cisco asked me to look at it, all I can
> > say is if your network looks like that of their experiments (set up,
> > RTTs, traffic mix), then perhaps the results apply. There is a body
> > of measurement work that shows that most networks look 
> rather different
> > from this. I'm personally interested in results that show some
> > robustness,
> > but this may not be currently fashionable.
> >
> > Kathie Nichols
> >
>