[Iccrg] draft-irtf-iccrg-welzl-congestion-control-open-research-00.txt

[Bob Briscoe]

Lachlan,

At 02:30 08/08/2007, Lachlan Andrew wrote:
>Greetings Bob,
>
>On 07/08/07, dimitri papadimitriou <dpapadimitriou at psg.com> wrote:
> > Bob Briscoe wrote:
> > > - what's the minimum information intensity of congestion notification
> > > (More than 1-bit per packet? Is sensing congestion delay variation a
> > > sufficient alternative?)
> >
> > yes this is imho an important point. would deserve additional discussion
> > on this list. i would distinguish intensity from encoding granularity
> > and significance.
>
>Yes, you raised this point in October last year too.  At the time, I
>think the consensus was that we need to distinguish between "1
>information-theoretic bit per packet" and "1 protocol bit per packet",
>which generally gives much less information.

Yes, this is what I was trying to say (badly) by using the word intensity.

>That may be related to
>Dimitri's point about separating the signalling rate from the
>semantics of the signal.
>
> >From a control theory point of view, there's recently been a lot of
>work on the minimum information-theoretic signal rate required to
>"stabilise" a system (e.g,
><http://www.ee.unimelb.edu.au/staff/gnair/NairPIEEE.pdf>).  I'm not
>sure how much of that relates to congestion control, where
>undershooting the rate is much preferable to overshooting.

Tx for ref

Cheers


Bob

>To decide how much feed back is "needed", we need to decide what
>performance measures to use, and what performance level is "needed" --
>e.g. do we need unused bandwidth to be taken up again within   x
>RTTs/seconds/minutes of being released by another flow?  Do we need
>overload to abate within  x  RTTs?
>
>Cheers,
>Lachlan
>
>--
>Lachlan Andrew  Dept of Computer Science, Caltech
>1200 E California Blvd, Mail Code 256-80, Pasadena CA 91125, USA
>Phone: +1 (626) 395-8820    Fax: +1 (626) 568-3603

____________________________________________________________________________
Bob Briscoe, <bob.briscoe at bt.com>      Networks Research Centre, BT Research
B54/77 Adastral Park,Martlesham Heath,Ipswich,IP5 3RE,UK.    +44 1473 645196