Re: [PCN] Concensus questions from Thursday's PCN meeting

<philip.eardley@bt.com> Tue, 01 April 2008 15:55 UTC

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Thread-Topic: [PCN] Concensus questions from Thursday's PCN meeting
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From: philip.eardley@bt.com
To: menth@informatik.uni-wuerzburg.de
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Subject: Re: [PCN] Concensus questions from Thursday's PCN meeting
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"does not work" is over-stating it, I think Michael.

But yes, which edge behaviour is most naturally supported (or which ones
are slightly less well supported) does depend on the dropping behaviour
(which we said would be a SHOULD) 

phil

> -----Original Message-----
> From: Michael Menth [mailto:menth@informatik.uni-wuerzburg.de]
> Sent: 01 April 2008 16:44
> To: Eardley,PL,Philip,CXR9 R
> Cc: steven.blake@ericsson.com; pcn@ietf.org
> Subject: Re: [PCN] Concensus questions from Thursday's PCN meeting
> 
> Hi Phil,
> 
> philip.eardley@bt.com wrote:
> >>> Q4: Should the standards-track PCN scheme require (as a MUST
> >>>
> > implement
> >
> >>>     feature) that interior PCN routers support Excess-Rate
marking,
> >>>     according to the particular method of handling already marked
> >>>     packets and drops described in Anna Charny's presentation?
> >>>     http://www3.ietf.org/proceedings/08mar/slides/pcn-6.pdf
> >>>
> >>>
> >> Yes. But it ALSO requires the option for preferential dropping of
> >>
> > marked
> >
> >> packets and an option for random drops with equal importance.
> >>
> >
> > I believe we need to decide. A standard for marking behaviour with 3
> > options about dropping is not acceptable.
> >
> 
> I want to point out that preferential dropping of marked packets makes
> indirect measured rate termination work well while direct measured
rate
> termination does not work any more with packet loss as it would
require
> preferential dropping of unmarked packets. Thus, not supporting
> preferential dropping of unmarked packets as another option already
> rules out possible edge behaviors. Therefore, this decision about
> preferential dropping is already a decision about possible edge
behaviors.
> 
> Regards,
> 
>     Michael
> 
> > As long as
> >
> >> the edge behavior is not clear yet, no decision about preferential
> >> dropping can be made. Furthermore, packet size independent marking
> >> (PSIM) as described in
> >> http://tools.ietf.org/wg/pcn/draft-menth-pcn-emft-00.txt
> >> is useful to implement
> >>
> >
> > suggestion in Philadelphia is that this is a SHOULD (for excess rate
> > marking).
> >
> > because the fairness of any flow termination
> >
> >> scheme making use of marked packets to indicate flows to be
terminated
> >> profits from this feature. Evidence for that is documented in
> >>
http://www.ietf.org/internet-drafts/draft-menth-pcn-performance-02.txt
> >> or
> >>
> >>
> >
http://www3.informatik.uni-wuerzburg.de/staff/menth/Publications/Menth08
> > -
> >
> >> PCN-MFT.pdf
> >>
> >> This also applies to potential improvements of SM.
> >>
> >>
> 
> --
> Dr. Michael Menth, Assistant Professor
> University of Wuerzburg, Institute of Computer Science
> Am Hubland, D-97074 Wuerzburg, Germany, room B206
> phone: (+49)-931/888-6644, fax: (+49)-931/888-6632
> mailto:menth@informatik.uni-wuerzburg.de
> http://www3.informatik.uni-wuerzburg.de/research/ngn

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