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

[<[e-mail]>]

Hi Georgios,

Just trying to get my head round this scenario a bit better. I take it
you are envisaging the severely congested path having several points of
congestion so that at some routers early on the path packets are being
marked and at some point later on the path some packets are then having
to be dropped?

I have always sort of assumed (quite possibly wrongly) that the point at
which routers are so congested they need to be doing preferential drop
is significantly above the termination threshold and thus even with the
drop there should still be a strong enough termination signal reaching
the egress...

Toby 

> -----Original Message-----
> From: [e-mail] [mailto:[e-mail]] On 
> Behalf Of Georgios Karagiannis
> Sent: 19 March 2008 16:10
> To: Eardley,PL,Philip,CXR9 R; [e-mail]
> Cc: [e-mail]
> Subject: Re: [PCN] Concensus questions from Thursday's PCN meeting
> 
> Hi Phil
> 
> But in order to trigger the admission control and flow termination, 
> the situation CLE > 1% has to be first triggered.
> 
> Best regards,
> Georgios
>  
> 
> > -----Original Message-----
> > From: [e-mail] [mailto:[e-mail]] 
> > Sent: woensdag 19 maart 2008 17:07
> > To: [e-mail]; [e-mail]
> > Cc: [e-mail]
> > Subject: RE: [PCN] Concensus questions from Thursday's PCN meeting
> > 
> > Georgios,
> > 
> > I notice you refer to CLE below. Note that for termination 
> > the relevant parameter is the Sustainable rate, that is the 
> > rate of unmarked pkts (or, if SM being used, this rate is 
> > multiplied by the domain-wide parameter U). 
> > 
> > phil
> > 
> > > -----Original Message-----
> > > From: [e-mail] [mailto:[e-mail]] On 
> > Behalf Of 
> > > Georgios Karagiannis
> > > Sent: 19 March 2008 15:49
> > > To: 'Steven Blake'
> > > Cc: [e-mail]
> > > Subject: Re: [PCN] Concensus questions from Thursday's PCN meeting
> > > 
> > > Hi Steven
> > > 
> > > Okay, I will have to spend some time on this!
> > > 
> > > Best regards,
> > > Georgios
> > > 
> > > 
> > > > -----Original Message-----
> > > > From: Steven Blake [mailto:[e-mail]]
> > > > Sent: woensdag 19 maart 2008 16:43
> > > > To: Georgios Karagiannis
> > > > Cc: [e-mail]
> > > > Subject: RE: [PCN] Concensus questions from Thursday's 
> PCN meeting
> > > >
> > > > On Wed, 2008-03-19 at 16:24 +0100, Georgios Karagiannis wrote:
> > > >
> > > > > Hi Steven
> > > > >
> > > > > Please see that I have included some information into the
> > > > last bullet:
> > > > >
> > > > > - There is an ingress-egress aggregate whose traffic is
> > > > split across
> > > > > multiple paths via ECMP.
> > > > >  - Traffic is admitted along this split path.
> > > > >  - One (or more) of the paths fails.
> > > > >  - One (or more) of the remaining paths becomes severely
> > > > congested (for
> > > > >    example because there is traffic from other ingress-egress 
> > > > > aggregates flowing along that path).
> > > > > - <<Due to the ECMP routing not congested paths will
> > > > forward packets
> > > > > belonging to
> > > > >   the same ingress-egress-aggregate that will be unmarked.>>
> > Marked
> > > > > packets are
> > > > >   preferentially dropped at the severely congested
> > > > >   router(s). As a consequence, not enough marked 
> traffic arrives
> > at
> > > > > the egress router to drive the CLE for the ingress-egress
> > aggregate
> > > > > above the threshold needed to trigger a response (termination,
> > say).
> > > >
> > > > Ok.  To be specific, the egressrouter  will see some 
> fraction of 
> > > > packets from the severely congested router(s), some of 
> > which will be 
> > > > marked, and will see a larger fraction of un-marked 
> > packets from the 
> > > > un-pre-congested routers.
> > > >
> > > > So let me now ask you this: given N ECMP paths (after a path 
> > > > failure), with one being severely congested and the rest being 
> > > > un-pre-congested, and given a CLE threshold CLE_thresh at 
> > the egress 
> > > > router, can you solve for the minimum PCN_lower_threshold 
> > value at 
> > > > the severely congested router, where PCN still works (e.g., CLE 
> > > > crosses the threshold), for the two cases where (1) 
> > marked packets 
> > > > are preferentially dropped, and (2) marked packets are 
> > dropped with 
> > > > equal probability with un-marked packets?
> > > >
> > > >
> > > >
> > > > Regards,
> > > >
> > > > =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> > > > Steven Blake                <[e-mail]>
> > > > Ericsson/Redback Networks               [phone]
> > > >
> > > 
> > > 
> > > _______________________________________________
> > > PCN mailing list
> > > [e-mail]
> > > https://www.ietf.org/mailman/listinfo/pcn
> > 
> 
> 
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