Re: common method to count traffic volume on IX

[Tom Taylor <tom.taylor.stds () gmail com>]

On 17/09/2013 2:15 PM, Patrick W. Gilmore wrote:
> On Sep 17, 2013, at 12:11 , Martin T <m4rtntns () gmail com> wrote:
>
> > Thanks for all the replies!
> >
> >
> > Nick,
> >
> > counting traffic on inter-switch links is kind of cheating, isn't it?
> > I mean if "input bytes" and "output bytes" on all the ports facing the
> > IX members are already counted, then counting traffic on links between
> > the switches in fabric will count some of the traffic multiple times.
> >
> >
> >
> > Patrick,
> >
> > how does smaller sampling period help to show more traffic volume on
> > switch fabric? Or do you mean that in case of shorter sampling periods
> > the traffic peaks are not averaged out and thus peak in and peak out
> > traffic levels remain higher?
>
> The graph has a bigger peak, and DE-CIX has claimed "see, we are bigger" using such graphs. Not only did they not 
> caveat the fact they were using a non-standard sampling method, they have refused to change when confronted or even say what 
> their traffic would be with a 300 second timer.
That's easy to counter. just estimate some characteristics of the 
distribution from the sample, then apply extreme value theory to 
renormalize to 300 s.

(My math background talking. I once got similar stuff written into an 
ITU-T recommendation for provisioning trunk groups based on limited 
traffic samples.)

Tom T.