common method to count traffic volume on IX

Tue Sep 17 19:17:57 UTC 2013

On 17/09/2013 2:15 PM, Patrick W. Gilmore wrote:
> On Sep 17, 2013, at 12:11 , Martin T <m4rtntns at 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.