[e2e] number of flows per unit time in routers

Ramana Rao Kompella ramana at cs.ucsd.edu
Fri Oct 28 11:42:12 PDT 2005


Craig,

It is entirely dependent on the traffic mix. If you are faced with 
adversarial
traffic, the number of records is going to be too high. But most if it 
is going to
be junk (such as small one packet flows for DoS traffic).

You might want to take a look at our recent IMC 2005 paper titled
"Power of Slicing in Internet Flow Measurement" along with
Cristi Estan.

We propose an algorithm for reducing bottlenecks  including
storage/reporting bandwidth depending on the traffic mix. We also
propose mechanisms to preserve the accuracy  of various estimates by
choosing the right flow records to archive.

Of course, if the line rate is low ( < OC 12), NetFlow without sampling
might be alright, but you still run into adverarial traffic mixes that can
overwhelm the archival process.

Not sure if that answers your question directly, but just something that
you might require as a future step.

-Ramana

Craig Partridge wrote:

>Hi Bob:
>
>Sounds as if I need to provide a bit of context.  If you are tracking
>flows (imagine a router keeping track of flows, using, say something like
>NetFlow), one question is how many flows do I need to keep track of.
>Another question is how fast may I have to create new flows or expire
>old flows.  Yet another question, and the one I was aiming at, is that
>if I'm archiving flow records over time, at what rate do I have to
>archive?
>
>Note that for all but the first question, flows per second makes perfect
>sense.
>
>Thanks!
>
>Craig
>
>In message <200510281712.KAA11769 at gra.isi.edu>, Bob Braden writes:
>
>  
>
>>It seems to me that this question is ill-posed.  It seems to make
>>sense to talk about the number of flows per time T only when average
>>flow duration << T.  So, flows per hour might make since, assuming
>>few flows are longer than a few minutes, but flows per second makes
>>no sense.
>>
>>Bob Braden
>>    
>>



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