Subject: Re: flows stuff

From: [email-masked] (Noel Chiappa)
Date: Fri, 2 Dec 94 18:07:02 -0500

From: [email-masked] (Noel Chiappa)

    Packets per flow:
        Mean	      16.911
      Median	       3.000
         85p	      11.000
         95p	      36.000

    If I'm reading this table right, 80% of all those "flows" have less than 11
    packets? So, if we assume no flow setup for less than 10 packets (just cart
    them around on the datagram service, in presetup flows), now we're down to
    roughly 2000+ active flows per second total.

Argh. I knew there was a corrective term there I wasn't taking into account
here, but I only just figured out what it is. (My brain is getting too old for
this stuff! :-)

I was dividing the average of 10.6K "flows" active in a given second by 80%,
to get rid of the short ones. This is wrong. Long-lived flows (in terms of
time) bias this calculation. (For a simple example, consider the case with 101
flows, one lasts 100 seconds, and 100 last 1 second. Over the 100 second
period, at any given time, there are two flows active, a 1-second one, and the
100-second one, so the long-lived one is 50% of the flows active in any
second, but only 1% of the flows overall.)

I can correct for that using the graph of flow duration (in time) versus
number of flows, but not right now (gotta go to dinner). I'll do it later and
send it in. Since there's no definite correlation between length in packets
and length in time, this can't be completely accurate to get rid of all flows
of length less than N in *packets*, but it's better than what I've got. Oh
well! Sigh! :-)

	Noel