Re: [Phil Dykstra: more interesting numbers]


Phil Dykstra (phil@BRL.ARPA)
Thu, 21 Apr 88 1:22:25 EDT


The numbers that I posted for the NSFNET fuzzies the the ARPA/MILNET
Core gateways were for the week ending 21 March 88 (and came via Dave
Mills). Only one of the mailbridges and five EGP speakers had been
upgraded to 11/73's at that time. It would be interesting to see
how they have improved.

The numbers for the BRL gateway came from ~48 hours ending 30 March 88.
That gateway has three ethernets, one 10 Mbit proteon ring, and two
1822 IMP connections (one MILNET, one local). Packet counts were
half of in+out and included everything to/from the interfaces - EGP,
ICMP, etc., included. If I had been posting to this list originally
I would have spoken a bit more carefully.

To answer/comment-on a few replys:

> Mike Brescia
> ... "average" throughput is a measure of packets actually offered over the
> course of the day or week reporting period, ....
> ... is a measure of handling offered load rather than limitation.

Good point. They were all long term averages. For the record I believe
that we all agree that "one packet" goes both in and back out of a gateway.
Most vendors seem to count that as two, for obvious reasons.

> Phill Gross
> Do we understand why the mailbridges have such a higher drop rate?

Mike Brescia mentioned a few possible reasons. Another, which I have
heard about but don't know any details of, is a claim that the Core
gateways maintain max queue lengths of eight packets per destination
subnet (I would presume to avoid overloading the PSN's). That probably
causes many more drops than a more generous gateway would have (unless
there are only PSN's connected to it and they return the favor).

> Dave Mills
> I would like to believe the difference in drop rates is due to the design
> of the NSFNET backfuzz selective-preemption and source-quench schemes.

I note however that your numbers went from good to excellent. I am hoping
to be able to test that theory by playing the same game locally.

- Phil
<phil@brl.arpa>



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