NAP/ISP Saturation WAS: Re: Exchanges that matter...

Jim Van Baalen vansax at
Fri Dec 20 19:18:31 UTC 1996

> Let me add one more word to this discussion. In case of simple and solid
> FDDI or Ethernet protocol it's not big chance if the whole switch would be
> failed down by one crazy interface card or one crazy router.

In some sense isn't this what is occuring with head of line blocking?

> In case of ATM nobody can protect the whole ATM system  from being failed down due
> to some software bug since 1 / 5 after system was installed, because
> the number of different featires in ATM network and ATM interface is more
> then 10 - 100 times more in comparasion with FDDI. This means - if your

In that case we should get rid of all of our routers. They certainly support
much more complexity that ATM switches.

> FDDI switch works fine just now, it's more than 99% it'll work next

Really? I am surprised that everybody seems to be of the opinion that the
Gigaswitches are not causing any problems. This doesn't seem to me to be
consistent with early discussions from this thread.

> 2 years (may be it'll be saturated but would not crash totally); in case
> of ATM it's more than 20% the whole system would be crashed by some new
> neighboar with some new ATM software...

ATM PVCs, as used by the current ATM NAPs, don't require much sophistication.
They are basically just hardwired circuits.

> It's not my experience, but one of our partners are debbugging simple
> direct ATM link just about 3 months - there is 3 vendors (ATM provider,
> ATM's provider vendor, CISCO) and it's not possible to determine why
> this link loss more than 50% of packets sometimes. This is due to
> ATM is too complex system...

I have not had this experience, but I would guess that it is due to a lack of
debugging tools. These exist, but good ones are expensive. Good switches do
provide some helpful debugging, but there is certainly work to be done on this
front. I would add that FDDI was pretty lousy technology 5 or so years ago.


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