ATM Wide-Area Networks (was: sell shell accounts?)

R. Eric Bennett reb at
Wed Jul 24 05:52:25 UTC 1996

> At 9:33 PM 7/23/96, Curtis Villamizar wrote:
> In message <199607232130.QAA20147 at>, Tim Salo writes:
> >
> > "Good" ATM switches are doing Early Packet Discard and Partial Packet
> > Discard.  You can ask your favorite switch vendor for details, or look
> > at the following for a nice summary:
> >
> >
> Also in the "dead horse dept" (I hope) unless you are dealing with
> boneheaded switch vendors.  Some don't believe in EPD/PPD preferring
> ABR.  Are any of them still entirely clueless in this regard and not
> doing either EPD/PPD or ABR?

I think a better question is which switch vendors are supporting _any_ kind
of xPD besides Fore?  At my last recollection, though I am no switch
expert, only Fore.  Certainly other switch vendors were starting to throw
large buffers at the problem.  And still others said "ABR will solve this
problem.  Wait for ABR."  (And I'll add that this was said even when it was
clear ABR was a couple of years away.)

As for ABR, ATM vendors have been forecasting '96 and '97 deliverables
since at least '94.  As such, I would expect most of them to be doing or at
least working on bringing ABR to fruition.  But in order for ABR to be
useful in a router environment, routers need to understand ABR.  Anyone
know what routers do?

There are also issues wrt telcos' sunk investment in switches -- switches
built when switch vendors were nearly unanimously boneheaded.  Given
telcos' tendencies to depreciate equipment over long cycles, one can expect
those switches to be in telcos' networks for some time.  ISPs looking to
deploy their own ATM switches needn't be concerned with this but those
looking to buy ATM service from telcos most certainly do.

All hoping aside, I'm not so sure these issues are in the "dead horse dept"...


P.S. I took a stab at answering my own question and found that out of the
two vendors I checked, at least Cascade now implements EPD.

R. Eric Bennett <reb at>       |   Internet Engineering Group
313-669-8800 (v) 313-669-8661 (f)    |   122 S. Main, Suite 280                 |   Ann Arbor, MI 48104

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