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From: medin@lll-crg.ARpA (Milo Medin)
Newsgroups: net.dcom
Subject: Re: Ethernet/Fiber Optic Repeaters
Message-ID: <959@lll-crg.ARpA>
Date: Sun, 3-Nov-85 20:20:43 EST
Article-I.D.: lll-crg.959
Posted: Sun Nov  3 20:20:43 1985
Date-Received: Tue, 5-Nov-85 21:09:33 EST
References: <360@nrcvax.UUCP>
Organization: Lawrence Livermore Labs, CRG, Livermore Ca
Lines: 27
Summary: codenoll repeaters

Since they were mentioned, I thought I'd throw in some experience
I have had with the codenoll 3030 fiber modems in use with repeaters.
In short, they dont work.

The 3030's by themselves work OK, as long as you plug them into
an ethernet controller of the appropriate version number, things
work out.  To go long distances though, they deactivate
CD.  Depending on loading, this may not be a problem, but
its ugly in any case.

BGut when you combine them with a repeater such as a DEC DEREP-AA
(local repeater), they don't work.  Note we got our DEREP by
buying it from codenoll as part of their repeater package.
You pay $2000 extra for having a codenoll sticker on it, there
are no internal differences.  Well, the thing simply wouldnt
work at all with the 3030's.  After a long debate with the
manufacturer, they came out and tried to make it work themselves.
After cutting various things in the 3030's, it came up.
BUT, we were showing anywhere from 16-50% collisions on the
cable, where it used to be 1%!  ANd, the really weird thing was
that initailly deffered packets were close to zero, and multiple
collisions were very high.  We took the thing off the link
and sent it back.  In short, don't buy Codenoll for fiber-coax
technology!

					Milo Medin
					NASA Ames Research Center