Re: Fiber 802.3 ring

Tim Krauskopf (
Wed, 30 Mar 88 16:06:09 CST

I'm surprised that no one else has volunteered experience with Fibercom
modems or other fiber used to bridge Ethernet at the MAC level.

We have three fiber rings now, in use as backbones for our level-2
Ethernet (Suns). We have run as many as seven 900-1000 foot
thin Ether segments off of a central ring. Until we split it, traffic
from 40+ Suns traversed this ring along with a couple hundred PCs, Macs,
etc. Yes, we broke all the rules, it worked for a while, now we have
split it with IP routers.

I think the technology is fairly straightforward. They use a proprietary
ring system to emulate an 802.3 bus. Even jams and shorts are emulated
across the ring. There is a lockout switch on each fiber modem which
can isolate a coax segment without affecting the ring.
The "documentation" says up to 2km per station, 10's of kms total ring
length. We run them on fairly short runs (100m) with excellent reliability.

Justifiable cost per backbone is probably in question here, but . . .
"If it ain't broke, don't fix it"

 Tim Krauskopf (ARPA)
 National Center for Supercomputing Applications National Center for Supercomputing Applications 14013@ncsavmsa (BITNET)
 University of Illinois
 Standard disclaimer: "Just a customer"

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