Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!asuvax!ukma!hsdndev!camb.com!bruce
From: bruce@camb.com (Barton F. Bruce)
Newsgroups: comp.dcom.lans
Subject: Re: how to connect thin wire segements to thick wire backbone
Message-ID: <1991Jun6.035458.39766@camb.com>
Date: 6 Jun 91 08:54:58 GMT
References: <1991May13.085357.4785@uniwa.uwa.oz>
Distribution: comp
Organization: Cambridge Computer Associates, Inc.
Lines: 43

In article <1991May13.085357.4785@uniwa.uwa.oz>, doug@psy.uwa.oz.au (Doug Robb) writes:
> 
> A friend of mine works in a building that has two segments
> of thin wire ether-net on each floor (there are 3 floors)
> and a thick wire ethernet running up the riser between
> floors. Each thin wire segment runs back to the riser on
> each floor. What he would like to know is what needs to be done

If you truely ONLY need 2 segments per floor, and IF there are only 3
floors, and if you are not stretched to the outer end of your 185 meter
thin segment limit already, THEN totally eliminate the Etherhose backbone.
You can easily stick it in later if necessary. True that suitable
repeaters come in 1 or 8 ports typically (DESPR , DEMPR) and the 1 port
ones are SO expensive and limiting you always buy the 8 port one because
over its life it will be redeployed and you will need more ports.

So get 1 (only) DEMPR. Stuff the green-eyed loop back plug into its
AUI port to turn it into your backbone in a box. Mount it on the middle floor.
Run your loops from there. 

The DEMPR has a terminator built in, so you can't go 2 ways using a T, and
you can't use a T and add a second terminator. You just plug one cable end in.

The returning far end of the cable is 'nice' if you can afford the length
(not $s, this stuff is cheap, but you are only allowed 185 meters per
segment). That far end MUST end in a 50 ohm terminator. But, with it
physically back at the closet, and with only 6 of 8 ports used, if some
segment gets broken in some wall, feed BOTH ends of the old segment from DEMPR
ports, and terminate the 2 new shorter segments after the last connected 
computer in each effectively cutting out the broken segment.

At such time as you need a DEMPR per floor, I would buy 3 mini tranceivers
that now LIST for $125, and that plug right onto the AUI connector - no 
AUI cable needed. These have a BNC connector and you stick a T on each,
run thin net between the floors, and terminate the ends. For 3 floors
thin net is fine as a backbone. It is fine at 10 floors or 20 floors, 
even. 

By the time you might start looking at ether-hose, you probably should be 
into some fiber solutions! Many folks NEVER use thick ethernet these days.

NEVER use RG58 stuff, use the premium Belden 9907 or 89907 if you are
rich or NEED Teflon.