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From: bobkil@ibmpcug.UUCP (Bob Kilgore)
Newsgroups: comp.dcom.lans
Subject: RE: Thin Ethernet Question
Message-ID: <11147@ibmpcug.UUCP>
Date: 4 Aug 89 10:49:58 GMT
Organization: The IBM PC User Group, UK.
Lines: 54


There have been a number of posting's to Kenneth Herron who
apparently had a "simple thin ethernet question".  I can't
seem to find the original posting and therefor can't E-Mail
to him directly.  I think, Kenneth, you have discovered that
there is no such thing as a 'simple' ethernet question.  For
each question you can ask you can get any number of answers.

While simple in concept, Ethernet (8802-3) can be complex
enough to accommodate a wide variety of solutions.  Since
the real requirements are fairly loose a number of these
solutions may fall outside the domain of ethernet.  The
majority of the responses to your question were correct and
I am sure are viable.  Some however imply further
constraints on the system.

One in particular imposes a constraint that may not be
acceptable.  That is the response from Frank Rahmani that
suggested the 'glued' cable.  Everything was OK until the
suggestion that you use a 'right-corner' piece in the
attachment to the tee.  The area of interest in the
standard, 8802-3, is paragraph 10.5.3 the total segment DC
loop resistance shall not exceed 10 ohms.  Each in-line
connector pair shall contribute no more than 10 milli-ohms.

In Mr. Rahmani's solution he has placed 2 (?) more mating
pairs at each node.  This will reduce your total node count
per segment to about 10 from 30.  For small segment node
count a good way to go.  If more nodes per segment  are
required then you may have to remove the corner connectors.

Yet another possible answer is to use the AUI (transceiver)
cable attachment on you PC interface card and run the coax
inside the walls.  You then have the choice of using thin or
thick coax since the user will never see the cable.  You
could use any one of the new subminiature MAU's
(transceivers) now beginning to appear on the market.  For
example the Fujikura FN 2400 series.  Some of these can have
an AUI cable permanently attached.  ie: FN2100 series.

My preferred solution, however, is to run fiber-optic cable
now for the new installations, and eliminate the problems
associated with electrical drop and transmission systems.

Good Luck on your Ethernet

bob

         bobkil@ipmpcug.co.uk
         !uunet!ibmpcug.co.uk!bobkil
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