From: rfranken@mcs213d.cs.umr.edu (Richard Brett Frankenberger)
Subject: Re: Token Ring vs. Ethernet
Date: Sat, 21 Nov 1992 16:29:54 GMT
Organization: University of Missouri - Rolla

In article <1992Nov20.235027.16623@nntpd.lkg.dec.com> mitton@dave.lkg.dec.com (Dave Mitton) writes:
>	In fact it is trivial to break a token ring totally in many ways:
>- cut the trunk(as above),
   Yes, but the trunks don't run to every workstation.  I would have to get to
the MAUs to do it.  The single ethernet cable runs to every workstation, and if
it gets damaged, there goes the whole net.

>- put an adapter cable (no loop on end) in a RI/RO port
>- crosswire RI/RO ports (took me a while once on this one), 

Both true.
I would imagine an ethernet can be brought down by a miswired cable also.

>- stick a lobe cable in a PC monocrome jack (never tried it myself)
>	(rumor has it that it satisfies phantom current requirements)

I've heard it also ... I've also heard that VGA jacks will supply the
necessary voltage.
 
Note that NONE of the above will donw a token-ring that is using a smart hub as
opposed to the passive MAUs.

>- always a favorite: insert a station of the wrong speed
>	(station alternately causes the ring to beacon and drop out
>	but keeps re-inserting because it's local lobe test works)

Not true.  The card is supposed to give up after a set number of tries at
initial insertion.  (It is NOT supposed to keep trying - and MOST do
not.  HP JetPorts are an exception (I found out the hard way...))
With workstations; however, the ring beacons for a moment a few times, and then
the workstation says ERROR INSERTING and stops.
 
Note that EtherNet would likely have a similar problem if it supported multiple
speeds.

>- a stuck lobe relay  (I've never figured out how this happens, but
>	some people swear that the relay reset gadget that comes with
>	the 8228 has fixed their rings many a time)

It does happen, but not the commonly.  I have never seen it happen with our
(many) IBM MAUs.  Some cheaper third party MAUs have had this happen.  It 
didn't take long to fix.  I just checked what the beaconing address was,
found where that PC was connected in the MAUs (easy if you have good records),
and worked backwards from there to get to where the signal was being
interrupted at.
 
>	A better measure of a LAN technology's "goodness" is how easy
>it is to avoid problems.  While 802.5 seems easy at the drop level, at the
>ring trunk level there are many things that still can go wrong.  
>	Have you ever tried to figure out exactly how
>much cable you can use and how long the lobe loops can be?  It takes charts
>and charts.  Try to correlate those charts between vendors.  Try to figure
>them out from first principals?

So token-ring rules are a bit more complicated.  I never said Token-Ring was
easier to install.  It isn't (especially when compared to thin-net). 
True - token-ring at the trunk level isn't much better than Ethernet; but 
Since ether net at the trunk level is the same as ethernet at the drop level,
but token-ring is much more robust at the drop level ...
 
(Don't bring up 10BaseT & Active 10BaseT hubs ... sure - that's much more
robust that regular EtherNet - but Token-Ring with a smart active hub is
more robust than regular token-ring).
 

          - Brett

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