Path: utzoo!censor!geac!torsqnt!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!seismo!sundc!newstop!sun!imagen!atari!portal!portal!cup.portal.com!John_Robert_Breeden
From: John_Robert_Breeden@cup.portal.com
Newsgroups: comp.dcom.lans
Subject: Re: Cost of 10BaseT
Message-ID: <27543@cup.portal.com>
Date: 4 Mar 90 18:12:31 GMT
References: <1990Feb26.082610.7963@hellgate.utah.edu>
  <27314@cup.portal.com> <8670@rosevax.Rosemount.COM>
Organization: The Portal System (TM)
Lines: 79

>>1) If I go the 10BaseT route, what are the pieces of hardware I need to
>>buy, and what are the costs?  I realize I need 5 10BaseT cards and the
>>RJ45.  What else?
>
>First, you need the chassis that the 10BaseT cards go into.  3Com has a
>box that the call a MultiConnect repeater.  I have one here.  It holds
>about 15 cards, I think (you don't really expect me to walk to the other
>end of the building to verify that, do you?)  3Com also has a device that
>they call a PairTamer.  It converts thinnet to 10BaseT.  If you use a thinnet
>card in the MultiConnect box, then you need a pair of PairTamers for each
>TP wire.  I hear that 3Com will soon have a card for the MultiConnect that


DANGER WILL ROBENSON, DANGER!!! The 3Com pairtamer IS NOT A 10BASET DEVICE!!!
it is a BALUN - A PASSIVE DEVICE, if you bother to read the 10baseT draft, 
you'll find the BALUNS ARE A NONO!!! <--tech. term. To hook a thick/thinnet
to TP you need an AUI (UB calles it a TPAU), it's an ACTIVE device with all
kinds of goodies like receiver, transmitter, signal processor etc. It adds the
nessessary precomp and jitter to the signal among other things and it's what
gives you the 100 meters in 4pair or 25 pair. Is the Pairtamer cheaper than
an AUI - you bet!, does it work - it might, is it 10baseT? - NO WAY JOSE!!


>is 10BaseT, so then you would only need a single 10BaseT converter on the far
>end of the TP wire.
>
>Note that at the far end of the TP, the coverter gives you thinnet.  So if
>you have workstations that are reasonably close to each other, you can
>hang several on the same thinnet line.  This will reduce the number of 10BaseT
>lines that you will need.


NO, NO, NO, NO, NO! Don't call nodes hooked up in a daisy chain 10baseT,
it ain't!!! READ THE DRAFT! IT MUST BE IN A STAR CONFIGURATIONS. NODES
THAT HAVE THINNET GO TO AN AUI ADAPTER (active device NOT A BALUN) and
then DIRECTLY TO A HUB (I hate to tell you this, a 10baseT hub must be
A ACTIVE REPEATER - NOT A CONCENTRATOR!).


>>2) I have heard some people express concerns that the 10BaseT vendors
>>manufactured their cards before the spec was finished.  Is this a 
>>concern, or did the spec that was used to build cards end up being
>>the final spec?  In particular, will I be safe buying 3COM's 10BaseT
>>cards?
>
>My understanding is that the approved standard (which is basically decided
>upon) will match what 3Com has been selling as 10BaseT.  (3Com made a gamble,
>and it looks like they won)

If the idea of using baluns and daisy-chaining nodes with TP is is matching
"what 3Com has been selling as 10BaseT" - that's just, well WRONG.

In defense of 3Com they have announced intended support of 10baseT and
have, in fact, released a 10baseT version of the EtherLink II. They where
one of the participents in the 10baseT "let's hook it alltogther" 10baseT
interoperability demonstration at Interop in Boston last month along with
AT&T, UB, Nextworth, Cabletron, HP and others (notice lack of one of the
big TP vendors).

When I talked to a spokesman at 3Com about six months ago, 3Com stated they
"would release 10baseT product when the draft was a standard" - along with
the rest of the world.

So the bottom line is if you use the solution above, you are NOT 10baseT
but instead are running a PROPRIATARY 3COM SOLUTION - nothing wrong with
that as long as you are prepared to live with the fact that you may (read
most likely) will not be able to use other vendor's  true 10baseT product 
in the same network.

BTW, this is NOT a flame of 3Com, they have been an active, and I under-
stand, supportive member of the 10baseT committee. They where in fact, one 
of the first companies to offer 10meg support on TP long before the WAS
a 10baseT committee (that's where the Pairtamer/balun came from). Compair
that to another Silicon Valley TP vendor who will remain un-named (it starts 
with an "S") who has used their seat on the committee to confuse and
delay the release of the draft to protect their propriatery position.


john_robert_breeden@cup.portal.com