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From: kemp@uiatma.atmos.uiuc.edu (John Kemp)
Newsgroups: comp.dcom.telecom
Subject: UTP-THIN Warning
Message-ID: <14570@accuvax.nwu.edu>
Date: 9 Nov 90 21:12:11 GMT
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X-Telecom-Digest: Volume 10, Issue 808, Message 9 of 9


This is a warning if you are planning on installing an Unshielded
Twisted Pair (UTP) repeater and using UTP-THIN transceivers to extend
your network...

UTP-THIN has problems with existing platforms !!!

In particular, we have a Vaxstation 2000 in a Local Area Vaxcluster
running the DECNET protocol that repeatedly drops and reestablish
connections for up to a minute.

And we have seen an IBM RS/6000 320 come up and subsequently lose it's
connection network after a number of hours.  The connection is never
reestablished.

Both machines worked fine on AUI-THIN repeater segments.  Putting the
IBM on an AUI-UTP transceiver appears to have corrected the problem.
It should also be noted that two MacII's were on the same segment with
the IBM when UTP-thin was being used.  On the Vaxstation, it was the
only station on the net.  Various cable lengths were tried.  Cable
continuity was checked in both cases.

Moral:  don't count on UTP-THIN transceivers!  

If you do, you had damn well better try before you buy, and even then,
if you add a different type of machine to the segment you may be
hosed.  Our system was a Plexnet repeater with Plexit 10baseT UTP-THIN
transceivers.  (Your mileage may vary.  I am only speaking from
painful experience.)

You have been warned.


john kemp   internet - kemp@uiatma.atmos.uiuc.edu   decnet - uiatmb::kemp
univ of illinois       bitnet - {uunet,convex}
dept of atmos sci      !uiucuxc!uiatma!kemp
105 s gregory ave      phone - (217) 333-6881
urbana, il 61801       fax - (217) 444-4393