Date: Fri, 25 Dec 92 23:59:24 CST
From: Jack.Winslade@ivgate.omahug.org (Jack Winslade)
Newsgroups: comp.dcom.telecom
Subject: Strange LD Problem With Modems
Reply-To: jack.winslade%drbbs@ivgate.omahug.org
Organization: DRBBS Technical BBS, Omaha
X-Submissions-To: telecom@eecs.nwu.edu
X-Administrivia-To: telecom-request@eecs.nwu.edu
X-Telecom-Digest: Volume 12, Issue 916, Message 7 of 11

We feed a site down in Lawrence, KS.  They usually poll once every
evening using dial-1 AT&T.  We had good transfers up until recently.
They bought a new modem, a Supra v.32bis.  It worked fine for a while,
but ...
 
I got a call from him tonight stating that his sessions are being cut
off as if the carrier was dropped after a few minutes.  He forced a
poll while I was watching, and I noticed garbage streaming and the CD
flashing on and off.  I suggested that he change back to the original
modem (a USR Dual, square LEDs) and try the poll again.  He did, and
the session barfed about two minutes into the data transfer.  It was
as if somebody had simply pulled the plug.  I watched this a couple of
times, and BOTH ends showed hangup and failed session.
 
I then had him repeat the poll with Sprint, with the same results.
 
I then forced a call to him.  The session went perfectly.  Several
batches, about 1.5 megs total.  I was using AT&T.
 
Has anyone ever encountered anything like this?  I've seen hundreds of
random failed sessions and idiopathic disconnects, but never those
that were as easily repeatable.
 
We're using a TB Worldblazer with the latest non-fax ROM revision on
this end.  We have a rather new but burned-in #5 ESS <tm> on this end
and, from the sound of the call-waiting clicks on his voice line, it
appears that he has a #1 or #1A ESS <tm> in Lawrence.  He's noticed
this on both the Supra and the USR.  (The Supra is definitely bad, and
is going back.)
 
It amazes me that the sessions are totally clean one way, but
regularly and repeatedly disconnect the other way.  I think we've
shown that it is not the modem on his end or the LD carrier.  Anyone
care to guess?

 
Good day.   JSW

Ybbat (DRBBS) 8.9 v. 3.14 r.1
DRBBS - Merry Christmas -- Happy Hanukkah  (1:285/666.0)


[Moderator's Note: Let's use a process of elimination. What is the one
thing in common about all the bad, failed connections?  He originated
the call.  The Supra and the USR modems couldn't change it. Two
different modems: both bad ... doubtful. First on one carrier, then on
another (Sprint): neither carrier able to deal with it ... doubtful.
When you call him, the modem works fine and the carrier handles it
with no problems. Try these things:

Call him a few more times. See if it always works okay using various
carriers and even various modems on his end. Have him try to call some
other site on the opposite end of the earth, or at least in some other
part of the Land of Ahs ... still screwing up? Maybe inadvertently
some obscure piece of code in the uucp software went bad; something
that is only used when he originates uucp ... but not when he receives
uucp.  Have him use the phone line normally used to poll to call your
line voice; the two of you can chat for a few minutes and see if the
line is (or gets) trashed out after a few seconds or a couple minutes.
If so, then the problem may be with telco. Keep these tests up until
you find one unique element always present in the bad connections.  PAT]