Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!vsi1!octopus!pete
From: pete@octopus.UUCP (Pete Holzmann)
Newsgroups: comp.dcom.modems
Subject: Telebit answers international calling questions! (Part 1)
Message-ID: <559@octopus.UUCP>
Date: 23 Mar 89 14:14:14 GMT
References: <4377@drivax.DRI> <1445@altger.UUCP> <12374@microsoft.UUCP> <1454@altger.UUCP>
Reply-To: pete@octopus.UUCP (Pete Holzmann)
Organization: Octopus Enterprises, Cupertino CA
Lines: 56

Rather than try more homebrew solutions, I actually called Telebit product
support yesterday. Here's what they said (and the remaining questions I
will call back for today, and post a second message with the answers):

1) No need to go back to rev 3.0. The new 'micropackets' in the 4.0 ROMs
    can cause havoc on low quality connections. Setting S120=12 disables
    micropackets and makes your connection look just like rev 3.0. If that
    isn't enough, go to S120=2, which also disables short packets, leaving
    you just 'long' packets. That will make interactive response terrible,
    but should make things happier for file transfers.

2) It turns out that the retrains-leading-to-connection-death syndrome is
    usually caused by the following: on an international connection, the
    first part of any burst of information is often chopped off by the
    phone connection (satellite echo cancellers? I don't know...). Normally,
    this would destroy the first part of a data packet. If too much of this
    happens, the modems will retrain. If it happens a LOT, they'll retrain
    a LOT, and eventually give up. To solve this, use the J6S36 register
    (that is NOT a typo: it is a hidden debug register...). The default
    value is 0. As you increase the value to 1,2, or 3, you cause an
    increasing period of "guard tone" to be inserted before each packet
    is sent. The guard tone gets chopped rather than your data, and you
    don't have any retrains any more. The guy I talked to suggested starting
    at J6S36=2, increasing to 3 if that doesn't help, decreasing to 1 if
    it works great (just in case you can get along with less tone).

3) If S120 is non-zero, it will show up in your ATN?. J6S36 will never show
    up.

4) From personal experiment, S120 *is* saved by AT&W. I have no easy way
    to tell whether J6S36 is saved.


My remaining questions, which will hopefully be answered in a call to Telebit
today, are:

a) Is J6S36 saved? (And what about Naomi? :-) (old, very old, Sesame Street
	Joke)

b) Must these parameters be used at both ends of the line?

c) Does J6S36 exist in earlier versions of the ROM

d) Why not auto-increase the J6S36 value if there is trouble?


Hope this helps! I am anxious to hear about results! I'm trying to help
some people get a trans-pacific connection to work correctly...

Pete

-- 
Peter Holzmann, Octopus Enterprises   |(if you're a techie Christian & are
19611 La Mar Ct., Cupertino, CA 95014 |interested in helping w/ the Great
UUCP: {hpda,pyramid}!octopus!pete     |Commission, email dsa-contact@octopus)
DSA office ans mach=408/996-7746;Work (SLP) voice=408/985-7400,FAX=408/985-0859