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Posting-Frequency: Weekly
Last Modified: 09 Aug 1998
Version: 1.9
Changes: MINOR
<URL:http://www.pierrot.demon.co.uk/faq/dtm.faq>
<URL:ftp://ftp.demon.co.uk/pub/doc/faq/dtm.faq>

==============================================================================

The Demon Tech Modems FAQ              Compiled by Tez Boyes

0.1 Contents
============

    0.2 PreRamble
    0.3 Changes
    0.4 Why are we here?
        0.4.1 What is the purpose of demon.tech.modems?
    0.5 Do I have a problem?
        0.5.1 What is the source of the problem?
        0.5.2 Where do I report problems?
        0.5.3 How do I report problems?

1.0 References

2.0 General Questions

    2.1 What kind of modems do Demon use?
    2.2 Do I have a problem with my modem?
    2.3 How do I find out the ROM version of my modem?
    2.4 How do I use a Comms/Terminal package to get this information?
    2.5 What are all these AT commands anyway?
    2.6 I've RTFM and I still don't understand what these AT commands do
    2.7 The modem always answers calls before I can!

3.0 K56Flex, X2, 56K

    3.1 Which versions of 56K technology are supported by Demon?
    3.2 Which versions of 56K technology are usable with Demon?
    3.3 Which 56K modem should I buy?
    3.4 Where do I get a flash upgrade for my modem?
    3.5 What is the "best" init string for my modem?
#   3.6 And what are these new AT commands?
    3.7 Where do I report faults with the test number?

4.0 Slow, Dropped and No Connections, Network Death, Loss of Routeing

    4.1 I only get xxxk/s from Demon, why?
    4.2 Overruns & Errors
    4.3 Why did my connection drop after x mins?
    4.4 What's "Loss of Routeing"?
    4.5 What's Network Death?
    4.6 My modem doesn't seem to work at all, what could be wrong?

5.0 The Need For Speed

    5.1 How do I tell what speed I connected to Demon at?
    5.2 How fast should I be able to download files?
    5.3 Why is COLT so much slower than Energis?
    5.4 Why do large uploads (or downloads) grind to a halt?

6.0 Setting Init Strings and Modem Responses (32-bit Windows)

    6.1 Why does my modem claim to connect at 115,200 bps ?
    6.2 How do I change the modem init string in Turnpike/DUN?
    6.3 How do I change the modem init string in Win95
    6.4 AT&V1 gives no last connect info
    6.5 How can I see the CONNECT and CARRIER speeds with DUN

7.0 Misc. Stuff

    7.1 Modems, Soundcards and Phonecalls
    7.2 Caller ID
    7.3 Connection Protocols

8.0 Example Init Strings

    WILL BE HERE eventually...

9.0  Legalese


# marks a change or new section

==============================================================================

0.2 PreRamble
=============

Thanks all who pointed out errors, helped clarify a few points,
sent submissions, posted questions and/or answers, etc... whilst
this document was being prepared. Of course any errors and omissions
still present are all my fault and any suggestions are welcome at

dtm-FAQ@pierrot.co.uk

This is the first "release" version, posted to demon.answers as
well as demon.tech.modems, followups are set to demon.tech.modems
as usual.

0.3 Changes
===========

MINOR a couple of typos and some small clarifications
TODO  Glossary (suggestions welcome)
      Init strings for various modems
      Modem recognition guide!
      HTML version
      Expanded References


0.4 Why are we here?
====================

0.4.1 What is the purpose of demon.tech.modems?
      -----------------------------------------

from "FAQ: *** Which News Group? ***"
<URL:ftp://ftp.demon.co.uk/pub/doc/general/whichgrp.faq>

demon.tech.modems       Modems & non-Internet comms software discussions

Please note however that if your comms software question is platform
specific (especially for some of the "minority" platforms, or if it's
a particularly obscure application) you may well be better off asking
in the demon.tech.platform group that is most appropriate. Please
see the Which Group FAQ for help in deciding where to post.

And this is _not_ the newsgroup to complain about such issues as
too many engaged tones or the lack of support for 56K modem
technologies. All such posts should go to demon.service.

In addition this is a text-only newsgroup. HTML, encoded binaries,
MIME and other such things should not be posted. Specifically do
not post modem flash, inf or similar files. And if posting logs
please ensure that they're ASCII text.

0.5 Do I have a problem?
========================

0.5.1 What is the source of the problem?
      ----------------------------------

The first thing you need to do when you think you have any kind
of connectivity problem is to try and track down the cause. The
best place to start is Demon's "status" finger status@gate or check
the Web site.

Then read though the last couple of days of demon.tech.modems and
any other Demon support groups you take. It may be that it's a known
problem. If it doesn't seem that other people are currently
experiencing problems then it's worth checking your setup.

See Section 4 for some common connectivity problems and Section 5
for a discussion on how to test speed.

0.5.2 Where do I report problems?
      ---------------------------

You could try posting to the newsgroup demon.tech.modems, or
emailing Demon at either

helpdesk@demon.net or dialup-faults@demon.net

depending on the type of problem, and what response you want.

helpdesk is the email equivalent of the 24 hour phone support
(0181 371 1010) and is in fact answered by the same staff!

dialup-faults is mostly an address that is used to collect
information, you are unlikely to get any direct response from
a report there. However your report combined with those of other
users can be very useful in helping solve general dialup problems.

There is also a Web-based report form

<URL:http://www.demon.net/feedback/dialup-faults.html>


0.5.3 How do I report problems?
      -------------------------

The following information can be of use both in the newsgroup and
in fault reports to Demon. See elsewhere in this FAQ for methods
of obtaining some of the information.

Exactly what setup is in use (PC Spec (hardware/OS/stack summary,
Modem including any ROM or other version info., speeds, init string,
type of line (BT, Mercury, Cable), number called (and where you're
calling from, eg 0181 371), exact times and dates,
which line you logged into and the version of the firmware being
run on it - you should see these during the CONNECT/LOGIN, weather
conditions at the time)

Results of pings, traceroute and similar debugging tools. Or logfiles
that help put the problem in context (and show such info as CARRIER,
compression, error control, etc....) These should all preferably
be copied/pasted or otherwise included verbatim to help avoid
any problems with typos. Please note that many mail/news packages
will encode such things if they are "Attached" so they should be
"Included" instead.

Important: what you were doing at the time. i.e. http, telnet, ftp,
gopher, news, etc., one or more at once, what URL.

Applicable software installed, such as Office 95/97, browser(s)
installed (including version number), browser in use (if applicable),
ftp software in use (if applicable), etc.

Any phone extensions and equipment on the line.

And of course any results from the checklist that you think may
help others work out what's going on.

==============================================================================

1.0 References
==============

Miscellaneous sources of further information, some of which is
a pre-requisite for understanding modems, others expand on many
of the questions/answers below, some give detailed technical
explanations of areas that have been glossed over.

<URL:ftp://ftp.demon.co.uk/pub/doc/demon/modem.txt>

Is in my opinion essential even though some of the specifics are
mostly out of date.

#There an FAQ on 56K technologies on the Demon FTP server, though
#like this document it is a little out of date having been written
#at a time when 56K was first introduced.

#<URL:ftp://ftp.demon.co.uk/pub/doc/faq/dtm-56k1.faq>
#<URL:ftp://ftp.demon.co.uk/pub/doc/faq/dtm-56k2.faq>

The Tuning FAQ <URL:ftp://ftp.demon.co.uk/pub/doc/ka9q/Tuning.faq> was
written primarily for the KA9Q software, but contains many general tips
for improving the performance of your comms link.

And again though fairly old "How to connect to Demon reliably"
<URL:http://www.ftech.net/~horizon/richard/modem.hts> has much general
help on the "black art".

<URL:ftp://ftp.demon.co.uk/pub/doc/demon/isdn.txt> is a quick
discussion about what ISDN is all about.

Other sources of useful information that are specifically modem
related are

<URL:http://www.aimnet.com/~jnavas/modem/faq.html>

Also available as a uuencoded zip file by sending an email message to
ModemFAQ@NavasGrp.Dublin.CA.US with a Subject of "send modem faq".

Note a comprehensive list of manufacturer Web sites can be found at:
<URL:http://www.aimnet.com/~jnavas/modem/manfs.htm#Contents>

A page of links to firmware upgrade sites for a long list of modem
manufacturers is at <URL:http://www.56k.com/firmware/>

and if you're having problems identifying your modem, then
<URL:http://www.sbsdirect.com/fccenter.html> may help.

Or just try www.manufacturer.com ! (substitute your modems manufacturer) 

The latest on Demon and 56K <URL:http://www.dispatches.demon.net/56k.html>

For information about 56K technology, try <URL:http://www.56k.com>
<URL:http://www.56kstandard.com> <URL:http://www.v90.com>

And a couple of FAQs about K56Flex modems
<URL:http://www.unicorn-connection.co.uk/k56/index.htm>
<URL:http://www.nezumi.demon.co.uk/hardware/56k/56k.htm>

A list of UK ISPs can be found at
<URL:http://www.limitless.co.uk:/inetuk/providers.html>

Another very useful resource is the DIS Meta FAQ
<URL:ftp://ftp.demon.co.uk/pub/doc/general/dis-meta.faq>

Which has many handy hints on where to find useful information and
the best places to start looking for help on many problems.

And of course if you've got a problem it's always worth checking
demon.announce, status@gate, the Demon help desk.

Several of the Demon specific documents mentioned are always
available on the Demon Web site.

<URL:http://www.demon.net/connect/dial-up/modem.html> Connect by Modem
<URL:http://www.demon.net/connect/dial-up/orange.html>Connect by Orange
<URL:http://www.demon.net/connect/dial-up/isdn.html>Connect by ISDN
<URL:http://www.demon.net/connect/dial-up/ndu.html>Connect by NDU (Networked Dial-Up)
<URL:http://www.demon.net/connect/dial-up/services/modem/>Modem Connections
<URL:http://www.demon.net/faq/ascend.html>Frequently Asked Questions about Ascends

==============================================================================

2.0 General Questions
=====================

2.1 What kind of modems do Demon use?
    ---------------------------------

They don't!

What they do use are Ascend Terminal Servers

<URL:http://www.ascend.com>

For most purposes however these can be regarded as black boxes that
look like modems when we connect to them. In fact so that they can
deal with the analogue modems in general use they have "modem cards"
in them. If used with ISDN however they are "fully" digital. See
the Ascend Web site for further details.

You may see the Ascends referred to in a number of ways, TNT and
MAX are both model names. You may also see them called "not modems".

2.2 Do I have a problem with my modem?
    ----------------------------------

Please clarify the problem...

But seriously, there are certain pieces of information that are
vital to solving any given problem, and there are some that are
generally useful. So please, in any initial post to the group
asking about a problem with a specific modem or piece of software,
give as many useful details as you can about your setup and the
nature of the problem. See Section 0.5 for examples of information
that may be of use.

2.3 How do I find out the ROM version of my modem?
    ----------------------------------------------

Win95 users can get this information from

Control Panel/Modems/Diagnostics/More info

A more generic method however is to start up a general Comms/
Terminal package.

For Hayes/Rockwell modems these commands give the firmware version
of the ROM, the modem model and the data pump version.

ATI3
ATI4
ATI6

USR modems use ATI7.


2.4 How do I use a Comms/Terminal package to get this information?
    --------------------------------------------------------------

It's a program that allows you to "talk" to your modem directly.
Fully featured programs will also include automatic dialers,
terminal emulation and so on. They are available on many platforms,
either as part of the OS software, commercial or public domain.

Windows3.x users should have a program called Terminal. Some have
reported problems using Terminal, if you can't get it working try
<URL:http://www.delta.com> and download the shareware version of
Telix for DOS.

For 32-bit Windows try the supplied HyperTerm. One important thing
to note with HyperTerm is that you need to use the "Direct to COM#:"
option when you start it up (where # is the number of the com port
that the modem is plugged into of course!).

If you don't like HT Then try ZOW from <URL:http://www.emtec.com>

Alternatively do a search for a program called kermit, there are
versions available on a multitude of platforms.

Once you've located such a program for your platform, follow the
setup instructions and you should be presented with some kind of
command line prompt. Try typing ATZ then Return/Enter, the modem
should come back with OK. If not, ask on the newsgroup!

2.5 What are all these AT commands anyway?
    --------------------------------------

Your modem should come with some documentation detailing what
all the commands do. Of course it might not, if your modem uses
a Rockwell chipset then the site

<URL:http://www.rockwell.com/>
<URL:http://www.nb.rockwell.com/techinfo/pc/resource_files/at_commands.html>
<URL:http://www.rss.rockwell.com/technical/pc/resource_files/1048r2.pdf>

should help.

And of course since Hayes originated the ATtention command set

<URL:http://www.hayes.com>

is also a good source for general information on them.

USR/3COM users should try

<URL:http://www.usr.com>
<URL:http://www.totalservice.usr.com>
<URL:http://www.usr.co.uk/index>
<URL:http://www.3com.co.uk/56k/56k.html>
<URL:http://www.3com.com/56k/europe.html>

Or email

<URL:mailto:uksupport@usr.com>


2.6 I've RTFM and I still don't understand what these AT commands do
    ----------------------------------------------------------------

OK, there are a few commands that are used a lot, here's a brief
description of a few of them, in use they should be preceded by AT,
though you only need one AT per line (note that there is a limit on
the length of the command line with at least some modems, tests here
have shown it to be in the region of 55 chars).

Some fairly generic commands

DT#######   - dial tone the number #######
,           - pause for 2 seconds
Hn          - go on(n=1) or off(n=0) hook
&Fn         - reset the modem to factory defaults
Zn          - reset the modem to the last settings, or to the nth
&Wn         - write the current settings to memory n
Sn?         - return value of status register n (NB that many of
            - these registers are model specific

For Hayes/Rockwell firmware

&V          - see how the modem is setup
&V1         - see some information about your last connect
I3          - firmware version
I4          - product name
I6          - data pump version
\Nn         - is for setting error correction mode (see manual for n)
%Cn         - is for setting compression mode (see manual for n)

see also the K56Flex section for some other commands.

And for USR

I3 = Product Type
I4 = Current modem settings
I5 = NVRAM settings
I6 = Link Diagnostics
I7 = Product config.
&Mn         - is for setting error correction mode (see manual for n)
&Kn         - is for setting compression mode (see manual for n)

2.7 The modem always answers calls before I can!
    -------------------------------------------

This is known as AutoAnswer, you can disable it by starting up your
terminal program and typing ATS0=0&W (the S0=0 turns it off, and the
&W stores this in the modem so you won't have to do it again tomorrow..)


==============================================================================

3.0 K56Flex, X2, 56K
====================

3.1 Which versions of 56K technology are supported by Demon?
    --------------------------------------------------------

Today, none, but that doesn't mean that they can't be used.

However once the new standard, V90 (AKA v.pcm) has been ratified
by the ITU <URL:http://www.itu.ch>, and there are "modems" available
to Demon that implement that technology, then they will support the
standard. See also <URL:http://www.56kstandard.com> and 
<URL:http://www.v90.com> for the latest news.

The current situation is that the major players have agreed the
standard in principle. Target date for full ratification is
September 1998. Some modem manufacturers (USR/3COM and Modular
Technologies for a start) have already produced V90 code.
Others are likely to follow soon.

Demon have been testing various kit from Ascend and 3COM, which
is capable of 56K access. This will shortly be rolled out into
live use.

Please see Demon Dispatches Issues 12 and 13 which have more
details on the plans and <URL:http://www.dispatches.demon.net/56k.html>
Though note that due to the lead times in printing a magazine and
problems with testing Dispatches 13 is a little ahead of itself.

3.2 Which versions of 56K technology are usable with Demon?
    -------------------------------------------------------

Very soon 

                Energis         Colt            Cable & Wireless
----------------------------------------------------------------
Up to 33.6kb/s  0845 079 8666   0845 353 5666   0845 301 1666

K56Flex         0845 079 8666                

X2                                              0845 301 1666       

NB Energis includes the "local" numbers.

Currently however K56Flex is enabled on the test number, 0845 079 8668,
and X2 on the new C&W number 0845 301 1666.

Note well that the 8668 number is likely to be removed at some
point in the future to be replaced by a testers only Ascend number.
Similarly there will be a testers only 3COM access number.

NB these testers numbers are _not_ for public use, and Demon may
at any time not only remove it but may set things up so that only
members of the testers group can use it.

Should they limit access to testers, this can only be done after
a call has been established and a log in attempted. Non-testers
calling are thus going to be charged 5p for a failed call.

Anyone interested in joining the testers group should see
<URL:http://www.demon.net/external/testers/> about (please be
aware that Demon add new testers to the group in batches at
infrequent intervals, so don't expect to join up immediately!).

3.3 Which 56K modem should I buy?
    -----------------------------

The short answer is none... However, as noted above, K56flex, X2
and V90 may work on unsupported numbers now.

There have been varied reports of connect speeds, problems, etc...
with most of the popular models when connecting at 56K.

Basically it should be safe to buy any modem that claims to
be cheaply (or freely) and easily upgradable to the ITU standard.
Of course current K56Flex, X2 and V90 modems should work with
Demon at v34 now.

And obviously if your old modem has just died, or you're upgrading
from a non-v34 capable modem then it may make more sense to buy a
flashable 56K model. A flashable modem is one that contains a ROM
which can be upgraded by software. In most cases you just connect
the modem to your PC as normal and run a program which does the
upgrade.

One particular note on Hayes modems, some models made in France
and with V0.520 are not fully flashable. If you have one of these
modems you should contact Hayes (or your supplier) for a
replacement.

3.4 Where do I get a flash upgrade for my modem?
    --------------------------------------------

In general most modem manufacturers have a web site or bulletin
board where they post the upgrade files.

Motorola: 01293428490
Hayes: 01252775599 * this is out of date!

The best place to ask is where you bought the modem from! Or try
the References section of this FAQ.

And it is often well worth getting the latest upgrade, eg v1.120
has increased many Motorola users connections by 4000.

NB though that it is unlikely that V90 updates will connect to
(m)any ISPs for a while. Wait until you know your ISP supports
V90.

3.5 What is the "best" init string for my modem?
    --------------------------------------------

A very difficult question, however...

Try the default settings first, they work well in the great
majority of cases. If you are unsure as to how well your settings
are working, then test the setup out as per "The Need for Speed".
For those unfortunates for whom default settings do not work well,
there are a wide range of possible causes and so finding an init
string that helps can be a difficult problem.

Technology has changed over the years (modem protocol standards
being widely used, better quality phone lines, etc...), and unless
they have a specific problem most people find that changing the
default values (or those setup by a .inf, .mdm or similar) only
results in worse performance.

The reason that there is no "best" init string (and indeed why init
strings are changeable by mere users), is that when modems try to
connect they use a very sophisticated protocol which probes the
characteristics of the connection before choosing one of a number
of variants of the modulation scheme. For a few users who have
problems, the eventual solution may be to make settings to restrict
the choices that the modem makes in order to exclude choices which
appear plausible but don't actually work well in practice for this
particular modem or phone line.

See Section 8.0, there may be an example init string there for
your modem. Many other sections of this FAQ are aimed at isolating
any possible problems, once you've done that it may be possible
that an init string could help you.

However here is some general advice on how to construct your own
init string.

* Factory default profiles

Start your string with an &F .  If your modem has more than one set of
factory defaults then choose those for hardware flow control.

* Hardware flow control

One of &Q3 , \Q3 or &H1&R2 should usually set bi-directional CTS/RTS
hardware flow control.

* Carrier detect

&C1 will ensure that your computer can see if the carrier drops.

* Hardware hangup

&D2 will make sure that your modem will drop the line and will reset if
the DTR line is turned off by your computer

* Connection report

Where possible, get your modem to tell you as much as possible about the
kind of connection achieved.  Modern Rockwell chipset modems will accept
a setting of \V1 which shows on a single CONNECT line the DTE rate, the
receive DCE rate and the transmit DCE rate.  For older Rockwell chipset
modems an S95=46 is the best, showing the DTE rate in the CONNECT line
and the DCE rate in the CARRIER line.  If your modem will only show one
rate when it connects, then make sure that it shows the DCE rate -
because that is the most interesting one to you, often W1 does this and
\V1 will give an indication of whether error correction is achieved.

* Error correction and data compression

Try to make sure that your modem is at least able to negotiate error
correction and data compression, often called auto-reliable mode.  \N3
often does this, but USR modems use &M4.

Where possible tell your modem to only accept an error corrected
connection, often called auto-reliable mode.  Any non-error corrected
connection is a waste of your time and your phone bill money.  Settings
for this vary more widely for this than for auto-reliable.  For Rockwell
chipset modems \N4 will require V.42 error correction, for USR modems
&M5 will require error correction.

* Loudspeaker

L1, L2, L3, M0, M1, M2

* auto-answer

S0=0


3.6 And what are these new AT commands?
    -----------------------------------

For Hayes modems,

%E0     Disable line quality and auto-retrain.
%E1     Enable line quality monitor and auto-retrain.
%E2     Enable line quality monitor and fallback/fall forward.
+MS=11,,,,,  force v34 connect
#+MS=12,,,,,  force V90 connect
+MS=56,,,,,  force 56K connect
+MS?         Report current setting
+MS=?        Report valid settings

The following is recommended for a K56 connect

+MS=56,1,34000,56000

and S91=15 has been known to improve some users connections.

#no such strings are needed for X2.

#V90 modems and later versions of the K56Flex code use a similar
#pattern to K56

#+MS=12,1,34000,56000,1,0,33600

#The additional numbers relating to the TX (transmission rate).

Forcing a v34 connect can be useful in some circumstances. Eg
several of the recent software versions on the test number were
causing "Loss of Routeing" type problems with my modem if I connected
using K56, but not using v34. These went away with release
1.3ap20 of the Ascend code. This version number can be seen between
connection and login to the Ascends, eg

test-finch-237.access.demon.net (2.0.0)

Note that this is very useful information if you're reporting
a fault.

3.7 Where do I report faults with the test number?
    ----------------------------------------------

Once the new lines go "live" the "test numbers" should only be
used by the Demon Testers Group, who should report results as
advised on the list.

There may be new addresses at Demon set up to deal with reports
of problems on the 56K numbers, note however that these numbers
are not supported.

Please see <URL:http://www.dispatches.demon.net/56k.html> for
the latest information.


==============================================================================

4.0 Slow, Dropped and No Connections, Network Death, Loss of Routeing
=====================================================================

4.1 I only get xxxk/s from Demon, why?
    ----------------------------------

Well there are several possible reasons, mostly out of the scope
of demon.tech.modems. Eg "bandwidth" problems. The only speeds we
can be relatively sure are usable for testing is when downloading
known files directly from Demon by ftp. See Section 5 for details
on how to test your connection speeds.

a) modem badly configured - check the modem setup Section 3.5

b) your setup can't handle the data as fast as the modem - check
for "Overruns", reduce the DTE as a temporary measure, Section 4.2

c) the modem doesn't work properly - always a possibility.

d) an internal line problem - if you have the modem plugged in
via a long cable, have several other devices connected via
splitters, and the like, then this _may_ cause problems. It's
well worth trying first to disconnect all other equipment from
all your sockets. If that doesn't work then try plugging the modem
on its own directly into the master socket. At worst you can eliminate
that as being the problem.

e) bad phone lines - there are several ways to check this, BT
have a basic number, 17070, that does some checking. Simply pick
up your phone, dial it and follow the prompts (2 for Quiet Line
test).

Netcom, 0845 079 8022, have a number that tests to see if your
line is X2 capable (and also gives some potentially useful
information on the quality of the connection). For this you need
to use a Comms/Terminal program (see Section 2.4). You may
wish to post this information to the group. If so please answer
N)o to the question about ANSI/colour graphics, and set your
newsreader/editor _not_ to wrap the lines at <80 chars.

NB any modem users should be able to use this number, you don't
need an X2 capable modem.

Check with your Telco (be it BT, Mercury, Cable, Whatever) directly,
they may find a fault.

Ask BT (150) to turn off the AGC and turn the gain up about 3 or 4 db.
This will hopefully increase your speed, some users have reported
substantially better connections (eg 38k going up to 46k). On the
other hand others have had worse connections after having the gain
turned up. The likely cause of their problems is "line noise" (see
subsection d above).

Check whether or not DACS is on your line. DACS is a method that
BT use to get two circuits on one wire. It has little adverse
effect on voice calls but can cripple data calls.

Note: Very few people are refused ISDN by BT because their line
cannot do 192Kbits/sec (ISDN is 2x64K + 1x16 + some overhead).
However there are differences between using ISDN, 56K or other
modem protocols and currently K56Flex is definitely a lot more
sensitive to small variations in line quality.

4.2 Overruns & Errors
    -----------------

If you are getting low download speeds, with a high CARRIER and
CONNECT, then you may be suffering from Overruns. Ask in the
appropriate ip.support group for details of how to check this.
(Turnpike users see it as "Errors" in the Connect window, and
should look up Errors in their Help File).

An overrun occurs when your computer can't receive data from the
modem as fast as it's set to. And even though it may only be
one character that has been lost it is necessary for the whole
packet (500 bytes+) to be resent. And all this takes extra time.

If you are getting overruns the first thing to try is reducing
the DTE. In general this should be set to ~ max CARRIER * 4 if
possible, eg

v34 modem - 115200
v32 modem -  57600

However it is only rarely that you'll ever see throughput this
high in normal situations, so you won't lose much by reducing
to 57600 or 38400 respectively.

56K modem users may be able to set DTE=230400, however most
standard PCs cannot currently handle that.

A lot of overrun causes are hardware (or software) specific, as are
solutions to them. However there are some general areas that can be
checked.

The first is the serial port (assuming you use an external modem).

Clone/IBM PC users should check to see what UART they have installed.
If an 8250 they should upgrade to a 16550A, which may well solve the
problem. Ask in demon.tech.pc if you're unsure how to do this.

Users of other platforms are best advised to check in an appropriate
tech newsgroup as to the capabilities of their serial ports, and any
upgrades possible.

Another cause of problems are old software drivers, where possible
please ensure that the most recent serial/modem drivers are being
used.

Clone/IBM PC users should also check their video drivers (some
old S3 drivers in particular have been known to cause severe
overruns). Similarly any hardware that uses the main bus could
cause problems. Another area to check is your mouse drivers
especially if using a serial mouse!. Again try demon.tech.pc

And of course users of all platforms may need to reduce the
overall load on your machine whilst you're connected to the
net. Any program requiring disk or CPU usage may be causing the
overruns.

4.3 Why did my connection drop after x mins?
    ----------------------------------------

There can be several reasons, the first question is always,
was there any traffic at the time. Your setup and Demon can
have timeouts set (at Demon it's typically 4 mins but can be
overridden at the Protocol: prompt by idle=n where n is in secs)
see the ip.support group for your platform for details of how
to set this, or any other, timeout.

If there was traffic flowing then it may be due to a bad connection.
Many modems have both AT commands and S register settings that can
modify how they react to a momentary loss of carrier.

If you have Call Waiting an incoming call can make the modem drop
the line, similarly so can the "pips" on payphones.

A few other points that may also be worth noting are

  - Check your hardware connections, both from within your Operating
System, and on the physical side. Are the cables securely in? Is the
telecom socket quite a way away from your computer and modem?

  - Check the modem configuration, init strings, .inf files

  - Are you always using one (or more) specific piece(s) of software
when getting the fault?

  - Are the weather conditions the same when the fault occurs (wet
weather has been known to provide additional electrical conductivity, so
dry conditions may deteriorate your connections)? And vice-versa!

  - Try at different times of the day (try to avoid Wednesday morning
connects as this is the most likely time of maintenance at Demon),
Morning, Afternoon, Evening, at both weekdays and weekends.

  - One very good way of determining a fault is to borrow another modem.
If this proves to be the fault, try the original modem under different
circumstances (e.g. with another ISP or from another location). It could
prove that particular modems have particular difficulty in this area.
On the other hand, should the new modem give the same result, it could
point to the modems not being at fault (unless they both happen to have
the fault!), in either case mention which modem make/model/software
version you are using. Making a purchase of a new modem on the basis
that it will cure the problem(s) is not recommended!

And remember to take a look at your logs. The modem you are using may
be able to provide a good source of information, both current and over
the total connected time, on both statistics and quality of line.
Alternatively, if you are using Windows 95 DUN (Dial Up Networking),
you can produce a modemlog.txt.

Noting down your results to these points may help you build up a picture
of what may be going wrong. Even if it doesn't, it may help to include
these details in any fault reports to Demon or to the newsgroup (see
Section 0.5) at a minimum it will save wasted time (it's likely that
people will ask you to check these things!)

Another possibility is

4.4 What's "Loss of Routeing"?
    --------------------------

It means that somewhere between your computer and the server
that you were connected to, that data is effectively getting
lost. There's no known path between them anymore (see
demon.ip.support for a real explanation). When this symptom
spreads and you find that you cannot get any data from any
site you get something resembling Network Death. Try using
traceroute[1] to the server that you're trying to connect to.

[1] many platforms have this builtin, for those that don't
try <URL:http://www.demon.net/external/ntools.html>
if you can get any response! Of course you might not be able to
use these tools if the problem is loss of routeing or similar.

If that fails then try

ping 158.152.1.222 - if this works then your connection is still up
ping 158.152.1.43 - if this works then DNS is still working
ping 158.152.1.58 - (these are the main nameservers)
ping demon-du.demon.co.uk - if this works then either you've got the
                            address for demon-du cached, or DNS is
                            working
ping gate.demon.co.uk     - again as above, but also data is getting
                            past your gateway (if it fails it may
                            be because gate is down so try
ping post.demon.co.uk     - as above
telnet post.demon.co.uk smtp - you should not only get a connection,
                               but also a welcome message, if this
                               fails then it may well be ND

"Loss of Routeing" is a specific issue with the routers at Demon 
(which have lost the dynamically made static routes from the Ascend
to the rest of the Internet). Note that it is unlikely to be caused
by your setup, and in most cases the problem won't recur (though
as usual it's worth checking status@gate, the problem may have been
widely spread enough to be reported).

This can then cause Network Death. As can the Ascends getting
detached from the Ethernet they live on, or a fault in the Ascend
or... or almost anything.  


4.5 What's Network Death?
    ---------------------

A catchall term used loosely to describe several sets of similar
symptoms that cause a cessation of traffic between our machines
and the Internet.

Very similar to loss of routeing in symptoms, typically with your
modem sending the ping request to the server (see the SD light on
external modems), but without reply (no RD light). This may be a
transitory problem at Demon, or it may be down to some incompatibility
between your setup/modem/phone and Demon. Some specific models have
been known to be more problematic than others (Motorola 3400 is top
of the list). But Demon/Ascend/Motorola/Others are working on solving
the various problems.

If you think you are suffering from this phenomenon then try connecting
to the COLT ROMP (08453535666), Energis ROMP (08450798666), local
Energis number (see pops.txt) and Test number (08450798668).

You may well find that your modem works fine on some numbers but
not others. Either way remember to put the info. that you have
tried different numbers in any fault report. For one thing it'll
stop people suggesting that you do so... And it can help Demon
create some kind of pattern (if possible) of the problems.

A lot of discussion has been going on in the various demon newsgroups
for a while now, with Demon admitting that a problem does exist with
the minority of it's customers, and that a solution is being worked
upon in co-operation with Ascend. It is highly probable that the
cause is either a problem with your setup, telecom connection or a
temporary problem (e.g.  maintenance) at Demon, especially if the
problem is of an intermittent nature. It's always worth checking
status@gate and/or contacting Demon HelpDesk by either email or phone.

However if you're still getting these symptoms regularly after 
checking out the possible causes of connectivity problems detailed
in section 4.3 above then it is likely that you're a sufferer.

One other point of interest is that some users have reported that if
you can get an external site to "ping" you whilst it's happening then
the problem disappears. This may be worth trying if you are able to
set it up for someone at the HelpDesk to ping you at a certain time,
perhaps 10 minutes following the termination of your phone call (or
immediately if you have two lines) to them, by which time "Network
Death" could well have struck. 

Reports of "Network Death" problems should go to
dialup-faults@demon.net - please include your setup (including software
versions), the first six digits of you phone number, the number you
are dialing, any logs you have, any traceroutes you have, and the ATIx
responses from your modem.

4.6 My modem doesn't seem to work at all, what could be wrong?
    ----------------------------------------------------------

If it's an external modem check all the cabling. Note that using
cables from other modems may not work at all. And the serial cable
from the PC to the Modem should have pins 2,3,4,5,6,7,8 & 20 connected
through ? 

==============================================================================

5.0 The Need For Speed
======================

5.1 How do I tell what speed I connected to Demon at?
    -------------------------------------------------

The modem should report what speed it connected at, however
there are several different ways it can do it. This is further
complicated for users of Microsoft DUN by .inf files that
translate this information (see section 6.1).

In general most modems have AT commands and S register settings
that allow you to modify the format of the reply code. If these
don't give you the information you want then try using the Link
Diagnostics for your modem type after dropping the connection.

5.2 How fast should I be able to download files?
    --------------------------------------------

That varies dependant on several factors.

And usually most of the factors are not only outside our control
but also outside the scope of demon.tech.modems and therefore this
FAQ. These include issues such as bandwidth, load on servers, etc...

What we can help with though are ways of testing how well your
modem is setup for use with Demon. First of all, please read
modem.txt, and use support@demon.net, from which I quote

" Alternatively, you can request help documents for a wide range
" of topics, by emailing support@demon.net and supplying the
" following subject line (in lower case only please):

" Subject: send filename

" where filename refers to the document you want, eg.windows.

Filenames that are of particular interest include

" ascend             Information on connecting to an Ascend server
" isdn               Information on using ISDN to connect to Demon
" modem              Configuring your modem for an Internet connection
" tnt                Using very old modems on the Ascend TNT's
" ftp                How to use FTP to transfer files
" ftpdemon           How to transfer files to and from Demon's servers

and of course any platform specific files, or FAQs as appropriate
(see the MetaFAQ).

Now you've got your modem setup as best you can using the above
it's time to test it. And hence the reason for getting the ftp
help files. To do this kind of testing you need to be connecting
to ftp.demon.co.uk from a Demon node and not running any automatic
news/mail collection, or in fact any other up or download. It's
also best to do this testing when Demon are not likely to be
heavily loaded.

OK, start up your FTP program, connect to Demon, cd /pub/test
There are several files in there

fullfile
emptyfile
regularfile

Also check the new and rockwell subdirs which contain

htmlfile
newsfile
basefile
vfullfile

Download speeds should vary markedly between most of the files
(unless you're using ISDN in which case they should be 7.24K/s
assuming a single 64K channel). Some of these speeds are purely
of intellectual or indicative interest, some however show the
maximum speeds you can download files.

emptyfiles - max = CONNECT/divisor
fullfiles  - max = CARRIER/divisor
the rest   - max is somewhere between the above 2

where CONNECT is the computer=modem (or DTE) speed, which is set
by you in your software. Generally the higher it's set the better,
however if your setup is not capable of supporting that speed
your downloads will be slower. See Overruns elsewhere in the FAQ.

and CARRIER is the modem-modem speed. Generally your modem should
be set to negotiate the highest speed it can. Sometimes this, like
the DTE, can cause more problems and you may need to limit the
CARRIER (most likely cases currently are 56K modems, see the 56K
section for details).

The divisor can vary, see modem.txt for why it's not always 8.
For emptyfile the limit should be CONNECT/10 , this is because
the async bytes are sent 1 start bit, 8 data bits, 1 stop bit
per byte at the DTE rate.

Empirically PPP has shown figures very close to the above
(emptyfile at CONNECT/11, fullfile at CARRIER/9), SLIP has
been slightly worse. CSLIP should give figures similar to PPP.

Another factor to consider is where you retrieve the file to,
eg /dev/null, NUL: NIL: may give slightly faster speeds (though
obviously that's not much use for real downloads!)

Now onto the reason why fullfile uses the CARRIER, and emptyfile
uses the CONNECT. It's all down to modem compression, assuming
it's enabled on your modem, and everything else permits it!

Basically fullfile is not compressible at all, hence no gain over
the CARRIER. emptyfile however is very compressible, so much so
that even with a 28800 CARRIER it can still be received at in
excess of 115200.

So emptyfile is a test of the modem compression and the DTE,
fullfile is a test of the maximum number of bytes that can be
received per second.

Speed tests done using a DTE of 230400 have shown emptyfile/
regularfile topping out at 21K/s as expected.

Please note that these are only indicative speeds, you are unlikely
to achieve them in real world usage. But if your modem/setup comes
close to the theoretical max speeds above there should be no need
to try and tweak things any further!

5.3 Why is COLT so much slower than Energis?
    ----------------------------------------

The COLT ROMP is using (in the main) different Ascends running
a different version of software than the Energis numbers (there
are also a few other setup differences). Note that some new
Ascends have been added to the end of the COLT search group, so
it is possible that you'll get a "TNT" rather than a MAX4000 on
a connection to COLT at busy times.

And of course the different ROMPs also terminate in different parts
of the network. This should not under normal circumstances affect
overall speed (Demon have a 155Mb link between their 2 main sites).

Similarly some of the ISDN lines may answer calls to the 5666
hunt group when demand for ISDN is low and demand for Energis
is high (typically early evening). So remember to note the id
of the Ascend that takes your call as well as which number you
called.

5.4 Why do large uploads (or downloads) grind to a halt?
     ----------------------------------------------------

Some people have reported that whilst normal connectivity seems
fine there can be problems with either uploading or downloading
large files. Though these are two different problems they may have
a common source in Win95 (NT and 98 probably), incorrect settings
in the registry. You may want to examine or edit the registry
yourself (taking normal precautions - backup) or use a small app.
designed for the job, eg

EasyMTU <URL:http://members.tripod.com/~EasyMTU/index.html>

If the problem is with uploading then you may want to examine

HKEY_LOCAL_MACHINE/System/CurrentControlSet/Services/Class/NetTrans/000?
                                                            
Check that the value of MaxMTU is set to 576 (if it's not set at
all then it's probably best to use EasyMTU or similar). You may also
want to check in

HKEY_LOCAL_MACHINE/System/CurrentControlSet/Services/VxD/MSTCP/

that the variable PMTUBlackHoleDetect is set to 1.

==============================================================================

6.0 Setting Init Strings and Modem Responses (32-bit Windows)
=============================================================

6.1 Why does my modem claim to connect at 115,200 bps ?
    ---------------------------------------------------

This is the DTE rate and is reporting the speed of your com port
setting (the speed at which data can flow between your modem and
your computer). In order to display the initial connection speed
it is necessary to use an appropriate command in your init string
to display DCE (modem to remote modem speed).

Windows users should note that the use of an out-of-date modem
.inf file for a high speed modem can result in DTE always being
displayed instead of DCE.

It's worth checking the manufacturers Web site for the latest
.inf file. If that doesn't help, and you really need to see
the actual CARRIER value there are ways to change the .inf
files.

This does not affect users of Turnpike 3.04 and before if they
have TP set to use its own Connect program. However from v3.05
onwards it uses Win95 DUN, so it will also affect those users.

Also note that as long as your setup doesn't force a modem
reset, and consequent loss of information, you can often
find details of the last connect using some of the AT commands
detailed in section 2.6.

6.2 How do I change the modem init string in Turnpike/DUN?
    --------------------------------------------------

Turnpike (prior to version 3.05 for Win95) drives the com port
directly, using a *.mdm file that contains the init string. The
universal modem file works well for most modems, and should not be
altered, but *.mdm files for specific modems can be altered in a
text editor.

Win95 users can use DialUp Networking (DUN), your modem should
come with a .inf file (similar in concept to the .mdm file). This
should be setup for you automatically, however if you ever need
to update it

Control Panel/System/Device Manager/Modem/Properties/Driver

Click on Update and choose your new .inf file.

Or to add a completely new mode

Control Panel/Add New Hardware/Choose/Modems/Have Disk

and again choose the new .inf file.

6.3 How do I change the modem init string in Win95
    ----------------------------------------------

Control Panel/Modems/General/Properties/Connection/Advanced/Extra Settings

Those migrating from Turnpike 3.04 to 3.05 can extract the old
init string from their old Turnpike .mdm file. This will be in 
the Turnpike install dir, simply open it in a text editor and
cut/paste the init string. Remove the \r from the end of the
line, and replace all occurrences of \\ with \

6.4 AT&V1 gives no last connect info
    --------------------------------

Some modems reset this info. on receipt of ATZ. And some dialers send an
ATZ after hangup (DUN is one). The fix for DUN is to run the Registry
Editor, "regedit", and disable the reset by editing the "Reset" key in

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Class\Modem\0003
                                            or some other number-^^^^
                                   (whichever key refers to your modem)

or for NT RAS

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Class\{modem hex key}\0003\Reset
                                            or some other number-^^^^

to show "AT<cr>" instead of "ATZ<cr>" 

NB that with some modems you may appear to get no response from
your terminal program. This is probably because the init string
has set Local Echo off (and it was relying on ATZ to restore it).
In these cases try replacing the ATZ by ATE1 instead.

Another possibility is that your Init string contains &D3,

&D3 generally sets modems up to do a soft reset on loss of DTR.  If
the software uses DTR drop to end a call (as Trumpet Winsock does)
this will initiate a modem reset and hence clear the data from AT&V1

&D2 is a better option - it drops the line and returns to command
mode, leaving the data intact.

6.5 How can I see the CONNECT and CARRIER speeds with DUN
    -----------------------------------------------------

The fastest way to see the initial connection speed is to hover your
mouse over the DUN icon which appears in the Win95 tray (on the RHS of
the Start menu bar) when you are connected, or right-click on it. A more
detailed output can be obtained by selecting "Record a log file" in
Control Panel/Modems/General/Properties/Connection/Advanced
The information will be recorded in "modemlog.txt" in the Windows
directory.

INF Files

HKR, Responses, "<cr><lf>CARRIER #####<cr><lf>", 1, 02, 00, zz, yy, xx, 00, 00, 00, 00, 00 ; CARRIER #####

where xx, yy, zz are (in that order) the hex value of the ##### carrier.

==============================================================================

7.0 Misc. Stuff
===============

7.1 Modems, Soundcards and Phonecalls
    ---------------------------------

If your modem is one with 'speakerphone' or 'voice' functions, then
you're in business- read the manual (on-line or paper) for details
appropriate to your modem. And appropriate software should have been
included in the box.

The modem should be able to connect to your existing sound card
for complete functionality, but most have their own microphone and
speakers (or at least sockets for them).

If your modem is not one of these, then in all likelihood you're
out of luck since the modem would need some special hardware and firmware
in order to route the sound in and out of the phone socket, and through
various other magic things.

7.2 Caller ID
    ---------

There are (at least) two forms of Caller ID in use by telcos in
the UK. And different modems can read different forms of it.

e.g. USR Sportster Vi is only capable of reading the CLI delivered
by the Bellcore system (as used in the US, and also by *some*
UK cable telcos). Some Pace and Hayes models (always check first!)
are capable of reading the CLI delivered by the BT system (which
is also used by some other UK cable telcos).

The two systems are totally incompatible; the Bellcore one sends the
data between the first and second rings, whereas the BT design sends the
data *before* the first ring.  It is also capable of sending more data
than the American scheme.  (Please do NOT refer to it as "UK CLI"
however, since both the BT and Bellcore systems are in use in the UK.)

If CLI arrives, it will be presented as an ASCII string *after* the first
RING indicator (even with the BT system, where the data arrives before
the first ring; both Pace and Hayes, the only other modem manufacturers
capable of handling BT CLI, do this for compatibility with software,
such as TAPI, written for the Bellcore system).  The message will give
the CLID, the date, time, etc.   

And please note that 1471 is not the same as CLI delivered. You
have to order it from BT, and PAY for it. (check for any current
offers that BT or your telco may have on the service).

7.3 Connection Protocols
    --------------------

Protocol negotiation: V.8

  This is the initial phase of modem connection where they try
  to negotiate the optimum settings for the connection. This is
  based on init settings of both modems and the line quality of
  that connection.

Data modulation: V.32bis, V.34, 56KFlex, X2

  What method is used to transmit the data. This is the base
  "speed" commonly known as the CARRIER. This is setup during
  the negotiation phase.

Error correction: V.42, MNP4

  What method is used to check that any data sent is not mangled
  during the process. This is setup during the negotiation phase.

Data Compression: V.42bis, MNP5

  What method is used to compress any data sent. Note that the
  different methods of compression have varying results on
  different files. This is setup during the negotiation phase.

Link protocol: PPP, SLIP, CSLIP

  PPP = Point to Point Protocol
  SLIP = Serial Line Interface Protocol
  CSLIP = Compressed SLIP - note this is packet header compression
                            not data compression

  Nothing to do with the modem, it's defined by your dialing
  software. Demon supports both SLIP and PPP, some client
  software may allow you to use both, some only one or the other.
  There are various advantages of PPP, in tests it's faster than
  SLIP, but about the same speed as CSLIP. And Line Quality
  Monitoring is also available (see a platform specific
  ip.support newsgroup for details about your software).

Network protocol: TCP/IP, IPX

  Again, nothing to do with the modem, it depends what software
  you're using. Typically most dialup users will use TCP/IP most
  of the time. Some games, eg Network Doom, use IPX.

==============================================================================

8.0 Example Init Strings
========================

WILL BE HERE!

I already have a few, I'm just trying to work out a good way to
both present them, and store them for reference. Any ideas or init
strings - preferably with an explanation of why anything out of the
ordinary has been done.


==============================================================================

9.0  Legalese
=============

(which may bear more than a passing resemblance to that used in
the dis.newuser FAQ :)

  The advice given in this FAQ is of necessity generalised, so you
  follow it entirely at your own risk. Always back up valuable data! The
  details have been carefully checked, but the Internet develops at a
  rapid rate. Things will probably be inaccurate or out of date
  and I apologise in advance. I welcome corrections whether they be
  factual or simply typo's or matters of grammar!.

  The original author (Tez Boyes) has no commercial interest in any
  of the products or services mentioned. My motive for writing this
  FAQ is to try and help keep the noise down on dtm (especially
  re: 56K!) as well as providing a useful reference for common
  questions and helping other users not only get the best from their
  modems but also understand why to some extent...

  My thanks go to the many posters to Demon news groups, who
  have helped shape my thinking (references to FAQs and other
  documents they have written are aplenty above!), and particularly
  those in dtm who helped review the original draft and to all those
  who have sent me suggestions (even sections) and comments.
  Unfortunately they are too numerous to list here and I'd be bound
  to forget at least one, but they know who they are (and anyone
  reading the newsgroup for any length of time should recognise the
  contributors!)

  If you have any corrections or suggestions for improvement of this FAQ,
  please email the following:

            Tez Boyes      <URL:mailto:dtm-faq@pierrot.co.uk>

  However please direct any questions not covered in the FAQ to
  the newsgroup (whence I can glean the answer for the FAQ :)

  This document may be freely distributed provided that it remains
  unaltered from its current form.

  Copyright 1998 Tez Boyes
  ------------------------

==============================================================================

--
<URL:http://www.pierrot.demon.co.uk/faq/dtm.faq>               Team AMIGA