Re: Dial-Up Modem Questions

Thanks Mr. painkiller,

Turns out that it was indeed the initialization string. I had
originally left blank in the configuration. Since I did not know what
the appropriate one for a USR 5686 was I did a web search and from
http://www.burk.com/support/knowledgebase/R19ZZ005.html

found that it should be ATB1S0=1 I entered that in the appropriate
place using /usr/bin/system-control-network. I have not noticed the
hanging anymore so I assume that was the cause.

Question, if it was the initialization string, what diagnotic(s)
would/should demonstrate a measurable change? The output from
/sbin/ifconfig looks the same -- always shows 1 error

Moe Trin wrote:
On 17 Jun 2006, in the Usenet newsgroup comp.os.linux.networking, in article
<1150605156.756041.325170@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
dpdoughe@xxxxxxxxxxxxxx wrote:

1) I have a USR 56K v.92 Modem. I've noticed that it speed really
slows if it has been on for more than an hour. A quick
disconnect-reconnect seems to improve speed temporarily for example and
then it slows down again after a bit.

You are posting from a Level 3 address (Level 3 is a presence provider in
major US cities), and they do no filtering, so you could be seeing
bandwidth loss due to skript-kiddiez and windoze messenger spam (UDP to
ports 1025-1050 or so). One of my ISPs has a access number from Level 3,
and I avoid using it as much as practical.

The modem is hot to the touch so I'm wondering if it is a heat issue.

In Detroit??? I've no idea what your room temperatures are like, but
as I write this, it's 104F/40C on the patio outside this room. Inside,
it's 77F/25C, thanks to 7 Tons of central air-conditioning. None of my
hardware is running hot.

Has anyone had any similar experience? Is there a cooling system
recommended?

That _shouldn't_ be a problem, though I suppose you could try as
a temporary measure directing a fan at the modem to see if that is a
problem. I'd also look at the modem setup. First, see that you are
using an appropriate init string. Most dialin helper tools use some
bizarre string that the author visualized while on a really bad acid
trip - the manual probably is suggesting 'AT&F1'. Next, fire up something
like minicom or seyon after configuring that tool to NOT initialize or
reset the modem, and send the command to get the modem stats (perhaps
'ATI6' - that's ati6) and look at the 'Retrains Requested' and 'Speed'
parameters. (If you don't have a manual, see the built in help that's
available with 'at$', 'at&$' and 'ats$'.) Is the link speed starting
high, and retraining down?

Another thing to look at _during_ the connection is the '/sbin/ifconfig
ppp0' stats, paying attention to the error counts. The values should
stay very close to zero - as these typically indicate a problem getting
past the modem error correction, and possibly caused by local configuration
issues. Something more than three or four errors in an hour (the count is
cumulative for the duration of the call) is cause for concern.

2) Some ISP's offer 5X web acceleration. My understanding is that they
all require Windows or Mac to run the software although my
understanding is that they are just doing compression before the send
and the software does the decompression.

Snake-oil. There are three forms of data compression. There is the
link compression that your modem may negotiate with the peer - you'll
see this in the CONNECT stanza if you are logging it, as something like
'CONNECT 53333 V42BIS' with the V42BIS being hardware data compression.
This is less common than it once was, because of the added CPU cycles
needed on the ISP end to do the data compression (they aren't using
the same analog modem you are), but typically results in a 2:1 to 4:1
improvement in speed (subject to the typical RS-232 hardware speed
limit of 115200 BPS).

The second form is associated with the ppp protocol. I suspect this isn't
working for you (you'd have to use the debug option to pppd, and set your
syslogd daemon to log appropriately to find out), as there are several
algorithms, and they aren't compatible, AND windoze defaults to using a
proprietary method, while ANU ppp that you are using can't use that
because of license problems. This would show up in the logs as a CCP
ConfAcq line, indicating success, and a CCP ConfRej, CCP TermReq or LCP
ProtRej in the debug log output indicating failure.

The third form depends on the data you are downloading. If the stuff you
are downloading is already compressed - mpegs, jpegs, stuff where the
filename ends with .zip, .Z, .tgz, .gz, or .bzip2 - compression of any
other kind isn't going to help, and actually could _reduce_ the transfer
speed trying to compress the incompressible.

Old guy

.

Relevant Pages

  • Re: Best fax modem settings to receive from multifunction devices?
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    (microsoft.public.windows.server.sbs)
  • Re: Dial-Up Modem Questions
    ... slows if it has been on for more than an hour. ... I'd also look at the modem setup. ... There are three forms of data compression. ... This would show up in the logs as a CCP ...
    (comp.os.linux.networking)
  • Re: Lots of noise about user agent strings
    ... it should be measured as bits transmitted by the modem after the ... addition of network stuff and compression. ... modems are optimised to compress text for transmission and so ... read explanations how to do this with the user agent string. ...
    (comp.lang.javascript)
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    (microsoft.public.windowsce.embedded)
  • Re: answering calls
    ... The modem is auto-answering because some software application is telling it to do ... to establish a dial-up connection, ... setting the modem's initialization string to turn off auto-answer, ... and then, in the window for extra initialization commands, type s0=0 (those are ...
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