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<TITLE>The Answer Guy 34:
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RE how to find out the serial connect speed of a modem
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RE how to find out the serial connect speed of a modem
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<H4>"Linux Gazette...<I>making Linux just a little more fun!</I>"
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<H1 align="center"><A NAME="answer">
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<img src="../../gx/dennis/qbubble.gif" alt="" border="0" align="middle">
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<a href="../index.html">The Answer Guy</a>
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<BR>
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<H4 align="center">By James T. Dennis,
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<a href="mailto:linux-questions-only@ssc.com">linux-questions-only@ssc.com</a>
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<BR>Starshine Technical Services, <A HREF="http://www.starshine.org/">http://www.starshine.org/</A>
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<p><hr><p>
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<!--endcut ========================================================= -->
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<p>The original message in this thread appeared in
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<a href="http://www.ssc.com/lg/issue31/tag_connect.html"
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>Issue 31</a>, and the
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<a href="news:comp.unix.questions"
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>comp.unix.questions</a> newsgroup.
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This volley resulted:</p>
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<hr width="40%" align="center">
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<p><strong>From Michael Schwab on 30 Sep 1998</strong></p>
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<p><strong>Hello,
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I just read the article about
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</strong></p>
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<p><strong>So please don't say "WHO CARES ABOUT THAT?"
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</strong></p>
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<blockquote><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)" height="28" width="50" align="bottom">I'll say what I bloody well feel like saying!
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</blockquote>
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<blockquote>(And I expect my editors, and readership to
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respond as they see fit).
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</blockquote>
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<blockquote>I'm sorry if that seems like a harsh thing to say
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but frankly I think you missed the whole point of what
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I was trying to say before.
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</blockquote>
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<blockquote>First, I don't know of a general way to get the
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connect speed. It's probably modem specific, so you
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could probably write a script that queries your modem
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to get the info. Your script would probably not work
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with most other modems, and you'd have to hack it into
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whatever communications package you were actually using
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on that modem (pppd, uucico, minicom, kermit, slip,
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whatever).
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</blockquote>
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<blockquote>Another point I made is that the speed is likely to
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fluctuate frequently throughout the duration of a
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connection (particularly with any 28.8 or faster modem).
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It's likely to start out a bit high and be adjusted
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downward until the corrected error rate attains an
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suitable threshold.
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</blockquote>
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<blockquote>So, if you had your script reporting a connection
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speed at one instant --- it would tell you almost nothing
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about your sustained throughput.
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</blockquote>
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<p><strong><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)" height="28" width="50" align=""bottom">I do !!
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</strong></p>
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<blockquote><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)" height="28" width="50" align="bottom">More power to you. I didn't ask <EM>who</EM> cares? I asked
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what benefit those who "think" they care hope to derive
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from this statistic.
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</blockquote>
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<blockquote>I can test the temperature in my house to with an arbitrary
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precision. However, the numbers on a thermometer will not
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motivate me to reset my thermostat or go out and buy a
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new furnace or air conditioner. It's a meaningless
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statistic that is no benefit to me.
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</blockquote>
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<blockquote>Also there isn't just one temperature in my home -- there's
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a whole range of fluctuating temperatures. So precise
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measurement would be non-trivial.
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</blockquote>
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<blockquote>For subjective issue there's no point in going to
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great measurement effort. When I'm cold I either turn
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up the thermostat, or (more likely) toss on a sweater or
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some little fuzzy booties.
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</blockquote>
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<blockquote>Now, it is the case that I might do some measurements
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when I'm troubleshooting a line. I'd certainly expect a
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telco technician to do so if I was complaining about
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line quality --- and I might do so to "motivate" a telco
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(or to file my complaint with a public utility commission).
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</blockquote>
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<blockquote>If course if I was <EM>really</EM> serious about a line quality
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issue I'd rent an oscilloscope and look through a Fluke (TM)
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catalog to find a chart-strip recorder for the job.
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</blockquote>
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<blockquote>So these numbers aren't completely useless in all
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contexts. However, the number of people who can make
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reasonable use of them is fairly limited.
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</blockquote>
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<p><strong><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)" height="28" width="50" align=""bottom">How can you tell the connection speed that a modem auto-negotiates
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when dialing an ISP? My system log (/var/log/messages in RH5.1)
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does tell me the line speed I have set in the chat script, but I
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would like to know the connect speed as well (56K, 33.6, etc). I
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know this info must be available somewhere/somehow.
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</strong></p>
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<blockquote><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)" height="28" width="50" align="bottom">Modern modems don't just auto-negotiate at the beginning of
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a call. The "retrain" (negotiate speed changes) throughout
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a call's duration.
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</blockquote>
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<blockquote>You'd "like" to know. Put what would you do with this?
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Order you phone company to pull new copper to your house?
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Return your modem and try another one? Switch to tachyon
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beams?
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</blockquote>
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<blockquote>As for "this info must be available" --- look in the
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programming manual for your modem, <EM>if</EM> you can find one.
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It used to be standard for modems to come with a pretty
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decent technical manual --- providing details on a couple
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hundred AT commands that comprised that manufacturer's
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extensions beyond the based "Hayes" set for that particular
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model. These days you'll be lucky if you pry a dinky little
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summary of a tiny subset of their diagnostics and commands
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out of most of these manufacturers.
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</blockquote>
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<p><strong><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)" height="28" width="50" align=""bottom">I don't know how to really get the connect speed but that might be
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not so important. Since I have a leased line to the Internet with
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a modem it is important for me to know how fast my line is running
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because sometimes this Line might have a lot of noise on it and
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the connect might be only 4800 bps instead of 33600 bps. In this
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case I have to call my Telecommunications provider to check the
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line !!!
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</strong></p>
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<blockquote><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)" height="28" width="50" align="bottom">If your connection varies by this much you'll know it.
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You won't need any numbers to tell you that it's *slow*.
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</blockquote>
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<blockquote>If you are trying to serve your customers (web site
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users, whatever) over this line --- it does make sense
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to monitor the bandwidth and latency. However these
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are higher level networking issues that are only
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marginally related to the underlying connection speed.
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</blockquote>
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<p><strong><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)" height="28" width="50" align=""bottom">But its easy to detect just send a ping to the other side when the
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line has low traffic. I do this by sending approx 20 pings and
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then look at the (lowest) roundtrip time. You can send a ping
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containing 8192 or 16384 bytes of data and you will detect nearly
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every change in bandwith.
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</strong></p>
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<blockquote><IMG SRC="../../gx/dennis/bbub.gif" ALT="(!)" height="28" width="50" align="bottom">Aha! Now this is a totally different metric. You aren't
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measuring "modem connection speed" you're measuring
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latency and throughput! Doing this once every two or
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three hours with about 5 pings and setting "watcher" to
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monitor those and warn you when the latency get's too
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high or the throughput gets too low would make sense
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--- for a dedicated line where you are concerned that
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you customers/users are waiting "too long" for their
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traffic.
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</blockquote>
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<blockquote>There is a package called MRTG --- the "multi-router
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traffic grapher" which can be used to create web page
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graphs of your network traffic statistics over
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time. It seems to be primarily used by larger sites
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for ethernet. However it might have some facilities for
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monitoring PPP (even SLIP) lines.
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</blockquote>
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<blockquote>Actually MRTG depends on SNMP so I should say that
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you might figure out how to configure the CMU SNMP
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agents for Linux to interface to your serial interfaces
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--- and then MRTG could provide the graphs. However,
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you don't technically <EM>need</EM> to run SNMP under MRTG
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--- their docs suggest that you can use various
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commands to provide it statistics to graph.
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</blockquote>
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<blockquote>You can read more about MRTG at:
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</blockquote>
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<blockquote><A HREF="http://ee-staff.ethz.ch/~oetiker/webtools/mrtg/mrtg.html">http://ee-staff.ethz.ch/~oetiker/webtools/mrtg/mrtg.html</A>
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</blockquote>
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<p><strong><IMG SRC="../../gx/dennis/qbub.gif" ALT="(?)" height="28" width="50" align=""bottom">Best Regards
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Michael Schwab
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</strong></p>
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<!-- end body -->
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<hr width="40%" align="center">
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<H3><img src="../../gx/dennis/qbub.gif" alt="(?)"width="50" height="28"
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align="left" border="0">RE how to find out the serial connect speed of a modem </H3>
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<p><strong>From Michael Schwab on 30 Sep 1998</strong></p>
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<!-- begin body -->
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<p><strong>OK the Intention of the Mail send by me was mainly to give a short help
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on what might be a suitable answer on the quistion posed in Linux Gazette.
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Despite of this THANKS FOR YOUR VERY LONG MAIL, now it's much clearer what
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you were saying and why. I agree with you when you say the connect speed
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is unimportant because it changes anyway during the connectiontime.
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Sinec the guy who send the question to you said that he connects to his ISP
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so I suggested that might monitoring bandwith ans latency also might be
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more meaningfull for him than just getting the connect speed !
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</strong></p>
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<p><strong>Anyway thanks for your Answer .....
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</strong></p>
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<p><strong>see you soon <IMG SRC="../../gx/dennis/smily.gif" ALT="" height="24" width="20" align="middle">
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</strong></p>
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<p><strong>Michael Schwab
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</strong></p>
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<!--startcut ======================================================= -->
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<P> <hr> <P>
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<H5 align="center"><a href="http://www.linuxgazette.com/copying.html"
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>Copyright ©</a> 1998, James T. Dennis <BR>
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Published in <I>Linux Gazette</I> Issue 34 November 1998</H5>
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<P> <hr> <P>
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