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Connect Speed (line vs. port)

Posted on 1998-12-31
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Last Modified: 2013-12-27
When connecting to the net with my 3 Com PCI WinModem, the reported connect speed is usually the line speed (e.g. 33600 bps) as expected.  But sometimes, it is the port speed (e.g. 115200 bps) that is reported.  Can you tell me why this happens and what to do to fix it
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Question by:lennyh
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trath earned 70 total points
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This is a driver problem. The only way to fix it is to go to the 3com website and download the newest driver for your modem. Even if you have only had your modem for 2 days chances are great that there is a updated driver for your modem.

The address is...
http://www.usr.com/home/online/

choose diver .inf files and find you modem. downlaod and install the driver.
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by:trath
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Sorry. Or choose Upgrades/Updates I'm not really sure since US Robotics bought out 3Com
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by:lennyh
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trath, thank you for your response.  I checked the website, but it wasn't clear that any of the updates were associated w/ my modem.  I sent a note to 3-com.  We'll see if they have anything to say.

Interestingly enough, I have buddies w/ other modems/systems that experience similar connect-speed-reporting anomolies.
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by:trath
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Also even though it may say 115200 that doesent mean anything. You connection speed should still be 53***k. The 115200 is the fastest that the windows port recognizes, which is 28,800, because that is the port speed without a compression algorythm.
basicly anything below 28,800 uses no compression Everthing above it does, so your windows is recognizing the actual port speed only, but as long as you have the "use compression" box checked in modem properties you are still connecting at 56k. So

Its a pain but I wouldnt worry about it, its really not w
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by:trath
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Sorry didnt complete my thought....
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by:vikiing
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Basically, there are three links when you connect to a remote computer:

   Your Computer <--> Your modem <--------> Their modem <--> Their computer


One link is between your computer and your modem, one between the two modems, and one between their modem and their computer. What might surprise you is that each of these three rates can be, and often are, completely different. So you know, DCE stands for Data Communications Equipment (i.e. a modem to modem link) and DTE is Data Terminal Equipment (i.e. terminal to modem link). You are not concerned with the final link, the remote DTE rate. That is up to the  remote site, and does not matter at all to you. Once the data leaves your modem, and is received by theirs, it is out of your hands.

Thus, your DTE speed can be 115200, while DCE link runs at 56K; of course the MAXIMUM speed of THE WHOLE thing you can achieve will be the MINIMUM of the 3 links; if you have a modem running at 14,400 bauds, you'll never get a connection faster than that, no matter the other extreme has a 28, 33 or 56K.





The link between your computer and your modem is

               DTE rate           DCE rate            DTE rate
                38,400             14,400              57,600


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by:vikiing
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Opps !!, I left a final line saying "the communication speed will be as faster as 14.4k".
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by:lennyh
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vikiing, thanks for your response.

I am familiar with the distinction between port speed and line speed.  What I'm puzzled about is why, on only some occasions, the connect speed reported by the modem is the port speed rather than the line speed and what can be done to fix this  In the past, I've tried adding extra AT sequences to the modem string w/o avail.
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by:vikiing
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There are a couple of AT commands (some modem don't recognize them) that tells the modem to inform one speed or the other.

When you receive CONNECT XXXX, that "XXXX" can be line or port speed, depending on how the modem is set. You should read your modem's manual to see if it has something like that.

Just only as an example, Zoltrix modems report DCE speed with an ATW2 command; on the other hand, ATW0 (zero) makes modem to report DTE speed instead.
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by:lennyh
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Thanks for your response.

Perhaps I didn't make myself clear.  Most all the time, the line speed is properly reported as the connect speed.  Only sometimes is the port speed reported as the connect speed. So my questions are: What is it that causes this to happen and how can it be remedied?
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by:vikiing
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Parhaps modem is set in different modes depending on the different software packages you use, i.e., a fax program can set modem to report DCE speed, and a terminal program initializes it to show DTE speed.

What is sure: if you use ATZ command, modem will be set at the same state. Thus, CONNECT must show ALWAYS the same value, be it DCE or DTE (but not DCE now and DTE tomorrow in a random scheme).

How to remedy?, that's depends on what is the command your modem uses to specify one report or the other.
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by:lennyh
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Vikiing, thanks for your response.

I understand your comments regarding the different applications.  In this case, however, the variablitlity in reported connect speed occurs in the same application - my DUN internet dialer.  Lauching the dialer usually results in the line speed (DCE) being reported as connect speed. But once in a while, launching the dialer results in the port speed (DTE) being reported as the connect speed. ??


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by:vikiing
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As I've said over there: computers are living creatures... :) :)

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by:Moondancer
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GREETINGS!

This question was awarded, but never cleared due to the JSP-500 errors of that time.  It was "stuck" against userID -1 versus the intended expert whom you awarded.  This corrects the problem and the expert will now receive these points; points verified.

Please click on your Member Profile and select "View Question History" to navigate through any open or locked questions you may have to update and finalize them.  If you are an EE Pro user, you can also choose Power Search to find all your open questions.

This is the Community Support link, if help is needed, along with the link to All Topics which reflects many TAs recently added.  Also in the Community Support link is a question on how experts can help, if they wish, on the cleaning of old and abandoned questions.

http://www.experts-exchange.com/jsp/qList.jsp?ta=commspt
http://www.experts-exchange.com/jsp/zonesAll.jsp
 
Thank you,
Moondancer
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