A rchive Date
[ 14-10-2000 ]
Category
[ Information Technologies ]
sub-Categoy
[ Computers ]

http://computingcentral.com/topics/pccommunications/newsletter0

900.asp

My Kingdom for a Stable Connection--Part 1

PC Communications Forum Manager and Harold Stevens

September 2000--A common question in the message boards is why Internet connections disconnect all the time. Our crystal ball tends toward cloudy and it’s hard to tell for sure from where we sit, but after doing some testing with a Rockwell/Conexant WinModem, some ideas surfaced.

Modem history

Before we get to the details, a little history lesson is in order. What is a modem? It’s a device that converts computer information to sound, so it can travel over a phone line, and then converts the sound back into computer information at the other end. This process is called modulation/demodulation and the term got shortened to something easier to pronounce: modem.

Originally, modems were hardware-based, with chips on the modem doing all the work. Around the time that 14.4 modems became popular, Rockwell (one company that makes the chips that modems use, now called Conexant) found a way to reduce the overall cost of building a modem by removing one of the hardware components and substituting a program running on the host computer to do the same thing. These modems were referred to as “RPI" modems, and caused grief for some users, especially with slower computers because the host computer could not keep up with the process resulting in data loss or dropped connections.

As modems got faster, RPI went by the wayside and we thought we had seen the last of that situation. Unfortunately, that was not to be the case. As host computers got faster, manufacturers started to look at more ways of trimming costs and went back to having the computer do some of the work.

Hardware vs. software

The modem process can be divided into three stages: the controller, which handles all the controlling activities; the data pump, which is responsible for the modulation/demodulation function; and a data access arrangement, which is the part that connects to the telephone line.

If a modem has all three parts on the card or in the case it’s considered a hardware-based modem. Internal hardware-based modems are a rare breed today because of the higher costs involved. Usually, a driver that runs on the host computer, leaving just the telephone connection on the interface card replaces both the controller and the data pump. This is why WinModems can be sold for $20 or less; the major chips that perform those functions have been removed.

So what seems to be the problem with all of this? It appears that the functions that the modem hardware used to do have not been duplicated exactly, resulting in subtle differences. These differences may be causing the connection difficulties some people are experiencing.

My phone line can’t handle a 56K connection. I have checked and rechecked the lines and it’s just not going to happen. I verified this using the 3Com line test. More information about this valuable test is available at the 3Com

Web site

and is worth checking out.

I installed a Rockwell/Conexant WinModem to test some things for a client, and I found that the modem was defaulting to using a V.90 (i.e. 56K connection) even though the phone line can’t handle it. When using a hardware-based modem, the handshake sequence, all that hissing and squealing you hear when the modem connects, showed v.90 was a problem and the modem switched down to V.34, which has a maximum speed of 33.6K. This is the fastest speed non-56K modems can handle.

The Rockwell/Conexant WinModem I was using did not detect that V.90. It would not work during the handshake sequence and went ahead and tried to use it anyway. This resulted in many problems with all connections dialed. I tried a variety of remote systems and in each case, the result was the same: connection problems.

I used the proper command to tell the WinModem to default to using V.34 instead and in all cases; I was able to establish a clean connection each and every time I tried. I could not get the connection to fail.

What does this mean? I’m not sure, but I suspect I’m not the only one with a less than pristine phone line and this may be the reason for some dropped connections. If you have a Rockwell/Conexant-based WinModem, making these changes may be worthwhile. The connection will be slower, since 33.6 is the maximum allowed, but it may turn out to be more reliable, which will be faster overall.

The fix

1. Perform the

56k line test

. If you need a terminal program installed, I recommend HyperTerminal, a free program available

here

2. If the line test shows your line can’t handle 56K, open up Control Panel | Modems | Diagnostics | point to your modem | More info. See if Rockwell or Conexant is listed in the information that is displayed.

3. If Rockwell or Conexant is listed, try this change: Control Panel | Modems | point to your modem | Properties | Connection | Advanced. In the box marked “Extra Settings", type this, exactly as it appears: +ms=v34,1,75,33600,75,33600, then click OK. Go online and see if your connection is more reliable.

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