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Dan Albrich
Manager, Microcomputer Services
dalbrich@uoregon.edu
If you connect to the UO network via dial-up modem and are either experiencing slow connectivity, connections that drop, or are completely unable to connect, you may wish to try slowing down your modem.
That's right, in some cases slowing down the modem's connection speed will actually improve your connection!
This tactic is particularly effective when the modem is experiencing errors due to line noise. Imagine your modem connection to be a conversation between two people, and line noise to be a loud train whistle that causes words to be lost to the receiver. If the speaker is talking very fast, more words are lost than if the speaker is talking slowly over the same time interval. This oversimplifies the issue, but it gives you a general idea of why slower communications are easier to sustain, even given the presence of line noise.
Modern modems also have the capability to change speed during communication, adjusting to transient line noise by speeding up when the noise is not present. This process is called retraining. Unfortunately, in the real world this feature can actually slow you down, or cause the connection to drop entirely.
For example, your modem connects at 26,400, notices a small error rate, and decides to retrain (speed up) to 28,800. At this speed it observes an unacceptable rate of error and retrains back to 26,400. The problem occurs when the modem starts looping between these two speeds, and the only communication that's occurring is that required to retrain (i.e., your data is not being transmitted).
In this scenario, you would experience more reliable---and effectively faster---connections by setting the ceiling connect speed at 26,400 "baud" (or bits per second).
Macintosh Users: On the Mac, modem speed is controlled with the modem setting. In OS X, go to System Preferences ---> Network--->Modem. (If Ethernet is selected as the connection method, you must use the drop-down menu to select the modem first). Slowing down your modem is as easy as selecting "Apple Internal 56K Modem (v.34)" instead of "Apple Internal 56K Modem (v.90)" or (v.92).
Windows Users: Microsoft Windows users need to manually type a modem initialization string, using the following procedure:
Please note that if your modem does not support this particular command, it may fail to dial the next time you try to connect. If this occurs, remove this setting (or change it).
Although the +MS=V34 command will work on many modems, some models will require a different specific initialization string. For example, all Supra models can use F17 as the string to slow them down, and all US Robotics modems can use &U1&N12.
If these strings don't work with your modem, contact Microcomputer Services for assistance (346-4412, microhelp@lists.uoregon.edu). Note that in order to help you, we will need to know which modem you have (in Windows, you'll find this information under the "Phone and Modems" control panel).