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[ The PC Guide | Troubleshooting and Repair Guide | The Troubleshooting Expert | Troubleshooting Specific Components | Troubleshooting Modems | Speed Issues ]

My connection is working, but I have noticed that the transfer rate I am getting on downloads is much lower than it should be

Explanation: You can connect to the remote host you are dialing and are not having any problems with the modem or the connection, except that the transfer rates you are getting are much lower than you would expect.

Diagnosis: The theoretical maximum download transfer rate of a modem, in characters per second, is approximately equal to the connection speed of the modem times 0.1125. This means that a 28800 connection should allow transfers of around 3200 characters per second. If you are getting a throughput much lower than this, then one possible cause is that you are connecting at a much lower rate than is theoretically possible for your modem (which isn't necessarily abnormal). Otherwise, there may be a bandwidth problem either within the PC or the remote host that is making transfer performance worsen. Software settings can also definitely be a factor.

Recommendation:

  • Make sure that the connection speed is in fact as fast as you think it is. If you have a 33.6 KB or faster modem, you are most likely not connecting at the theoretical top speed of your modem.
  • It is common to see low bandwidth on downloads retrieving a file from a very busy remote host. If you are trying to download a huge file from a popular site, you are most likely going to see bandwidth reductions caused by network traffic. To eliminate this possibility, try doing a download of a local file from your own account and gauge the download performance that way.
  • Try a different host or dialup line, if possible, to eliminate the possibility of the remote host being the cause of the problem. I have used internet service providers that simply had overloaded servers that refused in many cases to provide adequate bandwidth for downloads. No matter what I downloaded from this account the transfer rate was much lower than I would have expected and when I tried other accounts they worked much better.
  • Double-check all of your software settings. Make sure that items such as connection speed and flow control are set correctly.
  • The software that you are using could easily be part of the problem. In particular, doing large file downloads using a web browser will frequently be slower than using a more direct file transfer protocol such as FTP, in my experience. Try using FTP and see if performance improves.
  • If you are using Windows 95's dial-up networking, and you are finding that your transfers are only going at around half the speed they should be, you may be experiencing a well-known condition called the "MTU problem". There is a specific problem with Windows 95 that is related to the way its dial-up networking works that causes transfers to run at half-speed. See this section on John Navas's modem FAQ for more information on this problem, and a solution.

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