Internet Providers connection / Internet / Web Server

Bottlenecks between the Internet Providers Modems and the web site that is trying to be reached can often cause problems such as pages being slow to appear and slow downloads.

Compression

Both the Modems and the PPP protocol can do compression. This will increase the speed that information is actually transmitted over the modem.

Renegotiations / Retrains

Whenever a modem has to renegotiate it's speed or retrain, the modem will have to pause. This stops all data from flowing until it is done. A retrain will pause significantly longer than a renegotiation. If a modem is doing either / both of these frequently then this will cause large problems with overall throughput speed.

Error Correction

Error correction can also slow throughput considerably. An overall drop in throughput can occur if a modem has to resend information because of errors.

Problems caused by Error Correction or Renegotiations can usually be solved quite easily by getting the modems to connect more reliably with each other. This normally means slowing the actual modem speed down. This might sound a bit counter intuitive, but it can often make a large difference. As an example of this, many USR modems will connect at 49333 and have an overall slow throughput, yet if you set them to 48000 they will send data much quicker because they don't have to do as much error correction. Obviously there is a limit on how much throughput will improve by decreasing speeds.