How to disable the TCP autotuning diagnostic tool
This article describes how to disable or enable the transmission control protocol (TCP) window autotuning diagnostic tool in Vista. The autotuning diagnostic tool diagnoses and fixes problems related to autotuning. However, in some cases (for example, network performance testing) you may want to disable the diagnostic tool. This article describes the autotuning feature, the diagnostic tool, and how they help prevent problems.
The TCP receive window autotuning feature in Vista lets the operating system continually monitor conditions such as bandwidth, network delay, and application delay. The operating system can configure connections by scaling the TCP receive window to maximize the network performance based on these parameters. To determine the optimal size for the receive window, the receive window autotuning feature measures the product of the network delay and bandwidth, and also looks at the application retrieve-rates. Then, the receive window autotuning feature changes the receive window size of the ongoing transmission to take advantage of any unused bandwidth.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB967475.