Vista-kb9 Resolve slow Vista network performance

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Slow network performance
Slow network performance

Version: 1.1.1
Difficult level: 3/5
Status: Tested and works, more scenarios and different solutions needed.

Introduction

Microsoft Windows Vista has a new rewritten networking system with a lot of new features speeding up TCP/IP traffic. These new functions require that the hardware such as routers/switches and other servers supports it, QoS (Quality of Service).
In certain network environments these new features does the opposite and slow down your connection speed or doesn't work at all, one such feature is Receive Window Auto-Tuning that allows the system to feel the network speed and adjust the maximum receive window after the speed. (Windows XP and Windows server 2003 has a set value that can be changed in the registry, HKEY_LOCAL_MACHINE\System \CurrentControlSet\Services\Tcpip\Parameters\TCPWindowSize)

Disable Receive Window Auto-Tuning in Vista

If you encounter network performance with a Vista machine in a network with legacy operating systems and hardware try to disable Receive Window Auto-Tuning with the following command in an elevated cmd prompt:

netsh interface tcp set global autotuninglevel=disabled

Image:Vista-kb9-disableautotuning.png


If you for some reasons what to enable it again run:

netsh interface tcp set global autotuninglevel=normal

Image:Vista-kb9-enableautotuning.png

Disable receiver-side scaling

If the above doesn't fix your problem it could be worth testing to disable receiver-side scaling (rss) with the following command in an elevated cmd prompt:

netsh interface tcp set global rss=disabled

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