Windows Vista, Windows 7, and Windows Server 2008 adjust the TCP window scaling dynamically with a TCP auto-tuning feature which causes slow performance when network appliances do not comply with RFC 1323 standard. When the receive window autotuning feature is enabled older routers, firewalls, and operating systems that are incompatible with the receive window autotuning feature may sometimes cause slow data transfer or a loss of connectivity between clients.
Check the state or current setting of TCP Auto-Tuning.
Open elevated command prompt with administrator’s privileges.
Type the following command and press Enter: “netsh interface tcp show global”
The system will display the following text on screen, where you can check on the Auto-Tuning setting:
Querying active state…
TCP Global Parameters
———————————————-
Receive-SideScaling State : enabled
Chimney Offload State : enabled
Receive Window Auto-Tuning Level: normal
Add-On Congestion Control Provider : none
ECN Capability : disabled
RFC 1323 Timestamps : disabled
To disable autotuning, follow these steps:
Click Start, type the following in the Start Search box, and then press ENTER:
runas /user:Local_Computer_Name\administrator cmd
When you are prompted for the administrator account password, type the correct password, and then press ENTER.
At the command prompt, type the following command, and then press ENTER:
netsh interface tcp set global autotuninglevel=disabled
This command disables the Receive Window Auto-Tuning feature.
Exit the Command Prompt window.
Restart the computer.
To enable autotuning, open a command prompt, type the following command, and then press ENTER:
netsh interface tcp set global autotuninglevel=enabled
Using Registry Editor incorrectly can cause serious problems that may
require you to reinstall your operating system. Microsoft cannot guarantee
that problems resulting from the incorrect use of Registry Editor can be
solved. Use Registry Editor at your own risk.
