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Network connectivity fails when you try to use Windows Vista behind a firewall device
Article ID: 934430 - View products that this article applies to.
When you try to use a Windows Vista-based computer behind a firewall device, and you try to make a non-HTTP network connection, the network connection fails. When the network connection fails, the following programs may crash or respond slowly:
This issue may occur if the firewall device has a problem with handling the Receive Window Auto-Tuning feature in Windows Vista. This article helps you work around this problem.
To work around this problem, use one of the following methods:
Method 1. Disable auto-tuning and determine whether Windows scaling is handled correctly by the firewall deviceTo have us disable auto-tuning for you, go to the "Fix it for me" section. If you would rather disable auto-tuning yourself, go to the "Let me fix it myself" section.
Fix it for meTo disable auto-tuning automatically, click the Fix this problem link. Then, click Run in the File Download dialog box, and follow the steps in this wizard.
Fix this problem
Microsoft Fix it 50056
Note this wizard may be in English only; however, the automatic fix also works for other language versions of Windows.
Note If you are not on the computer that has the problem, you can save the automatic fix to a flash drive or to a CD, and then you can run it on the computer that has the problem.
Now go to the "Did this fix the problem?" section.
Let me fix it myselfTo disable auto-tuning, follow these steps:
Did this fix the problem?
(http://blogs.technet.com/fixit4me/), or send us an e-mail
(mailto:firstname.lastname@example.org?Subject=KB934430 - Disable TCP auto-tuning)message.
For information about how to contact the manufacturer of the firewall device, visit the following Microsoft Web site:
http://support.microsoft.com/gp/vendorsMicrosoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.
Method 2. Run the Internet Connectivity Evaluation ToolThe Internet Connectivity Evaluation Tool checks your Internet router to see whether it supports certain technologies. The tool is intended to be run from a home network behind a home Internet (NAT) router. Running this tool from behind a corporate firewall or on operating systems other than those specified in the "Applies to" section will not produce accurate results. This tool requires administrator credentials to run.
This issue may occur if the firewall device has a problem with its implementation of the TCP Window Scale Option that is defined in Internet Engineering Task Force (IETF) Request For Comments (RFC) 1323. By default, the Receive Window Auto-Tuning feature in Windows Vista uses a Window Scaling factor of 8 for non-HTTP connections. This issue does not occur when you try to make an HTTP connection.
The following list describes some firewall devices that may experience this issue together with the cause of the issue on the device:
http://technet.microsoft.com/en-us/magazine/cc162519.aspxThe third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.
Article ID: 934430 - Last Review: September 11, 2012 - Revision: 9.0