Microsoft KB Archive/307991

= A TCP Session Is Reset After You Apply the Security Rollup Package =

Article ID: 307991

Article Last Modified on 10/27/2006

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APPLIES TO


 * Microsoft Windows NT Workstation 4.0 Developer Edition
 * Microsoft Windows NT 4.0 Service Pack 6a
 * Microsoft Windows NT 4.0 Service Pack 6a

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This article was previously published under Q307991



IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry



SYMPTOMS
After you apply the Windows NT 4.0 Security Rollup Package (SRP), you may not be able to connect to HTTP or FTP services on that Windows NT 4.0-based server. You can connect again if you remove the SRP.



CAUSE
If the following registry value is set to 2, clients can establish a TCP session with the server:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\SynAttackProtect

If the client then sends additional requests to the server, the server resets the TCP session immediately.



RESOLUTION
A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix should have the following file attributes or later:   Date         Time   Version        Size     File name  Platform ---  15-Nov-2001  21:30  4.0.1381.7109  308,912  Tcpip.sys  Alpha 15-Nov-2001 21:34  4.0.1381.7109  174,928  Tcpip.sys  x86 NOTE: Because of file dependencies, this hotfix requires Microsoft Windows NT 4.0 Service Pack 6a.



WORKAROUND
WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To work around this problem, change the SynAttackProtect registry value to 0.

NOTE: This setting may expose the Web server to a synchronization attack.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

Keywords: kbbug kbfix kbqfe kbhotfixserver KB307991

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