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After you enable the dynamic backlog settings on a Windows Server 2003-based computer, the System Handle count and the nonpaged pool usage may increase significantly

Article ID: 951162 - View products that this article applies to.

SYMPTOMS

On a Windows Server 2003-based computer, you may decide to use the Afd.sys driver to enable the dynamic backlog settings. You do this to harden the TCP/IP stack against SYN attacks.

Note You configure the dynamic backlog settings according to the instructions in the following Microsoft Knowledge Base article:

142641

(http://support.microsoft.com/kb/142641/ )

Internet server unavailable because of malicious SYN attacks

In this scenario, the System Handle count and the nonpaged pool memory usage may increase significantly. Eventually, the nonpaged pool memory may be exhausted, and then the system stops responding (hangs).

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CAUSE

When the dynamic backlog is triggered to create new connections, the Afd.sys driver creates connections according to the value of the DynamicBacklogGrowthDelta registry entry. However, under certain circumstances, the driver may incorrectly create connections according to the value of the MaximumDynamicBacklog registry entry.

Because of this incorrect behavior, the Afd.sys driver creates many unnecessary connections. Therefore, the System Handle count and the nonpaged pool memory usage increase significantly.

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RESOLUTION

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

(http://support.microsoft.com/contactus/?ws=support)

Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

To apply this hotfix, you must have Windows Server 2003 Service Pack 1 (SP1) or Windows Server 2003 Service Pack 2 (SP2) installed.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other previously released hotfixes.

Registry information

To use this hotfix, you do not have to make any changes to the registry.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.