High CPU usage occurs when a Windows Server 2008 R2-based server is under a very heavy UDP load

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Article ID: 2685007 - View products that this article applies to.
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Symptoms

Consider the following scenario:
  • You have a server that is running Windows Server 2008 R2 and that communicates with many clients.
  • The server is under a very heavy User Datagram Protocol (UDP) load. For example, there are more than 15,000 concurrent connections between the server and the clients.
In this scenario, the server is unresponsive. Additionally, you notice that the CPU usage of the computer reaches 100 percent.

Cause

This issue occurs because a table is too aggressively scavenged.

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 the problem described in this article. 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 website:
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 be running Windows Server 2008 R2 Service Pack 1 (SP1). For more information about how to obtain a Windows Server 2008 R2 service pack, click the following article number to view the article in the Microsoft Knowledge Base:
976932 Information about Service Pack 1 for Windows 7 and for Windows Server 2008 R2

Registry information

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows
After apply this hotfix, you must create a new registry value. To have us create the registry value for you, go to the "Fix it for me" section. If you prefer to create the registry value yourself, go to the "Let me fix it myself" section.

Fix it for me



To create the registry value automatically, click the Fix it button or link. Then click Run in the File Download dialog box, and follow the steps in the Fix it wizard.


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assets fixit1
Fix this problem
Microsoft Fix it 55002
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assets fixit2


Notes
  • Install the hotfix in the "Hotfix download available" section at the top of this Knowledge Base article before you run this Fix it solution.
  • The MaxEndpointCountMult registry value is a multiplication factor that applies to the default scavenge value of 15,000.
  • You can set the MaxEndpointCountMult registry value from 1 to 50,000. The recommended value is 10.
  • This wizard may be in English only. However, the automatic fix also works for other language versions of Windows.
  • If you are not on the computer that has the problem, save the Fix it solution to a flash drive or a CD and then run it on the computer that has the problem.

Then, go to the "Did this fix the problem?" section.



Let me fix it myself

After apply this hotfix, you must create a new registry value. To do this, follow these steps:
  1. Click Start
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    start button
    , type regedit in the Search programs and files box, and then press Enter.
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    UAC
    If you are prompted for an administrator password, type the password. If you are prompted for confirmation, provide confirmation.
  2. Locate and then click the following registry subkey:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\BFE\Parameters\
  3. On the Edit menu, point to New, and then click DWORD Value.
  4. Type MaxEndpointCountMult, and then press Enter.
  5. Right-click MaxEndpointCountMult, and then click Modify.
  6. In the Value data box, type 10, and then click OK.
  7. Exit Registry Editor.

Notes
  • The MaxEndpointCountMult registry value is a multiplication factor that applies to the default scavenge value of 15,000.
  • You can set the MaxEndpointCountMult registry value from 1 to 50,000. The recommended value is 10.

Did this fix the problem?

  • Check whether the problem is fixed. If the problem is fixed, you are finished with this section. If the problem is not fixed, you can contact support.
  • We would appreciate your feedback. To provide feedback or to report any issues with this solution, please leave a comment on the "Fix it for me" blog or send us an email.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

File information

The global version of this hotfix installs files that have the attributes that are listed in the following tables. The dates and the times for these files are listed in Coordinated Universal Time (UTC). The dates and the times for these files on your local computer are displayed in your local time together with your current daylight saving time (DST) bias. Additionally, the dates and the times may change when you perform certain operations on the files.
Windows Server 2008 R2 file information notes
Important Windows 7 hotfixes and Windows Server 2008 R2 hotfixes are included in the same packages. However, hotfixes on the Hotfix Request page are listed under both operating systems. To request the hotfix package that applies to one or both operating systems, select the hotfix that is listed under "Windows 7/Windows Server 2008 R2" on the page. Always refer to the "Applies To" section in articles to determine the actual operating system that each hotfix applies to.
  • The files that apply to a specific product, milestone (RTM, SPn), and service branch (LDR, GDR) can be identified by examining the file version numbers as shown in the following table:
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    VersionProductMilestoneService branch
    6.1.760 1.21xxxWindows Server 2008 R2SP1LDR
  • The MANIFEST files (.manifest) that are installed for each environment are listed separately in the "Additional file information for Windows Server 2008 R2" section. MANIFEST files and the associated security catalog (.cat) files, are extremely important to maintain the state of the updated components. The security catalog files, for which the attributes are not listed, are signed with a Microsoft digital signature.
For all supported x64-based versions of Windows Server 2008 R2
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File nameFile versionFile sizeDateTimePlatform
Fwpkclnt.sys6.1.7601.21985288,62402-May-201205:37x64
Tcpip.sys6.1.7601.219851,901,42402-May-201205:37x64
For all supported IA-64-based versions of Windows Server 2008 R2
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File nameFile versionFile sizeDateTimePlatform
Fwpkclnt.sys6.1.7601.21985483,18402-May-201204:26IA-64
Tcpip.sys6.1.7601.219853,812,20802-May-201204:26IA-64

Status

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More information

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates

Additional file information

Additional file information for Windows Server 2008 R2

Additional files for all supported x64-based versions of Windows Server 2008 R2
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File nameAmd64_550d55349b938a872373e98f4c2a75f1_31bf3856ad364e35_6.1.7601.21985_none_bdc93c5a117ebb6b.manifest
File versionNot applicable
File size706
Date (UTC)02-May-2012
Time (UTC)07:34
PlatformNot applicable
File nameAmd64_microsoft-windows-tcpip-binaries_31bf3856ad364e35_6.1.7601.21985_none_11830b14965b3f64.manifest
File versionNot applicable
File size3,838
Date (UTC)02-May-2012
Time (UTC)06:09
PlatformNot applicable
Additional files for all supported IA-64-based versions of Windows Server 2008 R2
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File nameIa64_63bc2537b6a8403b5d1242f8792d0b65_31bf3856ad364e35_6.1.7601.21985_none_cb15966b9a456615.manifest
File versionNot applicable
File size704
Date (UTC)02-May-2012
Time (UTC)07:34
PlatformNot applicable
File nameIa64_microsoft-windows-tcpip-binaries_31bf3856ad364e35_6.1.7601.21985_none_b5661386ddfbd72a.manifest
File versionNot applicable
File size3,836
Date (UTC)02-May-2012
Time (UTC)05:59
PlatformNot applicable

Properties

Article ID: 2685007 - Last Review: October 10, 2012 - Revision: 2.0
Applies to
  • Windows Server 2008 R2 Enterprise
  • Windows Server 2008 R2 Datacenter
  • Windows Server 2008 R2 for Itanium-Based Systems
  • Windows Server 2008 R2 Foundation
  • Windows Server 2008 R2 Standard
  • Windows Web Server 2008 R2
Keywords: 
kbautohotfix kbqfe kbhotfixserver kbfix kbsurveynew kbexpertiseadvanced kbfixme kbmsifixme KB2685007

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