Microsoft KB Archive/328626

= Network Load Balancing Server does not release ownership of TCP connections in a Windows 2000 Server cluster environment =

Article ID: 328626

Article Last Modified on 10/26/2006

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APPLIES TO


 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Server
 * Microsoft Windows 2000 Professional Edition

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This article was previously published under Q328626



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
In a Microsoft Windows 2000 Server Network Load Balancing Network Load Balancing cluster environment, you may experience the following symptoms:
 * Network Load Balancing Server (NLBS) does not give up ownership of connections even after the client has requested to close the session by sending an acknowledgement Finish (FIN) packet, and the server remains in the “LAST_ACK” state.
 * NLBS does not accept the client connection attempt package (SYN package) from a client that is trying to reconnect through the same client port and server port.
 * The server has a substantial increase in memory usage and the server performance is noticeably decreased.



CAUSE
This problem occurs because Network Load Balancing does not see the acknowledgement FIN packet that the client sends.

Network Load Balancing keeps a FIN count of all connections. Termination of a connection requires both the client and the server to send and to receive one FIN packet.

When Network Load Balancing receives a FIN packet, it switches to the “LAST_ACK” state and expects to see two &quot;FIN&quot; packets for a particular connection before it gives up ownership of that connection.

The server generates a FIN packet after it receives the client’s FIN packet. The FIN packet from the server is sent to the client through the non-NLB network adapter, and Network Load Balancing does not see the outgoing FIN packet. Network Load Balancing may not recognize the acknowledgement packet from the client as a FIN packet because the outgoing FIN packet was not registered by NLB. Therefore, Network Load Balancing remains in the “LAST_ACK” state, and you experience the symptoms that are described in the preceding section.



Service Pack information
To resolve this problem, obtain the latest service pack for Windows 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

260910 How to obtain the latest Windows 2000 Service Pack

Hotfix information
A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Windows 2000 service pack that contains this hotfix.

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

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

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 hotfix has the file attributes (or later) 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 tool in Control Panel.

  Date         Time   Version        Size    File name 23-Oct-2002 16:21  5.0.2195.6101  65,808  Wlbs.sys



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
After you apply the service pack or hotfix, you must disable FIN counting by adding the FINCountingEnabled value to your registry. To do this, follow these steps:  Click Start, and then click Run. In the Open box, type regedit, and then click OK. Locate, and then click the following registry subkey:

 On the Edit menu, click New, click DWord Value, and then add the following:

Value Name: FINCountingEnabled

Value Data: 0

Note If you set the FINCountingEnabled entry to any non-Zero value, FIN counting will be enabled.</li> Quit Registry Editor</li> Restart the computer.</li></ol>

For additional information about how to obtain a hotfix for Windows 2000 Datacenter Server, click the following article number to view the article in the Microsoft Knowledge Base:

265173 The Datacenter Program and Windows 2000 Datacenter Server product

Keywords: kbqfe kbhotfixserver kbbug kbfix kbwin2000presp4fix KB328626

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