Microsoft KB Archive/927695

= You cannot host TCP connections when Receive Side Scaling is enabled in Windows Server 2003 with Service Pack 2 =

Article ID: 927695

Article Last Modified on 12/4/2007

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APPLIES TO

 Microsoft Windows Server 2003 Service Pack 2, when used with:  Microsoft Windows Server 2003, 64-Bit Datacenter Edition

 Microsoft Windows Server 2003, Enterprise x64 Edition

 Microsoft Windows Server 2003, Standard x64 Edition

 Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)</li></ul>

 Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)</li></ul>

 Microsoft Windows Server 2003, Standard Edition (32-bit x86)</li></ul>

 Microsoft Compute Cluster Pack</li></ul>

 Microsoft Windows Server 2003 Compute Cluster Edition</li></ul> </li> Microsoft Windows Server 2003 Service Pack 1, when used with:  Microsoft Windows Server 2003, 64-Bit Datacenter Edition</li></ul>

 Microsoft Windows Server 2003, Enterprise x64 Edition</li></ul>

 Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)</li></ul>

 <li>Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)</li></ul>

<ul> <li>Microsoft Windows Server 2003 Compute Cluster Edition</li></ul> </li> <li>Microsoft Windows Server 2003, Enterprise x64 Edition</li> <li>Microsoft Windows Server 2003, Standard x64 Edition</li> <li>Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)</li> <li>Microsoft Windows Server 2003, Standard Edition (32-bit x86)</li> <li>Microsoft Windows Small Business Server 2003 Premium Edition</li> <li>Microsoft Windows Small Business Server 2003 Standard Edition</li> <li>Microsoft Windows Small Business Server 2003 R2 Premium Edition</li> <li>Microsoft Windows Small Business Server 2003 R2 Standard Edition</li></ul>

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<div class="notice_section">

Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry

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SYMPTOMS
Transmission Control Protocol (TCP) connections are reset when Receive Side Scaling is enabled in Microsoft Windows Server 2003 with Service Pack 2 (SP2). This problem occurs if you use Network Address Translation (NAT), if you use Windows Firewall, or if the host computer is configured to be an Internet Connection Sharing host server computer.

Note This problem may also occur when you use the following products:
 * Windows Server 2003 Service Pack 1 (SP1) together with the Windows Server 2003 Scalable Networking Pack
 * Microsoft Internet Security and Acceleration (ISA) Server 2004 or ISA Server 2006
 * Other add-on Firewall or network address translation (NAT) software

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CAUSE
This problem is caused when the software hash code for the connection and the hardware hash code for the connection do not match. Receive Side Scaling works by offloading the TCP secure hash function to the network adapter hardware. Therefore, the network adapter calculates the hash value for the connection when Receive Side Scaling is enabled. Internet Connection Sharing also modifies the addresses and the ports that are provided by the IP header for the connection. When this occurs, the hash value that is generated by the network adapter is invalidated. When the invalidated hash value is used, the TCP connection is reset.

This problem may also occur if the IP source address, the IP destination address, the TCP source port, or the TCP destination port are modified during receive processing. These addresses and ports are provided in the TCP and IP headers for the connection. This problem may occur in some NAT scenarios.

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WORKAROUND
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

To work around this problem, disable Receive Side Scaling when the computer is configured as an Internet Connection Sharing gateway. To do this, follow these steps: <ol> <li>Click Start, click Run, type regedit, and then click OK.</li> <li>Locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

</li> <li>On the Edit menu, point to New, click DWORD Value, and then type EnableRSS .</li> <li>Double-click EnableRSS, type 0, and then click OK.</li> <li>Restart the computer on which you changed the EnableRSS value.</li></ol>

<div class="status_section">

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

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