After you install Windows Server 2003 Service Pack 2 (SP2) or Windows Server 2003 Scalable Networking Pack (SNP) on a computer that has a TCP/IP Offload-enabled network adapter, you may experience many network-related problems.

The following issues may occur when Windows Server 2003 SNP is turned on:

•	When you try to connect to the server by using a VPN connection, you receive the following error message: Error 800: Unable to establish connection.
•	You cannot create a Remote Desktop Protocol (RDP) connection to the server.
•	You cannot connect to shares on the server from a computer on the local area network.
•	You cannot join a client computer to the domain.
•	You cannot connect to the Exchange server from a computer that is running Microsoft Outlook.
•	Inactive Outlook connections to the Exchange server may not be cleaned up.
•	You experience slow network performance.
•	You may experience slow network performance when you communicate with a Windows Vista-based computer.
•	You cannot create an outgoing FTP connection from the server.
•	The Dynamic Host Configuration Protocol (DHCP) server service crashes.
•	You experience slow performance when you log on to the domain.
•	Network Address Translation (NAT) clients that are located behind Windows Small Business Server 2003 or Internet Security and Acceleration (ISA) Server experience intermittent connection failures.
•	You experience intermittent RPC communications failures.
•	The server stops responding.
•	The server runs low on nonpaged pool memory

Note SNP features are currently not supported on Itanium-based systems.

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These issues occur because of several problems with the Windows Server 2003 SNP features that are enabled in Windows Server 2003 Service Pack 2. These features include Receive Side Scaling (RSS) and TCP/IP Offloading. Specifically, these problems include the following:

•	RSS is incompatible with NAT or with Network Load Balancing (NLB).
•	TCP/IP Offload has a problem with the Window Scaling feature. This problem typically occurs when you communicate with a Windows Vista-based computer. Windows Vista uses the Window Scaling feature.
•	Some TCP/IP Offload-enabled network adapters do not send TCP keep-alive messages. However, Exchange servers use TCP keep-alive messages to clean up inactive client sessions.
•	The TCP/IP Offload-enabled network adapter may consume lots of nonpaged pool memory. This may cause other problems in the operating system.
•	In some cases, the TCP/IP Offload-enabled network adapter may request large blocks of contiguous memory. This makes the computer stop responding when it tries to free the memory.

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Update information

This update turns off default SNP features. After you install this hotfix, you can manually re-enable these features by modifying registry values. The following files are available for download from the Microsoft Download Center:

Download the update for Windows Server 2003, x86-based versions (KB948496) package now. (http://www.microsoft.com/downloads/details.aspx?FamilyId=062E954C-FDEC-45AF-A09C-5A05B8F010A5)

Download the update for Windows Server 2003, x64-based versions (KB948496) package now. (http://www.microsoft.com/downloads/details.aspx?FamilyId=38E66572-5D47-4219-82D7-DB0C57478950)

For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.

Prerequisites

You must have Windows Server 2003 Service Pack 2 installed.

Restart requirement

You have to restart the computer after you apply this update.

Hotfix replacement information

This update does not replace any other previously released updates.

File information

This update does not replace any files.

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To work around this problem, use one of the following methods. You must restart the computer after you try any of these methods.

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Method 1: Manually disable RSS and TCP Offload in the network adapter driver

To manually disable RSS and TCP Offload in the network adapter driver, follow these steps:

1.	Click Start, click Run, type ncpa.cpl, and then click OK.
2.	Right-click a network adapter object, and then click Properties.
3.	Click Configure, and then click the Advanced tab.
4.	In the Property list, click Receive Side Scaling, click Disable in the Value list, and then click OK.
5.	In the Property list, click TCP/IP Offload, click Disable in the Value list, and then click OK.
6.	Repeat steps 2 through 5 for each network adapter object.

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Method 2: Update the network adapter drivers

To determine whether an updated network adapter driver is available, contact the network adapter manufacturer or the original equipment manager (OEM) for the computer. The driver must meet Network Driver Interface Specification (NDIS) 5.2 or a later version of this specification.

For information about how to contact computer program manufacturers, visit the following Microsoft Web site:

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Method 3: Manually disable RSS and TCP Offload in the registry

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:

To manually disable RSS and TCP Offload, follow these steps:

1.	Click Start, click Run, type regedit, and then click OK.
2.	Locate the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3.	Right-click EnableTCPChimney, and then click Modify.
4.	In the Value data box, type 0, and then click OK.
5.	Right-click EnableRSS, and then click Modify.
6.	In the Value data box, type 0, and then click OK.
7.	Right-click EnableTCPA, and then click Modify.
8.	In the Value data box, type 0, and then click OK.
9.	Exit Registry Editor, and then restart the computer.

If you set the value of the EnableTCPChimney registry entry to 1, the TCP Chimney functionality is enabled. Similarly, if you set the values of the EnableRSS and EnableTCPA registry entries to 1, the RSS functionality and the TCPA functionality are enabled.

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

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For more information, click the following article number to view the article in the Microsoft Knowledge Base:

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For more information about SNP, click the following article number to view the article in the Microsoft Knowledge Base:

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.

Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

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