Error message when an application connects to SQL Server on a server that is running Windows Server 2003: "General Network error," "Communication link failure," or "A transport-level error"

Consider the following scenario. A server is running Windows Server 2003 and Microsoft SQL Server. You have an application that connects to SQL Server by using TCP/IP. In this scenario, you may intermittently receive one of the following error messages when the application connects to SQL Server:You may also receive one of these error messages when the network load on SQL Server is high. For example, you may receive one of these error messages when you replicate databases in SQL Server. Or, you may receive one of these error messages when a multiple-user application accesses databases in SQL Server.

This problem occurs because the TCP Chimney Offload feature is enabled on the server. The TCP Chimney Offload feature is enabled by the Windows Server 2003 Scalable Networking Pack.

Typically, this problem occurs when the network adapter uses the Broadcom 5708 chipset. For example, the following network adapters use the Broadcom 5708 chipset:

• Broadcom NetXtreme II
• Hewlett-Packard NC373i Multifunction Gigabit Server Adapter

This problem may also occur when the network adapter uses other chipsets.

To resolve this problem, ask the hardware vendor if the hardware vendor has the following updates:

• The latest basic input/output system (BIOS) update for the server
• The latest firmware update for the network adapter
• The latest driver update for the network adapter

If the hardware vendor has no updates, see the "Workaround" section to work around this problem.

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 work around this problem, disable the TCP Chimney Offload feature. To do this, follow these steps:

1. Click Start, click Run, type cmd, and then press ENTER.
2. At the command prompt, type the following command, and then press ENTER:
   Netsh int ip set chimney DISABLED
   Note You do not have to restart the server after you run this command.

If the performance of Windows Server 2003 decreases after you disable the TCP Chimney Offload feature, follow these additional 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. Double-click the EnableTCPChimney registry entry.
4. In the Edit DWORD Value dialog box, type 0 in the Value data box, and then click OK.
5. Double-click the EnableRSS registry entry.
6. In the Edit DWORD Value dialog box, type 0 in the Value data box, and then click OK.
7. Double-click the EnableTCPA registry entry.
8. In the Edit DWORD Value dialog box, type 0 in the Value data box, and then click OK.
9. Restart the server.

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

The Windows Server 2003 Scalable Networking Pack provides the following features:

• TCP Chimney Offload
• Receive-Side Scaling (RSS)
• Network Direct Memory Access (NetDMA)

These features optimize the performance of Windows Server 2003 when Windows Server 2003 is processing network traffic.

To obtain the Windows Server 2003 Scalable Networking Pack, you must install Windows Server 2003 Service Pack 2 (SP2). Or, you must install the update that is described in Microsoft Knowledge Base article 912222. For more information, click the following article number to view the article in the Microsoft Knowledge Base: To enable the TCP Chimney Offload feature, the server must have a network adapter that supports offload technologies.

How to use a network trace to determine whether the TCP Chimney Offload feature is enabled

When you directly capture a network trace on the server, the network trace contains only TCP three-way handshakes and UDP traffic if the TCP Chimney Offload feature is enabled. The network trace does not contain other traffic because the TCP Chimney Offload feature lets the network traffic bypass that specific part of the TCP/IP stack. The driver that captures packets resides in that specific part of the TCP/IP stack.

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