We've seen quite a few issues recently from customers having network problems on Windows Server 2003 SP2. These issue range from connections being reset to seeing things like database mirroring issues, etc. In other words, anything involving network traffic. In many of these issues, the problem is a new setting in Windows Server 2003 SP2 called TCP Chimney.

TCP Chimney is a new feature that improves network performance by offloading handling of TCP packets to the hardware layer, specifically to the network interface card (NIC). It works great if your NIC and NIC driver are capable. If they aren't, you will see strange network issues such as I described in above.

If you're experiencing problems with your network on SP2, the first step is to look for a new driver for your NIC. A new driver will sometimes correct the problem. In cases where it doesn't, disabling TCP Chimney is a good idea. If that resolves the issue, you can chalk your issue up to a NIC and/or NIC driver that just doesn't work correctly with this new feature.

1. To disable TCP Chimney, follow these steps:

2. Click Start, click Run, type cmd, and then click OK.

3. At the command prompt, type:

Netsh int ip set chimney DISABLED

4. Press the ENTER key.

No reboot or restart is required for this to take effect. It will take effect immediately.

Jim