Network performance and data throughput may be significantly slower after installing Windows XP Service Pack 2

After you install Microsoft Windows XP Service Pack 2 (SP2), you may experience a significant slowdown in network performance and in data throughput on your computer.

This issue may occur because Windows Firewall does not work correctly with Large Send Offload (LSO) if all the following conditions are true:

• You use a high-speed network environment. For example, you use gigabit network cards, hubs, switches, routers, and target file servers.
• Your network card and its driver support using LSO.
• Your Windows XP-based computer sends lots of data to a server.

To work around this issue, disable the Windows Firewall/Internet Connection Sharing service. To do this, follow these steps:

1. Click Start, click Run, type services.msc, and then click OK.
2. In the Services list, right-click Windows Firewall/Internet Connection Sharing (ICS), and then click Properties.
3. On the General tab, in the Startup type list, click Disabled, and then click OK.
4. In the Services dialog box, on the File menu, click Exit.

Note This is not equivalent to turning off Windows Firewall in the Security Center. Setting Windows Firewall to Off leaves the component running, and you will still experience the issue. To work around this issue, you must disable the Windows Firewall/Internet Connection Sharing service.

Large Send Offload (LSO) is a technology where the work of segmenting data into network frames is performed by the network adaptor instead of by the TCP/IP stack. With LSO, TCP/IP sends very large data packets down to the network adaptor driver and the network adaptor hardware. The network adaptor breaks up the data into smaller network-sized frames. This both increases the speed of high-end send operations and decreases the computer's CPU usage because the work is performed on the network adaptor itself. LSO must be implemented in the TCP/IP stack, in the network adaptor hardware, and in the network adaptor driver.

For more information about LSO, visit the following Microsoft Web site: