Network performance becomes very slow when TCP/IP packet filtering is enabled on a Windows Server 2003-based or Windows XP-based computer that has a Large Segment Offload (LSO)-enabled network adapter


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Symptoms


Consider the following scenario:
  • You have a computer that is running Windows Server 2003 or Windows XP.
  • The network adapter on the computer is Large Segment Offload (LSO)-enabled.
  • TCP/IP packet filtering is enabled for the network adapter on the computer.
In this scenario, the LSO feature does not function. This behavior is by design. However, the network performance becomes very slow. Specifically, network applications are delayed when the TCP connections are being closed.

Cause


This problem occurs because of a delay when the TCP/IP protocol sends FIN packets. The TCP/IP protocol sends FIN packets requesting that the remote party close a TCP connection. This delay causes network applications to close TCP connections very slowly.

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 LSO in the TCP/IP protocol. To do this, follow these steps:
  1. Click Start, click Run, type regedit, and then click OK.
  2. Locate and then right-click the following registry subkey:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
  3. Point to New, and then click DWORD Value.
  4. Type DisableLargeSendOffload, and then press ENTER.
  5. Double-click DisableLargeSendOffload, type 1 in the Value data box, and then click OK.
  6. Exit Registry Editor.
  7. Restart the computer.

Status


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

More Information


Some data must be split into segments before it can be transmitted over the network. This process is known as segmentation. Segmentation is usually done by the TCP protocol on the host computer. The feature that transfers the segmentation work to the network adapter is called Large Segment Offload (LSO). This is also known as TCP segmentation offload.