Microsoft KB Archive/933118

= 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 =

Article ID: 933118

Article Last Modified on 12/27/2007

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APPLIES TO


 * Microsoft Windows Server 2003, Standard Edition (32-bit x86)
 * Microsoft Windows Server 2003, Web Edition
 * Microsoft Windows Server 2003, Enterprise Edition (32-bit x86)
 * Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
 * Microsoft Windows XP Professional

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Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

322756 How to back up and restore the registry in Windows XP and Windows Vista



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:  Click Start, click Run, type regedit, and then click OK. Locate and then right-click the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

 Point to New, and then click DWORD Value. Type DisableLargeSendOffload, and then press ENTER. Double-click DisableLargeSendOffload, type 1 in the Value data box, and then click OK. Exit Registry Editor.</li> Restart the computer.</li></ol>

<div class="status_section">

STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.

<div class="moreinformation_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.

Keywords: kbexpertiseinter kbtshoot kbprb KB933118

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