TCP Chimney Offload is Incompatible With the Neverfail Packet Filter

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Summary

This Knowledgebase article explains why you must disable the TCP Chimney Offload when the Neverfail Packet Filter is to be installed as part of the Neverfail installation process.

More information

Symptoms

If TCP Chimney Offload has been enabled and is operational and the Neverfail Packet Filter is installed, then TCP Chimney Offload ceases to function.

Cause

TCP Chimney Offload will not work in the presence of NDIS Intermediate drivers. The Neverfail Packet Filter is an NDIS Intermediate driver, and hence there is an incompatibility between TCP Chimney Offload and the Neverfail Packet Filter driver.

Resolution

TCP Chimney Offload is supported on Windows Server 2003 SP2, Windows Server 2008 and Windows Server 2008 R2. Depending on the OS version there are different commands to disable the TCP Chimney Offload

  • Windows Server 2003

According to Microsoft: http://support.microsoft.com/kb/912222 the TCP Chimney Offload is enabled by default, and can be configured using the following commands:

  • Netsh int ip set chimney ENABLED
  • Netsh int ip set chimney DISABLED

On Windows Server 2003 there is no command to view the current setting for TCP Chimney Offload and the current setting can be viewed by looking at this registry value.

  • Windows Server 2008

According to Microsoft: http://support.microsoft.com/kb/951037 the TCP Chimney offload is disabled by default, and the configuration for TCP Chimney offload can be determined by issuing the following command line:

  • Netsh int tcp show global

This produces results:

Querying active state...

TCP Global Parameters
----------------------------------------------
Receive-Side Scaling State                : enabled
Chimney Offload State                     : disabled
Receive Window Auto-Tuning Level    : normal
Add-On Congestion Control Provider  : ctcp
ECN Capability                                 : disabled
RFC 1323 Timestamps                     : disabled

The following commands can be used to enable / disable TCP Chimney offload:

  • Netsh int tcp set global chimney=enabled
  • Netsh int tcp set global chimney=disable
  • Windows Server 2008 R2

According to Microsoft: http://technet.microsoft.com/en-us/library/gg162682(WS.10).aspx it appears to be the same as for Windows 2008 and states that TCP Chimney offload is disabled by default, however by issuing the following command it was found to be automatic:

  • Netsh int tcp show global

This produces results:

Querying active state...

TCP Global Parameters
----------------------------------------------
Receive-Side Scaling State                : enabled
Chimney Offload State                     : automatic
NetDMA State                                  : enabled
Direct Cache Access (DCA)                 : disabled
Receive Window Auto-Tuning Level    : normal
Add-On Congestion Control Provider  : none
ECN Capability                                 : disabled
RFC 1323 Timestamps                     : disabled

The following commands can be used to configure TCP Chimney offload:

  • Netsh int tcp set global chimney=automatic
  • Netsh int tcp set global chimney=enabled
  • Netsh int tcp set global chimney=default
  • Netsh int tcp set global chimney=disabled


Applies To

Neverfail Heartbeat all versions, on Windows Server 2003 SP2, 2008, 2008 R2


Related Information

http://support.microsoft.com/kb/951037
http://support.microsoft.com/kb/912222

KBID-2288

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