Article ID: 2518676 - Last Review: June 15, 2011 - Revision: 2.0

FIX: The final ACK packet during an orderly closure of a SecureNAT client TCP connection may be dropped in a Forefront Threat Management Gateway 2010 environment

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SYMPTOMS

During the orderly closure of a SecureNAT client TCP connection in a Microsoft Forefront Threat Management Gateway (TMG) 2010 environment, TMG may drop the final acknowledgement (FIN ACK) of the connection closure handshake.

This could lead to re-transmissions of the final FIN ACK packet, and these re-transmissions can lead to application delays, depending on the behavior of the application.
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CAUSE

This issue occurs because of a handling bug in the Firewall Engine driver for TMG.
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RESOLUTION

To resolve this issue, install the software update that is described in the following Microsoft Knowledge Base article:
2517957  (http://support.microsoft.com/kb/2517957/ ) Software Update 1 Rollup 4 for Forefront Threat Management Gateway (TMG) 2010 Service Pack 1

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STATUS

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

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684  (http://support.microsoft.com/kb/824684/ ) Description of the standard terminology that is used to describe Microsoft software updates

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APPLIES TO
  • Microsoft Forefront Threat Management Gateway 2010 Enterprise
  • Microsoft Forefront Threat Management Gateway 2010 Standard
  • Microsoft Forefront Threat Management Gateway 2010 Service Pack 1
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Keywords: 
kbexpertiseinter kbbug kbsurveynew kbqfe kbfix KB2518676
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