FIX: ISA Server 2006 or Forefront TMG 2010 does not detect a TCP reset response when you enable HTTP compression

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Article ID: 980066 - View products that this article applies to.
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SYMPTOMS

Consider the following scenario:
  • You enable HTTP compression in Microsoft Internet Security and Acceleration (ISA) Server 2006 or in Microsoft Forefront Threat Management Gateway (TMG) 2010.
  • On a client, you use ISA Server 2006 or Forefront TMG 2010 as a Web proxy to connect to a Web server. However, the Web server takes a long time to respond to HTTP requests from the client.

    Note When the Web server sends data to ISA Server 2006 or to Forefront TMG 2010, ISA Server 2006 or Forefront TMG 2010 accumulates data. ISA Server 2006 or Forefront TMG 2010 does not send any data to the client until the Web server finishes the HTTP request.
  • You close the Web browser before the Web server is finished responding.
  • The client sends a TCP reset response to ISA Server 2006 or to Forefront TMG 2010 on a TCP session that was opened.
  • You try to access the Web site again, and the client or an intermediate proxy server uses the same source port from the previous TCP session that just obtains the TCP reset response.
In this scenario, ISA Server 2006 or Forefront TMG 2010 does not detect the TCP reset response until Web server sends a complete HTTP response, and ISA Server 2006 or Forefront TMG 2010 rejects the new client connection by using the same client port. Therefore, you cannot access the Web site by using the same source port.

Note The supported fix for Forefront TMG 2010 is included in Forefront TMG 2010 Service Pack 1 (SP1).

RESOLUTION

Service pack information

This problem is fixed in Forefront TMG 2010 Service Pack 1.

For more information about how to obtain Forefront TMG 2010 Service Pack 1, click the following article number to view the article in the Microsoft Knowledge Base:
981324 List of problems that are fixed in Forefront Threat Management Gateway 2010 Service Pack 1

Hotfix rollup information


Hotfix installation information

To resolve this issue, follow these steps:
  1. Install the hotfix rollup package that is described in the following Microsoft Knowledge Base (KB) article:
    980067 Description of the ISA Server 2006 hotfix package: February 22, 2010
  2. Copy and paste the following script into Notepad:
    Const SE_VPS_GUID = "{143F5698-103B-12D4-FF34-1F34767DEabc}"
    Const SE_VPS_NAME = "AllowPrematureClientTermination"
    Const SE_VPS_VALUE = true
    
    Sub SetValue()
    
        ' Create the root obect.
        Dim root  ' The FPCLib.FPC root object
        Set root = CreateObject("FPC.Root")
    
        'Declare the other objects needed.
        Dim array       ' An FPCArray object
        Dim VendorSets  ' An FPCVendorParametersSets collection
        Dim VendorSet   ' An FPCVendorParametersSet object
    
        ' Get references to the array object
        ' and the network rules collection.
        Set array = root.GetContainingArray
        Set VendorSets = array.VendorParametersSets
    
        On Error Resume Next
        Set VendorSet = VendorSets.Item( SE_VPS_GUID )
    
        If Err.Number <> 0 Then
            Err.Clear
    
            ' Add the item
            Set VendorSet = VendorSets.Add( SE_VPS_GUID )
            CheckError
            WScript.Echo "New VendorSet added... " & VendorSet.Name
    
        Else
            WScript.Echo "Existing VendorSet found... value- " &  VendorSet.Value(SE_VPS_NAME)
        End If
    
        if VendorSet.Value(SE_VPS_NAME) <> SE_VPS_VALUE Then
    
            Err.Clear
            VendorSet.Value(SE_VPS_NAME) = SE_VPS_VALUE
    
            If Err.Number <> 0 Then
                CheckError
            Else
                VendorSets.Save false, true
                CheckError
    
                If Err.Number = 0 Then
                    WScript.Echo "Done with " & SE_VPS_NAME & ", saved!"
                End If
            End If
        Else
            WScript.Echo "Done with " & SE_VPS_NAME & ", no change!"
        End If
    
    End Sub
    
    Sub CheckError()
    
        If Err.Number <> 0 Then
            WScript.Echo "An error occurred: 0x" & Hex(Err.Number) & " " & Err.Description
            Err.Clear
        End If
    
    End Sub
    
    SetValue
  3. Save the file as a Microsoft Visual Basic script file by giving the file a .vbs file name extension. For example, save the file under the following name:
    EnableKB980066.vbs
  4. Double-click the .vbs file to run it.

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. This problem was first corrected in Forefront TMG 2010 Service Pack 1.

REFERENCES

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates

Properties

Article ID: 980066 - Last Review: October 6, 2011 - Revision: 3.0
APPLIES TO
  • Microsoft Internet Security and Acceleration Server 2006 Service Pack 1
  • Microsoft Internet Security and Acceleration Server 2006 Enterprise Edition
  • Microsoft Internet Security and Acceleration Server 2006 Standard Edition
  • Microsoft Forefront Threat Management Gateway 2010 Enterprise
  • Microsoft Forefront Threat Management Gateway 2010 Standard
Keywords: 
kbexpertiseinter kbfix kbsurveynew kbqfe KB980066

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