ISA Server 2004, ISA Server 2006 or Windows Essential Business Server 2008 blocks requests that include the Accept-Encoding HTTP header when a forward proxy is used

Service pack information

To resolve this problem, install ISA Server 2004 Service Pack 3 (SP3), and then run the Microsoft Visual Basic script that is mentioned in this section. For more information about how to obtain the latest ISA Server 2004 service pack, click the following article number to view the article in the Microsoft Knowledge Base:

891024 How to obtain the latest ISA Server 2004 service pack

After you install the service pack, run the following script to enable a new configuration parameter. This new parameter lets ISA Server forward requests that include the Accept-Encoding HTTP header if the compression filters are disabled in a forward proxy scenario. To do this, follow these steps.

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1. Click Start, point to All Programs, point to Accessories, and then click Notepad.

2. Paste the following code into the Notepad document.

   Const SE_VPS_GUID = "{143F5698-103B-12D4-FF34-1F34767DEabc}"
   Const SE_VPS_NAME = "AccessRuleSendAcceptEncodingHeader"
   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 Notepad file as "AccessRuleSendAcceptEncodingHeader.vbs."

4. Double-click the .vbs file to run the script.

To disable the new configuration parameter, follow these steps:

1. Click Start, point to All Programs, point to Accessories, and then click Notepad.

2. Paste the following code into the Notepad document.

   Const SE_VPS_GUID = "{143F5698-103B-12D4-FF34-1F34767DEabc}" 
   Const SE_VPS_NAME = "AccessRuleSendAcceptEncodingHeader" 
   Const SE_VPS_VALUE = false 
   
   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 
        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 Notepad file as "Disable_AccessRuleSendAcceptEncodingHeader.vbs."

4. Double-click the .vbs file to run the script.