You receive an error message when you access a Web site through ISA Server 2004 that has the Compression Filter Web filter enabled


Symptoms


Consider the following scenario:
  • You access a Web site that is published in Microsoft Internet Security and Acceleration (ISA) Server 2004. Or, you access a Web site by using ISA Server 2004 as the Web proxy.
  • The Compression Filter Web filter is enabled in ISA Server 2004.
  • The Web site sends an HTTP/0.9 response to the client.
In this scenario, you receive one of the following error messages.

Error message 1
HTTP/1.1 502 Proxy Error (The specified network name is no longer available.)
Error message 2
Error Code 64: Host not available
Background: The gateway or proxy server lost connection to the Web server.

Cause


An HTTP/0.9 response has only a body, but no headers. The Web site closes the connection to indicate the end of a response.

However, the Compression Filter Web filter in ISA Server expects an HTTP/1.0 or HTTP/1.1 response. The Compression Filter Web filter does not recognize an HTTP/0.9 response. Therefore, the Compression Filter Web filter assumes that the connection is lost or reset before the Web site can send all the HTTP response headers.

Resolution


To resolve this problem, follow these steps:
  1. Apply the hotfix package that is described in the following Microsoft Knowledge Base article:
    945043 Description of the ISA Server 2004 hotfix package: November 12, 2007

  2. Start Notepad.
  3. Copy the following code, and then paste it into Notepad.
    Const SE_VPS_GUID = "{143F5698-103B-12D4-FF34-1F34767DEabc}"
    Const SE_VPS_NAME = "EnableHotfix944114"
    Const SE_VPS_VALUE = true

    Sub SetValue()

    ' Create the root object.
    Dim root ' The FPCLib.FPC root object
    Set root = CreateObject("FPC.Root")

    'Declare the other required objects.
    Dim array ' An FPCArray object
    Dim VendorSets ' An FPCVendorParametersSets collection
    Dim VendorSet ' An FPCVendorParametersSet object

    ' Get references to the array object
    ' and to 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
  4. Save the file as a Microsoft Visual Basic script file by using the .vbs file name extension. For example, use the following name to save the file:
    EnableHotfix944114.vbs
  5. At a command prompt, change to the location where you saved the file in step 4, and then run the following command:
    cscript EnableHotfix944114.vbs
Note To revert to the default setting, edit the script by changing "Const SE_VPS_VALUE = true" to "Const SE_VPS_VALUE = false." Save the script, and then run it again.

Workaround


To work around this problem, disable the Compression Filter Web filter in ISA Server.

Status


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