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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.


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.


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


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

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