Microsoft KB Archive/933717

= When an FTP client tries to close an FTP connection, the FTP connection is reset instead of closing gracefully in Windows Server 2003 =

Article ID: 933717

Article Last Modified on 10/11/2007

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APPLIES TO


 * Microsoft Windows Server 2003, Standard Edition (32-bit x86)
 * Microsoft Windows Server 2003, Enterprise Edition
 * Microsoft Windows Server 2003, Datacenter Edition (32-bit x86)
 * Microsoft Windows Server 2003, Web Edition
 * Microsoft Windows Server 2003, Standard x64 Edition
 * Microsoft Windows Server 2003, Enterprise x64 Edition
 * Microsoft Windows Server 2003, Datacenter x64 Edition
 * Microsoft Windows Server 2003, Enterprise Edition for Itanium-based Systems
 * Microsoft Windows Server 2003, Datacenter Edition for Itanium-Based Systems

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SYMPTOMS
Consider the following scenario:
 * Windows Firewall is enabled on a server that is running Microsoft Windows Server 2003.
 * The Application Layer Gateway Service is also running on the computer.
 * An FTP client application tries to close an FTP connection.

In this scenario, the FTP connection is reset instead of closing gracefully. If you trace the network traffic when this problem occurs, the network trace indicates that an extra TCP reset packet is sent. The following is an example of the network trace. 60 1575.966128   TCP TCP: Flags=..R.A..., SrcPort=1079, DstPort=FTP control(21), Len=0, Seq=1821626642, Ack=2458418212, Win=0 (scale factor 0) = 0 In most cases, you are not affected by this problem because this problem does not prevent data from being transferred over an FTP connection. However, some FTP server applications may detect the state of FTP clients. For example, a server application may be designed to stop when it detects that the FTP client has failed. When the FTP connection is reset, the server application assumes that the client has failed. In this case, the server application stops unexpectedly.



CAUSE
This problem occurs because of a race condition in the FTP application-layer gateway. The Application Layer Gateway Service incorrectly initiates a hard reset action when the service closes a socket connection.



RESOLUTION
After you apply this hotfix, the Application Layer Gateway Service closes the socket connection by using a graceful close and a time-out period.

Hotfix information
A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that is described in this article. Apply it only to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Windows Server 2003 service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites
To apply this hotfix, you must have an x64-based version of Windows Server 2003, Windows Server 2003 Service Pack 1, or Windows Server 2003 Service Pack 2 installed. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

889100 How to obtain the latest service pack for Windows Server 2003

Restart requirement
You must restart the computer after you apply this hotfix.

Hotfix replacement information
This hotfix does not replace any other hotfixes.

File information
The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

Windows Server 2003 with Service Pack 1, Itanium-based versions


STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
For more information about the Application Layer Gateway Service, visit the following Microsoft TechNet Web site:

http://www.microsoft.com/technet/security/guidance/serversecurity/tcg/tcgch07n.mspx#EPH

For more information about the terms that are used to describe software updates, 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

Keywords: kbbug kbfix kbqfe kbpubtypekc kbexpertiseinter kbhotfixserver kbwinserv2003postsp2fix KB933717

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