Some TCP/IP packets are dropped when they are parsed by the NAT module on a Windows Embedded CE 6.0 R3-based device


Consider the following scenario:
  • You have a Windows Embedded CE 6.0 R3-based device that has Network Address Translation (NAT) enabled.
  • You use the device as a router.
  • You run an application on the device that opens a connection to an external device. For example, you open a connection to an FTP server.
In this scenario, some incoming TCP/IP packets are dropped by the NAT module. Additionally, some other errors may occur after the incoming TCP/IP packets are dropped. For example, the application stops responding when a function is called to receive data from the TCP/IP layer. Or, the connection reports an error.


This issue occurs because the IP module on the device calculates the header size of the incoming packets incorrectly. This behavior causes some packets to be put into the wrong code path in the TCP/IP stack and not to be routed to the NAT module. Therefore, the sequence numbers of the expected packets that are calculated by the NAT module do not match the sequence number of the incoming packets. This causes the issue that is described in the "Symptoms" section.


Software update information

A supported software update is now available from Microsoft as Windows Embedded CE 6.0 Platform Builder Monthly Update (August 2010). You can confirm this by scrolling to the "File information" section of this article. The package file name contains the product version, date, Knowledge Base article number, and processor type. The package file name format is:
Product version-yymmdd-kbnnnnnn-processor type

For example: Wincepb50-060503-kb917590-armv4i.msi is the ARMV4i Windows CE 5.0 Platform Builder fix that is documented in KB article 917590 and that is contained in the May 2006 monthly update. To resolve this problem immediately, click the following article number for information about obtaining Windows CE Platform Builder and core operating system software updates:
837392 How to locate core operating system fixes for Microsoft Windows CE Platform Builder products


This update is supported only if all previously issued updates for this product have also been installed.

Restart requirement

After you apply this update, you must perform a clean build of the whole platform. To do this, use one of the following methods:
  • On the Build menu, click Clean Solution, and then click Build Solution.
  • On the Build menu, click Rebuild Solution.
You do not have to restart the computer after you apply this software update.

Update replacement information

This update does not replace any other updates.

File information

The English version of this software update package 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.
Installer files
File nameFile sizeDateTime
Files that are included in this hotfix package
File nameFile sizeDateTimePath
Windows embedded ce 6.0_update_kb2291255.htm7,65609-Aug-201021:55100809_kb2291255


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

More Information

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


Article ID: 2291255 - Last Review: Sep 14, 2010 - Revision: 1