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Article ID: 931618 - Last Review: November 30, 2007 - Revision: 1.1

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You use a Windows XP-based computer that has Microsoft Office Communicator installed. When you make an audio call to another computer that has Communicator installed, the two sides of the call may not hear one another. In some cases, only one side of the call may hear the audio.

If you capture the network traffic when this problem occurs, you find that the User Datagram Protocol (UDP) packets do not have the Encapsulating Security Payload (ESP) header.

Note Any application that provides peer-to-peer audio and video communication may be affected by this problem.


Under certain circumstances, the ESP header is not included in the peer-to-peer UDP traffic between two client computers. Therefore, the packets may be dropped on the recipient computer without notification. Additionally, the Winsock client may not send the packet to the recipient computer.


Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: (
Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


Windows XP Service Pack 2 (SP2) must be installed before you apply this hotfix.

Restart requirement

You must restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

Registry information

To use one of the hotfixes in this package, you do not have to make any changes to the registry.

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 XP, x86-based versions
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File nameFile versionFile sizeDateTimePlatform


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


For more information about how to capture network traffic, click the following article number to view the article in the Microsoft Knowledge Base:
148942  ( ) How to capture network traffic with Network Monitor
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

  • Microsoft Windows XP Home Edition
  • Microsoft Windows XP Professional
kbautohotfix kbexpertiseadvanced kbfix kbqfe kbhotfixserver KB931618
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