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Real-Time Communication (RTC) client communications may not work if the client is located behind a Network Address Translation (NAT) device. The hotfix that is described in this article enables NAT-aware programs to configure the RTC API to use the correct address and port when it sets up the audio or video streams. After you install this hotfix, clients that are located behind the NAT device can use audio and video communications with other clients or gateways that are located outside the NAT device. Note that this hotfix does not help clients that are located behind a NAT device to connect to the Session Initiation Protocol (SIP) server. This hotfix does not enable Microsoft Windows Messenger clients that are located behind a NAT device to use audio and video with each other. However, the hotfix does enable Windows Messenger clients that are located behind a NAT device to communicate with phone gateways.
The RTC client was not originally supported behind a NAT device.
To resolve this problem, obtain the latest service pack for Windows XP. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
322389 How to Obtain the Latest Windows XP Service Pack
The following file is available for download from the Microsoft Download Center:
For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:
119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help to prevent any unauthorized changes to the file. The English version of this fix should have the following file attributes or later:
Date Time Version Size File name ------------------------------------------------------ 12-Oct-2001 14:10 5.1.2601.0 139,264 Aec.sys 11-Dec-2001 16:43 5.1.2600.16 844,288 Dxmrtp.dll 06-Feb-2002 15:41 5.1.2600.28 549,888 Rtcdll.dll 12-Oct-2001 14:22 5.1.2600.16 6,016 Splitter.sys 27-Nov-2001 14:20 5.1.2600.21 56,832 Usbaudio.sys 30-Jan-2002 18:07 5.1.2600.28 19,200 Usbuhci.sys
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article. This problem was first corrected in Windows XP Service Pack 1.
The RTC client Application Programming Interface (API) is a new feature of Windows XP. This feature is designed to facilitate the rapid development of real-time programs such as instant messaging and video-conferencing software.
Session Initiation Protocol (SIP) is an emerging Internet standard that allows flexible integration of messaging, presence, multimedia conferencing, and real-time communications such as telephony. SIP is designed to be modular to integrate programs in innovative ways, and is extensible to support new technologies