Fragmentation of Multicast UDP Packets May Cause Performance Degradation and Packet Loss (252360)

IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry

CAUSE

Windows Media Server can generate UDP packets that are greater than 1500 bytes when you deploy high bit-rate content. This can cause IP packets to be fragmented for Windows Media Server streams because Ethernet packets have a maximum size of 1500 bytes. Fragmentation can cause performance degradation and packet loss.

RESOLUTION

A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem. This fix may receive additional testing. Therefore, if you are not severely affected by this problem, Microsoft recommends that you wait for the next Windows Media service pack that contains this hotfix.

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

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

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 typical support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix should have the following file attributes or later:

   Date      Time    Version      Size    File name   Platform  
   -------------------------------------------------------
   12/09/1999  06:24p           1,021,136 NsRex.exe   x86

MORE INFORMATION

Use Wmsu3462.exe to install the fix. Wmsu3462.exe can be downloaded from the following location:

http://download.microsoft.com/download/winmediatech40/Update/3462/WIN98/EN-US/WMSU3462.EXE

The Nsrex.exe fix cannot be extracted from the installer. You must do this using Registry Editor.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

Start Registry Editor (Regedt32.exe).
Locate the following key in the registry:
Hkey_Local_Machine\Software\Microsoft\Netshow\Rex\
On the Edit menu, click Add Value, and then add the following registry value:
Value Name: MaxPacketSize
Data Type: REG_DWORD
Value: Maximum packet size in bytes
Quit Registry Editor.

NOTE: The issue was also resolved in the Windows Media Encoder version 7.x or higher. Now the maximum packet size can be configured using the Encoder interface. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

304513 Controlling UDP Packet Fragmentation in Windows Media Encoder