Windows Media Services
To obtain the new features and tools available in Windows Media Services for Windows Server 2008, such as the built-in WMS Cache/Proxy plug-in, you must obtain and run the appropriate Streaming Media Services role installer file on the updated platform.
http://www.microsoft.com/downloads/details.aspx?familyid=9ccf6312-723b-4577-be58-7caab2e1c5b7&displaylang=en&tm