Announcing the Bit Rate Throttling module Customer Technology Preview

Bit Rate Throttling, the first feature in the upcoming IIS7 Media Pack, is now available for download at

The IIS7 Bit Rate Throttling module was first announced at the National Association of Broadcasters (NAB) show last April as part of the TCO advantage for Silverlight.  It enables Web administrators to throttle the delivery of any file based on the file type, with additional functionality for digital audio/video files. Throttling can be set at the following levels within Internet Information Services (IIS) Manager: server, site, virtual directory, and file.

For audio and video files, this module automatically detects the encoded bit rate of the file, sends a short burst of data to the client at full throttle to ensure a fast start to their playback experience, and then delivers the content at a throttled rate that is equal to or slightly greater than the encoded bit rate. Several popular digital media file types are pre-defined in the module, and others can be added. Data files are throttled at a configurable constant rate.

The Bit Rate Throttling module includes the following key features:

·         Integration with IIS 7.0. The Bit Rate Throttling module is tightly integrated with this new administration interface and configuration store in IIS 7.0. In addition, IIS 7.0 has a new administration tool, and the new Bit Rate Throttling module plugs seamlessly into that paradigm.

·         Throttling for any file type. Any file type can be throttled at a constant rate. An administrator can easily specify a new file type and throttling settings through the user interface.

·         Advanced media throttling. One of the most significant features in the new Bit Rate Throttling module is the advanced support of audio/video media formats. This includes automatic detection of the encoded bit rate in a file, and intelligent progressive-download throttling based on that. Built-in support is included for digital media with the following file name extensions: .asf, .avi, .flv, .mov, .mp3, .mp4, .rm, .rmvb, .wma, .wmv. An administrator can simply enable Bit Rate Throttling and start intelligently delivering these common media types using the default throttling settings.

·         Extensibility. The new Bit Rate Throttling module supports developer extensibility, making it possible for software vendors and hobbyists to add support for additional media formats using simple XML editing. Microsoft is using this extensibility feature to implement the built-in media format support.

·         Shared hosting support. By fully integrating into the IIS 7.0 pipeline and configuration model, the new Bit Rate Throttling module makes it possible to host Web page content and intelligently deliver a variety of media from the same Web server, site, or virtual directory. This level of granularity also provides the ability to isolate users through per-user virtual directories. 

Bryan Fleming and Eric Woersching have both written about the Bit Rate Throttling value proposition provided by this module for folks who are hosting media content on Web servers.  If you are wondering whether to deliver media content using IIS7 or Windows Media Services, please read my previous blog post.

We'd love to get your feedback on this module - please post a comment below, or join the discussion at the new IIS7 - Media forum


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