[woinrigod]

From an article on how to play ISMV file, we learn that:

ISMV file is used by Microsoft IIS web server to deliver one video on different bitrate to Silverlight client over HTTP. This technology is called Smooth Streaming. Actually, ISMV is one kind of MP4 file. The video in it is split into 2-second chunks. Client can request video chunk by chunk.

To publish a video with Smooth Streaming, web master encode the video into several ISMV files with Expression Encoder, each for different bitrate. It will generate one ISM file and one ISMC file to describe information about these ISMV files, one for server and one for client. When Siverlight player plays a video, it request ISMC file at first to know how many bitrate available. Then it request the first chunk of loweast bitrate ISMV file to test network and CPU speed. If speed is enough, it will request following chunks in higher bitrate ISMV file. And it will switch between different bitrate to get highest quality and keep playing smooth at the same time.

Or

Go to http://forums.iis.net/t/1181405.aspx