CDNs vs Multicasting

It is pretty well known fact nowadays that in order to organize streaming to the wide array of clients you will need to use services of the Content Delivery Network. Well, at least that's what I thought up to few days ago. :). But fortunatly that isn't always the case.

When you're using CDN's services you're paying for Gig's they've streamed. So if you have 1000 of viewers and they are viewing 1 Gb each you will have to pay for 1000 * 1 Gb * $1.60 (approx. price of Gig) = $1600. Pretty impressive, isn't it?

Now, when you're streaming live event (sports event, music concert, or even you on your webcam) in each specific time all the users should have the same picture on their screen. And that's where multicasting fits perfectly in. Using multicasting you are streaming to the group address, and users who want to view your stream connect to that group address. So you only stream your audio/video to the group once and that's it. So for the same sittuation if you have 1000 clients viewing 1 Gb you would have to pay only for 1 Gb traffic to your ISP....or you would pay nothing extra if you have unlimited plan;)

The drawback of multicasting is that your ISP has to support it. The stats says only 5% of ISPs support multicasting. Another drawback - you're broadcasting a steam, and user does not choose when he wants it to start. So ondemand scenario is hardly possible.

More info on multicasting:
http://technet2.microsoft.com/WindowsServer/en/Library/9feb45d5-bf5a-4e55-8c71-a37b7e7c3b311033.mspx

The good example of how it all works with multicasting is here:
http://www.americafree.tv ..well they are broadcasting movies that are sooooo old, but still...makes my point :).