Thus spake "David Sinn" <dsinn@microsoft.com>
There is also a "cart and horse" issue here: Where is the pervasive content?
No, it's a "chicken and egg" problem :)
Most content providers don't want multicast because it breaks their billing model. They can't tell how many viewers they have at a given moment, what the average viewing time is, or any of the other things that unicast allows them to determine and more importantly bill their advertisers for. There is no Nielsen's Ratings for multicast so that advertisers could get a feel for how many eyeballs they are going to hit.
That assumes there is no signaling. Commercial content will be encrypted and clients will have to get a key (possibly for free). Key distribution can be tracked and billed perfectly. Even for cleartext content, clients should be sending RTCP reports periodically. I think a bigger issue is that multicast is only truly compelling for high-bandwidth applications, and there's just not a critical mass of users with enough bandwidth to justify deployment today. Even worse, multicast is truly only suitable for live applications; on-demand content can't be realistically mcasted, and users will not settle for "the movie starts every 15 minutes" when they've been used to live VOD with unicast. The only saving grace may be things like TiVo, where an intelligent agent slurps up live mcasts in hopes that the user may want to watch it "live" later. S