How much does multicast help?

Hello fellows.

I recently saw a post here in this forum and got amazed with 5000 users.

I want to set up a AMS based live streaming service, and thought if you, as more experiencied users could give me some advices.

My biggest concern is about the internet bandwidth. I like AMS because it have the multicast feature, but it is a little bit confusing for me if it only works at LAN, for intern corporate communications, or if it can be used to live stream video worldwide.

I would like to know how big is your internet bandwidth. I need to calc how much the multicast does help.

I would really apreciate if you could give me any tip.

Thank you very much.