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How would you do multicast over the internet? That seems like a disaster/not possible.

There actually is a multicast standard on the internet. It uses UDP. Basically, instead of sending out multiple streams of packets for each viewer you send only one stream and the routers copy the packets into new streams as needed along the way.

http://en.wikipedia.org/wiki/Multicast

I am not sure how often it is used and whether the newer routers still support it even.

I have a huge dream about multicast, but on the public internet, it doesn't happen.

Most of the time it happens on private IP networks (think FiOS TV, Uverse, etc., though i'm not sure if they use it.)

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