Outside a few niches (zeroconf, IPv6 SLAAC, financial data distribution) in closed environments, I don't believe we ever reached the point of figuring out how t

Outside a few niches (zeroconf, IPv6 SLAAC, financial data distribution) in closed environments, I don't believe we ever reached the point of figuring out how to handle Internet-sized multicast deployment. Not sure what the state of the art here is, but IIRC multicast introduces significant extra state into every router and switch involved, and with limited ability to control who is able to transmit to a multicast group. On the radio network side, I don't think IP multicast has any specific support in e.g. LTE, so even if a mobile client could subscribe to a group its bandwidth usage over the air would be equivalent to a unicast stream. Guess this was omitted for the reasons from the previous paragraph. LTE has something called multicast but AFAIK it's totally unrelated to the IP/Ethernet concept. edit: whoa, apparently 802.11 networks handle multicast properly - stations don't generate layer 1 ACKs for reception like they handle unicast traffic. There's a ton of cool stuff you could build with this on a LAN!