"So assuming router state based multicast, how do you bill on that if the stream is exploded on the opposite end of, or in the middle of, a transit network?"

"You're likely getting it from a settlement free peer at the request of your customer who has paid for you to deliver it to them. You can choose to carry it once per customer or once for all your customer paths. Using multicast the latter means you get to keep a proportion of your extra users payment as profit instead of paying network costs"

The simplified answer of "only as the stream actually transiting the network" won't fly with most bean counters, because in their eyes, every packet going through the network should be billed as bandwidth consumed.

Pardon me for suggesting they get themselves a viable business model for their current traffic first. All you can eat flat rate broadband is wonderful but not compatible with this argument If heads were to be extracted from sand they may find people willing to pay for a viable multicast model, extra cash for what their customers have already paid for. End of net neutrality debate, supply something extra people want to buy.

because while multicast saves bandwidth generally, the bandwidth multiplies as it transits a for-pay network, meaning that more resources are consumed and thus ... could be billed for money.

Or not if we do P2P instead. "Would you like your network lightly or totally spammed?"

Traditional v4 multicast, then, is unlikely to see deployment outside of an organiation's own garden network, and you have near zero uptake.

User demand isn't going away, lots of those gardens will have multicast when they find it useful. As we agree such islands will exist it's a short step to thinking what if all this was connected together into one big network, we could call it an internet Alternatively, if they stay islands an enterprising company may decide there's value in getting access to each island and selling a one stop easy access service. Others may follow and then we're back to that internet thing. brandon