An idea for router powered multi-cast–the end goal being that routers with and without multi-cast and both exist and multi-cast still work
Basically use the BGP tables to compute a path to an end, and, when you do, retain in memory which was your next hop within that path of routers that are multi-cast aware.
Maybe have this information added to the TCP header: destination ‘group’
each router would retain, per group, port information [this group, these next hops]. Could use a bloom filter for such, I suppose.
mbone is related
rsvp is related.
More background research is necessary.