Data-MDT tunnels for multicast over VPNs

Eliminate the need to flood multicast packets to provider edge (PE) routers within a virtual private network (VPN) group that do not need to receive those packets (PE routers that have no end recipients for the multicast traffic). A tunnel is established between the source router and its PE router. Other PE routers that have receivers for the multicast traffic connect to this tunnel. The tunnel, called a data-driven multicast distribution tree (data-MDT) tunnel, is created based on the multicast data in the VPN.