The invention provides a method and system for multicast packet routing, in which only selected routers in a network subset (in a preferred embodiment, those routers on the border of the domain) maintain routing information external to the network subset, while all other routers in the network subset...http://www.google.de/patents/US6078590?utm_source=gb-gplus-sharePatent US6078590 - Hierarchical routing knowledge for multicast packet routing
