A method and apparatus for a downstream router to inform an upstream router by use of packets of a new router command protocol that the upstream router is to forward multicast packets of a specified group to the downstream router. First the downstream router transmits a HELLO packet to upstream router...http://www.google.ca/patents/US20050157741?utm_source=gb-gplus-sharePatent US20050157741 - Multicast system for forwarding desired multicast packets in a computer network
