Patent ID: 7400646

Claim:
A method of relaying multicast packet in a converting apparatus located between an IPv4 network and an IPv6 network for realizing IP multicast packet communication between an IPv6 terminal connected to said IPv6 network and a plurality of IPv4 terminals connected to said IPv4 network, comprising the steps of: receiving an instruction to become a member of a multicast group of an IPv6 multicast address which is a destination address of an IPv6 multicast packet to be relayed; storing said IPv-6 multicast address of said multicast group which received said instruction and an IPv4 multicast address held in said converting apparatus in a manner that said IPv6 multicast address of said multicast group is correlated to said IPv4 multicast address held in said converting apparatus; receiving an IPv6 multicast packet including said IPv6 multicast address as the destination address from said IPv6 terminal connected to said IPv6 network; converting said IPv6 multicast address to said IPv4 multicast address that is correlated thereto and stored in said converting apparatus; creating an IPv4 multicast packet including said IPv4 multicast address as the destination address from said IPv6 multicast packet; transmitting said IPv4 multicast packet created to said plurality of IPv4 terminals connected to said IPv4 network; and discarding a received IPv6 multicast packet when the IPv6 multicast address which is a destination address of the received IPv6 multicast packet is not stored.