Patent ID: 7577141

Claim:
A communication system comprising: an IPv4 network for transferring packets according to an IPv4 multicast (MC) address; an IPv6 network for transferring packets according to an IPv6 MC address; an MC adaptive translator T 1 having an IPv6 MC address translation table in which MC group address and MC server address of IPv6 and virtual MC group address and virtual MC server address of IPv4 are stored in association with one another, the translator T 1 mutually connecting the IPv4 network and the IPv6 network and carrying out IPv4-IPv6 MC packet conversion; an IPv4 DNS server D 1 that is connected to the IPv4 network and responds to a Domain Name System (DNS) request from an IPv4 MC client; a DNS proxy D 3 that is connected to the IPv6 network and has an IPv6 MC address managing table for storing a domain, an MC group address, an MC server address, a virtual MC group address and a virtual MC server address in association with one another; and an IPv6 network DNS server D 2 that is connected to the IPv6 network and has an MC address managing table for storing a domain, an MC group address and an MC server address in association with one another, wherein the MC client of the IPv4 network transmits a DNS request 1 as an MC address notifying request to the IPv4 DNS server D 1 by using as a key a domain of an MC server of the IPv6 network whose content is viewed/listened to; the IPv4 DNS server D 1 transmits a DNS request 2 of the domain concerned while a virtual IPv4 unicast address of a DNS proxy D 3 existing in the IPv6 network is set as a destination address; the DNS proxy D 3 transmits a DNS request 3 of the domain concerned to the IPv6 DNS server D 2 ; the IPv6 DNS server D 2 searches the MC address managing table and returns the MC group address and the MC server address of the MC server of the domain to the DNS proxy D 3 ; the DNS proxy D 3 registers the received MC group address and MC server address into the IPv6 MC address managing table, and transmits a request for generating the virtual MC group address and virtual MC server address corresponding to both the addresses concerned to the translator T 1 ; the translator T 1 generates the virtual MC group address and the virtual MC server address of IPv4 corresponding to the received MC group address and MC server address respectively, registers the virtual MC group address and the virtual MC server address into the IPv6 MC address translation table and transmits the virtual MC group address and the virtual MC server address to the DNS proxy D 3 ; the DNS proxy D 3 registers the received virtual MC group address and virtual MC server address into the IPv6 MC address managing table and transmits the virtual MC group address and the virtual MC server address to the IPv4 DNS server D 1 ; and the IPv4 DNS server D 1 transmits the virtual MC group address and virtual MC server address of the MC server of the domain to the MC client of the IPv4 network NW 1 .