Patent ID: 7561570
Filing Date: 2009-07-14
Classification: H04L

Abstract:
1. An IP multicast distribution system comprising: a distribution server which generates an IP multicast packet with UDP packet format; a multicast/unicast conversion gateway which receives the multicast IP packet generated by the distribution server and which converts the IP multicast packet to an IP unicast packet; and an NAPT gateway which receives the IP unicast packet converted by the multicast/unicast conversion gateway and which transfers the IP unicast packet to a recipient host in a private network, wherein: if the NAPT gateway receives an IP unicast packet whose destination IP address is the global IP address of the NAPT gateway and whose destination port number has been designated by the NAPT gateway: the NAPT gateway converts the value of the destination IP address included in the IP unicast packet to the local IP address of the recipient host in the private network, and converts the value of the destination port number included in the IP unicast packet to a port number which the recipient host has designated to receive data; and the NAPT gateway sends the IP unicast packet to the recipient host through the private network, wherein the IP multicast packet transmits streaming data, and wherein: before receiving the IP unicast packet by the NAPT gateway, the recipient host sends a distribution request for the IP unicast packet to the NAPT gateway, the distribution request comprising the global IP address of the multicast/unicast conversion gateway as its designation IP address, a source port number which the distribution server has designated in order that a recipient application program executed on the recipient host receives packets corresponding to the request, and a designation port number as an acceptance port number for the multicast/unicast conversion gateway; in response to the distribution request, the NAPT gateway designates the global IP address of the NAPT gateway as a source IP address, and the acceptance port number as a source port number; and the NAPT gateway sends the distribution request to the multicast/unicast conversion gateway.