IP MULTICAST NETWORK

PROBLEM TO BE SOLVED: To provide a multicast network in which the processing load of a multicast server and consumption on the network band are reduced. SOLUTION: A packet is transferred from the multicast server through a router (MR 1) to a host belonging to a multicast group. The multicast server transmits an communication confirmation request packet with a multicast address as a destination to a host belonging to the multicast group in order to confirm communication with the host. When the communication confirmation request packet from the multicast server is received, each of hosts transmits a response packet to the multicast server, and the router which accommodates a plurality of hosts transmits a single communication confirmation response packet to the multicast server. The confirmation response packet contains: a response identification code of the same code as a request identification code contained in the communication confirmation request packet; and address information of the host that transmits the response packet. COPYRIGHT: (C)2005,JPO&NCIPI