Patent ID: 7715388

Claim:
A multicast system comprising: a plurality of terminal units; a first communication apparatus that sends a request for transmission of multicast data to a second communication apparatus and delivers multicast data to at least one of the terminal units upon receiving the multicast data from the second communication apparatus; and the second communication apparatus that establishes a connection with the first communication apparatus upon receiving a request from the first communication apparatus and transmits requested multicast data to the first communication apparatus through the connection, wherein the first communication apparatus includes a first multicast-control message receiving unit that receives a first multicast-control message from a terminal unit among the terminal units requesting delivery of multicast data; a determining unit that determines whether a connection needs to be established for multicast data specified by received first multicast-control message based on the first multicast-control message; and a connection-control message transmitting unit that transmits, according to the determination by the determining unit, a connection-control message to request connection establishment when a connection is required, and a connection-control message to request connection removal when a connection is not required, and the second communication apparatus includes a connection-control-message receiving unit that receives a connection-control message from the first communication apparatus; a connection controlling unit that controls a connection to the first communication apparatus according to received connection-control message; and a storage unit that stores therein a connection established by the connection controlling unit in association with corresponding multicast data.