Patent ID: 7630637

Claim:
An optical network unit that is connected to an optical line terminal (OLT) connected to a wide area network via an optical splitter and a first line connected to the optical splitter and selectively sends unicast data and multicast data received via an optical splitter and a first line connected to the optical splitter from the OLT to a user terminal, comprising: a multicast monitor for receiving the multicast data sent from wide area network to the OLT according to the requirement of the other ONT connected to the OLT via the optical splitter and a second line connected to the optical splitter and sent from the OLT via the optical splitter and monitoring the distribution state of the multicast data without the requirement of the user; and a first table showing the distribution state of multicast data monitored with the multicast monitor corresponding to a multicast group identifier, wherein, when receiving a control message indicating a request of participation in the multicast group from any of the user terminals, the optical network unit determining whether multicast data of the multicast group specified by the control message is in service from the wide area network to the OLT according to the requirement of the other ONT based on the first table, and wherein, when the multicast data of the multicast group specified by the control message is already in service from the wide area network to the OLT, the optical network unit starting distribution of the multicast data received via the first line and being in service according to the requirement of the other ONT to the sender user terminal of the control message without sending the control message to the optical line terminal.