DIGITAL CABLE BROADCAST SYSTEM AND BROADCAST DATA TRANSMITION METHOD USING IP MULTICAST TRANSFORMATION MECHANISM

摘要

PURPOSE: A digital cable broadcast system using the change method of IP(Internet Protocol) multicast and broadcast data transmission method are provided to promote the compatibility of a system by enabling a user to use a cheap cable modem instead of an embedded type cable modem. CONSTITUTION: A head-end system(100) creates a first type multicast packet for a first type cable modem(211). A destination address of the first type multicast packet changes the destination address of a multicast change server(180) in order to be separated from a multicast group address of the first type cable modem. A CMTS(Cable Modem Termination System)(170) changes the multicast group address of the first type multicast packet into a DSG(DOCSIS Set top-box Gateway) tunnel. The CMTS does not change the multicast group address of a second multicast packet into the DSG tunnel.