For PCCW’s 6M network service, the ADSL modem has four RJ-45 ports. If a NOW set-top box is connected to one of the ports, the IP address obtained is internal IP address 192.168.X.Y. Only this IP address range is able to access the multicast network for viewing NOW broadband TV.
However, for desktop or notebook PC connected to the ADSL modem port, the IP address obtained is a routable public unicast IP address. How come the set-top box get a private IP address and PC gets a public IP address. The answers are simple. The MAC address of the set-top box is known so a special IP address range can be assigned upon the DHCP connection. If PCCW assigns public IP addresses to both PC and set-top box, it will have to double the IP address resource. So long as private IP address can serve the IPTV delivery, there is no reason to deploy another IP address.
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