Abstract: The present invention provides one kind of IP telecom network system and its realizing method, and a method of building virtual private network and carrying out multicast based on this IP telecom network, and a method of managing resource in this IP telecom network etc. The IP telecom network system includes at least one complex address no-connection data network including at least one address mapping device, several IP networks and several edge pass devices for connection between the IP network and data network address. Each of the devices and the edge pass devices in the data network has one distributed data network address, each of the devices and the edge pass devices in the IP network has one distributed IP address, and the mapping relation between the IP address and the data network address is maintained in the address mapping table in the address mapping device.