Whenever a host belonging to a subscriber is activated (when a PC or set-top box (STB) is turned on), the host typically requests an IP address from the network using DHCP. See the DHCP Management section for an explanation of DHCP and DHCP snooping in the router.
The DHCP ACK response from the DHCP server can be parsed and the contents of the message can be used to identify the class to which this host belongs, and therefore, the QoS and security settings to apply.
The information necessary to select these settings can be codified in, the IP address by the DHCP server and the Option 82 string inserted by the DSLAM or other access node.