In a Triple Play network, client devices can use SLAAC to dynamically obtain their IP address and other network configuration information.
During bootup, the client sends a Router Solicit (RS) message to get an IP prefix.
The BNG address server can assign a prefix statically to the subscriber through RADIUS or LUDB. Or, dynamically using the local address server.
The BNG address server replies to the client with a Router Advertisement which contains a /64 prefix.