Jack, a network engineer, is working on an IPv6 implementation for one of his clients. He deployed IPv6 on IPv4 networks using a mechanism where a node can choose from IPv6 or IPv4 based on an DNS…

Jack, a network engineer, is working on an IPv6 implementation for one of his clients. He deployed IPv6 on IPv4 networks using a mechanism where a node can choose from IPv6 or IPv4 based on an DNS value. After a successful implementation, Jack noticed that the nodes are still working in IPv4 network. He is trying to figure out which protocol is used by the nodes. What kind of technique did Jack use?