19. Dual Stack It is the most basic mechanism to support the connectivity between IPv4 and IPv6 protocols. This mechanism relies upon all the network nodes which have both IPv4 and IPv6 protocol stacks.
20. Tunneling This mechanism works to communicate among the IPv6 nodes. If the network has both IPv4 and IPv6 nodes then this mechanism is used to provide interconnection among IPv6 nodes.
21. Translation This mechanism handles the communication from IPv6 nodes to IPv4 nodes or vice versa. The translation mechanism provides a nice solution to the end users but it is a bit complex.