Stateless translation and stateless double translation/encapsulation technologies (IVI/MAP-T/MAP-E) define the address mapping and protocol translation/encapsulation algorithms between IPv4 and IPv6. IVI/MAP-T/MAP-E technologies maintain end-to-end address transparency between IPv4 and IPv6 and support communication initiated by IPv4-only or IPv6-only end systems. Therefore, they are the very critical techniques for the IPv4/IPv6 coexistence and transition.