China Mobile The period of IPv4/IPv6 transisation will last for a long time. Different phases of IPv4/IPv6 transisation have different scenarioes and requirements thus need different solutions. In the early stage of IPv4/IPv6 transisation, sicne the majority of the Internet resources locate in the IPv4 Internet, the main communication type of the IPv4/IPv6 transition is v6 to v4 which is the IPv6 clients iniate communication to the IPv4 servers. At the later stage of the IPv4/ IPv6 transisation, the servers may locate in the IPv6 network/ Internet, in this scenario, there is a need for the legacy IPv4 client to iniate communication to the IPv6 servers. This document analyses the problems of v4 to v6 communication and discusses a solution called PNAT-Lite.