It is becoming increasingly apparent that the IETF Mobile IPv6 protocol will have a role to play in future mobile and wireless networks. However, it is extremely likely that even after a real world deployment of IPv6, a considerable number of
‘legacy’ IPv4 applications and devices will remain in regular use for many years to come. Recently, much work has been focussed on developing protocols and tools to ease the transition from IPv4 to IPv6, yet despite mobile systems being one of the primary motivations for IPv6 deployment, none of these protocols and tools are designed to operate in a mobile environment. This paper documents the motivation, design, implementation and experimental evaluation of Mobile 4-in-6, a mobile aware IPv4/IPv6 transitioning technology based upon the Mobile IPv6 standard, that provides transparent support for IPv4 only applications in IPv6 only environments