Perhaps the most changing requirement of IPng faced by the IETF is the need to support the transition from IPv4 to IPv6. The anarchistic structure, which gives the Internet many of its strengths, combined with the very large installed user base makes change to a new protocol a major headache. Not only is it impossible to co-ordinate a limited changeover period it is difficult even to guarantee that every node will eventually be upgraded. box.ps As a consequence the transition to IPv6 has been designed to allow node by node upgrade. The primary features of IPng that support piecemeal upgrade are:
While there is the potential for support for IPv4 to eventually be dropped some analysis believe that the need to further upgrade the IP protocol is likely to occur before all nodes are IPv6 capable.