The ultimate and preferred migration approach for applications that reside on a dual-mode TCP/IP host is to IPv6-enable the applications by migrating them from AF_INET sockets to AF_INET6 sockets.

There are multiple reasons why this approach is not always applicable, such as the following reasons:

• No access to the source code (vendor product, or source no longer available).
• The sockets API implementation does not yet (or never does) support IPv6.
• Resource availability or prioritization dictates a phased IPv6-enabling where not all applications can be available in an IPv6-enabled version at the same point in time where the stack is IPv6-capable.

For those applications that are not or cannot be IPv6 enabled, an alternative migration strategy is needed. The IETF has identified multiple approaches as summarized in draft RFC, An Overview of the Introduction of IPv6 in the Internet.

Some of the technologies that are defined by the IETF are supposed to be implemented on intermediate nodes that route traffic between IPv4 and IPv6 network segments. Other technologies are intended for implementation on the dual-mode IP nodes themselves.