1.6 TRANSITION MECHANISMS

One of the most important issues in this text involves IPv4 compatibility mechanisms that can be employed by IPv6 hosts and routers. This type of mechanism yields a complete implementation of both versions of IPv4 and IPv6. In addition, there is also the issue of tunneling IPv6 packets over IPv4 routing infrastructures. They are created to permit IPv6 nodes to hold on to total compatibility with IPv4. This should make the process of deployment of IPv6 in the Internet must easier. It will also assist in the transition of the whole Internet to IPv6.

The most important aspect of a successful IPv6 transition involves compatibility with a large installed base of IPv4 hosts and routers. In order to achieve compatibility with IPv4 as you deploy, IPv6 will smooth out the chore of transitioning the Internet to IPv6. This specification designates a fixed number of mechanisms which IPv6 hosts and routers may utilize in order to be compatible with IPv4 hosts and routers.

The specific mechanisms described here are intended to be used by IPv6 hosts and routers that must interoperate with IPv4 hosts and employ IPv4 routing infrastructures. You should expect that the majority of nodes in the Internet will require such compatibility for the foreseeable future.

Yet, IPv6 may be employed in some environments in which interoperability with IPv4 is not necessary. IPv6 nodes which must be used in specific environments do are not required to use or implement these specific mechanisms.

The mechanisms described above...