Methods for IPv4-IPv6 transition

The future internet networks are expected to use IPv6 version rather than the IPv4 one. This is mainly due to the limitations of IPv4 in terms of addresses, routing and security. QoS issues developed by the internet Community are also tailored for both versions and will be easily deployed in both sides. Since a huge amount of sub-networks are already installed for the v4 version, it is difficult to imagine ISPs starting deploying the v6 version without some assurance that old legacy networks will still be able to connect to the internet. In this paper we present some mechanisms that have been proposed to ease this transition especially for v4 users that still want to communicate with their old applications. We present also an IPv6 tunneling mechanism that has some advantages over the other models. We show how one could use such a mechanism to transparently establish hybrid communications between the two worlds in both ways and discuss some important issues like scalability and performance.