IPv6 Tunneling Techniques[/caption]
IPv4 to IPv6 tunneling refers to using the existing routing infrastructure of your IPv4 address to carry the imminent IPv6 traffic. This helps to successfully transition to IPv6 by ensuring compatibility with the IPv4 hosts and routers installed at present. Besides, maintaining compatibility between the infrastructure systems also allows you to streamline the process of transitioning to IPv6. That is because you can still use the IPv4 routing infrastructure while deploying IPv6 to make the most of the available resources.
IPv4 or IPv6 routers and hosts can tunnel IPv6 datagrams over IPv4 address routing topology by including them within the available IPv4 packets. In general, IPv4 to IPv6 tunneling can be done in the below ways.
- Router-to-Router: Here, the IPv4 or IPv6 routers are interconnected via an IPv4 infrastructure to tunnel IPv6 packets between the systems. This means that the tunnel covers any specific segment of the end-to-end path taken by the IPv6 packet.
- Host-to-Router: In this case, the IPv4 or IPv6 hosts tunnel the IPv6 packets to an intermediary IPv4 or IPv6 router that is accessible via the existing IPv4 infrastructure. Here, the tunnel covers only the first segment of the end-to-end path of the IPv6 packet.
- Host-to-Host: This refers to interconnecting the IPv4 or IPv6 hosts through an IPv4 infrastructure to tunnel the IPv6 packets between the systems. In this scenario, the tunnel covers the entire end-to-end path taken by the IPv6 packet.
- Router-to-Host: Here, the IPv4 or IPv6 routers tunnel the IPv6 packets to the final destination host, be it IPv6 or IPv4. This means that the tunnel covers only the last segment of the IPv6 packet’s end-to-end path.
IPv4 Address Routing Topology[/caption]
Usually, the IPv4 to IPv6 tunneling techniques are classified based on the method that is used by the encapsulating node to determine the IP address of the node at the end of the path. For instance, in case of router-to-router or host-to-router tunneling techniques, the IPv6 packet is tunneled to a router, whereas in a host-to-host or router-to-host scenario, the IPv6 packet is tunneled to the final destination.
In any case, the encapsulating node or the entry node of the tunnel creates the IPv4 header to include and transmit the IPv6 packet, while the exit node of the tunnel receives the IPv6 packet, takes out the IPv4 header, updates the packet with an IPv6 header, and processes the packet for further use. Nonetheless, the entry node of the tunnel is always required to maintain soft state information, such as the maximum transmission unit, to process the IPv6 packets transmitted to the exit node.