Three Transition from IPv4 to IPv6 strategies are 1. Dual Stack 2. Tunnelling 3. Header Translation
1. DUAL STACK
In this kind of strategy a station has a dual stack of protocols run IPv4 and IPv6 simultaneously. To determine which version to use when sending a packet to a destination, the source host queries the DNS. If the DNS returns an IPv4 address, the source host sends an IPv4 packet. If the DNS returns an IPv6 address, the source host sends an IPv6 packet.
Fig. Dual Stack
2. Tunnelling
Tunnelling is a strategy used when two computers using IPv6 want to communicate with each other and the packet must pass through a region that uses IPv4. * To pass through this region, the packet must have an IPv4 address. So the IPv6 packet is encapsulated in an IPv4 packet when it enters the region. * To make it clear that the IPv4 packet is carrying an IPv6 packet as data the protocol value is set to 41.
Header Translation
In this case, the header format must be totally changed through header translation. The header of the IPv6 packet is converted to an IPv4 header see figure.
Fig. Header Translation