NAT is used only in IPv4. It is not necessary in IPv6, because IPv6 has enough addresses for every computer in the world to have a global address. IPv6 can, however, use network prefix translation, which translates the network prefix (usually the first 64 bits of the address) from private address space to public, but leaves the host identifier (usually the last 64 bits) the same. This creates a one-to-one mapping of IPv6 addresses and does not have the same drawbacks as traditional NAT.