Re: I-D ACTION:draft-bagnulo-v6ops-6man-nat64-pb-statement-00.txt

[Iljitsch van Beijnum <iljitsch@muada.com>]

On 23 nov 2007, at 12:27, David Miles wrote:

> again, why introduce translation between IPv6 hosts and legacy  
> servers when every OS I can think of that supports IPv6 also  
> supports IPv4 through dual stack.

Because that way operators need to keep running two versions of IP  
side by side. since everything is reachable over IPv4 anyway, this  
provides essentially zero benefit over the situation where you just  
have IPv4. This means people won't deploy IPv6 but will stick with  
IPv4 even when the layers of NAT are piled on.

With IPv6+NAT-PT on the other hand, the network can be IPv6-only which  
has a number of benefits over an IPv4 network, especially when IPv4  
addresses are scarce.

> After all, if we come up with a "translation" protocol for IPv6 to  
> IPv4 then we have not absolved ourselves from solving the issue for  
> non-IPv6 hosts.

Which issue?

> In an IPv4 address depleted world, non-IPv6 devices still need to  
> work!

They do, you just can't add new ones.

> The only scenario that I can see that we should at least discuss, is  
> a day when IPv4 addresses are scarce to the point that one cannot  
> assign a server a public v4 address, but we can assign it an IPv6  
> address. In this case an IPv6 host can communicate with the IPv6  
> server without issue, but an IPv4 client cannot. I have always  
> wondered why we are so fascinated with NAT64 instead of the reverse,  
> NAT46?

See section 4 of

http://www.ietf.org/internet-drafts/draft-van-beijnum-modified-nat-pt-02.txt