Re: draft-ietf-v6ops-nat64-pb-statement-req-00 - are changes in dualstack hosts acceptable or not?

[Iljitsch van Beijnum <[e-mail]>]

On 25 jul 2008, at 17:11, Rémi Denis-Courmont wrote:

>> So, the question is: is a dual stack host a v6 host (i.e. changes are
>> acceptable) or is it a v4 host (i.e. changes are not acceptable)?

> Regardless of the current requirements, I would argue it is not  
> acceptable
> that dual-stack nodes need to be modified, for the exact same reason  
> as it is
> not acceptable that IPv4-only nodes need to be modified: deployment  
> would be
> highly impractical.

Note that these issues aren't necessarily binary.

If a dual stack host is presented with synthetic AAAA records along  
with A records, the host will try to use translated connectivity when  
it could have used native connectivity. The requirements require that  
this is avoided. One way to avoid this is to upgrade hosts so they  
automatically prefer real A records over synthetic AAAA records. This  
is rather inconvenient, bu there are only 10 - 20 operating systems in  
the world. Another way to avoid this situation is to make sure that  
dual stack hosts are never served by a recursive nameserver with DNS64  
functionality. However, there are many thousands of ISPs and hundreds  
of thousands of organizations running significant networks in the  
world, which would all have to do this.

So yes, requiring host modifications is bad, but imposing operational  
restrictions has the potential to be much worse in time and money. On  
the other hand, everyone can change their own network, while few  
people can change their OS.