Old / new NAT-PT coexistance?

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

Question for the WG:

Do we care about coexistance of old style and new style NAT-PT?

The new style that Brian and I are working on is going to require  
changes on the IPv6 side, which won't be made over night: looking up A  
records by the hosts themselves rather than having a DNS ALG generate  
synthetic AAAA records for IPv4-only destinations.

The problem is that you would have to provision different DNS  
resolvers for hosts that are IPv6-only and do not support the new  
style NAT-PT versus the ones that do and dual stack hosts. This could  
be a problem. Solution: have hosts that do DNS lookups over IPv6  
transport indicate that they support new style NAT-PT and don't need  
the synthetic AAAA records through EDNS0.

Is this something we want or can we assume that old style NAT-PT is  
dead so we don't have to consider issues relating to it?