Yahoo and IPv6

[gbonser at seven.com (George Bonser)]

> 
> Because that way the IPv4 and IPv6 swarms remain disconnected in the
> absence of some dual stack peers. (I.e., if the swarm is small and
> you're the only IPv6 participant.)
> 
> It would be much better if you could go from IPv6 to IPv4 through a
> NAT64.

The problem is when the client is handed an explicit address rather than
a host name.  In that case, there needs to be some standard environment
variable for "IPv64 Prefix" that applications can query.

For a browser this might be something like the configured proxy.  Maybe
an OS such as Windows might have a registry value for this.  Maybe Linux
and other unix-like variations could have a sysctl for that.

There should be some standard way for a native v6 host to determine the
v6 to v4 prefix to use in a NAT64 environment.