[v6test] Test methodology

[Thorsten Behrens]

Thomas Butter wrote:
> I think Vista prefers IPv4 over Teredo.
>
> According to
> http://technet.microsoft.com/de-de/library/bb727035(en-us).aspx it
> doesn't even query for AAAA records if only Teredo is available and it
> found an A record.
>   
True. There's a discussion - or several - about Teredo over here: 
http://lists.cluenet.de/pipermail/ipv6-ops/2007-April/001132.html

One of the points coming out of that discussion is that due to the way 
Teredo relays are set up on the Internet - or rather not set up, they 
are largely absent - an attempt to connect to an IPv6 host over Teredo 
is extremely unlikely to succeed.

Beyond that, it gets a bit fuzzy. I couldn't quite make out what "the 
truth" is - some testing with v6.ipv6p*rn.com may be in order once it's 
registered and  up and running. The statements I could find are:
1) Vista prefers IPv4 over Teredo-only IPv6 (truth)
2) Vista prefers IPv6 over IPv4 otherwise (truth)
3) Vista will not query AAAA if there is only an IPv6-Teredo address 
present on the client, no other IPv6 address configured on the client 
(documented)
4) Vista will query AAAA with only an IPv6-Teredo address present _if_ 
the host in question does not have an A record (claimed, to be tested, 
partially contradicts 3) above)
5) Applications can force lookup of AAAA records on Teredo-only clients 
by explicitly using the DnsQuery API for AAAA records. This is 
application-specific and will not help with IE, Firefox, or any Vista 
system components. (documented, presumed truth)

If 4) is true, then v6.ipv6p*rn.com should resolve on a Teredo-only 
Vista host. If the claims about the absence of Teredo relays are true, 
then the client should still be unable to actually connect to 
v6.ipv6p*rn.com, although it can be resolved.

For Vista Teredo-only clients, we know that v4.ipv6p*rn.com will resolve 
to an A record, and so will v46.ipv6p*rn.com. A client would thus be 
able to load content from both, but still have IPv6 enabled and largely 
non-functional due to DNS issues and the absence of a good Teredo relay 
network.

I do have Vista around here and can disable autoconfig on my router so 
that Vista will be forced to use Teredo. Give me a AAAA-only record - 
ideally not just a record but something that would load a page - and 
I'll do some testing, document my findings, and come back to the list 
with it.