single dns query for A and AAAA

[Tassos Chatzithomaoglou]

Havard Eidnes wrote on 19/2/2013 09:46:
>> So, i was wondering if anyone has compared the following two
>> scenarios in terms of speed, performance and IPv4v6/IPv4
>> preference:
>>
>> 2 simultaneous dns queries (a & aaaa)
>> 1 single dns query (any)
>>
>> I'm almost 100% sure that the "any" query will be too heavy for
>> many domains (esp with DNSSEC), [...]
> That's not the primary issue with that method.  The issue is that
> this will simply not work, for other reasons:
>
> For this to work, the client machine would have to ask one of the
> authoritative name servers for the zone in which the name you
> query for is located.  That's however not normally what you do:
> instead, a client machine (which normally just implements a stub
> resolver) sends its query to a local recursive resolver, who then
> takes it upon himself to find the name servers for the zone to
> query.  This recursive resolver has a cache, and if some other
> client has already asked the recursive resolver for the "A"
> record for the name you want to query with "any" for, you will
> get as a response to your "any" query whatever the recursive
> resolver has in its cache for the name at that particular point
> in time, in this case just the "A" record, even though there may
> exist an "AAAA" record (and other records) in the zone served by
> the authoritative name servers for the zone.  Such is the nature
> of "any" queries.
>
> I'll leave it to somoeone else to follow up on your other
> questions / suggestions.
>
> Regards,
>
> - Håvard
>
>
Thanks for the info Havard. So "any" is out of the question.

--
Tassos