At 10:41 AM 5/26/00 , Markku Savela wrote:
>I suppose following has been discussed to the death in the dawn of
>IPNG, but ...
>
>When an application is presented with a domain name, it cannot know
>whether it maps to IPv6 or IPv4 address. Thus the resolver library
>needs to make a query for both A and AAAA records. (Right?)
Correct
>
>Just writing a resolver based on reading the RFC-1035, the first idea
>was: hey! you can put both queries into same message, just have the
>QDCOUNT=2...
>
>... but, we quickly found that apparently nobody supports such thing.
>
>Anyone care to comment the background of this: why the multiple query
>feature of RFC-1035 is not implemented?
There is no specification on the relationship of the queries is it
first match, match all that apply, or some other one.
Then there is the issue of error reporting, if there is a query for
first A6 and secondly A, and A6 does not exist is but A does is this
an error or not ?
>
>The KAME resolver appears to first send an AAAA query, and if that
>results an error, it then sends A query.
>
>Another idea is to send both AAAA and A in parallel and then use the
>first good answer, if any arrives. And, when A6 is added, we have 3
>queries to send?
>
There has been a suggestion to use a META query for IPv6 address records
but that was shot down as AAAA records are supposed to die soon.
If your host does not care if the connection is IPv4 or IPv6 then
doing the queries in parallel does not seem such a bad idea.
But us DNS people are going to scream as it doubles the
number of queries. If your host has preference query for that type first.
If I recall correctly you support A6 you MUST try that first before
issuing AAAA queries. Thus there will never be more than two queries
in parallel.
It is not likely that multiple queries will be standardized in the near
term.
Olafur
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