Subject: RE: QType: ADDR

From: "Christian Huitema" <[email-masked]>
Date: Thu, 8 Aug 2002 09:35:33 -0700

> > Just a thought occurs...
> >
> > Instead of having a new query type 'addr', could we just define that
> > AAAA query returns both IPv4 and IPv6 addresses? (And if you want
> > uniform format in reply, put IPv4 addresses into IPv4 mapped format)
> 
> If I ask for MX, I want MX as the response. If I ask for AAAA, I want
AAAA
> in the answer. An option could be to respond to AAAA-queries with A in
the
> additional section, but that might also not be desirable, depending on
> your milage.

There is a difference between MX and AAAA: MX records for a domain may
point to another domain, for which the local server may or may not be
authoritative; also, there may be several MX records, and it is hard to
predict which of the records the client will select, and thus for which
of the names additional processing is the most useful. On the contrary,
the A and AAAA records are all attached to the same domain name.

We can predict that in most cases, a failing AAAA request will be
followed by an A request for the exact same name; in fact, there may be
strategies in which the host wants to consider the full set of AAAA and
A request and pick the "best one" according to some heuristic. This
looks like the definition for an "additional response": opportunistic
provision of records, because there is a high chance they will be
useful.

-- Christian Huitema

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