The AA bit is a useless bit of frippery in the DNS protocol.

KD> Is this important? I have yet to find an application that
KD> cares about the setting of the AA bit.

I've found three: dnstracer, Sendmail, and BIND.

<URL:http://homepages.tesco.net./~J.deBoynePollard/FGA/dnstracer-incorrect-algorithm.html#RFCNonCompliance>
<URL:http://groups.google.com./groups?selm=bdprmb%242ncu%241%40FreeBSD.csie.NCTU. edu.tw>
<URL:http://groups.google.com./groups?selm=c3o04s%248tn%241%40sf1.isc.org>

Of course, the "AA" bit in DNS responses *is* a useless bit of frippery
in the DNS protocol. In using it, all three of those applications are
broken.

<URL:http://groups.google.com./groups?selm=3E9C4ABF.D8DE6467%40tesco.net>

Indeed, for quite a few years now every few months in the various DNS
server discussion fora someone new has come along having hit the bug in
BIND that results from its daft "credibility" mechanism.

<URL:http://cr.yp.to/djbdns/bugtraq/20000112082807-15140-qmail@cr-yp-to>