Need clue: Underscore zones and hostnames

Hi,

Can someone please thwack me with the requisite clue-by-four and point me
at the RFC that Yea's or Nea's the use of the underscore character in
host and/or zone names? Google seems to not be helpful in finding a
definitive answer. Perhaps there is none?

Here's why I ask:
We current support Microsoft's Active Directory on our BIND nameservers,
with check-names disabled on the BIND8 machines, so we *have* zones with
underscore characters already working.

Recently for some odd reason people have been requesting hostnames like
martha_stewart.jailhouse.uga.edu. This "works" in as much as BIND doesn't
reject the name and does serve it (thanks to some legacy names :). We
also know that it's not recommended per various RFC's so we've been
rejecting these updates and manually going back to the user to get them to
fix it.

But since it works and we have zones that *depend* on this behavior, we're
wondering:
- Are we just missing an updated RFC that now allows this?
- Is an underscore allowed just for zones and still not for a host?
- Is this just an Microsoft-ism?
- Do we (or perhpas: should we) care enough to not let users shoot
themselves in their feet?

Note: I didn't setup the original AD-in-BIND infrastructure, and the
person who did is not here anymore. The docs we have fail to mention the
underscore issue and we're presently looking at various DNS changes we
want to make, including our request interface that can "fix" these before
they get to the update stage, hence my desire to have a clue about it :)

Thanks for any help anyone can give me.

-n

--
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nathan hruby <nhruby@uga.edu>
uga enterprise information technology services
production systems support
metaphysically wrinkle-free
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