Labels start with a letter or digit. Labels end with a
letter or digit. Letter, digit or hypen in the middle of
the label.
All labels meet the above with the exception of a mbox where
second to last labels meet the above.
A single period can also be used as a place marker.
The rules are applied to the owner names of A, AAAA and
MX records.
NS and MX records rdata.
IN-ADDR.ARPA and IP6.ARPA PTR records rdata.
(I don't think I've missed any cases).
Underscore was choosen for SRV records so that they would
*not* clash with hostnames.
Active directory similarly uses underscore to *not* clash
with host names, gc uses a A record but as *all* the
particiants in AD are *known* to cope it is not a problem.
Mark
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: [EMAIL PROTECTED]
