On 2/15/2013 3:17 PM, John C Klensin wrote:
--On Friday, February 15, 2013 14:10 -0800 Joe Touch
<touch(_at_)isi(_dot_)edu> wrote:
Let's just say that there doesn't appear to be disagreement
that the DNS can handle a-z/0-9/'-'.
Other values _may or may not_ be permitted or handled opaquely
in the lookup, AFAICT. It remains a question AFAICT.
Joe,
Except for IDNs (or labels starting with "xn--" more
specifically), for which there are special rules, it appears to
me that the spec is _extremely_ clear that a lookup operation
that fails to deal with those "other values" in labels
--including even properly-escaped embedded "." characters -- is
unambiguously non-conforming.
Seems clear to me:
RFC1035:
The labels must follow the rules for ARPANET host names. They must
start with a letter, end with a letter or digit, and have as interior
characters only letters, digits, and hyphen. There are also some
restrictions on the length. Labels must be 63 characters or less.
--
If any label were allowed, then why does IDN conversion go so far out of
its way to exclude particular strings, e.g., those beginning/ending with
'-' and encodes everything 0..7F into a-z/0-9?
(I was focused on looking up A records given FQDNs)
Joe