Mark Andrews wrote:
The Internet went to multi-label hostnames ~20 years ago.
As noted in RFC 2821 as "one dot required" syntax, also
mentioned in RFC 3696. Recently *overruled* by 2821bis.
There is a difference between allowing protocol to be used
in a "local" only mode (single label) and a "global" mode
(multi-label) and saying you must support single label in
a global context.
Single label names are local in scope. Attempting to use
them in a global context does not work. As the names in
"." get more interesting the probability of collisions with
existing names goes up. Not many people choose two letter
labels for the least significant parts of their host names
unless they are choosing their initials.
Museum on the other hand is a real English word. I'm sure
you will find lots other uses of "museum" in the DNS. The
same thing will happen with other TLD's as the rules are
relaxed.
Single label hostnames are not globally unique. They SHOULD
NOT be used in a context where globally unique names are
required.
Mark
Additionally we have RFC 1535 warning about the consequences
of treating global address as local in a addition to choosing
a bad definition of local for a search list.
The reverse is equally true. Mail that was intended for a
local receipient may end up being delivered globally. Not
everyone in a organisation tracks the comings and goings
of local addresses.
The sender may not even be local if a .forward contains
"user(_at_)tld" and tld goes away locally.
Mark
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: Mark_Andrews(_at_)isc(_dot_)org
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