> > > 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@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@xxxxxxx _______________________________________________ Ietf@xxxxxxxx https://www.ietf.org/mailman/listinfo/ietf