As I understand it, one of three things will happen:
(1) If the system implements mDNS, the .local domain is treated
specially, so this just goes out as a link-local request.
(2) If the system implements LLMNR, there will first be a global DNS
lookup for "twiki.local", which will fail. Then, a link-local name
request will be tried.
(3) If the system doesn't implement any link-local name resolution,
there will be a global lookup for "twiki.local" which will fail.
So, if people use .local domains on systems that implement LLMNR
instead of mDNS, this can result in lookups for .local in the global
DNS.
But, given that choices (2) and (3) involve the same interaction with
the DNS, I'm not sure how one can argue that LLMNR makes things any
worse than things would be without it. Perhaps you could argue that
mDNS makes things better, but that is only true for this one
non-existent TLD -- all three systems would generate a bogus global
DNS query if I did a DNS lookup for "isoc.frog".
Margaret
There's one other relevant difference to note here: If you do a DNS
lookup for "isoc.frog" you generate a bogus global DNS query. This is
true. But... do you habitually do DNS lookups for "isoc.frog"?
Well, in case 1 (mDNS), no, because it won't return a useful result, so
why keep doing it?
In case 3 (conventional DNS), no, because it won't return a useful
result, so why keep doing it?
In case 2 (LLMNR) the answer is yes, all the time, if you chose to call
your printer "isoc.frog", which LLMNR allows and encourages.
Stuart Cheshire <cheshire(_at_)apple(_dot_)com>
* Wizard Without Portfolio, Apple Computer, Inc.
* www.stuartcheshire.org
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