Re: Last Call: 'Linklocal Multicast Name Resolution (LLMNR)' to Proposed Standard

[Stuart Cheshire <[e-mail]>]

>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 <[e-mail]>
 * Wizard Without Portfolio, Apple Computer, Inc.
 * www.stuartcheshire.org


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