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

[Margaret Wasserman <[e-mail]>]

Hi Brian,

>I'm afraid I don't understand. As far as I can understand,
>mDNS uses the .local pseudo-domain and LLMNR does not.
>So how can LLMNR be blamed for bogus queries for *.local?

The .local doesn't come from either mDNS or LLMNR...  The user types 
it and/or an application includes it in the domain name look-up.  So, 
if the user tries to look up "twiki.local", what happens?  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



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