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

From: Stuart Cheshire <[email-masked]>
Date: Thu, 25 Aug 2005 18:51:34 -0700

>In The Public-Root there used to exist a domain ".local". I know at least
>of one ISP who complained we did break a lot of windowed PCs.
>
>I dont know why queries for ".local" would leave their private LANs and
>reach even our root servers. They did!
>
>That is why we set up a dummy and returned localhost, to get rid of those
>bogus queries. That is what finally broke their windows and dropped our
>root server traffic some 25%. :)

I don't think this has anything to do with mDNS or LLMNR.

Stuart Cheshire <[email-masked]>
 * Wizard Without Portfolio, Apple Computer, Inc.
 * www.stuartcheshire.org

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From: Stuart Cheshire <[email-masked]>
Date: Tue, 30 Aug 2005 08:44:08 -0700

>Peter,
>
>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?

Simple: If you call your printer "myprinter.local", and then type
"ping myprinter.local", LLMNR will *always* send a DNS query to the
root first, before rolling over to a local multicast query, whereas
mDNS (except when operating in "Microsoft compatibility mode") will
*never* send a dot-local query anywhere other than the local LAN.

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From: "Christian Huitema" <[email-masked]>
Date: Tue, 30 Aug 2005 10:28:26 -0700

> I cannot garantie it was LLMNR. I was told these are windows boxes
> using the default enabled LLMNR and it defaults to ".local". I know
> that newer windows boxes do have LLMNR but it is not normally used.
> Nevertheless it comes up.

Windows 98, Windows 2000 and Windows XP do not enable LLMNR by default.
Name resolution in these systems is performed through DNS or
NetBIOS/WINS. Hosts using these systems are not expected to be aware of
a complete list of top-level domains. Queries for "unknown domains" will
indeed be routed by default to the local DNS servers. 

One could argue that special knowledge for some reserved names (.local
or .example) should be "wired" in every host. But it is simpler to
program this knowledge in the local name servers, thus avoiding undue
traffic to the root servers without risking interop issues and name
conficts in local naming plans.

-- Christian Huitema

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From: Stuart Cheshire <[email-masked]>
Date: Wed, 31 Aug 2005 14:10:40 -0700

>Windows 98, Windows 2000 and Windows XP do not enable LLMNR by default.

Christian, could you please tell us, for each OS mentioned, how to enable 
LLMNR? That would enable everyone participating in this discussion to 
witness for themselves exactly how it works and what it does.

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From: "Christian Huitema" <[email-masked]>
Date: Wed, 31 Aug 2005 14:24:32 -0700

> witness for themselves exactly how it works and what it does.

You would have to get an experimental implementation of LLMNR from some
developer site. To the best of my knowledge, Microsoft is not shipping
this code. In these systems, ad hoc names are resolved through NETBIOS.
The ".local" queries observed in Peter's root servers is most certainly
not caused by an LLMNR implementation. 

In the absence of LLMNR, if an application tries to resolve "host.local"
through, say, gethostbyname, then the query will indeed be forwarded to
the local DNS service. The responsibility for the ".local" traffic lies
mostly into whoever is promoting use of this top level domain and coding
that use in applications.

-- Christian Huitema