Re: clarification re mdns/llmnr

Rob Austein <sra+namedroppers@hactrn.net> Wed, 11 September 2002 18:03 UTC

Date: Wed, 11 Sep 2002 13:44:59 -0400
From: Rob Austein <sra+namedroppers@hactrn.net>
To: Aidan Williams <aidan.williams@motorola.com>
Cc: namedroppers@ops.ietf.org, levone@microsoft.com, bernarda@microsoft.com, dthaler@microsoft.com
Subject: Re: clarification re mdns/llmnr
In-Reply-To: <3D7E915C.2000601@motorola.com>
References: <200208281155.HAA24447@ietf.org> <3D7E915C.2000601@motorola.com>
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At Wed, 11 Sep 2002 10:42:04 +1000, Aidan Williams wrote:
> 
> On the zeroconf mailing list i recently wrote this:
> 
>   > Before leaping into the next set of comments I should summarise what
>   > I believe the state of play is with zeroconf naming.  I have been
>   > following the discussion in dnsext, and my understanding was that
>   > there was general agreement on the following points:
>   >
>   >   - mDNS/LLMNR was *not* DNS,
>   >     rather it was a seperate protocol, seperate port,
>   >     seperate cache, etc
>   >
>   >   - there was agreement that mDNS/LLMNR should not be used
>   >     as a substitute for DNS -- ie should not be used for
>   >     looking up "one true DNS names"
>   >
>   >   - that mDNS/LLMNR should not be used to transport DNS requests
>   >     to a "back end resolver"
>   >
>   > In my opinion, these comments also apply to the IPv6 Node
>   > Information Query proposal as well.

I think I believe all of the above.

>   > Right now, the -12 LLMNR document has examples with FQDNs in them.
>   > Unless there have been conversations that I am unaware of, I
>   > believe it was the intent of the working group *not* to support
>   > the resolution of names such as mylaptop.microsoft.com using LLMNR.

I don't think I believe this one, although I could of course be wrong.

If it's a separate namespace, it's a separate namespace.  The fact
that a name in one might happen to look like a name in the other is
not in itself a reason to forbid it.

The real question underlying all of this, however, is how these names
are going to be used.  In particular, how applications are going to
deal with the general problem of having multiple discrete namespaces,
most particularly applications that were not designed to support such
a thing.  Solve that, and the question of whether there's a strong
reason to restrict the syntax of LLMNR names will probably be obvious.

Once upon a time (back when dinosaurs still roamed the machine rooms
in mighty herds) I used a mailsystem on which a fully-specified
address in the MUA looked like

  sra@xx.lcs.mit.edu.#Chaos
  sra@xx.lcs.mit.edu.#Internet

while saying just

  sra@xx.lcs.mit.edu

was an invitation to the MUA to pick whichever naming realm it felt
good about today.  The mail software of course stripped the .#whatever
tag off the end before handing the message off to the MTA, so this was
strictly a user interface issue, not a protocol issue.

I'm not suggesting reviving that particular user interface or
notation, just pointing out that this is not the first time that this
problem has arisen, and that there's more than one way to attack this
kind of problem.

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Re: clarification re mdns/llmnr Rob Austein