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

[Jeffrey Hutzelman <[e-mail]>]

On Tuesday, August 30, 2005 15:55:56 -0700 Ned Freed 
<[e-mail]> wrote:

> IMO this needs major work even before being approved as experimental. The
> overlapped namespace approach in particular seems hugely problematic and
> IMO needs to be replaced.

I've only read this document briefly, but based on what I've seen and on 
the descriptions and explanations in the current discussion, I have to 
agree.  The overlapped namespace approach has significant problems, which 
have been mentioned here.  It generates load in the form of additional 
queries on caching servers and on the global DNS roots for names those 
servers are never expected to be able to resolve, and in the form of 
multicast traffic on the local link for potentially every failed query 
against the global DNS.


It also creates massive ambiguities in the namespace, by allowing any host 
on the local link to claim any global DNS name which happens not to resolve 
at the moment (even if due to a temporary failure).  This means that names 
which are intended to be part of the global DNS namespace may resolve 
differently depending on one's location, or what hosts might be responding 
to LLMNR requests on the local network.

This is a problem so egregious that the IAB wrote a document about it 
(RFC2826).  While the majority of that document pertains specifically to 
recurring "alternate root" proposals, much of it applies equally well here 
-- "alternate roots" are a bad idea because they split what needs to be a 
single global namespace into several alternate namespaces.  The use of the 
overlapped-namespace approach with LLMNR does the same thing, only instead 
of creating a few alternate roots, it creates millions.


> P.S. Please note that I have taken no position on the LLMNR vs mDNS
> debate.  I haaven't even looked at the mDNS specifications.

Me either.

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