Subject: Re: Who hates the DNAME?

From: Edward Lewis <[email-masked]>
Date: Tue, 10 May 2005 09:28:30 -0400

At 20:55 +0100 4/27/05, Niall O'Reilly wrote:

>What it comes down to is, not mixing the kinds of synthesis you use.
>
>Simple terminal (non-NS, non-DNAME) wildcard specifies a synthesis which
>might be called "default terminal substitution".  This is synthesis because
>the given QNAME does not match the NAME of any existing RR; an RRset is
>brought into existence on demand.
...
>Simple DNAME specifies "non-terminal substitution".  This is 
>synthesis because,
>just like the simple wildcard case, the given QNAME does not match the NAME of
>any existing RR.

About 2 trans-oceanic flights ago, I began to reply to this but put 
it aside.  Just know I came to grok the message - sometimes a message 
haunts you for a reason.

"* DNAME" is attempting a "simple terminal synthesis of a 
non-terminal substitution rule."  This is "non-deterministic 
synthesis" of a *rule*, not data, which is at the heart of the 
conflict with the operation of caching (non-authoritative, recursive, 
etc.) servers.

When rules are generated in a non-deterministic manner and fed to 
different caches, coherency of the database is lost.

-- 
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Edward Lewis                                                +1-571-434-5468
NeuStar

If you knew what I was thinking, you'd understand what I was saying.

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