Subject: closest encloser

From: Edward Lewis <[email-masked]>
Date: Fri, 11 Mar 2005 14:52:08 -0500

I've been getting mail asking to clarify words involving "closest 
encloser" in the context of negative answers.  Since I cannot devote 
enough time *at this moment* to the issue, here is a short "guide."

Assume this is one zone (no cut points), no DNAME anywhere...

"Normal" example:
                         .
                         |
                       example
                     /   |    \
                    *   bar  zed
                             /  \
                        alpha    omega

QNAME=foo.example.

The closest encloser is example.
The source of synthesis is *.example.
If there is a QTYPE match with the types at *.example, synthesize.

QNAME=foo.bar.example.

The closest encloser is bar.example.
There is no source of synthesis, *.bar.example. is not on the tree.

"Abnormal query, normal tree"

QNAME=foo.*.example.

The closest encloser is *.example.
There is no source of synthesis, *.*.example. is not on the tree.

"Abnormal tree"
                         .
                         |
                       example
                     /   |    \
                    *   bar  zed
                    |        /  \
                    *   alpha    omega

QNAME=foo.example.

The closest encloser is example.
The source of synthesis is *.example.
If there is a QTYPE match with the types at *.example, synthesize.

QNAME=foo.*.example.

The closest encloser is *.example.
The source of synthesis is *.*.example.
If there is a QTYPE match with the types at *.*.example, synthesize.

Notice that in the first example, *.example is a source of synthesis. 
In the next example it is a closest encloser.  The role the name 
takes on is relative to the QNAME value.  For any QNAME, no domain 
can be both the closest encloser and the source of synthesis.

QNAME=*.*.example.

This results in an exact name match, you're in part a (1034/4.3.2/Step 3).

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

Achieving total enlightenment has taught me that ignorance is bliss.

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