Re: [dbound] [DNSOP] Over on the dbound list: draft-dcrocker-dns-perimeter-00

[Dave Crocker <[e-mail]>]

Bob,

On 4/4/2019 7:17 AM, Bob Harold wrote:
> I have two questions:
> 
> If I want to separate these levels:
> example.
> a.example.
> b.a.example.
> 
> Then a.example is both a 'begin' and 'end' node.  Do I put in two 
> records,  one for 'begin' and one for 'end'?

First, note that Perimeters are actually /between/ node names.  So the 
above would be:

 > example.
   {perimeter}
 > a.example.
   {perimeter}
 > b.a.example.

Some choices for marking these will depend upon the specific Schema that 
is defined.  So, for example, I could imagine a Schema that demands an 
'end' above a 'begin' and I could imagine a Scheme that merely requires 
either one to be in place, or requires a specific one.

So for a simple hierarchy there might a schema specification might 
merely mandate that each perimeter down a hierarchy be marked by a new 
'begin':


   {perimeter}

 > example.
   \
    ._perim TXT begin <schema>

   {perimeter}

 > a.example.
   \
    ._perim TXT begin <schema>


   {perimeter}

 > b.a.example.
   \
    ._perim TXT begin <schema>


Each _perim record, in the above sequence, for example., is declaring 
that there is a Perimeter above the associated DNS node name.

but yes, the requirement might be for more verbosity:


   {perimeter}

 > example.
   \
    ._perim TXT begin <schema>
    ._perim TXT end <schema>

   {perimeter}

 > a.example.
   \
    ._perim TXT end <schema>
    ._perim TXT begin <schema>


   {perimeter}

 > b.a.example.
   \
    ._perim TXT end <schema>
    ._perim TXT begin <schema>

And my having to write this response makes me suspect there's some 
benefit in adding an end-begin shorthand to the specification, to reduce 
the verbosity and permit a single record to declares Perimeters both 
above and below the node.  It's purpose would be for Perimeter hierarchy 
have a one-name level, such as your example (and I suspect would be a 
common use.)


> Secondly, if I have:
> a.example.
> b.a.example.
> c.a.example.
> d.a.example.
> ...
> z.a.example.
> 
> And I want to separate z.a.example, but not the others, and there are 
> often changes to the list.  Without having to mark every one, how can I 
> (as a.example), mark above the cut that z.a.example is separate?

Cool.  Subset of branches.

 > a.example.
 > b.a.example.
 > c.a.example.
 > d.a.example.
 > ...
 > z.a.example.
   \
    ._perim TXT begin <schema>

would clearly work.

If there were a need to instead have a.example make the declaration, I 
don't see an obvious answer.

My first thought is for the Scheme to have a sub-notation, to indicate 
that the presence of the Perimeter is not for all branches, such as by 
having it list the children links it applies to.  But that's not feeling 
terribly satisfactory.

d/

-- 
Dave Crocker
Brandenburg InternetWorking
bbiw.net