[dns-operations] finding the longest encloser
jim at rfc1035.com
Tue Feb 16 23:50:24 UTC 2010
On 16 Feb 2010, at 22:27, Crist Clark wrote:
>> The SOA record does not contain the longest existing suffix. I think
>> you really need to know that the root is delegation-centric, or that
>> all delegations have a single label, combined with the SOA trick to
>> deal with the arpa. special cases.
> Shouldn't it always contain the longest valid zone? I mean, that's
> what it's there for right?
Yes and no. Once upon a time, I was co-author of a draft that
suggested using the SOA record in an NXDOMAIN response to find the
closest enclosing delegation. This was to be used in ENUM domain names
with ~20 labels and could have contain a handful of delegations:
walking up the domain name label at a time to find the deepest
delegation point (=> "closest" default SIP/PSTN terminator) would have
I was told that this was too clever by half and it wasn't acceptable
for clients to treat SOA records in this way because they were in the
Authority Section. Clients were supposed to only act on whatever was
in the Answer Section.
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