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Re: is reverse dns required? (policy question)

  • From: Henning Brauer
  • Date: Sat Dec 04 10:23:40 2004

* william(at) <[email protected]> [2004-12-04 16:14]:
> On Sat, 4 Dec 2004, Henning Brauer wrote:
> >    Thus we propose expanding the reverse DNS tree with a subdomain with
> >    the well known name
> > 
> >        _srv
> > 
> >    This subdomain MAY be inserted at any level in the DNS tree for IPv4
> >    IN-ADDR.ARPA reverse zones.  For IPv6, to limit the number of DNS
> >    queries, _srv is only queried at the /128 (host), /64 (subnet) and /
> >    32 (site) level.  That way it can either provide information for a
> >    specific IP address or for a whole network block.  More specific
> >    information takes precedence over information found closer to the top
> >    of the tree.
> So if I want to check on, I first do lookup on 
>   _srv.
> if that does not give any answer, I'll have to do lookup on
>   _srv.2.1.127.IN-ADDR.ARPA
> if that does not give any answer, I'll have to do lookup on
>   _srv.1.127.IN-ADDR.ARPA
> And if that does not work, I still have to do lookup on
>   _srv.127.IN-ADDR.ARPA

that is how it works.

> Is that how you expect it to work? If that is so, I do not like it
> because it forces to do these multiple lookups.

these lookups are cheap, and with increasing deployment I expect the 
the vast majority of lookups to have matches on /32 (1st query) or /24 
(2nd query). but anyway, these lookups are reasonably cheap.

Henning Brauer, BS Web Services,
[email protected] - [email protected]
Unix is very simple, but it takes a genius to understand the simplicity.
(Dennis Ritchie)