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Re: Weird DNS issues for domains

  • From: Todd Vierling
  • Date: Thu Sep 29 15:50:34 2005

On Thu, 29 Sep 2005, Randy Bush wrote:

> >> You might want to consider reading RFC 2182 though, particularly the
> >> part about geographically diverse nameservers.
> > Yeah, yeah,  that is overrated.  If my site goes dark and my DNS goes
> > down it doesn't really matter as the bandwidth and the web server
> > will also be down.
>
> and folk who would otherwise spool mail for you will throw it
> on the floor.  enjoy.

As I tried to explain in the other response, if this were the case with said
unnamed MTAs, then a simple tier-1 outage (which is not all that uncommon)
or a site under packet flood attacks would cause immediate bounces due to
DNS timeouts.  The same thing applies to a site whose DNS is simply
unreachable because its link is down.

When a MTA gets a failed lookup response, it should retry.  When the domain
*does* resolve, but resolves to *empty or nonexistent*, then the mail should
bounce.  When a DNS server is unreachable, it can hardly return a NXDOMAIN
back to the requestor.  8-P

-- 
-- Todd Vierling <tv@duh.org> <tv@pobox.com> <todd@vierling.name>




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