DNS hosting issues

Randy Bush randy at
Sat Apr 4 17:41:12 CDT 2009

> IMHO, fate-sharing as a strategy for increasing availability is
> somewhat underrated.

from rfc 2182 

3.3. A Myth Exploded

   An argument is occasionally made that there is no need for the domain
   name servers for a domain to be accessible if the hosts in the domain
   are unreachable.  This argument is fallacious.

     + Clients react differently to inability to resolve than inability
       to connect, and reactions to the former are not always as
     + If the zone is resolvable yet the particular name is not, then a
       client can discard the transaction rather than retrying and
       creating undesirable load on the network.
     + While positive DNS results are usually cached, the lack of a
       result is not cached.  Thus, unnecessary inability to resolve
       creates an undesirable load on the net.
     + All names in the zone may not resolve to addresses within the
       detached network.  This becomes more likely over time.  Thus a
       basic assumption of the myth often becomes untrue.

   It is important that there be nameservers able to be queried,
   available always, for all forward zones.


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