does bind caches no replies ?

[Simon Waters]

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Ladislav Vobr wrote:
>
> I did some
> research but could not discovered how often bind is retrying
or what are
> the time-outs.

With BIND 9 I remember visiting the source code to try and
understand some of these stranger behaviours.

If a name server is unresponsive (within timeout settings), BIND
9 associates a large time penalty. Since it tries the server
with the fastest response first this server is thus last to
query for a domain.

However if all servers for a domain are unresponsive, all
servers get the penalty, and thus they are queried much as usual.

It is a no win situation as the usual cause is that your network
connection is bust (so all remote name servers are
unresponsive), so if we then said lets wait 10 minutes before we
try again, we'd be overwhelmed with "why does it take 10 minutes
for my name server to work after my modem/ISDN/leased line is
interrupted?" questions.

I think you have to hope that the authors of the clients will
build in exponential back off or similar safeguards, like most
mail servers, or scale your DNS for a worst case scenario.

Don't be shy in suggesting such sites try an offsite DNS server,
or longer TTL. If you're an ISP you could offer to be a
secondary if it makes your life easier, or tell one of your
salesmen that they need your help ;-)
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