recursive server querying authoritative - timeout before trying next server?

Kevin Darcy kcd at
Thu May 26 22:45:07 UTC 2011

On 5/26/2011 2:51 PM, Dan Pritts wrote:
> Hi,
> A question regarding BIND defaults.  I'd love the same answer for other nameserver software if anyone
> cares to share.
> I am a recursive nameserver.  I am looking for  i've learned from that has
> four NS records.  I've never tried to talk to these servers before.
> I send a query to the address listed in the first NS record.  I never get an answer?
> How long do I wait before trying the next one?
> I looked through several RFCs but couldn't find anything specific in the spec.  RFC1035 mentions
> that choosing this timeout would be up to nameserver implementors and suggests 5-10 seconds as
> a reasonable default.
> my google-fu is failing me on this one.  I found something at Microsoft that suggests that their DNS server
> waits 3 seconds although i may have interpreted that wrong.  I found a reference to a nameserver  called
> "deadwood" that defaults to 2 seconds.  But, I couldn't find anything on BIND.
         I don't know the exact timing, but with BIND it's on the order 
of tenths of a seconds (or 100s of milliseconds, if you prefer). 2 
seconds would be way too slow.

It shouldn't be hard to set up a test delegation with one "dead" 
nameserver and restart/query named a few times to see how long the 
failover takes...

                                                                 - Kevin

P.S. You guys are practically next door to where I live (Pitt Twp), let 
me know if you need any help with this :-)

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