Bind9.5.1 under no Root Name Servers

[Mark Andrews]

In message <200907171319.n6HDJs31003525 at dc.cis.okstate.edu>, Martin McCormick writes:
> What does bind9.5.1 do when there is an Internet issue and we
> loose all root name servers?
> 
> 	The bind9.3.x we had been running always began producing
> tons of lines saying that there were no more recursive clients. I
> had written a program that looked for the time stamp when the
> mess starts and then for the time stamp of the last distress
> call and we called that an outage since bind certainly wasn't
> happy.
> 
> 	We had a very brief outage on the day we switched to
> bind9.5.1 and I saw nothing remarkable in the named.log file
> during the period where we lost all roots. Either bind9.5.1
> doesn't produce this message or the hit just didn't last long
> enough for all the recursive slots to fill up.
> 
> 	We do allow recursion from within our network but
> disallow it for 3RD parties.
> 
> 	Bind is an excellent place to take the pulse of one's
> whole network since it is so closely tied to everything else.
> 
> 	Here is an actual example of the message we look for:
> 
> 08-Jul-2009 08:38:20.296 client 139.78.102.224#53631:
>  no more recursive clients: quota reached
> 
> Martin McCormick WB5AGZ  Stillwater, OK 
> Systems Engineer
> OSU Information Technology Department Telecommunications Services Group
> _______________________________________________
> bind-users mailing list
> bind-users at lists.isc.org
> https://lists.isc.org/mailman/listinfo/bind-users

	BIND 9.5.1 does a better job of shedding load when the
	nameservers for a query are unreachable than 9.3.x does.
	BIND 9.5.1 also detects duplicate queries and drops them,
	BIND 9.3.x doesn't.  Both of these will help prevent the
	recursive quota being reached.

	BIND 9.5.1 will only allow so many queries for a given
	<qname,qtype,qclass> to queue, after that it will just drop
	new queries (servfail TCP).  The pushes the queuing back
	into the clients.  The amount of queries auto tunes and
	ranges between 10 and 100 clients per query in a default
	configuration.

	Mark

-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org