Bind algorithm for Name server selection

[phn at icke-reklam.ipsec.nu]

Bryan Giordano <scapin at gmail.com> wrote:
> I'm trying to understand the algorithm that BIND 9.2.2 uses to figure
> out which Nameserver to use when there are multiple ones returned from
> a query.
> Situation :=20
> I want the address for foo.bar.com.  I query the root DNS servers and
> find out that foo.bar.com is served by ns1.bar.com and ns2.bar.com.
> =20
> 1. How does BIND decide which of the two NS servers should be queried? =
 =20
by observing their responses(if any) and the corresponding response time
> 2. What if NS1 goes down? =20
after a timeout another server ( the second best) will be tried, the=20
first will have it's "score" a lot worse
> 3. I've heard that there are weights assigned based on the number of
> successful queries made to each NS.  Is this so?
Sort of, response time is stored as a running-mean value,see the
source for details.
> 4. If weights are assigned, when are they reset? =20
the arn't. Againg, read the source or visit one of Crickets Liu's
dns-courses ( or mine :-)
> =20
> =20
> All help is appreciated. Thanks,
> -Bryan


--=20
Peter H=E5kanson        =20
        IPSec  Sverige      ( At Gothenburg Riverside )
           Sorry about my e-mail address, but i'm trying to keep spam out=
,
	   remove "icke-reklam" if you feel for mailing me. Thanx.