Maintained by: NLnet Labs

[Unbound-users] Forward zone query distribution

W.C.A. Wijngaards
Mon May 18 16:14:59 CEST 2015


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Hi İhsan,

On 18/05/15 15:56, İhsan Doğan wrote:
> Hi,
> 
> I've got a question how queries are distributed to forward 
> resolvers.
> 
> In this example, I've defined that all queries, which can't be 
> answered from the cache, are forwarded to Google's DNS servers:
> 
> forwared-zone: name: "." forward-addr: 8.8.8.8 forward-addr:
> 8.8.4.4
> 
> How are the queries distributed between 8.8.8.8 and 8.8.4.4? Are 
> all queries going to 8.8.8.8 because it's the first one, are they 
> distributed via round-robin or is the one with the lowest response
> time getting the most of the queries?

Initially at random.  Then, once the response time is known, one of
the fastest ones.  It picks one at random from the "RTT band", so
small differences in response time do not matter.  If ping time to
those two IP addresses is roughly similar, then it'll end up as a
50/50 split.

There is a lot more logic, mostly for interoperability with
malconformant servers or servers with DNSSEC-bogus content.  But for
this example that would not make a difference.

Best regards,
   Wouter

> 
> 
> 
> 
> Ihsan
> 

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