UDP timeout

Wouter Wijngaards wouter at nlnetlabs.nl
Tue Oct 1 07:09:47 UTC 2019

Hi Felipe,

On 10/1/19 1:59 AM, Felipe Gasper via Unbound-users wrote:
> Hello,
> Is there a control to adjust the UDP query timeout in the unbound resolver? I see a configuration item for TCP timeout but not for UDP.

Yes, in recent versions, there are settings, specifically for slow or 
very slow links (like satellite uplinks).  You can also select faster sites.

The unknown-server-time-limit can be increased if you are behind a slow 
link.  This makes the first UDP timeout value larger, so that it does 
not immediately start failing because of the slow uplink.  (It would 
otherwise pick up after a while, but this removes that time for it to 
figure out there is a slow link).

The delay-close can be set if you want the UDP timeout to be a little 
longer for firewall reasons.

The jostle-timeout controls how long queries are allowed to stay if 
there is an overdose of queries coming in.

With fast-server-permil, set to about 900 or so, you can control that 
unbound is going to select faster servers with lower UDP timeouts.  With 
fast-server-num you can control what faster servers it selects.

Best regards, Wouter

> Thank you!
> -FG

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