Adding root servers as local secondary zone to local caching server

[Benno Overeinder]

On 02/09/2021 16:10, Chriztoffer Hansen via Unbound-users wrote:
> On Thu, 2 Sept 2021 at 15:27, Charles Sharp via Unbound-users
> <unbound-users at lists.nlnetlabs.nl> wrote:
>> Do most of you use the root hints or forwarders?
> 
> Tried both. Now using forwarders.
> 
>> I currently use the following, in order:
>>
>> 1.1.1.1
>> 9.9.9.9
>> 8.8.8.8
> 
<snip/>
> 
> Side-note: Depending on your choice of local resolver software. Some
> implementations will ask the configured forwarders one at a time (i.e.
> try entry 1, try 2 if 1 fail, try 3 if 2 fail, etc.).
> Others (e.g. dnsmasq) defaults to ask _all_ configured forwarders
> simultaniously.
> Others will "regularly" test all configured forwarders to measure the
> response time and only use the fastest forwarder.

Unbound uses the last described behavior, but by default randomly 
selects one of the upstream name servers (forwarders) that falls within 
a 400 msec window, see also 
https://www.nlnetlabs.nl/documentation/unbound/info-timeout/.

There are options to prefer the faster over the slower 
upstream/forwarder within the time window, but eventually all of them 
are probed to keep the RTT updated.  (See the unbound.conf 
fast-server-permil and fast-server-num options.)

-- Benno

-- 
Benno J. Overeinder
NLnet Labs
https://www.nlnetlabs.nl/