[dns-resolver-tf] Default max-ttl (was: Final final draft of RIPE DNS Resolver Best Common Practices)

Thanks Shane

Before I wrote that I went and dug around looking for examples....and
looking at your link I know what I did.  I was reading the max-ncache-ttl
setting. DOH and double DOH.

I am chastised and thanks!

tim


On Fri, Mar 29, 2024 at 4:09 PM Shane Kerr <shane at time-travellers.org>
wrote:

> Tim,
>
> On 24/03/2024 20.00, Tim Wicinski wrote:
> > Some more and apologies as I was thinking the updates were in the git
> > repo which was what confused me.
> >
> >
> >      ### TTL Recommendations
> >
> >      Software typically defaults to a maximum stored TTL of 1 or 2 days.
> >      A lower TTL will mean removing rarely-used records that have long
> TTL,
> >      and should not have much operational impact from a CPU or network
> >      point of view
> >
> > Where did this 1 or 2 days come from?  From most s/w I've seen the
> default
> > max-cache-ttl is a few hours.
>
> For defaults...
>
> It came from a vague memory of mine from a DNS OARC presentation in the
> mists of history. I recall some presentation where someone measured this
> and found that most cache entries disappeared after 1 day, and
> everything else except for a rounding error after 2 days. Neither
> DuckDuckGo nor Qwant seem to be able to help me find said presentation,
> so it might be a LLM-style hallucination in my brain.
>
> I did check defaults from various open source resolvers:
>
> BIND uses 1 week:
>
>
> https://bind9.readthedocs.io/en/stable/reference.html#namedconf-statement-max-cache-ttl
>
> Unbound uses 1 day:
>
> https://unbound.docs.nlnetlabs.nl/en/latest/manpages/unbound.conf.html
>
> Knot Resolver uses 1 day:
>
>
> https://knot-resolver.readthedocs.io/en/stable/daemon-bindings-cache.html#cache.max_ttl
>
> PowerDNS Recursor uses 1 day:
>
> https://doc.powerdns.com/recursor/settings.html#max-cache-ttl
>
> Cheers,
>
> --
> Shane
>
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