AT&T / Verizon DNS Flush?

William Herrin bill at
Wed Apr 16 19:59:50 UTC 2014

On Wed, Apr 16, 2014 at 2:25 PM, Jimmy Hess <mysidia at> wrote:
> It's not hard to use WHOIS to lookup the registrar of each of the
> nameservers for
> (,
> Long TTLS are appropriate for a production zone,  but in my
> estimation, it is improper for
> a registrar to impose or select by default a TTL  longer than  1 hour,
> for a newly published or newly changed zone.
> The TTL can and should be  reasonably low initially  and
> automatically increased gradually over time,
> only after  the zone has aged with no record changes and confidence is
> increased
> that the newly published zone is correct.

There was a study on an unrelated topic a presented at a NANOG or ARIN
meeting a few years back. I don't recall the exact details. The
interesting bit was the analysis they did on DNS caching to see the
impact from varying the TTL. I don't remember the exact numbers, but
short TTLs exhibited only a small increase in query rate over long

There's really no driving need to set the TTL higher than 1 hour,
ever, under any circumstances.


William D. Herrin ................ herrin at  bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004

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