Configuring different TTLs in multiple RRs for the same domain name, TYPE, and CLASS
barmar at alum.mit.edu
Sat Mar 26 02:15:38 UTC 2016
In article <mailman.469.1458936922.73610.bind-users at lists.isc.org>,
Dave Warren <davew at hireahit.com> wrote:
> On 2016-03-25 07:21, Barry Margolin wrote:
> > In article <mailman.456.1458889802.73610.bind-users at lists.isc.org>,
> > Dave Warren <davew at hireahit.com> wrote:
> >> I'm more interested in the impact from the perspective of an
> >> authoritative server operator and in some respects sites that use short
> >> TTLs will increase the odds of my longer-TTL's records staying in the
> >> cache longer before it gets hit by a cache-size limit, but none of my
> >> zones are really large enough to do A/B testing.
> > IMHO, memory is so cheap these days that any server that has to eject
> > cache entries because of memory limits means the server operator isn't
> > really trying to do their job well.
> If you're running a dedicated public/ISP/massive-corporation resolver,
> sure, this is true. But if your resolver is some random DNS server on a
> small corporate Active Directory and one of dozens of services on a
> $1000 server with 1-50 users, who cares if your DNS cache only carries 5
> minutes, 30 minutes, or 6 hours of cache?
> In fact, if your resolver just forwards queries to your ISP, and your
> ISP has dedicated caches, there would be very little measurable
> difference at all. I'm not a fan of forwarding, but many admins set it
> up because it's there without considering whether it's needed or not.
If you're running a resolver for a small organization, the cache isn't
going to get huge in the first place. How many different names will 50
users access in a day?
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