[atlas] Effect of "Resolve on Probe"-option

Robert, thanks for your explanations. I now do understand this for all
measurements exept for those of type DNS.
DNS measurements with a central resolver somehow seem not that useful to
me. Am I missing the use case here?

Context: I want to measure the consistency of DNS records or how they are
seen inside the probes networks.
In my measurement I activated the option to use the probes resolver(s) and
left the option to resolve on the probe deactivated.
Does this simulate the scenario of a client asking its local DNS resolver
(e.g. assigned by DHCP)?

Thanks, Tim

Tim Wattenberg
mail at timwattenberg.de
+49 1578 8248731

2017-12-01 10:45 GMT+01:00 Robert Kisteleki <robert at ripe.net>:

>
> On 2017-11-30 20:27, Tim Wattenberg wrote:
> > Hi everyone,
> >
> > I think I don’t quite understand the effect of the „Resolve on Probe“
> option when creating a measurement. The form says it forces the probe to do
> DNS resolution, the API reference says that it indicates that a name should
> be resolved (using DNS) on the probe otherwise it will be resolved on the
> RIPE Atlas servers.
> >
> > Could someone explain what this means for example if I have a simple
> measurement for querying the A record of a given domain via the probe’s
> resolvers?
> >
> > Thanks, Tim
>
> Hi,
>
> When you measure something given with a DNS name and leave this option
> to its default settings, then the DNS resolution happens once, in the
> infrastructure (somewhere in Amsterdam, NL), and the probes are told to
> measure towards the resolved *IP*. This is more efficient, prevents DNS
> errors on the edges, but only works if DNS can only give one answer.
>
> If you turn on "resolve on probe", then the probes get to measure the
> *name* you entered, and do the DNS resolution themselves every single
> time they measure. This has a somewhat higher chance of failure, but
> it's needed if the resolved IP depends on the location of the vantage
> point.
>
> Hope this helps,
> Robert
>
>
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