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 m...@timwattenberg.de +49 1578 8248731 2017-12-01 10:45 GMT+01:00 Robert Kisteleki <rob...@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 > >
