DNS measurement using the Probe's resolvers
Hi Everyone, I have a question about using the probe's list of resolvers when creating a DNS measurement. It is unclear to me whether the probe would send the query to all resolvers at the same time or not! Also, does the probe send the query to all resolvers in its list or to a subset of those resolvers? Is DNS eyeball implemented in the probes? Sincerely, Rami
On Fri, Jul 06, 2018 at 04:30:11PM -0400, Rami Al-Dalky <rxa271@case.edu> wrote a message of 27 lines which said:
I have a question about using the probe's list of resolvers when creating a DNS measurement. It is unclear to me whether the probe would send the query to all resolvers at the same time or not!
By default, to all resolvers. Look at measurement #15260120, for instance. Probe 25020 used three resolvers, 2001:730:3e42:1000::53, 192.168.178.1, and 2001:730:3e42::53, and you can see the results for all three. On the other hand, probe 17929 has just one resolver, 8.8.8.8, so you see only one object in the resultset array. With blaeu, you can display results for all the resolvers or only for the first one: % blaeu-resolve -r 10 --measurement-ID=15260120 atlas.ripe.net [2001:67c:2e8:22::c100:69e] : 10 occurrences Test #15260120 done at 2018-07-17T16:55:55Z % blaeu-resolve -r 10 --measurement-ID=15260120 --severalperprobe atlas.ripe.net [2001:67c:2e8:22::c100:69e] : 17 occurrences [NETWORK PROBLEM WITH RESOLVER] : 1 occurrences Test #15260120 done at 2018-07-17T16:55:55Z (More results in the second case, since some probes have more than one resolver.)
Is DNS eyeball implemented in the probes?
I don't know.
On 2018/07/06 22:30 , Rami Al-Dalky wrote:
I have a question about using the probe's list of resolvers when creating a DNS measurement. It is unclear to me whether the probe would send the query to all resolvers at the same time or not! Also, does the probe send the query to all resolvers in its list or to a subset of those resolvers? Is DNS eyeball implemented in the probes?
Hi, The Atlas DNS measurement code sends one request at a time, in the order in which the DNS resolvers are listed in /etc/resolv.conf on the probe. In addition to measuring DNS, probe can also resolve a DNS name for the target of a measurement. In that case, the stub resolver that is built into libevent is used. That stub resolver does some clever and funky stuff. I don't know the details of how DNS queries are scheduled. Philip
participants (3)
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Philip Homburg -
Rami Al-Dalky -
Stephane Bortzmeyer