Hi Max,
do you know if this only affects ntp0.testdns.nl or could it be a
problem with NTP packets in general?
AFIK it's only with this (odd) server from Marco, which runs his own code:
https://github.com/mdavids/ntptools/tree/main/go/fake-ntp-server
I've done many measurements with NTP in the past and have not seen such
level of lack of responses.
I thought it could be some sanitation on Atlas side, like, if some
values would be too odd... like ,ref_timestamp > transmit_ts (violation
of RFC)
(I only found two probes which have strange processing time on the
client -- like, how long it took to capture the packet from when it was
crated -- one is -50s, the other is 100s)
But I could not find any other more severe issues for the other missing
40 probes (i pushed an update on the data analysis at [0])
Also, did you do traceroutes/MTRs to the affected probes to see, if
there are similarities in routing – like the same transit carrier?
In the past, some carriers (CenturyLink, as an example) had traffic
filter rules in place on their edges to prevent NTP reflection or
amplification attacks, that killed regular NTP traffic as well,
so I assume this could be the case here, too, not necessarily with
CenturyLink/Colt as the transit.
no clue, it could be
You could try doing a traceroute with port 123/UDP as the source towards
these probes to see, if the packets get eaten on some network demarcation:
traceroute -U --sport 123 <ip-of-the-probe>
I guess I need to update my traceroute for it.. the json on my
repositiory [0] has the probe Ips in case you wanna give a shot
If it helps, you can try with my server ntp2.301-moved.de as well – I
have access to sflow data from that host, so I can precisely tell if
there have been answer packets coming from that system.
Let's see if the Atlas folks can confirm something on their side.,like
sanitaion or something
thanks a lot for your help
-----
To unsubscribe from this mailing list or change your subscription options,
please visit: https://mailman.ripe.net/mailman3/lists/ripe-atlas.ripe.net/
As we have migrated to Mailman 3, you will need to create an account with the email matching your subscription before you can change your settings.
More details at: https://www.ripe.net/membership/mail/mailman-3-migration/
