Dear all, Thank you for highlighting the issue with NTP offset calculation. We have identified it and are working on a fix, which we expect to issue in an upcoming release. In the meantime, our suggestion towards users is to use the reported timestamps in the measurement results to perform the RFC-compliant offset calculation. We apologise for any inconvenience caused.
Best regards, -- Marios Mavropoulos Papoudas Software Engineer - RIPE Atlas RIPE NCC On Wed, 9 Jul 2025 at 11:22, via ripe-atlas <[email protected]> wrote: > > how does Atlas computes the `precision` field? > > I believe the format_8bit() function in the probe's ntp.c is responsible > for the conversion [1]. > > 4x10E-6 would be an NTP precision value of -18 (3.815 us), which isn't > great nowadays, but I think not completely out off whack. > > [1] > > https://github.com/RIPE-NCC/ripe-atlas-software-probe/blob/57515ad8a4a84f19af0d05c9696fd8d3304408eb/probe-busybox/eperd/ntp.c#L302 > > > On 09.07.25 09:47, Giovane C. M. Moura via ripe-atlas wrote: > > Hi Philip, > > > > > >> Looking at the code, it seems that the Atlas NTP measurement > >> computes the offset with exactly the opposite sign compared to the > >> NTP RFCs. > >> > >> I never noticed before. > > > > Thanks. Since we are on it, the timestamps are _correct_ , so any user > > can still compute the offset based on the data > > > > Question: how does Atlas computes the `precision` field? > > > > I had someone telling on the NTP pool that `Precision from RIPE Atlas > > probes looks rather low to me (4x10E-6).` > > > > Thanks, > > > > /giovane > > > > [0] https://community.ntppool.org/t/site-to-evaluate-ntp-servers/3931/2 > > > > > > > > > > > > ----- > > 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/ > > ----- > 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/ >
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