Hi, This indeed looks like a weird underflow/overflow bug -- 4294967296 in the RTT value happens to be 2^32... We'll see if we can find a bug around this. Regards, Robert On Sun, Nov 3, 2024 at 9:18 PM ripe--- via ripe-atlas <ripe-atlas@ripe.net> wrote:

Hi,

In the data to date of an NTP measurement (#80845985), I find a single strange outlier with respect to the RTT value calculated:

{ "fw": 5090, "mver": "2.6.4", "lts": 281, "dst_name": "time2.cloud.tencent.com", "ttr": 0.413039, "dst_addr": "119.28.229.79", "src_addr": "45.11.104.146", "proto": "UDP", "af": 4, "li": "no", "version": 4, "mode": "server", "stratum": 2, "poll": 8, "precision": 1.19209E-7, "root-delay": 0.0000915527, "root-dispersion": 0.0249329, "ref-id": "647a24c4", "ref-ts": 3939345482.4404373, "result": [ { "origin-ts": 3939346062.989854, "receive-ts": 3939346062.999974, "transmit-ts": 3939346063.0000167, "final-ts": 3939346062.995442, "rtt": 4294967296.005545, "offset": -0.007347 } ], "msm_id": 80845985, "prb_id": 7030, "timestamp": 1730357262, "msm_name": "Ntp", "from": "45.11.104.146", "type": "ntp", "group_id": 80845985, "stored_timestamp": 1730357293 },

When I do the math by hand, the "rtt" value I get is 0.0055453, nicely matching the fractional part found in the measurement data.

Does anyone have an explanation as to where the weird integer part might come from? Some overflow/underflow or other issue with decimal math on a binary machine? (I am not sufficiently versed in computer science to fully understand that topic, just that there are challenges in that area.)

Thanks!

Kind regards,

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