How to monitor one way delay (OWD) using chrony

[mlichvar]

@comperem

This is one approach, but it assumes symmetric outbound and return communication delays.

No, it assumes there is no offset between the two clocks, contrary to the offset meaured by NTP.

I’m hunting for a method of estimating one-way delay directly from ntp packets, or using chrony logs.

That’s what I described above.

The logs don’t record t1 , t2 , t3 , or t4 so it may not be possible from chrony logs.

The logs don’t have the four timestamps, but you can reconstruct t2 - t1 and t4 - t3 from the measured delay and offset. The math is straightforward:

delay = (t2 - t1) + (t4 - t3)
offset = ((t2 + t3) - (t4 + t1)) / 2

offset = ((t2 - t1) - (t4 - t3)) / 2
(t2 - t1) = 2 * offset + (t4 - t3)

(t2 - t1) = 2 * offset + delay - (t2 - t1)
(t2 - t1) = offset + delay / 2
(t4 - t3) = -offset + delay / 2