I am getting the following output from the ptp4l command on a slave PTP node. When I terminate it (with Ctrl+C), some global statistics are printed out at the bottom, but I cannot interpret the values, as I do not find any evident correspondences with the values in the above output. To be precise, I know what the fields offset, min, max should be referring to in general, but:
1. why are there pairs of values instead of single values for each of those fields? 2. what is "dev" actually? If it's the standard deviation "of something", what's the point in having the min and max subfields? 3. how are those pairs of values supposed to be computed or related to the above recordings? 4. can you explain the meaning of drift, especially? # ptp4l -p /dev/ptp0 -i eth0 -l 6 -m -s -2 ptp4l[156535.175]: selected /dev/ptp0 as PTP clock ptp4l[156535.179]: port 1: INITIALIZING to LISTENING on INIT_COMPLETE ptp4l[156535.181]: port 0: INITIALIZING to LISTENING on INIT_COMPLETE ptp4l[156535.183]: version=2 ports=2 ptp4l[156535.184]: access_delay=164000 ptp4l[156535.185]: UTC offset: 37 ptp4l[156535.187]: port 1: link up ptp4l[156536.340]: port 1: new foreign master 0010a1.fffe.9477ff-1 ptp4l[156540.354]: selected best master clock 0010a1.fffe.9477ff ptp4l[156540.355]: port 1: LISTENING to UNCALIBRATED on RS_SLAVE ptp4l[156541.044]: master offset 3199658 s0 freq -3906 path delay 0 ptp4l[156542.055]: master offset 3199829 s3 freq -3737 path delay 0 ptp4l[156543.066]: master offset 3199792 s1 freq -3737 path delay 38 ptp4l[156544.077]: master offset -8 s2 freq -3739 path delay 38 ptp4l[156544.078]: port 1: UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED ptp4l[156545.088]: master offset -25 s2 freq -3752 path delay 40 ptp4l[156546.099]: master offset -34 s2 freq -3759 path delay 40 ptp4l[156547.110]: master offset -43 s2 freq -3768 path delay 41 ptp4l[156548.111]: master offset -17 s2 freq -3757 path delay 41 ptp4l[156549.122]: master offset -19 s2 freq -3759 path delay 39 ptp4l[156550.133]: master offset -12 s2 freq -3757 path delay 39 ptp4l[156551.144]: master offset -7 s2 freq -3755 path delay 40 ptp4l[156552.155]: master offset -20 s2 freq -3764 path delay 40 ptp4l[156553.166]: master offset -9 s2 freq -3759 path delay 40 ptp4l[156554.177]: master offset -11 s2 freq -3761 path delay 40 ^C ptp4l[156554.674]: ptp4l[156554.674]: offset: ptp4l[156554.674]: dev = 4.716450, -12.571429 ptp4l[156554.674]: min = 4.716450, 12.571429; max = 4.966555, 14.000000 ptp4l[156554.674]: dev: ptp4l[156554.675]: dev = 1.903343, 3.305985 ptp4l[156554.675]: min = 1.903343, 2.691777; max = 1.959507, 3.305985 ptp4l[156554.675]: drift: ptp4l[156554.675]: dev = 2.623987, -3758.795853 ptp4l[156554.675]: min = 2.623987, 3758.372996; max = 2.934894, 3758.795853 ptp4l[156554.676]: avg: 12
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