Slave Clock Offset by 37 Seconds

Figure 1. Flowchart for Slave Clock Offset by 37 Seconds

PTP Master clocks use the atomic timescale (TAI). Servers in business networks use the UTC timescale (UTC).

The difference between the two timescales is the UTC offset (currently 37 seconds). This increments by one second whenever a leap second occurs.

If the sfptpd slave clocks are observed to be ~37 seconds offset from the master clock, you should collect a small tcpdump pcap file and examine the UTC offset values in the received Announce messages.

A pcap file allows you to examine the fields of the received PTP Announce messages:

flags: 0x023c
        0... .... .... .... = PTP_SECURITY: False
        .0.. .... .... .... = PTP profile Specific 2: False
        ..0. .... .... .... = PTP profile Specific 1: False
        .... .0.. .... .... = PTP_UNICAST: False
        .... ..1. .... .... = PTP_TWO_STEP: True
        .... ...0 .... .... = PTP_ALTERNATE_MASTER: False
        .... .... ..1. .... = FREQUENCY_TRACEABLE: True
        .... .... ...1 .... = TIME_TRACEABLE: True
        .... .... .... 1... = PTP_TIMESCALE: True
        .... .... .... .1.. = PTP_UTC_REASONABLE: True
        .... .... .... ..0. = PTP_LI_59: False
        .... .... .... ...0 = PTP_LI_61: False
      ...
    originCurrentUTCOffset: 37