Output of ntpq -p regarding stratum level - NTP

This is a discussion on Output of ntpq -p regarding stratum level - NTP ; Hello, although this is probably a beginner's question, I would like to understand this before I run into trouble caused by misunderstanding basic information. I think i misunderstood how to read the output of ntpq -p... The third column ("st") ...

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Thread: Output of ntpq -p regarding stratum level

  1. Output of ntpq -p regarding stratum level

    Hello,
    although this is probably a beginner's question, I would like to
    understand this before I run into trouble caused by misunderstanding
    basic information. I think i misunderstood how to read the output of
    ntpq -p...
    The third column ("st") shows the stratum.
    But beginning to monitor time synchronization in our network, I noticed
    a slight difference in the understanding of stratum levels between me
    and the monitoring tool (Nagios).
    When I use ntpq -p on one of our hosts I get the following output:

    remote refid st t when poll reach delay offset jitter
    ================================================== ======================
    ======
    *10.x.y.z .PPS. 1 u 338 1024 377 0.454 -1.559 0.078
    name1.name 10.x.y.z 2 u 471 1024 376 0.209 1.763 0.093
    name2.name 10.x.y.z 2 u 1461 1024 374 0.001 2.652 0.206
    name3.name 10.x.y.z 2 u 596 1024 376 0.385 0.052 0.322
    LOCAL(0) .LOCL. 5 l 59 64 377 0.000 0.000 0.001

    Until now I read this line :*10.x.y.z .PPS. 1 u 338 1024 377
    0.454 -1.559 0.078
    the following way:
    The host I ran ntpq -p on is synchronized to (*) server 10.x.y.z., whose
    time source is a PulsePerSecond clock. 10.x.y.z is a server at stratum 1
    and 338 seconds have passed since the last poll. The poll interval is
    1024 seconds.
    Because the time reference is located at stratum 1, this host is located
    at stratum 2.
    Similarily, if I look at server name1.name: name1.name is a server
    located at stratum 2 and is itself synchronized to server 10.x.y.z.
    If this is correct so far, the following output confuses me. I ran a
    check for time synchronization for Nagios. Nagios provides a couple of
    checks, one of them called check_ntp_peer. I use it to detect
    differences between expected and current stratum levels.

    //libexec/check_ntp_peer -H name1.name -W 4 -C 6 -v

    1 candiate peers available
    synchronization source found
    Getting offset, jitter and stratum for peer 4551
    parsing offset from peer 4551: -0.001193
    parsing stratum from peer 4551: 1
    NTP OK: Offset -0.001193 secs,
    stratum=1|offset=-0.001193s;60.000000;120.000000; stratum=1;4;6;0;16

    This output tells me, that name1.name is located in stratum 1 (instead
    of the expected stratum 2).

    In short: does the column st refer to the stratum of the remote host OR
    does it mean "If I synchronize to that remote host I will get to stratum
    x" ?
    Thanks and regards,
    Stefan Nottorf

  2. Re: Output of ntpq -p regarding stratum level

    Stefan.Nottorf@plath.de (Nottorf, Stefan) writes:

    >Hello,
    >although this is probably a beginner's question, I would like to
    >understand this before I run into trouble caused by misunderstanding
    >basic information. I think i misunderstood how to read the output of
    >ntpq -p...
    >The third column ("st") shows the stratum.
    >But beginning to monitor time synchronization in our network, I noticed
    >a slight difference in the understanding of stratum levels between me
    >and the monitoring tool (Nagios).
    >When I use ntpq -p on one of our hosts I get the following output:


    >remote refid st t when poll reach delay offset jitter
    >================================================== ======================
    >======
    >*10.x.y.z .PPS. 1 u 338 1024 377 0.454 -1.559 0.078
    >name1.name 10.x.y.z 2 u 471 1024 376 0.209 1.763 0.093
    >name2.name 10.x.y.z 2 u 1461 1024 374 0.001 2.652 0.206
    >name3.name 10.x.y.z 2 u 596 1024 376 0.385 0.052 0.322
    >LOCAL(0) .LOCL. 5 l 59 64 377 0.000 0.000 0.001


    >Until now I read this line :*10.x.y.z .PPS. 1 u 338 1024 377
    >0.454 -1.559 0.078
    >the following way:
    >The host I ran ntpq -p on is synchronized to (*) server 10.x.y.z., whose
    >time source is a PulsePerSecond clock. 10.x.y.z is a server at stratum 1
    >and 338 seconds have passed since the last poll. The poll interval is
    >1024 seconds.


    The PPS clock is stratum 0. The host synced to that is stratum 1. The host
    synced to a stratum 1 is stratum 2, etc.

    >Because the time reference is located at stratum 1, this host is located
    >at stratum 2.
    >Similarily, if I look at server name1.name: name1.name is a server
    >located at stratum 2 and is itself synchronized to server 10.x.y.z.
    >If this is correct so far, the following output confuses me. I ran a
    >check for time synchronization for Nagios. Nagios provides a couple of
    >checks, one of them called check_ntp_peer. I use it to detect
    >differences between expected and current stratum levels.


    >//libexec/check_ntp_peer -H name1.name -W 4 -C 6 -v


    >1 candiate peers available
    >synchronization source found
    >Getting offset, jitter and stratum for peer 4551
    >parsing offset from peer 4551: -0.001193
    >parsing stratum from peer 4551: 1
    >NTP OK: Offset -0.001193 secs,
    >stratum=1|offset=-0.001193s;60.000000;120.000000; stratum=1;4;6;0;16


    >This output tells me, that name1.name is located in stratum 1 (instead
    >of the expected stratum 2).


    This is an issue with nagios.



    >In short: does the column st refer to the stratum of the remote host OR
    >does it mean "If I synchronize to that remote host I will get to stratum
    >x" ?


    As you can see, the machine that is synced to the pps is stratum 1 .

    >Thanks and regards,
    >Stefan Nottorf


  3. Re: Output of ntpq -p regarding stratum level

    Nottorf, Stefan wrote:

    > remote refid st t when poll reach delay offset jitter
    > ================================================== ======================
    > ======
    > *10.x.y.z .PPS. 1 u 338 1024 377 0.454 -1.559 0.078
    > name1.name 10.x.y.z 2 u 471 1024 376 0.209 1.763 0.093
    > name2.name 10.x.y.z 2 u 1461 1024 374 0.001 2.652 0.206
    > name3.name 10.x.y.z 2 u 596 1024 376 0.385 0.052 0.322
    > LOCAL(0) .LOCL. 5 l 59 64 377 0.000 0.000 0.001
    >
    > In short: does the column st refer to the stratum of the remote host OR
    > does it mean "If I synchronize to that remote host I will get to stratum


    That of the remote host.

    Incidentally, why are you running the local clock driver at stratum 5?
    That should only be done if your machine is a server and is being
    synchronised to a reliable time source by means other than NTP. Local
    clock has no place at all on clients and should only be used on servers
    as a deliberate choice. When synchrnonised to an unreliable source,
    like the undisciplined local clock (including that clock as a fall back
    to external servers), it should be set to the highest stratum that is
    still acceptable to its clients, if used at all.

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