RE: [chrony-users] need help with large delays reported in ntpdata

[Charbonneau, André <Andre.Charbonneau@xxxxxxxxxxxxxx>]

Hi,

UPDATE:
We've just heard back from that unit's manufacturer and it looks like we've discovered a bug in their firmware related to the precision field calculation.  They are working on a fix.
Thanks everyone for the feedback on this; much appreciated.  It helped us narrow down on the issue and identify the root cause of the problem.
 
Best regards,
  Andre

--
Andre Charbonneau

Frequency & Time
Metrology Research Centre
National Research Council Canada / Government of Canada
andre.charbonneau@xxxxxxxxxxxxxx / 613-993-3129

Fréquence et temps
Centre de recherche en métrologie
Conseil national de recherches Canada / Gouvernement du Canada
andre.charbonneau@xxxxxxxxxxxxxx / 613-993-3129

-----Original Message-----
From: Charbonneau, André [mailto:Andre.Charbonneau@xxxxxxxxxxxxxx] 
Sent: April 6, 2021 5:10 PM
To: chrony-users@xxxxxxxxxxxxxxxxxxxx
Subject: RE: [chrony-users] need help with large delays reported in ntpdata

Thanks Miroslav.

The server is a Masterclock GMR1000.  Funny enough, as soon as I disconnected the 1pps input pulse to that GMR1000 unit, and it falls back to GPS for reference, then the precision is improved by a lot.  For example:

Stratum 1 with 1pps input (as reported in the output of chronyc ntpdata command):

Remote address  : ***.***.52.242 (***634F2)
Remote port     : 123
Local address   : ***.***.52.101 (***63465)
Leap status     : Normal
Version         : 3
Mode            : Server
Stratum         : 1
Poll interval   : 10 (1024 seconds)
Precision       : -5 (0.031250000 seconds)
Root delay      : 0.000000 seconds
Root dispersion : 0.000000 seconds
Reference ID    : 474D5200 (GMR)
Reference time  : Tue Apr 06 18:13:51 2021
Offset          : -0.000000193 seconds
Peer delay      : 0.031250019 seconds
Peer dispersion : 0.031250019 seconds
Response time   : 0.000412496 seconds
Jitter asymmetry: +0.00
NTP tests       : 111 111 1101
Interleaved     : No
Authenticated   : No
TX timestamping : Kernel
RX timestamping : Kernel
Total TX        : 8095
Total RX        : 8095
Total valid RX  : 8095


Same stratum 1 with 1pps disconnected, shortly after, using GPS as fallback:

Remote address  : ***.***.52.242 (***634F2)
Remote port     : 123
Local address   : ***.***.52.101 (***63465)
Leap status     : Normal
Version         : 3
Mode            : Server
Stratum         : 1
Poll interval   : 10 (1024 seconds)
Precision       : -18 (0.000003815 seconds)
Root delay      : 0.000000 seconds
Root dispersion : 0.000000 seconds
Reference ID    : 474D5200 (GMR)
Reference time  : Tue Apr 06 18:19:15 2021
Offset          : -0.000027722 seconds
Peer delay      : 0.000116265 seconds
Peer dispersion : 0.000003832 seconds
Response time   : 0.000400542 seconds
Jitter asymmetry: +0.00
NTP tests       : 111 111 1111
Interleaved     : No
Authenticated   : No
TX timestamping : Kernel
RX timestamping : Kernel
Total TX        : 8105
Total RX        : 8105
Total valid RX  : 8105

I wonder what might be causing this discrepancy between the 2 references.

Thanks,
  Andre
--
Andre Charbonneau

Frequency & Time
Metrology Research Centre
National Research Council Canada / Government of Canada andre.charbonneau@xxxxxxxxxxxxxx / 613-993-3129

Fréquence et temps
Centre de recherche en métrologie
Conseil national de recherches Canada / Gouvernement du Canada andre.charbonneau@xxxxxxxxxxxxxx / 613-993-3129


-----Original Message-----
From: Miroslav Lichvar [mailto:mlichvar@xxxxxxxxxx]
Sent: April 6, 2021 4:15 AM
To: chrony-users@xxxxxxxxxxxxxxxxxxxx
Subject: Re: [chrony-users] need help with large delays reported in ntpdata

***ATTENTION*** This email originated from outside of the NRC. ***ATTENTION*** Ce courriel provient de l'extérieur du CNRC

On Sat, Apr 03, 2021 at 07:33:13PM +0000, Charbonneau, André wrote:
> Precision       : -5 (0.031250000 seconds)
> Root delay      : 0.000000 seconds
> Root dispersion : 0.000000 seconds
> Reference ID    : 474D5200 (GMR)
> Reference time  : Sat Apr 03 18:55:15 2021
> Offset          : +0.000004316 seconds
> Peer delay      : 0.031250019 seconds
> Peer dispersion : 0.031250019 seconds

> These peer delay and peer dispersion values are quite large (being connected to the same switch) and constant over time (they don't change).  I was looking at the chrony code and this looks like this could be due because of large estimated error?

chrony as a client rounds up the peer delay and dispersion to the precision reported by the server. -5 is not great. What kind of server is that?

--
Miroslav Lichvar


--
To unsubscribe email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
with "unsubscribe" in the subject.
For help email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
with "help" in the subject.
Trouble?  Email listmaster@xxxxxxxxxxxxxxxxxxxx.


--
To unsubscribe email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
with "unsubscribe" in the subject.
For help email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
with "help" in the subject.
Trouble?  Email listmaster@xxxxxxxxxxxxxxxxxxxx.


--
To unsubscribe email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
with "unsubscribe" in the subject.
For help email chrony-users-request@xxxxxxxxxxxxxxxxxxxx
with "help" in the subject.
Trouble?  Email listmaster@xxxxxxxxxxxxxxxxxxxx.