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

Hi,

I currently have a Linux server getting its time from a 1pps source (atomic clock) and 2 stratum 1 servers (for time of day). My Linux server and stratum 1 servers are connected to the same switch.. The 1pps is from a Rb synchronized to UTC.

I’m seeing some weird peer delay and peer dispersion values in the output of chronyc ntpdata command:

Remote address : ***.***.52.242 (******F2)

Remote port : 123

Local address : ***.***.52.175 (******AF)

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 : Sat Apr 03 18:55:15 2021

Offset : +0.000004316 seconds

Peer delay : 0.031250019 seconds

Peer dispersion : 0.031250019 seconds

Response time : 0.000404820 seconds

Jitter asymmetry: +0.00

NTP tests : 111 111 1101

Interleaved : No

Authenticated : No

TX timestamping : Kernel

RX timestamping : Kernel

Total TX : 108

Total RX : 108

Total valid RX : 108

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?

Here is the output of chronyc sources:

$ chronyc sources

210 Number of sources = 3

MS Name/IP address Stratum Poll Reach LastRx Last sample

===============================================================================

#* PPS 0 4 377 11 +120ns[ +189ns] +/- 66ns

^- ***.***.52.204 1 5 377 38m +2040ns[ +347ns] +/- 62us (this seems very large… I’ve seen this jump to 47ms)

^- ***.***.52.242 1 5 377 39m +1913ns[ +232ns] +/- 62us

The LastRX values for the 2 stratum 1 servers is very large, even though the maxpoll is set to 5.

So this seems to indicate that there is a NTP test that fails constantly for these 2 entries.

I’m not sure where to look next to try to figure out what is the root cause of this problem. Any information about what might explain these constant large delays reported by the ntpdata command and large LastRX values would be much appreciated.

Thanks,

Andre

CentOS Linux release 7.9.2009 (Core)

chronyd (chrony) version 3.4 (+CMDMON +NTP +REFCLOCK +RTC +PRIVDROP +SCFILTER +SIGND +ASYNCDNS +SECHASH +IPV6

+DEBUG)

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