[ntp:questions] Negative delay in 4.2.6p2
Terje Mathisen
"terje.mathisen at tmsw.no" at ntp.org
Tue Oct 11 16:12:03 UTC 2011
Marco Marongiu wrote:
> Hi all
>
> Yes, negative delay. We see this on one of our clients (real IPs concealed):
>
>> $ ntpq -c pe -c as
>> remote refid st t when poll reach delay offset jitter
>> ==============================================================================
>> -10.100.100.142 22.222.222.6 3 m 66 64 376 -3.302 1.517 0.022
>> +10.100.100.141 22.222.222.7 3 m 63 64 376 -6.828 0.083 0.025
>> +10.100.100.161 222.2.22.84 3 m 54 64 376 -7.786 -0.756 0.035
>> *10.100.100.162 22.222.222.3 3 m 50 64 376 0.314 0.609 0.031
>>
>> ind assid status conf reach auth condition last_event cnt
>> ===========================================================
>> 1 61991 731a no yes ok outlyer sys_peer 1
>> 2 61992 741a no yes ok candidate sys_peer 1
>> 3 61993 741a no yes ok candidate sys_peer 1
>> 4 61994 761a no yes ok sys.peer sys_peer 1
>
>
> It's a multicast client with symmetric authentication, running ntpd
> 4.2.6.p2 on Linux Debian Squeeze. From our munin graphs, this started to
> happen three weeks ago, and all in a sudden.
You can get this if either the client or the server has a broken (i.e.
stock Windows HAL or similar) timing kernel, with 10+ ms granularity.
:-(
Terje
--
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"
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