[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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