[ntp:questions] Odd reachability with local clock on XP

Philip Prindeville philipp_subx at redfish-solutions.com
Thu Oct 10 02:28:48 UTC 2013


On Oct 9, 2013, at 6:26 PM, unruh <unruh at invalid.ca> wrote:

> On 2013-10-09, Philip Prindeville <philipp_subx at redfish-solutions.com> wrote:
>> Hi,
>> 
>> I'm running ntp-4.2.6p5 on Windows XP (SP3).  I have, amongst other things, the following in my config:
>> 
>> server 127.127.1.0 noselect minpoll 4 maxpoll 6
>> fudge 127.127.1.0 stratum 10
> 
> Why would you have that? It is really dumb in almost all cases. 

I have it for instrumentation purposes.  I'm trying to track the accuracy of an XP box as a local reference clock (it will not be peered with any other time servers nor have any external clocks) versus a reliable time source such as an appliance with a CDMA or GPS receiver.

A customer believes that PC time is "good enough" for their purposes, and I need to convince them otherwise.


> 
>> 
>> and I'm running ntpd as a system service, not from the command line.
>> 
>> I've disabled the firewall, though for loopback it shouldn't make a difference.
>> 
>> When I start the service, I see:
>> 
>> D:\>ntpq -n -p
>>     remote           refid      st t when poll reach   delay   offset  jitter
>> ==============================================================================
>> 72.14.188.52    129.7.1.66       2 u    1   16    1   57.919    2.743   2.143
>> 149.20.68.17    66.220.9.122     2 u    1   16    1   28.563   -1.284   3.361
>> 204.2.134.164   253.235.63.48    3 u    2   16    1   28.708   -2.060   3.291
>> 173.244.211.10  204.42.158.152   2 u    1   16    1   16.708    0.080   3.606
>> *10.9.160.101    .GPS.            1 u    2   16    1    0.292    0.229   0.082
>> 127.127.1.0     .LOCL.          10 l    7   16    1    0.000    0.000   0.000
>> 
>> but after a while this deteriorates and I see:
>> 
>> D:\>ntpq -n -p
>>     remote           refid      st t when poll reach   delay   offset  jitter
>> ==============================================================================
>> 72.14.188.52    129.7.1.66       2 u    5   16    7   57.919    2.743   2.258
>> 149.20.68.17    66.220.9.122     2 u    5   16    7   28.563   -1.284   3.117
>> 204.2.134.164   253.235.63.48    3 u    4   16    7   26.888   -1.318   2.446
>> 173.244.211.10  204.42.158.152   2 u    3   16    7   16.708    0.080   3.399
>> *10.9.160.101    .GPS.            1 u    2   16    7    0.251    0.213   0.050
>> 127.127.1.0     .LOCL.          10 l   37   16    4    0.000    0.000   0.000
>> 
>> ...
>> 
>> D:\>ntpq -n -p
>>     remote           refid      st t when poll reach   delay   offset  jitter
>> ==============================================================================
>> 72.14.188.52    129.7.1.66       2 u   13   16  377   59.664    3.959   2.797
>> 149.20.68.17    127.67.113.92    2 u   12   16  377   28.795   -1.356   3.391
>> 204.2.134.164   129.250.35.250   3 u   12   16  377   26.953   -1.621   3.173
>> 173.244.211.10  204.42.158.152   2 u   11   16  377   23.353    2.167   1.134
>> *10.9.160.101    .GPS.            1 u   10   16  377    0.289   -0.112   0.016
>> 127.127.1.0     .LOCL.          10 l  77m   16    0    0.000    0.000   0.000
>> 
>> Not really sure why only the first packet gets through and no subsequent ones do.
>> 
>> Anyone else seen a similar issue?
> 
> This sounds like a "Doctor, it hurts when I bang my head against a brick
> wall." question.
> Also why are you polling public servers with poll 4? Seems a bit
> unfriendly to me. 


That part I didn't set up.  But I can trim the maxpoll to 6.

-Philip



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