[ntp:questions] Unexplained steps

Pierre Dubuc pldubuc at yahoo.ca
Tue Sep 4 20:23:46 UTC 2007


Replying to message <ccadnTdE1bIKMkDbnZ2dnUVZ_q7inZ2d at megapath.net>

> Date: Tue, 04 Sep 2007 14:18:47 -0500
> From: Hal Murray <hal-usenet at ip-64-139-1-69.sjc.megapath.net>
> Newsgroups: comp.protocols.time.ntp
> Subject: Re: Unexplained steps
> 
>
>> I'm totally confused by this series of snapshots below. Running 4.2.4p3
>> under NetBSD-3.1/patch, I started seeing some strange steps this morning.
>> I added some logging instructions in ntp.conf and restarted the daemon,
>> and the steps keep happening.
>
>>      remote           refid  st t when poll reach   delay   offset  jitter
>> ==========================================================================
>> +bonnie.Concordi 128.233.154. 2 u  100  128  377    6.343    2.477   2.026
>> -menthe.telecom. 204.123.2.5  2 u  102  128  377    7.382    1.237   0.961
>> -ecmail1.cmc.ec. 18.26.4.105  2 u  106  128  377   10.624   -4.249   0.521
>> *time.nrc.ca     132.246.168. 2 u   32  128  377   11.493    1.803   9.186
>> +time1.chu.nrc.c 209.87.233.5 2 u   93  128  377   17.017    2.217   2.699
>> -sylvester.sraq. 18.26.4.105  2 u   98  128  377   13.797   10.346   0.756
>
> THe above looks reasonable to me.
>
>
>>
>>      remote           refid  st t when poll reach   delay   offset  jitter
>> ==========================================================================
>> +bonnie.Concordi 132.205.122. 3 u  909 1024  377    7.226   -1.739 499.407
>> +menthe.telecom. 204.123.2.5  2 u  779 1024  377   10.374   -3.187 498.440
>> +ecmail1.cmc.ec. 18.26.4.105  2 u  904 1024  377   10.529   -7.725 499.646
>> +time.nrc.ca     132.246.168. 2 u  848 1024  377   14.625    0.161  27.797
>> *time1.chu.nrc.c 209.87.233.5 2 u  254 1024  377  1014.49  496.743   0.644
>> +sylvester.sraq. 18.26.4.105  2 u    4 1024  377  1016.93  508.733   2.030
>
> That looks strange/bad.
>
>
>> Sep  4 13:57:16 mac ntpd[7566]: time reset +0.496903 s
>> Sep  4 13:57:49 mac ntpd[7566]: synchronized to 199.212.17.21, stratum 2
>> Sep  4 13:57:50 mac ntpd[7566]: time reset -0.505313 s
>> Sep  4 13:58:08 mac ntpd[7566]: synchronized to 132.208.250.3, stratum 2
>
> It stepped 1/2 second in one direction, and then stepped back
> roughly the same amount.
>
> What's your connection to the network like?  A link with a delay
> of about a second in one direction for a while might explain that
> sort of quirk.  It could also be something strange "out there"
> somewhere in the great network between your ISP and the rest
> of the world.
>

I didn't notice anything different about the connection. I tried to ping 
one of the servers a few minutes before the step, when the billboard looks 
like everything is about to bust, and got something like a 28ms round 
trip, which is perfectly normal.

I did turn off the router's logging feature. I don't know enough about its 
inner workings, but it may be performing some kind of reverse DNS lookup 
as part of its logging, and may very well hold up the connection until the 
lookup is complete. We'll see how that goes...

-- 
Pierre Dubuc
pldubuc at yahoo.ca




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