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List:       timekeepers
Subject:    Re: [time] Large S1 Offsets?
From:       mm_202 <mastermind202 () gmail ! com>
Date:       2009-07-22 0:11:19
Message-ID: 63de75710907211711g19fc90a9l9efe0b2be769c1b3 () mail ! gmail ! com
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Chuck,

Thanks for the reply.  I should of mentioned that I have other servers
in my config.

I am a NTP Pool Member (http://www.pool.ntp.org/user/mm_202), and I checked to
make sure that those S1's were 'OpenAccess' before I used them.

But yes, you are right, I should limit the polling on those S1's (ntpd
was just restarted).

Thanks again,

MM.

On Tue, Jul 21, 2009 at 6:38 PM, Chuck Swiger<cswiger@mac.com> wrote:
> Hi--
>
> On Jul 21, 2009, at 2:30 PM, mm_202 wrote:
>>
>> This may be a stupid question, but when you have multiple S1's that
>> differ greatly, how do you know which one to trust?
>
> Try adding some stratum-2 or -3 servers, and see which of the S1's tend to
> keep time close to that of the other sources.
>
>> I have 3 configured (Im not going
>> to keep all 3, but just setup the server in a new colo and want to see
>> which one is
>> best), and they are almost 20ms off from each other.
>>
>> *216.14.97.75    .CDMA.           1 u   67  128  377   32.364    1.141
>> 3.421
>> +68.216.79.113   .ACTS.           1 u   59  128  377   59.689   18.731
>> 1.403
>> +128.118.25.5    .WWV.            1 u   60  128  377   22.239  -18.805
>> 1.877
>>
>> All three use different methods, are certain methods less reliable than
>> others?
>
> The intersection algorithm chose the timesource in the middle.  Most
> timesources use GPS-derived clocking; but the older WWV is a shortwave radio
> broadcast, and I believe ACTS is a dialup modem timesource that can also
> provide a reliable PPS signal.  Historically, I've found that WWV
> timesources do tend to have a ~20 ms offset lagging behind the time reported
> by other sources.
>
> Also, of course, you should not be polling a stratum-1 faster than 1024 or
> maybe 512 seconds without making prior arrangements with them....
>
> Regards,
> --
> -Chuck
>
>
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