[ntp:questions] ntp server specs

Richard B. Gilbert rgilbert88 at comcast.net
Thu Apr 21 01:44:51 UTC 2011

On 4/20/2011 8:51 PM, unruh wrote:
> On 2011-04-21, Richard B. Gilbert<rgilbert88 at comcast.net>  wrote:
>> On 4/20/2011 5:49 PM, unruh wrote:
>>> On 2011-04-20, C BlacK<rblak at non.net>   wrote:
>>>> If I am setting up an ntp server for a lot machines, I have some questions.
>>>> If the timing on client machines needs to be tight, should the ntp server be an x86 machine with a less than accurate clock
>>>> or a ntp server with a very accurate clock.
>>> ? Clearly the server should have as good a clock as possible. And it
>>> should not CPU speed type power management. And it should not be on a GB
>>> network.
>>> Note that if you run the server with a GPS PPS you can get it down to
>>> 5usec accuracy, at which point the type of machine is largely
>>> irrelevant.
>>>> I want the clients to track closely to server.
>>> What does "track closely" mean? 1 hour? 1 sec? 1ms? 1us, 1ns?
>> <snip>
>> It's reasonable to expect NTPD to track the correct time within 10
>> milliseconds or better using a server that is close to you in *Net
> More like 10-100us.

Ten to one hundred microseconds over the net is a rare bird indeed.  At 
least it is here in the Philadelphia area.

Performance is MUCH better between 2:00AM and 5:00AM local time.  Delays 
are fewer and there is less "phase noise".


I use a GPS Timing Receiver that gets me within 50 ns. of the correct 
time.  Of course that gets a little muddled while it wends its way into 
my computer.

Anything around here that's smart enough to know about time has a 
reasonable approximation to the correct time.

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