[ntp:questions] Testing throughput in NTP servers

unruh unruh at invalid.ca
Wed Sep 12 20:47:20 UTC 2012


On 2012-09-12, Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
> On 9/12/2012 2:34 PM, unruh wrote:
>> On 2012-09-12, Ulf Samuelsson <ulf at invalid.com> wrote:
>>> Anyone knows if there are any available Linux based S/W to test the
>>> throughput of NTP servers?
>>> I.E:
>>>
>>> 	packets per second?
>>> 	% of lost packets
>>> 	etc?
>>>
>>> Best Regards
>>> Ulf Samuelsson
>>
>> I hope not. I can just see someone deciding to test one of the stratum 1
>> main servers (eg at the usno) Why in the world would you want this?
>>
>
> Sigh!  I'm sure it has happened and will happen again!  I'm sure that 
> there are people complaining to the National Bureau of Standards or
> the Naval Observatory that their time is incorrect! ;-)
>
> If you really want time with better than micro-second accuracy, consider 
> get a GPS Timing receiver. The one I bought several years
> ago claimed 50 nanosecond plus or minus of the correct time.

Unfortunately that is useless, if you are trying to use it discipline a
computer clock. The interrupt service routines on a computer are slow
enough and have enough variability (eg other interrupts occuring which
switch of interrupts briefly, disk reads, etc) that getting about
2-3usec standard deviation in the timing is about the best you can do. 
Also you have to be very careful about termination of the line from the
gps receiver to the clock, etc. 



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