perfSONAR User Q&A and Other Discussion

[Alan Whinery <>]

Because, as he said, owamp reports between two participants whose path
latency is similar or less than a typical NTP clock correction is more
noise than signal.

I wouldn't suggest hiding the latency, but in close-quarters owamp, the
loss really is the useful part.

Brian - As for clock discipline standards, you may want to look at
EndRun CDMA devices. They usually don't require the antenna-on-roof
aspect that a GPS install does, but provide similar precision.

http://endruntechnologies.com/time-frequency-reference-cdma.htm

http://net.its.hawaii.edu/network-performance/using-praecis/

Of course, you did say "not-too-expensive". In 2010, I paid $1,375.00
each for Praecis II.

On 12/5/2014 8:32 AM, Eli Dart wrote:
> Hi Brian,
>
> Just out of curiosity, why would you trust ping to measure latency if
> you're not satisfied with OWAMP?
>
> If NTP clock skew is causing you problems, I'm guessing you're measuring
> latency over very short distances, but I'd like to ask before I assume.
> What sort of network are you trying to measure?  I apologize if I've missed
> it in earlier threads.
>
> Eli
>
>
> On Fri, Dec 5, 2014 at 10:18 AM, Brian Candler 
> <>
>  wrote:
>
>> I'm finding that the latencies I'm trying to measure are less than the
>> differences in NTP-synced time, and this leads to very misleading graphs.
>>
>> 1. Does anyone have any suggestions for a good, but not-too-expensive, GPS
>> time source to use with perfsonar/CentOS?
>>
>> 2. Is it possible to configure perfsonar to graph the sensitive packet
>> loss from owamp, but hide the latency? (I can always use ping for
>> round-trip latency)
>>
>> Thanks,
>>
>> Brian.
>>
>>
>