[ntp:questions] NTP tunning for OWD measurements

unruh unruh at invalid.ca
Fri Oct 26 17:18:26 UTC 2012


On 2012-10-26, pret3nder at gmail.com <pret3nder at gmail.com> wrote:
> I'm sorry, I was writing this in Google Groups web interface.
>
> Maybe I didn't explain myself correctly: I don't want to use external time sources, only NTP,

I see. You want to do research but you want to let your
prejudices/laziness make sure you are not doing the best possible job?

Or else you have still not explained yourself. 


Your lines are still too long. 


> with the best tuning (and not tunning :D) possible. But I do have access to four stratum 1 servers, using
> GPS and PPS inputs, which I use as servers to synch my hosts to.

So what. ntpd cannot correct for systematic delays. 


>
> Kind Regards,
> Pedro
>
> On Friday, October 26, 2012 3:44:13 PM UTC+1, David Woolley wrote:
>> pret3nder at gmail.com wrote:
>> 
>> > 
>> 
>> > my name is Pedro Queir?s and I'm currently working on my master
>> 
>> > thesis
>> 
>> + related to open source probes to measure the QoS of internet link.
>> 
>> 
>> 
>> [ Your lines are too long. In internet mail, and other standards based 
>> 
>> on it, CRLF delimits lines, not paragraphs. ]
>> 
>> 
>> 
>> > One of the tools I'm using is OWAMP
>> 
>> + (http://www.internet2.edu/performance/owamp/), to measure one-way delay
>> 
>> + between hosts. This tool requires NTP running and synchronizing clocks
>> 
>> + so that it can measure correctly (to a certain point) the one-way delay
>> 
>> + between hosts.
>> 
>> 
>> 
>> You need directly attached radio clocks, and for GPS, you will need PPS. 
>> 
>>    You will need these on the actual machine, although, if you have 
>> 
>> older Ethernet hardware, the same LAN may be better than nothing.  NTP 
>> 
>> cannot correct for systematic one way delays.
>



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