[ntp:questions] NTP tunning for OWD measurements

pret3nder at gmail.com pret3nder at gmail.com
Fri Oct 26 14:22:15 UTC 2012

Hi all,

my name is Pedro Queirós and I'm currently working on my master thesis related to open source probes to measure the QoS of internet links.
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.

Now, after reading some articles on NTP, PTP, RADclock, I'm wondering what can I do to improve the NTP configuration, so clocks on my hosts are as close together as possible and measurements are as accurate as possible.
Following the suggestion on some of the RADclock articles I've read, I've configured my hosts with the minpoll/maxpoll 4 iburst options and I'm only using one stratum 1 server on ntpd.conf.
I have access to four stratum 1 servers scattered around the country (Portugal), using GPS as the source for true time, but I have not messed with their configuration.

What I'm looking for are ways to tune the configuration of both stratum 1 servers and the hosts I'm doing the measurements on (clients of the stratum 1 NTP servers), so I can have results as accurate as possible of the one-way delay between hosts.
Please keep in mind that I don't want to use external time sources on my hosts, but I have them on the stratum 1 servers.
My network consists of fiber optic links to connect several institutions together, so we have very low jitter. Here is the output of ntpq -p on one of the hosts:

[alias at probe ~]$ ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
*xxx01.xxx.pt  .DCFa.           1 u   12   16  377    5.686    0.082   0.384

If you need more information about my current setup (configurations, setup, locations, distances, etc), feel free to ask.

Thank you for your time!

Kind Regards,

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