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@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,
Pedro
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