[170727] in North American Network Operators' Group
Re: Recommendation on NTP appliances/devices
daemon@ATHENA.MIT.EDU (Dan Drown)
Fri Apr 4 11:57:49 2014
Date: Fri, 04 Apr 2014 10:57:24 -0500
From: Dan Drown <dan-nanog@drown.org>
To: Julien Goodwin <nanog@studio442.com.au>, "nanog@nanog.org"
<nanog@nanog.org>
In-Reply-To: <533EADA1.9060001@studio442.com.au>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Quoting Julien Goodwin <nanog@studio442.com.au>:
> Show my anything short of a classic SONET transmission system (or
> perhaps sync-E) where you actually have something with jitter that
> low [tens of microseconds].
Since you asked, here you go: http://i.imgur.com/DvMJd5y.png
Two EndRun Unison GPS NTP servers, one in New York metro and one in
London metro. They're connected via 10G over dark fiber (along with a
bunch of networking gear doing more than just measuring time).
Measurements taken from ntp running on the New York server, the blue
line is the offset between the two clocks (in ms, left labels) and the
pink line is the rtt (in ms, right labels).
90th percentile of the offsets is 34 microseconds, and 10th percentile
is 5 microseconds.
You can see a spike in one-way latency near sample "590". Most likely
culprit is of one of the firewalls being busy (there's two in this
path).
