Recommendation on NTP appliances/devices

Fri Apr 4 15:57:24 UTC 2014

Quoting Julien Goodwin <nanog at 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).