87Rb Stratum 1 NTP Server – Performances

I’ve  tested the server into two  different environments: LAN and WAN. I confirm the relatively small capacity of the Soekris to support  200-300 units connected to it for NTP UDP as ideal load without alter performances.Of course the major limits comes with Ethernet , T1 and line speed. We could never get  nanoseconds over there at least for now. So the happy part was to see the offset slowly stabilize (20 hours ca) around +/- 120 ns with peaks of 10 ns  even less remaining stable over those numbers, with a frequency error of -0.038 PPM and fixed jitter of 0.015

0nani

1ns

(the offset should be the difference between the system clock and PPS ,  the frequency error instead  of -0.038 PPM should be the frequency  offset of  0.333..(X)  Hz from the integer value that the FreeBSD kernel utilize  in its  computations.)

ntptime

_offset

_abs_frequency

fwe

This , for comparison, was the frequency offset of a x64 server using  the GPS 1PPS from its serial :

_abs_frequency-2

Of course all this was wasted as soon UDP packets travels along just the local area network under a wifi connection :

lan

Anyway i’ve done some stress tests on  WAN, through the NTP global address pool with a static IP addres and a bandwidth of 1Mbit/s   connecting  more than 3000 units   to the 4501 as stratum 1 (!) : Los Angeles often dropped the  board  from the pool , but the Soekris earn  some good points with this huge load of traffic over a normal ADSL as you see from the ntp.pool monitor graph :

wan offset ntp

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s