[time-nuts] Possibly off topic - Jitter on Ethernet over power adapters

[Rob Kimberley]

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of David J Taylor
Sent: 10 February 2013 11:39
To: 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Possibly off topic - Jitter on Ethernet over
poweradapters

From: Rob Kimberley
[]
I'm not sure if this is the best place to ask the question, but does anyone
have experience of using Ethernet over power line adapters? I have an
outside office, and my router is in the house plugged into the phone master
socket. I have used two Ethernet over power adapters, one at the router and
one in the office here to get internet access. The output of the adapter
then goes to a multi-port hub to give me Ethernet to all my office devices
including two Meinberg NTP servers.

I've noticed large jitter readings on Meinberg's NTP monitor program.  Can
be as low as 2ms, but much higher (50mS +), and at this point NTP goes
haywire.

Not sure if it is the physical set up or something else.

Any comments appreciated.

Thanks.

Rob
==================================

Rob,

It's not quite clear which direction you are measuring.  I take it your
Meinberg servers are "perfect" in NTP terms, and you are monitoring from the
house?  Or vice-versa?  Anyway, my first guess is that jitter might be not
dissimilar to Wi-Fi, in which case my lightly-loaded Wi-Fi results might be
a starting point:

  http://www.satsignal.eu/mrtg/performance_ntp_wifi.php

Note the improvement with Windows-8 and the latest NTP (top graph, PC
Bergen), and the others are somewhat variable.

Cheers,
David
------------------------------------------------------------

David, 

Thanks for the reply. I'm monitoring in the office at the end of the link
described above. The NTP servers are on the same hub as the PC. 

Next step is to move the PC into the house and measure directly at the
router. This means the NTP servers in the office will be at the other end of
the Ethernet over Power link. 

Will get back on this.

Rob