On 9/14/2013 2:45 AM, David Taylor wrote:
On 14/09/2013 05:48, W. eWatson wrote:
What have I gained? What does the data mean from ntpq -n -clpe -clas?
Please see:
http://www.satsignal.eu/ntp/setup.html#check
for a brief guide to checking that NTP is working.
The command "ntpq -p" or "ntpq -pn" will show the delay between the
servers and your PC (in milliseconds, expect 20-30 ms for network-locale
servers 100+ ms for servers on an inappropriate continent), and the
offset column shows how well NTP is doing, the lower the offset the
nearer to UTC is your PC running. The offset value will be highly
dependant on the OS (i.e. Windows of Linux/FreeBSD), the servers you are
using (i.e. Internet or local), and whether or not you have a PPS (pulse
per second) feed to your PC.
In general, you will see offsets in the tens of milliseconds range for a
purely Internet-synced Windows PC (but may be better with some versions
of Windows), and sub-millisecond for FreeBSD/Linux PCs. For best
performance, you may want a local Linux PC synced to the Internet (or
with a GPS/PPS source), and sync the Windows PCs to that server (but
sync them more tightly than you would to the Internet). I don't think
you're at that stage yet, but it's worth bearing in mind. The Linux box
could be as simple as the Raspberry Pi card PC, and even adding a GPS to
that only adds ~US $35 to the cost.
A little bit of data from the two XP PCs:
Older and more troublesome PC
Jitter high 300-650
Offset around 685
Delay about 100.xxx
Reach 80 jumped to 377 an hour later
One * for the single pool
Newer XP
Jitter low, 11-8
Reach 377
* + - + - on five servers
Delay 100-150
Those are fairly rough, as seen in a five minute span. To really make
any progress I would think a monitor of the data would be more helpful.
I noticed Broken Clock in the documentation mentioned above. It looks
tricky to evaluate.
In my situation, I would be happy if one of the important parameters
would sound an alarm in my den when one went out of bounds. Fat chance
of that.
_______________________________________________
questions mailing list
questions@lists.ntp.org
http://lists.ntp.org/listinfo/questions
