[ntp:questions] ntpd losing sync

David Lord snews at lordynet.org
Sat Feb 4 17:55:00 UTC 2012

A C wrote:
> On 2/4/2012 01:11, Harlan Stenn wrote:
>> A C wrote:
>>> Here's the current configuration for version 4.2.7p236:
>>> server          0.us.pool.ntp.org minpoll 9 iburst
>>> server          1.us.pool.ntp.org minpoll 9 iburst
>>> server          0.north-america.pool.ntp.org minpoll 9 iburst
>> You might try replacing the above 3 lines with:
>>   pool us.pool.ntp.org minpoll 9 iburst
>> I do not remember offhand if iburst is supported for the "pool"
>> directive but give it a shot.
>>> server ntp1.gatech.edu prefer minpoll 9
>> Is this server close enough that you want to "prefer" it?
> It's usually pretty stable, more stable than some of the pool servers 
> that I get which is why I have it set to prefer.
>>> server rolex.usg.edu minpoll 9
>>> server  minpoll 2 maxpoll 4
>>> fudge  time1 +0.000 flag2 1 flag3 1 refid PPS
>> 0.0 is the default for time1.
>> flag2 1 means PPS capture on the falling (clear) edge of the pulse.
>> flag3 1 enables the kernel PPS discipline.
>> I haven't been following this thread - what OS are you using?
> The time1 flag is in there from a point when I was fiddling with it on 
> PPS.  I just left it in there, I know the default is zero.  I need flag2 
> for the system to detect the pulse because it is inverted.  Kernel PPS 
> is enabled because I have compiled the kernel for PPS so that's correct, 
> too.  All of this is NetBSD 5.1 on sparc.

With NetBSD-5 on i386 I've moved back to using ntpd 4.2.6p5
and 4.2.6p3. I have used Garmin 18x-LVC and now Sure GP-GS010
without problem and still use the type 22 driver for PPS
because back in 2009 it was only way I could get it working.
I also have a 60kHz radioclock for MSF and that uses the
type 28 driver with radioclkd2 that decodes MSF, DCF etc.

I'd recommend getting ntpd working just with internet servers
and having your GPS drivers as noselect.

the server and fudge 127.127.20.n lines will depend on your
GPS device and firmware version. The fudge values required
for the Sure vs Garmin are different.

Just now for the "Sure" I have these:
    server  mode 18  minpoll  4  maxpoll  4  prefer
    fudge  time2 0.350  refid GPSb

    server  minpoll  4  maxpoll  4
    fudge  flag2 0  flag3 1  refid PPSb

Using noselect for both GPS and PPS you will be able to
determine the required time2 value and confirm the flags
for PPS are ok.


> No, my link shouldn't saturate.  I do have an asymmetric DSL but the 
> downstream rate is consistently above 22 Mbit/sec and upstream is 5 
> Mbit/sec.  I keep an eye on the rate through the router and it's fairly 
> flat with only occasional spikes.  In the past 24 hours the largest data 
> spike was 240 kbyte/sec (2.4 Mbit/sec) downstream for about one minute. 
>  The upstream at that time was nearly zero.  For the same 24 hour 
> period, the largest upstream spike was about 10 kbyte/sec (100 
> kbit/sec).  The delays are normally pretty good usually staying below 
> 100 milliseconds.  I only see delays like that when everything goes 
> haywire.

I have only 2Mbit adsl and have been using altq to limit my
outgoing connection rates. This actually increased my maximum
upload rate from under 150 kbit/s to above 250 kbit/s. My isp
graphs users connections and I could see massive latency during
attempted uploads until I started using altq.

I joined ntp-pool in 2009 and regretted it in my first week
when hit by Turk telecom with ntp requests that were above
the rate allowed by the daytime usage tariff for my line.
I was then reassured that the ntp-pool dns rotation averages
out such heavy loads and have since added a second server.

Mostly such high traffic levels only causes a slight blip
for ntp. Other high traffic attacks can take out my router
or firewall in which case I'm not bothered about ntp.


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