Using Go for NTPsec

[Richard Laager]

On 6/29/21 8:52 PM, Eric S. Raymond wrote:
> Richard Laager via devel <devel at ntpsec.org>:
>> On 6/29/21 3:41 PM, Eric S. Raymond via devel wrote:
>>> Well, first, the historical target for accuracy of WAN time service is
>>> more than an order of magnitude higher than 1ms.
>>
>> My two NTP servers are +- 0.1 ms and +- 0.2 ms as measured by the NTP pool
>> monitoring system across the Internet.
> 
> That's quite exceptionally good.  It's normally hard to get to within an
> order of magnitude of that on a LAN, let alone a WAN.

If this is surprising to you, perhaps I'm quoting the wrong thing. I was 
referring to the variance in the clock offset as plotted here:

https://www.ntppool.org/scores/69.89.207.99
https://www.ntppool.org/scores/69.89.207.199
https://www.ntppool.org/scores/2600:2600::99
https://www.ntppool.org/scores/2600:2600::199

There are only two systems involved, but in practice, IPv4 and IPv6 can 
have different paths through the Internet.

> Do you have any theory of why your deviation is that low?

Not particularly. Presumably it's just because of GPS PPS + good network?

Both systems are GPS PPS. One uses a ublox demo board. The other gets 
its PPS from a telecom GPS primary reference source (that is also a BITS 
source for SONET and a telephone switch).

The ublox one is the better of the two even thought it only has an 
indoor antenna. I think the GPS in that telecom PRS is not so great, and 
the oscillator is a TCXO, not Rubidium.

Both servers are (older) server-grade hardware, dedicated to this task 
(way overkill even for public pool servers). ntpd at this moment is 
using ~22% of a single Intel Xeon L5420.

They have 2x 1 Gig network connections (because that's standard here for 
redundancy) with two switches (a 1G then a 10G) before they hit my "core 
router". I'm the ISP.

The ublox uses gpsd via SHM while the other uses the ntpd PPS driver. I 
fiddled with maxpoll a bit to optimize.

The BITS clock PPS:
server 127.127.22.0 minpoll 3 maxpoll 3 prefer
fudge 127.127.22.0 refid PPS

The ublox PPS:
server 127.127.28.1 minpoll 1 maxpoll 1 prefer
fudge 127.127.28.1 refid GPS

-- 
Richard