[time-nuts] Re: Poor's man NTP

[Bob kb8tq]

Hi

Any time you run an “open loop” ( = delay asymmetry is not measured)  setup 
like NTP, you have multiple sources of error. If you have a requirement for always 
being in the microseconds rather than milliseconds, PTP is a better approach. 

Even with PTP, there are limits. As your network structure grows, it may struggle
as well. It will be struggling with microseconds rather than milliseconds, but it 
can indeed have problems. 

Bob

> On Dec 16, 2021, at 10:21 PM, Perry E. Metzger <perry at piermont.com> wrote:
> 
> I'm going to say something that may seem heretical but probably shouldn't be...
> 
> On 12/16/21 18:37, giuseppe at marullo.it wrote:
>> just wondering if a PI4 could be a suitable NTP server for a small lab (and
>> maybe with some other NTP servers for my company, about 2000 clients).
>> 
>> Main use is for correct timestamp on logs/computer time sync.
> 
> For log purposes, if you're down at the 2ms level you're probably utterly fine.
> 
>> Accuracy is *only* within 2ms after several hours (>24h). I was expecting
>> under 1ms.
> 
> I'm sure many people here will tell you what you would need to get better performance, and there are certainly situations where such performance is necessary and important. I've worked on such applications myself, in which microsecond accuracy timestamping of network events was actually useful.
> 
> For ordinary system logs, you will never notice the difference if your clocks are off by a marginal 1ms. Your logs probably don't even record milliseconds, and if you're trying to debug a problem in your systems, your logging subsystem probably doesn't have good guarantees that it's going to timestamp events within a ms of them occurring. I'd consider your situation pretty good already and call it a day unless, as with many of us, you find the idea of getting your machines better synchronized for its own sake personally satisfying.
> 
> Note that there really isn't anything wrong with wanting to do better for its own sake, but from an engineering requirements point of view, you've already succeeded.
> 
> Perry
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com -- To unsubscribe send an email to time-nuts-leave at lists.febo.com
> To unsubscribe, go to and follow the instructions there.