|Re: [chrony-users] Dealing with SNTP sources|
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On Wed, 4 May 2011 13:40:12 -0700 (PDT), Bill Unruh <unruh@xxxxxxxxxxxxxx>
> On Wed, 4 May 2011, Harald Krammer wrote:
>> Am 2011-05-04 20:04, schrieb Bill Unruh:
>>> On Wed, 4 May 2011, Harald Krammer wrote:
>>>> I have a question about dealing with SNTP sources.
>>>> when I interact with two SNTP servers (also named as NTP server),
>>> An sntp server must, AFAIK be a stratum 0 server.
>> Really? My opinion is, that the stratum behavior is equal. SNTP means
>> usage of simple algorithm. e.g. only hard time set after a query
>> Some SNTP implementation are extremely inaccurate. In my area NTP is
>> also used over GPRS connections ( round trip delay till 100 ms - 2 s).
>> Accuracy does not play a major role in some applications.
> That may be your opinion, but sntp has a specific definition within the
> standards and as far as I understand it, it is either a client only, or
> stratum 0 server. It is not ever something which takes time from one
> and serves it to some other client.
You are right. I also thought so, but in the field it's happen. My user
not care about it, so there are my strange solutions. I implemented also
IEC 60870-5-104 as time source for NTP. Our customers want such a thing.
> In fact, the staunch proponents (David Mills) would even regard chrony
> sntp and not allow a machine running chrony to serve time to anyone
> (Of course what you do in the confines of your own little private net is
> up to
I did tested the different NTP implementations in my environment and
chrony was my winner. I achieved an accuracy of + / - 500 us
for 30 devices on a network with typical cpu and network load.
Some customers want very precise times.
Target: Linux ARM 2.6.20 with uclibc / Cirrus EP9302 200 MHz
and Linux ARM 2.6.20 with uclibc / PXA270 520MHz
I'm very satisfied with Chrony.
Thanks for the great work
> Mills feels that he carefully designed ntp to give stable, reliable time
> others, and the simplifications stuck into sntp can easily destroy that
> you have done by relabeling stratum) reliability/stability, and that
> sntp into the time network would just bring it crashing down into chaos..
> I have some sympathy for his position.
With the hacks in my area it's hard to find problems. Fortunately,
they are not the standard for me - only exceptions.
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