[ntp:questions] simple nt.conf cases for ntp-client
brontolinux at gmail.com
Thu Jan 23 11:21:15 UTC 2014
On 01/23/2014 11:00 AM, ardi wrote:
> On Thursday, January 23, 2014 9:36:35 AM UTC+1, Marco Marongiu wrote:> Well, I have come across almost all of the pages, you are mentioning below,
> but it seems, i have "combined" the info wrongly for my example...:-)
> Does it mean these minpoll, maxpoll parameters are not needed in most
> of the cases?
Yes, that's what I mean.
> According to book Expert Network Time Protocol from PETER RYBACZYK:
I don't have that book. I'd appreciate that anyone in this list that has
reviewed the book can give their opinion about it.
> "The minpoll and maxpoll parameters represent minimum and maximum
> polling intervals for reference clock messages in seconds to the
> power of 2. For example, if minpoll=3 and maxpoll=4, the minimum
> polling interval would be 8 seconds, and the maximum polling interval
> would be 16 seconds."
> What does "minimum and maximum polling intervals for reference clock
> messages" mean?
> polling = messaging with NTP servers to estimate the offset ???
Yes, but you don't need to query the servers every 16 seconds. Normally,
once a peer is selected, ntpd gradually extends the polling interval
from 64 to 128 seconds, to 256, 512, and finally 1024. Querying every 16
seconds is a bit obsessive and doesn't bring much more accuracy than the
standard settings. Not to mention that your references may rate limit
you, or refuse to talk to you altogether.
>> First: don't use two servers, it's the worst possible configuration.
> Why not? what if one of the servers fail? then the client can get time from the other ntp-server.
Please, read this section and my previous message carefully:
I am not saying that you should use only one server: I am saying that
using two is bad, and that you should use four.
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