[time-nuts] can of worms: time-of-day in a community radio station

[Bob kb8tq]

Hi

Since “rogue” servers are rare, bumping up the number of servers fairly quickly
gets you to a very high degree of confidence. Is that 5, 7, 9, or 11? It sounds like
a wonderful topic for somebody’s thesis or dissertation :)  Given that this is a free
resource and that the network usage is negligible even with a dozen servers, the only
real downside is being tagged as a resource hog.

Bob

> On Nov 4, 2019, at 7:05 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
> 
> 
> attila at kinali.ch said:
>> This is a pretty baseless fear. The servers in the ntp pool are constantly
>> monitored and those that are off by more than 100ms are quickly removed
>> (within 2-3 hours, IIRC). Of course, if you are already using one of those,
>> then the removal will not help you. But you are most likely using 3-5 servers
>> anyways, which means ntp will remove the "rouge" server on its own. 
> 
> It's more complicated than that.
> 
> It depends on what code you are using and how you configured things.
> 
> If you are using  ntpd and you said in your ntp.conf
>  server <pool>
> Then it grabs one and sticks with it until you restart ntpd.
> 
> In the old days, it was common to use
>  server 0.pool
>  server 1.pool
>  server 2.pool
>  server 3.pool
> That used the pool before the pool code in ntpd was working.  I'm pretty sure 
> some distros set things up that way and some systems are probably still using 
> an old config file.
> 
> The pool code is supposed to drop bad servers and get replacements.  I'm not 
> sure of the details on what "bad" covers.  It could be not responding at all 
> or it could be time not good-enough.  I'll dig into the code if it matters.
> 
> 
> If you aren't running ntpd (classic or ntpsec) then I don't know what happens.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> 
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