On Tue, Apr 30, 2013 at 10:37 AM, Mouse <[email protected]> wrote:

> >> I am currently working on a project where 60 devices, all behind a
> >> router with one WAN IP, update their time from
> >> north-america.pool.ntp.org <http://north-america.pool.ntp.org> on
> >> boot.
>
> The included URL makes it look as though you're saying they get their
> time over HTTP somehow.  I can't see why or how you'd do that, but I
> also can't see why else you'd include an HTTP URL there.
>

My outgoing mail client parsed the domain name into a URL, and your mail
client inserted the actual URL that my mail client linked to. I'm not using
HTTP. :-)


But if you're actually using NTP and the HTTP URL is an error or a
> distractant or some such, then rate limiting is going to be up to the
> server hosts in question and hence there is no single "the actual rate
> limit"; it will depend on which pool hosts you get.  (If you get mine,
> for example, there is no single "this many pps is too much"; there's an
> exponentially decaying average which trips when it goes too high.)
>

Thanks, in that case, I'm just looking for a general rate limit that I can
apply that would be acceptable by a reasonably configured pool server.


All that said:

> For NTP, can you not run an NTP server locally on the router or such
> like?

I too would advise something like this.  The pool depends on people not
> abusing it excessively - cf the Turkish issues - and, while 60 is not a
> huge number of clients, it is enough that I think it's reasonable to
> ask that your setup redistribute time internally rather than having all
> 60 hosts using the pool directly - especially since they start up in
> sync and thus usually will get the same, or a very small set, of pool
> hosts.  Spread out over the whole pool, 60 clients aren't enough to
> notice; concentrated on the same servers it's...probably not enough to
> cause issues if spread out well temporally, but, bunched together,
> yeah, it strikes me as reasonable for rate-limit protections to trip.
>

Thanks (Jim Reid / Tim Bray), that's exactly what I'll do. Needed some
outside perspective, didn't consider a local server, definitely the better
solution, plus I can run a server on a device that can actually keep time
when power cycled in case of network/pool issues. :-)


Jason
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