NTP Issues Today

Ask Bjørn Hansen ask at develooper.com
Wed Nov 21 22:06:16 UTC 2012

On Nov 20, 2012, at 13:00, Darius Jahandarie <djahandarie at gmail.com> wrote:

Hi everyone,

I run the NTP Pool system - http://www.pool.ntp.org/ - so I have some opinions on some of this. :-)

> But beyond that, I'm honestly rather curious what server selections
> are a good idea. A first thought would be an adjacent country, but
> maybe there is a benefit to picking things outside of the pool.ntp.org
> selection entirely?

First of all: None of the ~3800 servers in the NTP Pool system were affected by this as far as I can tell from the (copious) monitoring data.

The big benefit to adding some non-pool servers is that you wouldn't be depending basically on a bunch of volunteers (and to a large extent me) for your time keeping. Though likely you'd just be depending on another group of volunteers.

In addition to depending on the server operators who run the ntpd servers you also depend on:

1) The monitoring system keeping accurate time.
2) The monitoring system does its job catching bad servers.
3) The process updating and distributing the DNS data working.
4) The DNS servers working (and not being under a DoS attack or similar).
5) Anything I haven't thought of!

Empirically I believe we've done a better job than just about anyone with a similar scale, but past performance is no promise of the future.

> I see that Jared used *.fedora.pool.ntp.org -- I wonder if there was a
> specific reason for that or if my questions are even worth thinking
> about at all :-).

The servers for x.fedora.pool.ntp.org are in the same "group" as x.pool.ntp.org.  If you are in a country with many servers in the pool then you'll very likely get different IPs for the two. If you are in a country with few servers your odds for that aren't so good and it'd be a bit pointless.

Anyone using the NTP Pool in a default configuration (like Fedora does) must get a "vendor zone" setup - http://www.pool.ntp.org/en/vendors.html - so we have at least a little bit of a chance to monitor and mitigate problems.

It also allows us to change what servers are selected, how many IPs are returned etc for a particular vendor.  For example if Fedora in the future changes to use 'pool' instead of 'server' in the configuration we could optimize for that.



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