[ntp:questions] Re: Do we need / should be have a refclock?

David J Taylor david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk
Sat Jul 8 09:08:14 UTC 2006

Robert Hulme wrote:
> Hi,
> I'm fairly new to NTP (although I have read a lot of the documentation
> on the site and in the wiki) and I'm trying to get some expert advice
> to help with an internal IT discussion occurring in the IT team at my
> company.
> We have about 20-30 linux servers collocated (on two sites - 95% of
> them on one site) and about 30 windows desktops at a different site.
> The new Linux sysadmin has noticed that the NTP client configuration
> on the servers is fairly random (they seem to use various random UK
> ISP's NTP servers (only one NTP server configured for each box)).
> Clearly that needs sorting out - but in the course of the discussion
> there was a debate about whether we ought to get a refclock.
> Could you give some advice on how we should be thinking about this,
> what we should consider, and what the pros and cons of using a
> refclock are.
> For reference we basically do web hosting for our clients on these
> servers - some run databases and so on but there is nothing
> particularly unusual that the servers do.
> If you think a refclock is a good idea or an important thing to have
> the one that has been suggested is this one
> http://www.atomic-clock.galleon.eu.com/Atomic-Clock-Time-Server/Atomic-C
> lock-Time-Server.htm
> If on the other hand there is a simple place I can RTFM then please
> point me to it :-)
> Robert Hulme


My broad view would be that if you are providing services for others then 

- you should have multiple physical connections to the Internet


- you should have your own stratum 1 server.

I rate a stratum 1 server as "desirable" rather than "essential".  If you 
have some in-house electronics experience making a stratum one server can 
be very simple, for example:


I would then recommend that you adopt a two-tier hierarchy for your NTP 
infrastructure, with some local servers talking to several Internet 
servers (and your own stratum 1 server if you get one), and the rest of 
the kit talking just to those local servers.  How exactly you spilt this 
depends (I think) on the connectivity between the sites themselves and 
between the sites and the Internet.


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