[ale] possibility of running an NTP server

[mike at trausch.us]

On 01/12/2012 01:36 AM, Ron Frazier wrote:
> I think a large part of the problem with Windows PC's is the obnoxious 
> crummy real time clock hardware. I think Windows periodically resets 
> it's clock to match the hardware. I have a Dell Laptop which drifts 15 
> sec / day without correction. I understand that the quartz clocks in 
> atomic radio controlled clocks are supposed to drift less than 1/2 sec / 
> day between synchronizations, so 15 sec / day is terrible. If a PC is 
> off by 45 minutes a day, I think there's something wrong with the 
> hardware, or maybe the CMOS battery. What I don't know is if the 
> hardware clock can be disciplined to adjust it's frequency, other than 
> resetting it every 15 minutes or so with an NTP utility.

Most PC clocks are complete shit.  They are absolutely unreliable.

This is why, for example, an Active Directory network is configured such
that all of the Windows workstations will actually subscribe to time
updates from a domain controller.  AD uses Kerberos, which itself
typically requires that the times on all of the computers involved are
within five minutes of each other.

For example, if I have a client "C-A" and a server "S-A", and the time
at a given moment is:

  C-A: 2012-01-12T07:21:45-0500
  S-A: 2012-01-12T07:28:30-0500

The two will not be able to talk to each other for the purposes of
establishing a Kerberos session or ticket acquisition, because the time
on the client is too far outside the range of the server's time.  The
only way to ensure that this works correctly is to ensure that the
client is in-sync with the server.

If the server syncs to a public NTP pool at the second stratum, then it
would be acceptable (though not ideal) to sync the clients to the same
time source.  It is, however, always best to keep clocks in-sync at the
organizational level.  (Or, in the case of home, at the home level.)

I actually wish commodity routers would automatically provide NTP for
home networks.  Why?  Because it doesn't truly matter what time the
systems on the network have, it is more important that they are
consistent with each other.

	--- Mike

-- 
A man who reasons deliberately, manages it better after studying Logic
than he could before, if he is sincere about it and has common sense.
                                   --- Carveth Read, “Logic”