PSN-L Email List Message

Subject: Re: Time
From: Keith Payea kpayea@...........
Date: Mon, 19 Aug 2002 21:00:07 -0700

The thing to look for is a time client that uses the full NTP spec.  It uses
four time stamps to calculate the transmission times so that they can be
factored out of the time.  Many free clients use Simple NTP, which doesn't
use all four time stamps.

A crucial part of NTP is also in the filtering.  A good client will make
many requests (up to once every 64 seconds) and filter the results over
time.  With a one-shot time request, an offset of 1 second isn't surprising.
Most of them will give better performance if you run them for a while.

I work for TrueTime, and we make Network Time Servers which synchronize to
GPS and then provide NTP to a network.  If you go to this page, you can
download a free time client we have called WinSync.  You have to register
for it, but they won't bug you much.  Here's the link:

Another excellent site is the home of NTP at the University of Delaware:



Keith Payea

----- Original Message -----
From: "J D Cooley" 
Sent: Monday, August 19, 2002 8:05 PM
Subject: Time

> I have been following the discussion about accurate time for PCs.  I'm at
> work right now, but at home I have 4 or 5 programs that get the "exact"
> time and update my computer, if I want.  I don't have the need for
> extremely accurate time, but the programs are interesting to use.
> My main question is:  which one is correct?  I think all of them have
> time based on the atomic clocks at NIST, but I can switch from one program
> to another and see a difference between them of up to nearly one
> second.  How does one know which one is the most accurate?  I'm sure at
> least two of the programs I use will first ping the server they are
> the time from to get the delay, which seems necessary.
> The radio I used to use to listen to WWV is broken, but perhaps that would
> be a good way to find out which programs are WAY off!
> "JD" Cooley
> San Diego County
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