[ntp:questions] Re: time

Richard B. Gilbert rgilbert88 at comcast.net
Thu Dec 1 02:08:57 UTC 2005

K wrote:

>So to summarize you guys.  I think that you are saying that
>ntpd v3 is accurate on a gigabit network that is congested  to 5-20ms  is 
>the accuracy is a reasonable expectation. What about IEEE 1588, since this 
>is also ethernet bases can I get any better time accuracy with that?
Well, I think I'm saying is you *can* get better than one millisecond 
accuracy on a LAN.  It is not, however, obtainable under all circumstances.

The accuracy obtainable depends on:
a. the utilization level of the LAN (how congested it is).
b. the LAN hubs or switches in use
c. the hardware the server runs on
d. the quality of the time source(s) used by the server (This, in turn, 
may depend on the quality of the internet                connection)
e. the O/S used on the server
f.. the hardware the client systems run on
g. the O/S running on the client systems.
h. the version of ntpd in use

I have demonstrated accuracy on a client to within less than 100 
microseconds using specific hardware and software on a home network.  
The environment could be duplicated, with used equipment, for less than 
$1000 US.   It would not surprise me to learn that still better results 
could be obtained on a gigabit network using high performance 
professional network switches rather than the $90 wonders sold for home 
use.   Faster computers than the seven year old machines I'm using might 
also provide better results.  Your mileage may vary!

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