[ntp:questions] Re: Tiime Sync solution

Richard B. Gilbert rgilbert88 at comcast.net
Mon May 30 14:04:08 UTC 2005

Eric Liu wrote:

>Hi all:
>  I need to implement time synchronization on LAN. And there should be 1ms
>accuracy. I have studied NTPv4 for several days and the protocol made me
>dizzy. It is too much complicated. However I realized that I don't have to
>code by myself at all. I found Ntpd daemon. But could it work for me very
>well? Any idea?
>Thanks and Best regards
For 1 millisecond accuracy you will probably need to install a hardware 
reference clock on your master server.  Getting such accuracy from 
servers on a WAN is chancy at best.  I'd suggest purchasing a GPS timing 
receiver.  They can be had from $200 US and up at
 Synergy Systems LLC <http://synergy-gps.com/>

Just be certain that the receiver you purchase is designed for timing; a 
navigation receiver is a slightly different thing.  The cost should be 
about the same but the timing receivers are optimized for timing and the 
navigation receivers for navigation!  Used equipment may be available on 

Accuracy (agreement with UTC) should be better than 100 microseconds.  
The GPS receivers are generally better than 100 nanoseconds but a 
computer may not be able to synchronize that closely.

The one caveat with GPS is that you MUST be able to place the antenna 
where it will have an unobstructed view of the sky.  Alternatives to GPS 
are available.  Among them are VLF receivers for the signal from WWVB,  
cesium or rubidium frequency standards, and various commercial NTP 
servers using the reference signal broadcast by cellular telephone base 

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