[ntp:questions] Re: ref clock for network POP locations

Jeff W. Boote boote at internet2.edu
Fri Sep 29 19:15:42 UTC 2006

Heiko Gerstung wrote:
> Richard B. Gilbert schrieb:
> I was referring to sub-microsecond accuracy over the network, it seems 
> that the OP has no chance to use a hardware ref clock.
>> My only knowledge of PTP is based on some earlier messages here but I 
>> believe that it must have the same problems as NTP over the internet.
> PTP uses hardware timestamping at the MII/PHY level, this will not help 
> when you use the Internet, but maybe the OP has his own nice WAN with 
> low-jitter connections available. You can get in the lower nanoseconds 
> with PTP over Ethernet, but only in very small networks or by using 
> PTP-aware infrastructure components like switches with integrated 
> hardware timestamping..

I do have access to a very nice WAN with extremely low-jitter connections. I can 
likely remove nearly all buffered devices from the path - and get nearly the 
equivalent of a really long cross-over cable.

>> <commercial for $1000+ product snipped>
> The mentioned LANTIME/NDT is basically an oscillator that is disciplined 
> by NTP. And yes, its too expensive for using it at home :-)

Right - eventually it all comes down to price. How much accuracy can you 
afford... But, this at least sounds interesting.

Thanks for the pointers.


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