[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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