[ntp:questions] frequency adjusting only

Unruh unruh-spam at physics.ubc.ca
Sat May 3 04:41:54 UTC 2008


"David L. Mills" <mills at udel.edu> writes:

>Brian,

>The longest delay NTP response was from the Moon, as simulated at JPL. 
>Next step is the Mars orbiters and then the rovers. JPL discovered the 
>max distance threshold had to be increased to handle the Moon delay.

Thats only a few sec. 
And it is symmetrical. Could probably still get usec resolution.


>The longest lived NTP headbanger was when I used ARPAnet IMP 29 back in 
>the late 70s. The banger continued without response until the ARPAnet 
>was dismantled in the early 90s. There are folks that have been banging 
>on our racket.udel.edu at its 128.4.1.1 address since 1981.

>So far, not response has arrived before the request was sent. The code 
>even checks for that. I'll let you know.

>Dave

>Brian Utterback wrote:

>> David L. Mills wrote:
>> 
>>> Suspecting such could be the case between NTP servers and clients, I 
>>> designed an experiment to detect such things and found small but 
>>> significant LRD effects with lags up to TWO WEEKS! At short lags up to 
>>> several network turns this can be explained by packet lengths, 
>>> buffering, retransmissions, etc., but at much longer lags you have to 
>>> look for routing flaps, provisioning changes, etc.
>>>
>> 
>> Dave, are you saying that you saw an instance of a NTP response arriving 
>> 2 weeks after the request was sent?
>> 
>> Brian Utterback




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