Subject: Re: Clock synchronization with ISDN
To: Perry E. Metzger <>
From: Jonathan Stone <jonathan@DSG.Stanford.EDU>
List: tech-kern
Date: 02/17/1997 11:53:59
Perry E. Metzger <> writes:

>Martin Husemann writes:
>> The (classical) question is: should I hand out the timestamps as a seperate
>> device, run the standard nntp deamon to use them, which in turn calls the
>> appropriate kernel functions to adjust the time?
>> Or should I shortcut this and adjust the time right inside the
>> kernel, without any device and userland daemon?

>I wouldn't bother. Line latency distribution is probably high enough
>to negate any advantage you would gain.

Isn't ISDN signalling *slow*?  If it's slow, then how much jitter is
that, and (at best) discretisation at the 9600-baud D channel line speed
adding?  Not  to mention  switching delays inside the telecom net?

> What *will* help is the kernel
>PLL stuff, since it will keep the clock better disciplined between

Um, not quite. I think you really want to run this in FLL mode, 
if you use it at all. But definitely in the kernel.