[Twisted-Python] a question about monotonic clock

Glyph glyph at twistedmatrix.com
Sun Oct 28 15:18:20 EDT 2012

On Oct 28, 2012, at 9:01 AM, Christopher Armstrong <radix at twistedmatrix.com> wrote:

> I'm not speaking from experience, admittedly. How big exactly are the steps in NTP skewing?

There are two things NTP can do: stepping and slewing.  (Skewing is not one of them.)

If you're stepping, the steps can be arbitrarily large.  This is what ntpdate does.

If you're slewing, there are no steps.  This is what ntpd does.  The frequency of your clock is just adjusted up or down by a small (configurable) amount.  Generally not enough to affect the pitch or network latency of 20ms sound sampling.  In fact, it would generally help, not hurt, because the only reason ntp would be issuing a slew is that your clock is faster or slower than real time anyway.

PEP 418 <http://www.python.org/dev/peps/pep-0418/> covers this stuff in a lot of detail; especially the glossary.


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