[ntp:questions] Sub-millisecond NTP synchronization for local network

Jeremy Leibs leibs at willowgarage.com
Fri Dec 5 19:56:51 UTC 2008


On Fri, Dec 5, 2008 at 11:35 AM, Unruh <unruh-spam at physics.ubc.ca> wrote:

> oberman at es.net (Kevin Oberman) writes:
>
> <SNIP>

>
> >I am puzzled by the reference to "rapid changes in network
> >latency". This is bad as it would seem to indicate network route
> >instability. Worse, it might mean that the path is sometimes
> >asymmetric. This is something NTPD can't handle.
>
> In his case it was because the network link is a wireless link and
> sometimes it is swamped by data being exchanged over it. There is not
> network route instability. There is simply more or less use of the network.
> Yes, ntp does not handle such things well. Its only defence is t othrow
> away 7/8 of the packets (Ie uses that packet of the last 8 which has
> minimum round trip time. )
>
>
Is there possibly a way of configuring the maximum acceptable latency of a
packet?  That is, as long as you know that for some fraction of the day
(when the system is not under load) your latency is going to be less than
some threshold, say, 2 ms, configuring the system to just throw away all
packets with latency greater than 2 ms?



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