[ntp:questions] Compensating for asymmetric delay on a per-peer/server basis?

Paul tik-tok at bodosom.net
Thu Sep 11 15:22:37 UTC 2014


On Tue, Sep 9, 2014 at 6:58 PM, Harlan Stenn <stenn at ntp.org> wrote:
> The issue is that the huff-n-puff filter will work in the case where a
> symmetrical delay becomes asymmetric, and it will "tolerate" or
> "accommodate" an asymmetric delay (caused by a large download, for
> example) for some period of time.

I was overly casual.  If you follow the breadcrumbs you find that
there is no general solution to the problem.

On Thu, Sep 11, 2014 at 9:35 AM, Martin Burnicki
<martin.burnicki at meinberg.de> wrote:
> The case mentioned by the original poster is just one possible reason.

Not to suggest that someone is doing something unreasonable but again
why does time derived from the back-up clock need to be as accurate as
the local clock (say .5ms versus 2ms)?  If there's a legitimate need
then trying to solve the problem with the wrong tool will only lead to
frustration and complaints that NTP is buggy.

If I *needed* highly available and accurate time at home I'd get a
constellation of stable oscillators to drive time rather than hoping a
remote clock or set of clocks was going to solve my problem.

As an aside has anyone tried shaping traffic to make the
upstream/downstream latencies similar?  It would seem more efficient
to apply network solutions to network problems if possible.


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