[ntp:questions] Re: NTP Synch >125msec Delays?

Terje Mathisen terje.mathisen at hda.hydro.com
Thu Nov 13 07:02:57 UTC 2003


Adrian 'Dagurashibanipal' von Bidder wrote:

> Clinging to sanity, Brian Utterback mumbled in his beard:
> 
> 
>>While the delay is important, it doesn't really matter how long it is, as
>>long as it is less than the current polling period and that the round-trip
>>is symmetric.
> 
> I was under the impression that ntpd can deal with a certain level of
> asymmetry in the round-trip, with only a very small decrease in accuracy.
> Is that a misunderstanding on my part?


Yes, sort of:

NTPD cannot _deal_ with any kind of _constant_ asymmetry: This will 
instead turn up as a fixed clock offset of half that asymmetry.

What NTPD can do, is to recognize and filter away fairly long periods of 
temporary asymmetry, i.e. as caused by a period of heavy one-way network 
traffic (big http/ftp downloads?).

To enable this extra filtering, you should look into the special options 
  for the configuration file, specifically 'tinker huffpuff':

   http://www.eecis.udel.edu/~mills/ntp/html/miscopt.html

Terje
-- 
- <Terje.Mathisen at hda.hydro.com>
"almost all programming can be viewed as an exercise in caching"




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