[ntp:questions] Re: Known asymmetry (DSL) compensation
David L. Mills
mills at udel.edu
Tue Feb 15 22:58:47 UTC 2005
Mark,
It would be nice to expand the fudge to non-refclocks, but this requires
rewrite of the configuration code as well as changes in the remote
configuration protocol. This in turn requires an asynchronous DNS
implementation. Besides providing a broader fudge application, this
would provide a really neat automatic pool capability. Nothing wildly
difficulat about this, but really down and dirty. Previous broad hints
for help in this area haven't raised any hands.
Dave
Mark Martinec wrote:
>>>I know it's not possible to know or compensate for all asymmetry in the
>>>packets between two machines. However where there is a fixed, known,
>>>asymmetry - like on a DSL line shouldn't it be possible to calculate a
>>>fudge factor?
>>
>>...
>>What you want to correct is the difference in latency in the upstream
>>vs. downstream directions. The trouble is that this cannot be readily
>>calculated from any known and constant values, such as the upstream
>>and downstream bitrates.
>
>
> I would very much like to see 'fudge time1' being applicable to
> network reference servers. Like John, I see a very predictive and
> stable offsets for network peers due to an asymmetric cable connection.
>
> Inability to correct for the systematic network offset forces
> one to either fudge local refclocks to wrong time, or declares
> networked references falsetickers.
>
> Mark
More information about the questions
mailing list