[ntp:hackers] Further to the timestamping issue
David L. Mills
mills at udel.edu
Tue Jun 17 01:46:23 UTC 2008
The the maximum error statistic is defined as half the root delay plus
the root distpersion. The root disperision is the error due to the
maximum credible frequency error of the primary reference source
multipled by the time since last synchronized by that source. Additional
minor statistics are added as defined in the specificiation. It may be
your opinion that a maximum error statistic is not userful, and you are
welcome to that opinion.
Yes, I did juju magic and managed to cram three 32-bit words into two
leap bits. But, you have to look further in the documentation to find
out how I did that. You might start by looking for the leapseconds file
and, should the mystery about how other machines find out about it, you
might enjoy the autokey specification. The leapseconds extension field
shouldn't require autokey. Gotta fix that someday.
Poul-Henning Kamp wrote:
> In message <485679D6.3010407 at udel.edu>, "David L. Mills" writes:
>> Poul-Henning Kamp wrote:
>>> I did not say they were not correct, I said they were of no use.
>> If other drivers don't follow the intended semantics, that's not the
>> fault of the semantics.
> I'm not saying it is, but I'm advocating adding some metrics with
> semantics people can understand and use.
> Even if they were correctly implemented, the root delay and root
> dispersion is of no use to NTP users.
>> The leapseconds values include the epoch of the next/last leap,
> I fail to fully appreciate how you compressed that into the
> two bit field of the NTPv4 protocol.
> Or are you talking about some undocumented extension field ?
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