[ntp:questions] Fwd: [ntpwg] RFC 5905 on Network Time Protocol Version 4: Protocol and Algorithms Specification

unruh unruh at wormhole.physics.ubc.ca
Sat Jun 26 06:54:33 UTC 2010

On 2010-06-25, Richard B. Gilbert <rgilbert88 at comcast.net> wrote:
> pc wrote:
>> At risk of stirring up a hornets' nest:
>> The RFC unequivocally states that "A primary server is
>> synchronized to a reference clock directly traceable to
>> UTC."
>> IMO, that is not a necessary condition. If I have a
>> hierarchy of NTP servers and clients with no external
>> connection to the Internet and I feed in Northern
>> Bongosooziland Spring Time (NBST) at the top of the
>> hierarchy, NTP will propagate that time throughout the
>> hierarchy. The only condition is that NBST must tick at a
>> rate of approximately 1 second per UTC second, otherwise the
>> finely-tuned FLL and PLL will not perform optimally.
>> Many users of this list have a requirement to synchronize a
>> number of machines within some user-defined limit, but they
>> don't care if they are all offset from UTC by a few minutes.
>> Time islands would seem to be a common use-case, and it's my
>> opinion that the RFC's assertion that genuine NTP networks
>> must be based on UTC is an unnecessary restriction. I
>> suggest that the RFC should mention that UTC-based NTP is
>> probably the most valuable use-case, and is the only form of
>> NTP that should be allowed on the Internet, whilst admitting
>> the existence of time islands.
>> Paul
> There may be people who cannot use UTC or who simply do not care what
> time it really is as long as all their clocks agree, but should we care
> what they want or what they believe???
> NTP is about time traceable to UTC and accurate to the extent permitted
> by the medium of transmission.

ntp is not a religion. It is process for synchronizing clocks via the
exchange or certain well defined packets. It is also a process for using
those packets to discipline the local clock on a computer or other
system. If in the future, MTC is defined (Mars Time Coordinate) ntp will
work equally well there without UTC. Nor should a new RFC be needed
simply to have ntp defined with MTC.

Now one might say that "primary" is defined in terms of UTC, and that
one should define a new term for MTC (maybe the martian term for
primary) but it would seem more sensible to define "primary" as a
machine which gets its time from an outside non-NTP source like GPS, UTC,
Rubidium clock, radio,....
> I'm not going to send assassins to deal with those who disagree. . . .
> It may also be worth noting that systems following an ultra 
> accurate/stable source seem to agree with each other more closely than 
> if the source is afflicted with random phase noise.

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