What IS the right NTP behaviour ?

[Poul-Henning Kamp]

As you probably know I'm working on a new NTP client called Ntimed.

It is no surprise that people have different expectations of how
timekeeping should behave, and I'm trying to figure out
what Do What I Want is.

I think I have identified three variations of "DWIW", which I have
named "eCommerce", "SCADA" and "Workstation"

Please let me know (private email to keep list noise down) if your
needs would not be served by any of these three variations or for
that matter any other comment or input on this topic.

Thanks

Poul-Henning


eCommerce
---------

	Correct system time is mandatory.

	Bootup fails if correct time cannot established.
		What do we mean by "fails" ?
			Does it hang until success ?
			Does it fail into single-user ?
			Does it raise a big red flag ?

	Stepping time after bootup is *never* allowed.
		If time drifts out of tolerance:
			Raise Alarm
				How ?
				Signal init(8) into single-user mode ?
			Slew clock, no matter how far.
			Syslog periodically how wrong system time is

SCADA
-----

	We don't need the system clock to be on time, as long as
	we know exactly how wrong it is.

	Startup should be as quick and reliable as possible.
		Configurable timer for how long we hold up startup.

	Startup step only allowed during this time interval.

	Stepping time after bootup is never allowed.
		If time drifts out of tolerance:
			Slew clock, no matter how far.
			Syslog periodically how wrong system time is
			Raise Alarm (optional)
				How ?

Workstation
-----------

	Startup should be fast-ish

	Steps are allowed any time necessary
		suspend/resume
		change in network topology
		clock drift

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.