[LEAPSECS] We can all be winners
M. Warner Losh
imp at bsdimp.com
Sun Dec 28 22:27:47 EST 2008
In message: <3BF733CC-BCAB-4B42-ACB1-C903E98EA40F at noao.edu>
Rob Seaman <seaman at noao.edu> writes:
: M. Warner Losh wrote:
: > Experience has shown that multiple time scales lead to confusion.
: The confusion is inherent in the system requirements. There are two
: different kinds of timescale. That is a simple fact. How do we deal
: with that reality? Wishing one away won't work.
I contend we don't actually need a mean solar time to the sub-second
time scale for civil time. A mean solar time to the hour is likely
sufficient for that.
: > Look at the problems that have been enumerated here when a GPS
: > receiver starts up cold. It knows right away what the GPS time is,
: > but takes as long as about 20 minutes to know what the UTC time is.
: > This causes grief for those systems that want to start faster than
: > that to display UTC time.
: Surely the GPS receiver should be fed into an NTP server and the
: systems you describe should be receiving their time from the normal
: ensemble of servers?
Except that these boxes aren't on any kind of network that have a
source of time. They are the source of time for this closed
: Your comment is a simple observation about how GPS works.
Yes. It illustrates one of the many problems of having multiple time
scales that are off by an integral number of seconds. The problems
likely get worse when seconds don't align (either because they are
different sizes or have a different offset or both).
: > I'm not sure that the ITU would have produced anything that's
: > significantly more functional and robust than the proposal on the
: > table today.
: The ITU doesn't have to go it alone. As rousing as the discussions on
: the NTP WG can get, I proffer it as a example of a better process.
Maybe, but many of the folks on the NTP WG are in the high precision
time community... The ITU member nations likely are a more diverse
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