David D. Hagood wrote:
Has any consideration been given to adding support for IEEE-1588
Precision Time Protocol (PTP) into NTP?
PTP (http://ieee1588.nist.gov/) is a standard for time synchronization
over LAN for instrumentation - it is a part of the LAN extensions for
Instrumentation (LXI - http://www.lxistandard.org/), and provides for
time sync to tens of nanoseconds (YMMV - routers screw that up). The
intended use is in a stack of instruments in a lab, connected to each
other and to a PTP source via a local hub.
The overall goals and methods of PTP are very much the same as NTP,
and I'd hate to have to put both NTPD and PTPD
(http://ptpd.sourceforge.net/) on the same machine as they would fight
like cats and dogs over who was master - ideally you'd have one daemon
doing both, and picking the "best" source.
Where I work we are building gear that is Linux based (and so can have
NTPD trivially) but I'd like to be fully LXI compliant which means
supporting PTP as well (plus some of the stuff we do we need time sync
to at worst hundreds of nanoseconds), and being a lazy cuss I'd rather
see something like that in the mainstream NTPD rather than having to
put it in myself on our own branch.
If possible, please reply to both my work email (David.Hagood at
aeroflex com) as well to the list (yes, I hate it too when somebody
asks that) - something between the list and my desk seems to be eating
the list mails.
David Hagood
Principal Software Engineer
Aeroflex Wichita
David (period) Hagood at Aeroflex (period) com
_______________________________________________
questions mailing list
[email protected]
https://lists.ntp.isc.org/mailman/listinfo/questions
NTP does not, typically, synchronize multiple systems to "hundreds of
nanoseconds". Hundreds of microseconds might be doable on a fast LAN.
Linux has been known to have timekeeping problems due to losing clock
interrupts. Each lost interrupt can introduce an error of one or ten
milliseconds. If the kernel parameter HZ is set to 1000, the clock
ticks 1000 time a second and the system is likeliest to lose
interrupts. It works much better if HZ is set to 100.
_______________________________________________
questions mailing list
[email protected]
https://lists.ntp.isc.org/mailman/listinfo/questions
