Harlan Stenn stenn at ntp.org
Sun Mar 1 17:25:36 EST 2015

Joseph Gwinn writes:
> On Sun, 01 Mar 2015 20:35:20 +0000, Harlan Stenn wrote:
> Once people get a system to work, they don't tend to go fixing things 
> that ain't broke.

There's breakage they know about and breakage they don't know about...

>>> 2.  Slide titled ""Possibilities for Future Improvements (2)":  In the 
>>> wish list for a kernel call to ask if the kernel runs UTC or TAI, a 
>>> couple of issues come to mind.  First, many systems set the GPS 
>>> receiver to emit GPS System Time via NTP (and IRIG), so a GPS System 
>>> Time option may be needed.  Second, we often have the GPS (or PTP 1588) 
>>> receiver to emit GPS System Time, but never share this with downstream 
>>> servers, who are configured for UTC (but strangely the leap seconds 
>>> never come).  The difference between UTC and GPS System Time is handled 
>>> in applications code.  The reason for this approach is so that the bulk 
>>> of the system is free from step discontinuities, and only the 
>>> interfaces need deal with UTC.
>> This issue is also address by NTF's General Timestamp API, as
>> "timescale" is one of the data elements of this timestamp.  We have
>> already done a proof-of-concept to get these timestamps used as the core
>> part of the kernel timekeeping API.  There is clearly more work to be
>> done here.  We know how to do this work, we just need technical and
>> financial support to make it happen.
> Great.  Is this API a parallel to the named clock interface of POSIX, 
> where the OS kernel vendor can add named clocks that are not in the 
> POSIX standard - what is standardized is the mechanism for defining and 
> using special purpose clocks unknown to POSIX.

I haven't looked, and my instant thought is that the POSIX named
clock interface could trivially use the GTSAPI.  The timestamps provided
would include both a timescale and a "clock ID".
Harlan Stenn <stenn at ntp.org>
http://networktimefoundation.org - be a member!

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