[LEAPSECS] W1K GPS rollover for some time servers (PTP motivation)

Joseph Gwinn joegwinn at comcast.net
Wed May 6 09:10:13 EDT 2015

On Tue, 5 May 2015 22:54:03 -0700, Steve Allen wrote:
> Like the TymServe 2100 units there will probably be other systems that
> fail because of a lack of leap seconds.  That means that 45 years ago
> the CCIR put us all into a Catch-22 situation, and the ITU-R inherits
> the undesired responsibility of doing or not doing something about it.
> On Tue 2015-05-05T21:37:48 -0600, Warner Losh hath writ:
>> Engineering is the choice of which consequences you want to have.
> It should be an informed choice, and an individual choice, and a
> choice.  What gets broadcast in the radio time signals is none of
> those, and that is presumably a major motivation for the adoption of
> IEEE 1588 (PTP).  IEEE 1588 gives those system managers a way to
> choose to disregard certain international standards in favor of a
> system with guaranteed robust behavior.  Such use of PTP is evident in
> older documents and recent press releases by the financial markets
> which basically read "We know our systems will be robust but we're not
> sure about yours, so we're changing the trading hours on June 30."

The original impetus behind IEEE 1588 PTP was the US Navy.  

A big reason to desire something like 1588 was to eliminate most of the 
various time distribution systems on Navy ships, such as IRIG, 
combining everything into ethernet.  There is a lot of money in this - 
cable plants are expensive, bulky, and heavy, and each independent 
distribution system requires lots of engineering labor to implement and 

But I will agree that forcing propagation of TAI as a practical (versus 
paper) clock is one good side effect, but that isn't sufficient reason 
for the Navy to have spent all that money.

Joe Gwinn

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