[LEAPSECS] Another vote on UTC, facebook

[Miroslav Lichvar]

On Wed, Mar 18, 2020 at 06:52:49PM -0700, Tom Van Baak wrote:
> "Facebook Switches to New Timekeeping Service"
> https://spectrum.ieee.org/tech-talk/telecom/internet/facebook-new-time-keeping-service
> 
> Unfortunately, I don't see a white paper, code, or technical details on
> positive/negative smear duration or slew rate, so we don't know if at the ms
> level it's the same as Google or Amazon or others on this bandwagon.

If I understand it correctly, they are using the time smoothing
feature of chrony with 1ppb/s wander, following the example from the
documentation. It's different from the linear smear implemented by
Google/Amazon. It starts at midnight and it's a two-piece quadratic
function. The duration is 2*sqrt(1e9) seconds (~17.57 hours).

The last section of the following blog post has some graphs that show
how the offset and frequency is changing during the leap smear.

https://developers.redhat.com/blog/2015/06/01/five-different-ways-handle-leap-seconds-ntp/

-- 
Miroslav Lichvar