[ntp:questions] IEEE 1588 (PTP) at the nanosecond level?

Joe Gwinn joegwinn at comcast.net
Thu Mar 20 00:25:17 UTC 2014

In article <i3glva-5vm.ln1 at ubuntu-server-1.py.meinberg.de>, Martin
Burnicki <martin.burnicki at meinberg.de> wrote:

> Joe Gwinn wrote:
> > I've used IRIG-B004 DCLS before, for cables two meters long within a
> > cabinet.  Worked well.  How well do they handle 100 meter cables, in
> > areas where the concept of "ground" can be elusive?
> You could use fiber optics to transfer an IRIG DCLS signal.

Now that you mention it, I do recall that option.

> However, if you want highest accuracy you need to take care how much 
> delay is inserted by the transceivers, and the length of the connection.
> PTP has the advantage that constant delays can be measured and 
> compensated automatically.
> In any case it's a good thing if you can measure the accuracy, e.g. 
> compare a 1 PPS slope generated by a time client to a 1 PPS slope 
> generated by the device providing the time.
> This helps to find out if the time transfer suffers from uncompensated 
> delays (IRIG) or asymmetries (PTP).

IOne can measure the delay and command the IRIG receiver card to

The original issue was to be able to drop IRIG support in honor of PTP
via the ethernet infrastructure we always need.

Joe Gwinn

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