[ntp:questions] GPS and the December 5/6 Solar Flare

Ronan Flood usenet at umbral.org.uk
Thu Apr 12 16:21:39 UTC 2007

On Sat, 7 Apr 2007 14:46:37 GMT, jra at febo.com (John Ackermann N8UR) wrote:

> There is, in my opinion, at least one very good reason to allow multiple
> prefer peers:  If the refclock provides only a PPS signal and not a
> timestamp (e.g., an atomic clock), it's necessary to use an external
> server as the prefer peer to provide the time.  Allowing multiple prefer
> peers greatly increases the robustness of such reference clocks by
> reducing their reliance on a single external server.  It's OK if only
> one serves as prefer peer at a time, but being able to switch the prefer
> role to a second server if the first becomes unreachable or insane is a
> big win.

Agreed, and I believe this will work with ntpd as it stands because
"prefer" sets a flag in that peer/server's config data, rather than
pointing a global variable at the prefer peer.  One of them will be
chosen as sys_prefer by clock_select().  I'm trying this now on one
of our servers with an Rb PPS and it looks happy.  ntpdc showpeer
or pstats will show that a peer is flagged prefer, but I don't see
any way of showing which is currently sys_prefer.

Ronan Flood <usenet at umbral.org.uk>

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