[evlatests] news

[Ken Sowinski]

On Tue, 5 Jun 2007, Ken Sowinski wrote:

> During one of Rick's observations early this afternoon and for
> a while afterward it appears that the EVLA antennas' idea of
> time seemed to differ from the rest of the VLA for while.  I
> planned to disable phase switching to pin down the source of
> the problem, but while discussing it with Jim Jackson it
> magically cured itself.  This raises the obvious question of
> whether the changed time multicasting contributed to this.
> Without further evidence I doubt it.  The same thing occurred
> for a while last week, albeit after many serious disturbances
> to the system.  Should the antennas continue to lose sync with
> the VLA over the next few days I think we should consider turning
> off the multicast of time from andy.

James explained to me that coincidentally there was a machine in
Socorro multicasting at the time Monday afternoon when the L302
mibs appeared to be confused about time.  There is no doubt that
these packets would have made it to the EVLA antennas.

While not a clear explanation it this seems a likely cause.  There
is still no reason to discontinue having both amos and andy multicast
time, but we should remain alert to possible timing errors.

James and I discussed the merits of letting the VLA network use the
GPS at the VLA as its primary NTP server.  This would insulate us
from drifting time if the network to the outside world is lost.
I believe it is possible to configure NTP so that it still looks at 
the outside time servers so that a failure of the GPS will be detected
and reported.  Is this a good idea?