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<== Date ==> <== Thread ==>

Subject: EPICS 3.13.1 (and earlier) - NTP issues
From: "Brian McAllister" <[email protected]>
To: [email protected]
Date: Tue, 20 Nov 2001 16:29:29 -0500
Folks -

Last month we discussed the bug in EPICS NTP support that caused the IOC
time to fall behind in 10 second increments.  This bug was fixed in
3.13.2.

At that time, I wrote that the only operational fix was to reboot the
IOC. As this is often inconvenient, I offer a somewhat less intrusive
solution.

As the problem has to do with NTP requests becoming out of sync with the
replies, it occurred to me that disconnecting the IOC from the network
would cause the queued (old) replies to be read as responses to subsequent
requests, while no new replies would be received.

Thus, the solution is to unplug the network connection and wait for
(amount_of_time_the_IOC_clock_is_slow + 15-20 seconds), by which time the
IOC will have emptied the receive queue.  On reconnecting the network, the
time will be correctly re-synced by the subsequent NTP transactions.

While this interruption in service may still not be acceptable, at least it
involves less time and disruption than rebooting.

----
Brian McAllister                    Controls Programmer/Beam Physicist
[email protected]                        MIT-Bates Linear Accelerator
(617) 253-9537                                           Middleton, MA


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