We help answer some of your questions in this article:https://support.ruckuswireless.com/answers/000001658
APs send heartbeats to the ZD, which keeps track.
Often due to network congestion, APs remote from the ZD over WAN links,
or possibly PoE issues, you may see 'lost heartbeat' reported, traps to SNMP.
If the outage lasts 20 minutes, a 'lost contact' email/alert gets sent. See notes
in the ZD 9.9 User Guide.https://ruckus-support.s3.amazonaws.com/private/documents/572/ZoneDirector%209.9%20User%20Guide%20-%...
Customizing Email Alarms that ZoneDirector Sends
Using the Alarm Event section of the Configure > Alarm Settings page, you can
choose which types of events will trigger ZoneDirector to send an email notification.
1 Click Alarm Event to select/deselect all alarm types.
2 Select or deselect those for which you want or don’t want to receive emails.
3 Click Apply to save your changes.
When any of the selected events occur, ZoneDirector sends an email notification to
the email address that you specified in the Email Notificationsection.
With the exception of the Lost contact with AP event, ZoneDirector only
sends one email alarm notification for each event. If the same event happens again,
no alarm will be sent until you clear the alarm on the Monitor> All Alarmspage.
On the other hand, ZoneDirector sends a new alarm notification each time the
Lost contact with AP event occurs.