September 2011
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V1.44
Copyright © 2011 Adept Systems, Inc. and Control Network Solutions Ltd All Rights Reserved.
Fig.3.7: Redundant Twin Mode Application
3.3.1. Definitions
For the purpose of clarifying the descriptions the following definitions are used:
Failure
: A failure is detected whenever a heart beat times out without receiving a monitoring
packet from both interfaces. Only the active node sends monitoring packets. The inactive node
passively listens for the monitoring packets. The inactive twin always forwards monitoring
packets. In order for an active node to receive a monitoring packet it has to complete a round
trip, such as, out IP side to twin, in IP side of twin, out 709.x side of twin, in 709.x side, or going
the other way, out 709.x side to twin, in 709.x side of twin, out IP side of twin, in IP side. A
failure may be detected on one or both interfaces.
Fault
: Once a failure is detected, both twins perform a diagnostic by actively interrogating each
other on both interfaces. If the interrogation on a particular interface fails then a fault has
occurred on that interface. An alarm is generated when a fault has been determined. A fault on
a particular interface is cleared whenever a monitoring packet is received or if a diagnostic
interrogation succeeds. A cleared fault generates an
alarm cleared
.
Both nodes independently report failures and faults. It is possible to have a failure but not a
fault. The converse is not true. It is possible for only one twin to report a failure. For example if
