threat propagation continues. Therefore, the role of forwarding tracing algorithm is
to localize damages, and where is possible block the threat propagation.
So far we have not mentioned how to deal with the reason or source of threat the
another algorithm was developed to perform Backward Tracing, Fig. 18.4. The
latter performs a searching of the reasons (for example, where, when and why a
threat appeared in DCS).
When Backward Tracing algorithm has completed the entire area of the damage
caused by the threat became known and defined. This eases recovery and optimize
the reconfiguration processes. This algorithm detects the source or reasons for the
potential order of manifested threats and caused consequences for each vertex
included. The threat propagation might be manifesting as inconsistency of data or
behavior at another node [4, 5, 10].
In one sentence—It is essential to start the recovery process from the vertex
where the threat appeared, so the treatment will start from the reasons not just the
symptoms.
Backward Tracing of the dependency matrix enables us to identify a suspected
element or elements.
Fig. 18.4 Backward tracing algorithm to determine the source of threat
260
18 Distributed Systems: Maximizing Resilience