Location is done with an on-line diagnostic. This diagnostic should not interfere with the operating portion of the system. The goal is to keep as much of the system operating as possible to avoid total outages. A typical metric for on-line fault identification is 95 percent fault location accuracy. Isolation is critical.
Recovery is more complicated for two reasons.
With nodes, a clean boundary can be placed around a node that hides the complexities of the system. This aspect of topology management becomes part of the critical path to restoring service. Another difficulty of fault recovery in this type of system is a result of incomplete encapsulation of faults. A failing device may push other devices into error states. After a defective device has been identified, all other error conditions must be cleaned up.