Faultbounded

Faultbounded is a term used in reliability engineering and fault-tolerant computing to describe systems, architectures, or algorithms that are designed to operate correctly or within acceptable limits when a bounded number of faults occur.

Formally, a system is faultbounded for a fault model M if there exists a bound f such that, for any sequence of faults in M involving at most f faults, the system's outputs remain correct or meet predefined safety and liveness properties.

Common fault models include crash faults (components stop functioning), omission faults (messages are lost), and Byzantine faults (arbitrary misbehavior). The bound f specifies how many faults may occur within the considered period or region.

Design approaches include redundancy, voting or agreement protocols, checkpointing and rollback, self-stabilizing protocols, error-detecting and error-correcting codes, and modular system design to limit fault propagation.

Applications include distributed databases with replicated state, aerospace and automotive control systems, and embedded devices where maintaining safe operation under faults is critical.

Limitations involve the need to know and enforce the bound f, potential performance and complexity overhead, and the possibility that certain rapid or correlated faults exceed the bound.

The concept relates to fault tolerance, resilience, and fail-safety, and is often discussed alongside Byzantine fault tolerance and redundancy techniques. See also: Byzantine fault tolerance, redundancy, self-stabilization.