availabilityalong

Availabilityalong is a metric used in reliability engineering and network design to quantify the end-to-end probability that a defined path remains operational. It captures the likelihood that a task completes from origin to destination, considering the availability of each segment along the route and any redundancies embedded within the path.

The term blends 'availability' with 'along' to emphasize end-to-end coverage. It appears in discussions of service chaining, multi-hop networks, and supply chains, where understanding overall path reliability is essential for planning and performance guarantees.

Calculation: for a serial path consisting of segments i = 1 to n with availabilities p_i, the end-to-end availability is A_path = ∏ p_i, assuming independence. If a segment contains parallel units, its availability is p_i = 1 − ∏_k (1 − p_i,k). In time-constrained analyses, availability can be defined over a window, yielding A_path(T) = ∏ p_i(T) or similar time-averaged measures.

Applications include end-to-end service level analysis for cloud service chains, content delivery networks, disaster recovery planning, and reliability assessment of industrial automation or logistics networks.

Limitations include the assumption of independence and uncorrelated failures. Real-world conditions may exhibit correlated risks, shared faults, and dynamic routing that violate simple product rules. Estimation relies on telemetry, MTBF and MTTR data, and scenario modeling.