Reliability indicators for the operation and maintenance services of communication networks and their calculations based on network characteristics are defined in this standard. The indices are intended to apply to telecommunication systems and defined regions.

This standard specifies system reliability indices for telecommunication systems. The indices apply to telecommunication systems and defined regions. A statement of the basic concepts is followed by definition, formula and influencing factors of indices. This standard does not cover network security and configuration.

The purpose of this standard is twofold. First, it is to present a set of terms and definitions that can be used to foster uniformity in the development of reliability indicators of operation and maintenance services of communication networks, and to aid in consistent reporting practices among utilities. Second, this standard assists O&M personnel, and establishes prerequisites for operation and maintenance decisions such as telecommunications network reliability assessment, fault handling, and performance management.