Methods and Procedures for System Reliability Analysis
Document Number SR-1171
Issue Number 03
Issue Date May 2012
ABSTRACT: Telecommunications consumers demand a high degree of availability of service. Telecommunications systems achieve this high availability
by employing fault-tolerant architectures (e.g., redundancy for critical system components) and efficient fault detection and recovery
mechanisms. The high reliability of the telecommunications network components makes the accumulation of system operating data that is
needed to quantify long-term reliability by straightforward methods difficult, if not impractical.
System reliability modeling and analysis (SRMA) is the means by which the reliability of telecommunications systems can be
quantified. System reliability modeling and analysis is defined as the reliability assurance discipline employed to assess the ability
of complex systems of moderately reliable components to meet high reliability, availability, and maintainability (RAM) objectives. With
the advent of new, complex architectures, there is a greater maintenance burden on a system owner. SRMA can quantitatively assess such
burdens to determine whether a system can meet maintainability objectives with the allotted maintenance resources. It can also be used
to optimize repair or maintenance strategies.
SR-1171, Issue 3:
What's New in Issue 3:
- Guides reliability analysts, especially those without course work in mathematical reliability, in the creation and analysis of
system reliability models.
- Guides personnel responsible for the purchase of telecommunications equipment in requesting and interpreting the results of system
reliability analyses from vendors of telecommunications systems or other equipment.
- Provides guidance on failure rate predictions (such as those made using SR-332) as key elements of a system reliability
Issue 3 of SR-1171, Methods and Procedures for System Reliability Analysis, replaces SR-1171, Issue 2. This document also
- Is now consistent with the latest version of SR-332, Reliability Prediction Procedure
- Characterizes service availability objectives for today's data networks
- Includes definitions for Device and System, as well as common reliability measurement parameters such as Failure Rate,
Mean-Time-Between Failure (MTBF), Mean-Time-To-Repair (MTTR), Availability, Unavailability, and Downtime.
- Describes the appropriate parameters of reliability for a series system (i.e., MTBF) versus a parallel redundant system (i.e.,
- Contains an example of optimizing repair and maintenance strategies when equipment is located on top of a cell tower
- Compares the relationship between availability and downtime, and provides the necessary operating and environmental conditions for
predicting component failure rate parameters.