User-Perceived Reliability of M-for-N (M:N) Shared Protection Systems

Abstract

SUMMARYIn this paper we investigate the reliability of general type shared protection systems i.e. M for N (M:N) that can typically be applied to various telecommunication network devices. We focus on the reliability that is perceived by an end user of one of N units. We assume that any failed unit is instantly replaced by one of the M units (if available). We describe the effectiveness of such a protection system in a quantitative manner. The mathematical analysis gives the closed-form solution of the availability, the recursive computing algorithm of the MTTFF (Mean Time to First Failure) and the MTTF (Mean Time to Failure) perceived by an arbitrary end user. We also show that, under a certain condition, the probability distribution of TTFF (Time to First Failure) can be approximated by a simple exponential distribution. The analysis provides useful information for the analysis and the design of not only the telecommunication network devices but also other general shared protection systems that are subject to service level agreements (SLA) involving user-perceived reliability measures.

User-perceived reliability of unrepairable shared protection systems with functionally identical units

“…In modelling and analysing the unrepairable shared protection system, we use the similar assumptions to those of our previous work (Ozaki et al 2009) but assuming the repair rate ¼ 0. That is…”

“…In our research, we have been developing the first model (Ozaki and Kara 2007;Ozaki, Kara, and Cheng 2009) which performs quantitative evaluation of the system performance viewed from the end user using stochastic analyses. Our model is not a modification of existing models viewed from the system administrator but a substantially new model with the end user's view point.…”

“…We derived simple closed-form formula for the availability and MTTF of one-for-N and two-for-N shared protection systems perceived by an arbitrary end user (Ozaki and Kara 2007). Further, we developed a computation method of the availability, mean time to first failure (MTTFF) and MTTF of more general M-for-N shared protection systems (Ozaki et al 2009). We also found an approximation of the time to first failure (TTFF) probability distribution (Ozaki et al 2009).…”

“…Further, we developed a computation method of the availability, mean time to first failure (MTTFF) and MTTF of more general M-for-N shared protection systems (Ozaki et al 2009). We also found an approximation of the time to first failure (TTFF) probability distribution (Ozaki et al 2009). …”

“…However, such an approximation does not hold when the repair rate is very small or it is equal to zero (i.e. the unrepairable case) (Ozaki et al 2009). The exact solution is required in such cases.…”