Computing the Availability and MTTF of Shared Protection Systems

International Journal of Quality &Amp; Reliability Management

2011

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PurposeThe purpose of this paper is to derive the user‐perceived availability of M‐for‐N shared protection systems composed of multiple user groups, each with a protection‐switching priority.Design/methodology/approachThe paper assumes a shared protection system with M protection units and N working units. The memoryless state transition diagram viewed from the system administrator, combined with combinatorial analysis of state probabilities on protection switching, yields a generic formula of the availability viewed from an arbitrary end user.FindingsThe numerical examples of availability reveal the effect of prioritized protection switching. It is observed that the total protection capacity is constant regardless of the ways of priority grouping. The shared protection system with multiple protection units enables more flexible availability allocation compared with the case of a single protection unit.Research limitations/implicationsUser‐perceived reliability is still an unexplored research area. Many variations of the system treated in this paper can be applied to various applications.Practical implicationsThe analysis provides useful information for the design and operation of, for example, telecommunication network devices. The analysis is applicable to general shared protection systems that are subject to service level agreement (SLA) involving user‐perceived reliability measures.Originality/valueThis paper establishes the model of the priority shared protection systems for the first time and shows a practical computation method of prioritized user‐perceived availability.

Section: Introductionmentioning

confidence: 99%

User‐perceived availability of priority shared protection systems

Ozaki

Kara

International Journal of Quality &Amp; Reliability Management

2011

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“…In the same way as in our previous research (Ozaki and Kara 2007;Ozaki et al 2009), we assume here that is equal to 0.0005 per day. Without redundancy, the MTTF is 2000 days.…”

Section: Examples and Analysismentioning

confidence: 96%

“…In our previous research, we have focused on the user-perceived reliability of shared protection systems under the condition that their components were repairable and replaceable. 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).…”

Section: Introductionmentioning

confidence: 99%

“…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.…”

Section: Introductionmentioning

confidence: 99%

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

Ozaki

Kara

International Journal of Systems Science

2012

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In this article, we investigate the reliability of M-for-N (M:N ) shared protection systems. 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 under the condition that the failed units are not repairable. Mathematical analysis gives the closed-form solution of the reliability and mean time to failure (MTTF). We also analyse several numerical examples of the reliability and MTTF. This result can be applied, for example, to the analysis and design of an integrated circuit consisting of redundant backup components. In such a device, repairing a failed component is unrealistic.The analysis provides useful information for the design for general shared protection systems in which the failed units are not repaired.

“…However, the maintenance manner of geographically fixed optical links considered in the analysis of WDM networks is different from that of the devices including routinely replaceable units. In our previous research, we derived simple closed-form formula for the availability and MTTF of one-for-N and two-for-N shared protection systems with an ordinary on-demand repair discipline from the standpoint of the end users [11].…”

Section: Introductionmentioning

confidence: 99%

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

Ozaki¹,

Kara²,

IEICE Trans. Inf. & Syst.

2009

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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.