User‐perceived availability of priority shared protection systems

Abstract

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.

Service‐level assurance in high‐availability multi‐unit systems using the M‐for‐N backup scheme

“…Note that the case for rule (17)‐(b) induces more discrimination of the availability between the two users than the case for rule (17)‐(a). Incidentally, in Table I, we can see that the average values of availability are identical for all four cases, confirming the conservation law of the mean‐user‐perceived availability (See13 for the proof).…”

“…The availability is computed by averaging the availabilities of the group members. (See13 for the proof.) As a result of the fair switching and re‐housing within a group, the system behaves as if an identical priority is given to all members of each group.…”

“…In our former study, we first focused on the user‐perceived reliability of shared protection systems without any priority control9–11. We further investigated the effect of prioritized protection switching12 and prioritized unit re‐housing13 individually. In the individual investigation of priority control (either protection switching or re‐housing), we assumed that the other control operation (re‐housing or protection switching, respectively) was subject to the FCFS (first failed first protected or the longest waiting first re‐housed) discipline.…”

“…In the individual investigation of priority control (either protection switching or re‐housing), we assumed that the other control operation (re‐housing or protection switching, respectively) was subject to the FCFS (first failed first protected or the longest waiting first re‐housed) discipline. In13, we investigated the effect of prioritized unit re‐housing only and gave a proof of a conservation law of the mean availability of shared protection systems that always holds irrespective of the user of prioritized switching and/or prioritized re‐housing.…”