METHOD FOR CALCULATING THE AVAILABILITY FACTOR FOR A SYSTEM WITH REDUNDANCY. PASSIVE MODE
DOI: 10.36724/2072-8735-2020-14-8-21-25
Vyacheslav P. Shuvalov, Siberian State University of Telecommunications and Information Sciences, Professor, Novosibirsk, Russia, shvp04@mail.ru
Boris P. Zelentsov, Siberian State University of Telecommunications and Information Sciences, Professor, Novosibirsk, Russia, zelentsovb@mail.ru
Irina G. Kvitkova, Siberian State University of Telecommunications and Information Sciences, Senior Lecturer, Novosibirsk, Russia, irin.creme@yandex.ru
Abstract
The use of fiber-optic communication lines allows for the transfer of huge amounts of information per unit of time. Even short-term failures significantly affect the quality of services provided. The level of network reliability depends on how resilient the network infrastructure is to failures and how quickly recovery occurs after them. Reliability guarantees are the main component of quality of service agreements between operators and consumers. Most often, redundancy is used to ensure the required level of reliability indicators. The disadvantage of this approach is the high cost of network bandwidth, the advantage – is a short time to switch at the reserve after a failure is detected. In order to reduce costs, in some cases, the 1:N backup option is used (one backup path is allocated for N working paths). In this paper, we consider the case of 1:2, when one backup path is allocated for two working paths. In this case active and passive switching modes are possible. When switching is active, if both working paths fail, the traffic of one of them switches to the backup path. After restoring the working path, traffic switches to the restored path, i.e. the backup path is freed. It is replaced by traffic from another failed path. A special feature of passive mode consists in that after the backup path is released, it does not deal with the traffic of the second failed path. There are several ways to restore traffic over a failed work path:. the second working path starts to recover after the first one is restored; the second working path starts to recover simultaneously with the first one. In either case, the traffic of the first path is switched back from the backup to the working path after it is restored. This paper presents a method for calculating the conditional probability that the backup path will be used for transmitting traffic from one of the working paths if both paths fail. The formula for calculating the unavailability factor of working paths is given.
Keywords: availability factor, unavailability factor, failure rate of working paths, recovery rate of working paths, homogeneous Markov process, redundancy by substitution, active and passive modes, competitiveness indicator.
References
1. Imtiaz W.A., Iqbal J., Qamar A., Ali H. and Idrus S.M. (2017), “Impact of fiber duplication on protection architectures feasibility for passive optical networks”, Intech, no. 17, pp. 340-359.
2. ROSSTANDART (2008), GOST 53111-2008: Stability of functioning of the public communications network. Requirements and check methods, STANDARTINFORM, Moscow, Russia.
3. Dixit A., Mahloo M., Lannoo B., Chen J.-J., Wolsinska L., Colle D. and Pickavet M. (2014), “Protection strategies for next generation passive optical networks-2”, Optical Network Design, Modeling, 2014 International Conference, pp. 13-18.
4. Shuvalov V.P. and Selyanina I.U. (2012), “Methods for ensuring fault tolerance in multiservice communication networks”, Problems of Informatics, no. 2, pp. 55-62.
5. Egunov M.M. and Shuvalov V.P. (2012), “Structural reliability analysis of transport network”, Vestnik SibGUTI, no. 1, pp. 54-59.
6. Shuvalov V.P., Egunov M.M. and Minina E.A. (2015), Providing reliability indicators for telecommunications systems and networks. Moscow: Goryachaya liniya –Telecom.
7. Wolsinska L. and Chen J. (2008), “Reliability performance analysis vs deployment cost of fiber access networks”, 7th Int’l Conf. Optical Internet, pp. 1-2.
8. Wolsinska L.W. and Chen J. (2010), “Cost vs reliability performance study of fiber access network architectures”, IEEE Communications Magazine, no. 48, pp. 56-65.
9. Zhang J., Zhu K., Zang H., Matloff N.S. and Mukherjee B. (2007), “Availability-aware provisioning strategies for differentiated protection services in wavelength-convertible WDM mesh networks”, IEEE/ACM Transactions on Networking, vol. 15, no. 5, pp. 1177-1190.
10. Zelentsov B.P. (2016), Matrix models of communication systems functioning, SIBSUTIS, Novosibirsk, Russia
Shuvalov V.P. (2018), Long-Reach passive optical access networks: monography, in Shuvalov V.P. and Fokin V.G. (ed.). Moscow: Goryachaya liniya –Telecom.
Information about authors:
Vyacheslav P. Shuvalov, Siberian State University of Telecommunications and Information Sciences, Professor, Novosibirsk, Russia
Boris P. Zelentsov, Siberian State University of Telecommunications and Information Sciences, Professor, Novosibirsk, Russia
Irina G. Kvitkova, Siberian State University of Telecommunications and Information Sciences, Senior Lecturer, Novosibirsk, Russia