Improved survivability analysis for SONET SHRs

摘要

Recently, a special type of Markov model called parametric state reward Markov model (SRMM/p) [H.C. Cankaya, V.S.S. Nair, in f IEEE Proceedings of GLOBECOM 97, vol. 1, IEEE Computer Soc. Press, Silver Spring, MD, l997, pp. 252--256] and a set of survivability metrics comprising reliability, availability, and restorability have been proposed for the evaluation of self healing SONET mesh networks IH.C. Cankaya, V.S.S, Nair, in f Proceedings of ISCIS 'XII, vol. 1, Bogazici University, Bogazici University Press, 1997, pp. 269--276]. The SRMM/p accommodates multiple consecutive link failures and uses topology-free approximation in order to calculate the average performance loss due to a failure. The SRMM/p is equally applicable to the analysis of self-healing SONET rings by considering a ring as a special case of a mesh topology [H.C. Cankaya, V.S.S. Nair, in f IEEE Proceedings of GLOBECOM '98, vol. 4, IEEE Computer Soc. Press, Silver Spring, MD, 1998, pp. 2276--2281]. Further, the topological uniformity and simplicity of rings allow one to include more detailed features of the network in the model so that the analysis will be more accurate. For this purpose, we propose an improved approach to the survivability analysis of self healing SONET rings which employs a probability- tree based evaluation of the probability of various system states resulting from all possible combinations of node and link failures. The corresponding tree-construction and traversal algorithms are presented. Survivability of rings with dis- tinctive demand patterns are studied with the improved analysis and compared experimentally. One limitation to the model is the high run-time complexity caused mainly by the disparity between transition rates amongst various states in the SRMM/p [H.C. Cankaya, V.S.S. Nair, ACM Comput. Commun. Rev. 28 (4) (l998) 268--277]. In this paper, we also present an approach to circumvent this problem by state aggregation method and compare the results in terms of run- time complexity and accuracy by conducting an experimental study. @ l999 E1sevier Science B.V. All rights reserved.