AVAILABILITY EVALUATION OF NETWORKS: AN APPROACH FOR N-TIER CLIENT SERVER ARCHITECTURE

Flávia S. Coelho¹     Jacques P. Sauvé²     Cláudia B. Abbas³

[1] U. Católica de Brasília, Brasil, Phone: +55-610-356-9314 Fax: +55-83-356-3010, fcoelho@uch.br

[2] U. Federal de Campina Grande, Dept. de Sistemas e Computação, Brasil, Phone: +55-83-310-1120, Fax: +55-83-310-1124, jacques@dsc.ufcg.edu.br

[3] U. de Brasília , Dept. Engenharia Elétrica, Lab. Redes, Faculdade de Tecnologia, Brasil, Phone: +55-61-3072308 Fax: +55-61-274-6651, barenco@redes.unb.br

ABSTRACT

Published work on computer network reliability frequently uses availability as a performance measure. However, although several ways of defining availability have been proposed, none capture the overall level of service obtained by client hosts in a modern n-tier client/server architecture. We propose such a measure by calculating the fraction of client hosts receiving complete services from the network. We also extend a published, efficient heuristic method for calculating availability to take into account our new proposed measure. The end result is a procedure of polynomial complexity O(nt4), where nt is the total number of components (hosts, links and interconnection equipment) in the network. Numerical results of applying the method to several networks are given.

Keywords: Evaluation of availability, network availability, dependability, n-tier client/server architecture

REFERENCES

[1] Bulletproofing; "Networks for High-Availability Computing", White Paper. www.3com.com/technology/tech-net/white-papers/500693.htm, 1998.

[2] V. Bonaventura; "Service Availability of Communication Networks", Proceedings 1980 National Telecommunication Conference, 1980.

[3] J. Buchanan, E. Weal; "High-Availability Networks", www.3com.com/nsc/netage/q1_1999/p24.html, 1999.

[4] High System Availability. Product Bulletin. Cisco Systems, 1999.

[5] Prerequisites for High-Availability Infrastructures. White paper. Cisco Systems, 2000.

[6] J. Edwards; "3-Tier Server/Client at Work", John Wiley & Sons, 1999.

[7] K. K. Aggarwal, J. S. Gupta, K. B. Misra; "A Simple Method for Reliability Evaluation of a Communication Systems", IEEE Transactions on Communications, Vol. 23, 1975.

[8] M. O. Ball; "Computing Network Reliability", Operations Research, Vol. 27, 1979.

[9] M. Ball, R. M. Van Slyke; "Backtracking Algorithms for Network Reliability Analysis", Annals of Discrete Mathematics, Vol.1, 1977.

[10] P. Kubat; "Estimation of Reliability for Communication Computer Networks - Simulation/Analytic Approach", IEEE Transactions on Communications, Vol. 37, 1989.

[11] D. Torrieri; "Calculation of Node-Pair Reliability in Large Networks with Unreliable Nodes", IEEE Transactions on Reliability, Vol. 43, 1994.

[12] R. Van Slyke, H. Frank; "Network Reliability Analysis: Part I". Networks, Vol. 1, 1972.

[13] M. O. Ball; "Complexity of Network Reliability Computations", Networks, Vol. 10, 1980.

[14] V. O. K. Li, J. A. Silvester; "An Approach for Studying the Performance of Networks with Unreliable Components", Technical Report CSI-02-01. University Southern California, 1983.

[15] V. O. K. Li, J. A. Silvester; "Performance Analysis of Networks with Unreliable Components", IEEE Transactions on Communications, Vol. 32, 1984.

[16] S. Even; "Graph Algorithms", Rockville, 1979.

[17]  Link Builder MSH Multi-Services Hubs; Product Data Sheet; www.3com.com/products/dsheets/400153.html, 2000.

[18] HSRP Support; Product Bulletin #768; www.cisco.com/warp/public/732/100/768-pb.htm, 1999.

[19] Deterministic Load Distribution; Product Bulletin#271;www.cisco.com/warp/public/732/102/271-pb.htm, 1999.

[20] High System Availability; Product Bulletin; Cisco Systems, 1999.

[21] Prerequisites for High-Availability Infrastructures; White paper; Cisco Systems, 2000.

[22] F. Coelho; "Avaliação de Disponibilidade de Redes de Computadores Baseadas na Arquitetura Cliente/Servidor em n Camadas", Master's Thesis, Universidade Federal da Paraíba, 2000.

[23] S. Pierre, A. Elgibaoui; "A Tabu-Search Approach for Designing Computer-Network Topologies with Unreliable Components", IEEE Transactions on Reliability, Vol. 46, 1997.

[24] A. Balakrishnan, T. L. Magnanti, P. Mirchandani; "Designing Hierarchical Survivable Networks", Operations Research, Vol.46, 1998.

[25] R. Perlman; "Interconnections"; Addison-Wesley, 1992.

[26] M. Ford, H. K. Lew, S. Spanier, T. Stevenson; "Internetworking Technologies Handbook"; Cisco Press, 1997.

Recibido el 19 de noviembre de 2002, aceptada el 02 de septiembre de 2003.