Stochastic Model for QoS Assessment in Multi-tier Web Services

  • Authors:

  • Ricardo M. Czekster;Paulo Fernandes;Afonso Sales;Thais Webber;Avelino F. Zorzo

  • Affiliations:

  • Pontifícia Universidade Católica do Rio Grande do Sul, Avenida Ipiranga, 6681 - Prédio 32, 90619-900 - Porto Alegre - RS - Brazil;Pontifícia Universidade Católica do Rio Grande do Sul, Avenida Ipiranga, 6681 - Prédio 32, 90619-900 - Porto Alegre - RS - Brazil;Pontifícia Universidade Católica do Rio Grande do Sul, Avenida Ipiranga, 6681 - Prédio 32, 90619-900 - Porto Alegre - RS - Brazil;Pontifícia Universidade Católica do Rio Grande do Sul, Avenida Ipiranga, 6681 - Prédio 32, 90619-900 - Porto Alegre - RS - Brazil;Pontifícia Universidade Católica do Rio Grande do Sul, Avenida Ipiranga, 6681 - Prédio 32, 90619-900 - Porto Alegre - RS - Brazil

  • Venue:
  • Electronic Notes in Theoretical Computer Science (ENTCS)
  • Year:
  • 2011

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Abstract

Service Level Agreements (SLAs) are used to guarantee quality of service (QoS) between customers and service providers. In an SLA, parties establish a common set of rules and responsibilities. In this paper we propose a practical stochastic modeling of a multi-tier architecture considering SLAs for specific transactions. The model is parameterized with available performance testing data for a real web service, and with a testing environment having unpredictable and unknown external workloads of simultaneous execution. In addition, we present multiple scenarios of external applications impacting on the SLAs in our target architecture. Having a previous knowledge about the average time demanded by some external applications, our model results can provide evidences when the system under test will not respect the agreed-upon SLAs. Finally, we discuss possible model extensions towards further unknown workload characterizations and considerations about application execution profiling.