Stochastic Model for QoS Assessment in Multi-tier Web Services

Ricardo M. Czekster*, Paulo Fernandes, Afonso Sales, Thais Webber, Avelino F. Zorzo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)53-72
Number of pages20
JournalElectronic Notes in Theoretical Computer Science
Issue number1
Publication statusPublished - 27 Sept 2011


  • Analytical Modeling
  • Performance Evaluation
  • Quality of Service
  • Service Level Agreements
  • Stochastic Automata Networks


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