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QoS control and guarantees for IP/MPLS VPN services are increasingly important for network service providers. The dynamic control of QoS parameters is still an open issue. A control theory based packet loss control system is proposed to dynamic maintain the preset packet loss probability targets for instantiated VPN services in the core network, where the transducer and the dynamic packet loss model have been studied in the previous studies, respectively. However, the identified linear model contains time-varying and norm-bounded uncertain parameters. This paper will extend the previous research to design a robust and optimal controller for the complete QoS control system. Specially, a Linear Matrix Inequality (LMI) approach for designing the robust and optimal Proportional- Integral (PI) controller is studied. By adopting the LMI expression, a symmetric positive definite matrix P with guaranteed overall system's quadratic stability is determined. The matrix P finally infers the robust PI controller parameters. A number of experiments are devised on the live NCIT*net network to evaluate the performance of the controller.
Date of Conference: Nov. 27 2006-Dec. 1 2006