Stochastic Petri Net Models of Service Availability in a PBNM System for Mobile Ad Hoc Networks

(Abstract) Policy based network management is a promising approach for provisioning and management of quality of service in mobile ad hoc networks. In this thesis, we focus on performance evaluation of this approach in context of the amount of service received by certain nodes called policy execution points (PEPs) or policy clients from certain specialized nodes called the policy decision points (PDPs) or policy servers. We develop analytical models for the study of the system behavior under two scenarios; a simple Markovian scenario where we assume that the random variables associated with system processes follow an exponential distribution and a more complex non-Markovian scenario where we model the system processes according to general distribution functions as observed through simulation. We illustrate that the simplified Markovian model provides a reasonable indication of the trend of the service availability seen by policy clients and highlight the need for an exact analysis of the system without relying on Poisson assumptions for system processes. In the case of the more exact non-Markovian analysis, we show that our model gives a close approximation to the values obtained via empirical methods. Stochastic Petri Nets are used as performance evaluation tools in development and analysis of these system models. Acknowledgements I would like to take this opportunity to express my deep appreciation and thanks to all those who helped me through the process of conducting this research. First and foremost, I am truly grateful to Dr. Luiz A. DaSilva for his constant support and encouragement throughout this research journey. He was an incessant motivating force in realizing this thesis. He was extremely patient and always provided me with an " active ear " to all the queries and problems I encountered during the course of this research. His relentless efforts to improve my technical writing skills are commendable. I would also like to thank Dr. Kaustubh Phanse for his instrumental role in driving me to conduct research in this area. He truly laid the foundation for this research by his own doctoral work and always provided a guiding hand through all the time he was at Virginia Tech. Away from Virginia Tech, he has been doing all he can in his ability as a mentor and a committee member to help me through various technical and non-technical difficulties I faced. One person who has always awed me as a teacher and a researcher is Dr. Midkiff. He …