Dynamic bandwidth allocation using infinitesimal perturbation analysis

Advances in network management and switching technologies make dynamic bandwidth allocation of logical networks built on top of a physical network possible. Previous proposed dynamic bandwidth allocation algorithms are based on simplified network model. The analytical model is valid only under restrictive assumptions. Infinitesimal Perturbation Analysis, a technique which estimates the gradients of the functions in discrete event dynamic systems by passively observing the system, is used to estimate delay sensitivities under general traffic patterns. A new dynamic bandwidth allocation algorithm using on-line sensitivity estimation is proposed. Simulation results show that the approach further improves network performance. Implementation of the proposed algorithm in operational networks is also discussed.published_or_final_versio

Protocol engineering from Estelle specifications

Bibliography: leaves 129-132.The design of efficient, reliable communication protocols has long been an area of active research in computer science and engineering, and will remain so while the technology continues to evolve, and information becomes increasingly distributed. This thesis examines the problem of predicting . the performance of a multi-layered protocol system directly from formal specifications in the ISO specification language Estelle, a general-purpose Pascal-based language with support for concurrent processes in the form of communicating extended finite-state machines. The thesis begins with an overview of protocol engineering, and a discusses the areas of performance evaluation and protocol specification. Important parts of the mathematics of discrete-time semi-Markov processes are presented to assist in understanding the approaches to performance evaluation described later. Not much work has been done to date in the area of performance prediction from specifications. The idea was first mooted by Rudin, who illustrated it with a simple model based on the global state reachability graph of a set of synchronous communicating FSMs. About the same time Kritzinger proposed a closed multiclass queueing model. Both of these approaches are described, and their respective strengths and weaknesses pointed out. Two new methods are then presented. They have been implemented as part of an Estelle-based CASE tool, the Protocol Engineering Workbench (PE!V). In the first approach, we show how discrete-time semi-Markov chain models can be derived from meta-executions of Estelle specifications, and consider ways of using these models predictively. The second approach uses a structure similar to a global-state graph. Many of the limitations of Rudin's approach are overcome, and our technique produces highly accurate performance predictions. The PEW is also described in some detail, and its use in performance evaluation illustrated with some examples. The thesis concludes with a discussion of the strengths and weaknesses of the new methods, and possible ways of improving them

Discrete Event Systems: Models and Applications; Proceedings of an IIASA Conference, Sopron, Hungary, August 3-7, 1987

Work in discrete event systems has just begun. There is a great deal of activity now, and much enthusiasm. There is considerable diversity reflecting differences in the intellectual formation of workers in the field and in the applications that guide their effort. This diversity is manifested in a proliferation of DEM formalisms. Some of the formalisms are essentially different. Some of the "new" formalisms are reinventions of existing formalisms presented in new terms. These "duplications" reveal both the new domains of intended application as well as the difficulty in keeping up with work that is published in journals on computer science, communications, signal processing, automatic control, and mathematical systems theory - to name the main disciplines with active research programs in discrete event systems. The first eight papers deal with models at the logical level, the next four are at the temporal level and the last six are at the stochastic level. Of these eighteen papers, three focus on manufacturing, four on communication networks, one on digital signal processing, the remaining ten papers address methodological issues ranging from simulation to computational complexity of some synthesis problems. The authors have made good efforts to make their contributions self-contained and to provide a representative bibliography. The volume should therefore be both accessible and useful to those who are just getting interested in discrete event systems