Selected papers from ValueTools 2009

In recent years, a range of performance evaluation methodologies and tools has been developed within disparate research communities for the purposes of analysis or design of real-life systems ranging from computer systems to communication networks, call centers, or road traffic. The aim of ValueTools, the yearly International Conference on Performance Evaluation Methodologies and Tools, is to bring theory and practice together, and to build bridges between communities, e.g. computer science and engineering, telecommunications, physics, control, operations research, and statistics. The fourth edition of the ValueTools conference was held in Pisa in October 2009, with five co-located workshops. The conference was co-sponsored by ICST and CREATE-NET, and it received the technical co-sponsorship of ACM SIGMETRICS, SCS (Society for Modeling & Simulation International), and the Italian Movement for Modeling and Simulation (MIMOS). A total of 69 papers were submitted in the open call, and 27 were selected for presentation at the conference after a review process. The eight best papers were selected for possible publication in two special issues. One is the present issue of Performance Evaluation, for which five papers were selected and four accepted after a second review involving new referees. The other one, including three papers, appeared in Discrete Event Dynamic Systems, volume 21, number 1, 2011. In ‘‘Spatial fairness in linear wireless random-access networks’’, by P. Van de Ven, J. Van Leeuwaarden, D, Denteneer and G. Janssen, Markovian linear loss networks are studied. In the model, an active node blocks its k closest neighbors. The authors show how to achieve equal throughput at each node by tuning the arrival rates. In ‘‘Markovian Agents modeling swarm intelligence algorithms in wireless sensor networks’’, by D. Bruneo, M. Scarpa, A. Bobbio, D. Cerotti, and M. Gribaudo, authors study a model of interacting agents, each of them being a discrete-space Markov process sending messages to other agents and reacting to received messages by modifying its behavior. In ‘‘Orchestrating parallel TCP connections: cyclic and probabilistic polling policies’’, by O. Czerniak, E. Altman, and U. Yechiali, the Internet TCP protocol is studied on a ring model assuming that the congestion signals are sent to nodes either randomly or cyclically. In ‘‘Markovian Queueing Network with Complex Synchronizations: Product Form and Tensor’’, by T.-H. Dao Thi and J.-M. Fourneau, the authors study a general framework of Markovian models. They are characterized by a tensor description which is used to obtain a product-form result. The framework encompasses networks with negative customers and signals and Stochastic Automata Networks.