Simulation Modeling and Performance Evaluation of Local Area Networks

This doctoral thesis deals with the design of simulation model for performance evaluation of LANs which have highly-transient input-load and the performance evaluation of LANs for educational computer systems with the simulation model. Large scale distributed workstation systems are widely used at computer training centers in universities in Japan. These systems have many registered users more than 10; 000 and hundreds of client workstations for students. Most of those systems maintain the users’ personal data contents and public data like educational materials and large size programs using distributed file systems like NFS or AFS. These data are stored in one or more file servers. When a user uses his data, his station accesses the file server through the LAN. In such educational systems, however, concentrated network access caused by many users’ operations affects the performance of the LAN. Accurate estimation of access concentration to the LAN is very important to design educational systems. The aim of this study is to find suitable network design and develop the environment for evaluating the performance of such LAN systems. Extreme network access concentration which takes place on LANs of educational systems causes highly-transient load to the LANs. However, evaluating the performance of such LANs with traditional analytical method of single-layer simulation is difficult. In this thesis, at first, a protocol-based modeling and simulation method of performance evaluation for heavy traffic and transient LAN is proposed. In the method a node on a LAN is modeled as a set of detailed communication protocol models. By parallel and event driven processing of the models, high accuracy and high time-resolution of evaluation of LAN behaviors can be obtained at multi-layer protocols. The LANs at computer education sites have highly loaded peaks, and it is very hard to design large scale educational LANs. Proposed method can be used to evaluate such cases of heavy traffic and transient LAN.