With the number of players of massively multiplayer online games (MMOG) going beyond the millions, there is a need for an efficient way to manage these huge digital worlds. These virtual environments are dynamic and sudden increases in player density in a part of the world have an impact on the load of the server responsible for that section of the virtual world. In this paper we propose the division of the world into several interacting microcells that can be dynamically assigned to a set of servers. We outline the architecture of such a system and describe a set of algorithms that assign the microcells to the available servers. The maximum load experienced by a server is used as a minimization criterion. The different algorithms are compared with each other and with the standard approach used in these games.

Abstract-Distributed systems often use a form of communication middleware to cope with different forms of heterogeneity, including geographical spreading of the components, different programming languages and platform architectures, etc. The middleware will, of course, impact the architecture and the performance of the system. This paper presents a model transformation framework to automatically include the architectural impact and the overhead incurred by using a middleware layer between several system components. Using this framework, architects can model the system in a middleware-independent fashion. Accurate, middlewareaware models can then be obtained automatically using a middleware model repository. The actual transformation algorithm will be presented in more detail. The resulting models can be used to obtain performance models of the system. From those performance models, early indications of the system performance can be extracted.

As Massively Multiplayer Online Games enjoy a huge popularity and are played by tens of thousands of players simultaneously, an efficient software architecture is needed to cope with the dynamically changing loads at the server side. In this paper we discuss a novel way to support this kind of application by dividing the virtual world into several parts, called microcells. Every server is assigned a number of microcells and by dynamically redeploying these microcells when the load in a region of the world suddenly increases, the platform is able to adapt to changing load distributions. The software architecture for this system is described and we also provide some evaluation results that indicate the performance of our platform.

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When designing and evaluating software architectures and network facilities for hosting demanding distributed applications, taking performance considerations into account is essential. A key factor in assessing the performance of such a distributed system is the network latency and its relation to the application behaviour. In this respect, it is important to include the performance impact of the network into the performance models used during the entire design cycle of the system.A framework is proposed that allows to model both the software and the network components separately and extracts a single set of performance estimates for the entire system. This has the advantage of allowing the network and software aspects to be modeled separately using the modeling languages and tools most suited to those system aspects. A case study is presented to illustrate the use of the framework and its usefulness in predicting system performance.