Em geral, jogos classificados como ‘jogos online maciçamente multijogador’, ou massively multiplayer online games (MMOGs) são simulações interativas, competitivas, em tempo real e em larga escala, de mundos virtuais gráficos. Atualmente, a maioria (se não todos) os MMOGs lançados comercialmente são implementados como serviços centralizados, onde centenas ou até milhares de máquinas servidoras, mantidas pelo provedor do serviço do jogo, são responsáveis por executar quase toda a simulação do mundo virtual. Isto implica em gastos significativos em equipamentos e comunicação por parte dos provedores do jogo. Vários trabalhos tentam reduzir o custo de hospedar um MMOG propondo modelos de distribuição da simulação mais descentralizados (peer-to-peer), onde a simulação é movida parcialmente ou totalmente dos servidores (máquinas dos provedores do jogo) para os nós clientes, tipicamente PCs de jogadores conectados por banda larga residencial. Porém, a tentativa de descentralizar um MMOG cria problemas de segurança, na medida em que a simulação passa a ser delegada a nós clientes, que são nós intrinsecamente não-confiáveis que ganham a oportunidade de trapacear no jogo, burlando as regras, visto que as regras da simulação serão executadas por estes. Existem vários tipos de trapaças, mas nós mostramos nesta tese que é possível argumentar que a trapaça de estado (state cheating) e ataques de negação de serviço são as ameaças mais significativas para MMOGs peer-to-peer. Como consequência, nós propomos o FreeMMG 2, um novo modelo de descentralização de MMOGs baseado na divisão do mundo virtual em células que são mantidas individualmente por grupos separados de peers voluntários que executam um processo daemon, não-interativo de simulação. Cada peer de uma célula contém uma réplica completa do estado da célula e se sincroniza de forma tanto conservadora quanto otimista com cada outro peer (réplica) da célula, enquanto ao mesmo tempo recebe comandos de jogo e dissemina atualizações de jogo para as máquinas ‘cliente’ dos jogadores do jogo. Devido à replicação e à seleção aleatória de peers para as células, nós mostramos que o FreeMMG 2 é resistente a trapaça de estado. E, devido ao uso de um peer back-up secreto para cada peer réplica primária da célula, nós mostramos que ataques de negação de serviço contra os peers não irão aumentar de forma significativa a probabilidade de ocorrência de trapaça de estado ou de perda total do estado da célula atacada. Através de simulação de rede, nós mostramos que o FreeMMG 2 é escalável e que utiliza a largura de banda dos clientes de forma eficiente. Assim, mostramos que uma abordagem baseada em replicação de suporte a MMOGs, considerando clientes com conectividade à Internet realística (sem IP multicast e com banda larga doméstica), é viável. / Typically, games classified as ‘massively multiplayer online games’ (MMOGs) are competitive, real-time, large-scale interactive simulations of graphical virtual worlds. Currently, most (if not all) commercial MMOGs are implemented as centralized services, where hundreds or even thousands of ‘server’ machines, maintained by the game service provider, are responsible for running almost all of the virtual world simulation. This incurs a significant equipment and communication cost for the game providers. Several works attempt to reduce the cost of hosting a MMOG by proposing more decentralized, peer-to-peer models for distributing the simulation among client (player-owned PCs with consumer-grade broadband) and server (provider-owned) machines, with some going as far as eliminating the need for provider-owned machines altogether. Decentralizing a MMOG, however, creates security issues, as the simulation is now delegated to untrusted client nodes which gain opportunities to cheat the game rules, as the rules are now executed by them. There are several types of cheats, but we show in this thesis that a case can be made for considering state cheating and denial-of-service attacks as the most significant threats for peer-to-peer MMOGs. In light of this, we propose FreeMMG 2, a new MMOG decentralization model based on the division of the virtual world into cells that are maintained individually by separate groups of volunteer peers that are running a non-interactive, daemon simulation process. Each peer of a cell contains a full replica of the cell state and synchronizes both conservatively and optimistically with every other peers (replicas) of the cell, while at the same time receiving game commands and disseminating game updates to actual player machines. Due to its cell replication and random peer selection, we show that FreeMMG 2 is resistant to state cheating. And, due to the use of one secret back-up peer for every primary replica peer of the cell, we show that denial-of-service attacks don’t significantly increase the odds of either state cheating or cell state loss happening. Through network simulation we verify that FreeMMG 2 is scalable and bandwidth-efficient, showing that a replication-based approach to peer-to-peer MMOG support, considering peers with realistic Internet connectivity (no IP multicast and consumer-grade broadband), is a viable one.

Tradicionalmente, utiliza-se um servidor central para prover suporte a MMOGs (massively multiplayer online games, ou jogos online maciçamente multijogador), nos quais o número de participantes é da ordem de dezenas de milhares. Muitos trabalhos foram realizados com o intuito de criar um modelo de suporte completamente descentralizado, par-a-par, para este tipo de aplicação, minimizando o custo de manutenção da sua infraestrutura, mas algumas questões críticas persistem. Exemplos de problemas do modelo de suporte par-a-par são: vulnerabilidade a trapaça, sobrecarga da banda de envio dos pares e dificuldade para manter a consistência da simulação entre os diferentes participantes. Neste trabalho, é proposta a utilização de nodos de baixo custo geograficamente distribuídos, operando como um servidor distribuído de jogo. O modelo de distribuição proposto e alguns trabalhos relacionados também são apresentados. Para tratar o custo de comunicação imposto aos servidores, foi projetado aqui um novo refinamento para a técnica de gerenciamento de interesse, reduzindo significativamente a largura de banda necessária ao jogo. Foram realizadas simulações utilizando o simulador ns-2, comparando diferentes algoritmos de área de interesse. Os resultados demonstram que a nossa proposta é a que tem a menor utilização de largura de banda, com uma redução em 33,10% do tráfego máximo, e em 33,58% do tráfego médio, quando comparada com outros algoritmos de gerenciamento de interesse. Além disso, em uma arquitetura de servidor distribuído para MMOGs, com recursos heterogêneos, os nodos servidores podem ser facilmente sobrecarregados pela alta demanda dos jogadores por atualizações de estado. Neste trabalho, é proposto também um esquema de balanceamento de carga que utiliza o tráfego de rede como a carga a balancear entre os servidores e tem como objetivos principais: alocar a carga nos servidores proporcionalmente à capacidade de cada um e reduzir tanto quanto possível o overhead introduzido pela própria distribuição. O esquema de balanceamento é dividido em três fases: seleção local de servidores para participarem, o balanceamento em si e o posterior refinamento da divisão de carga. Quatro algoritmos foram propostos: ProGReGA, ProGReGA-KH, ProGReGA-KF e BFBCT. Destes, o ProGReGA foi o que introduziu o menor overhead de todos e o ProGReGA-KF foi o que se mostrou mais eficiente para reduzir o número de migrações de jogadores entre servidores. / Traditionally, a central server is used to provide support to MMOGs (massively multiplayer online games), where the number of participants is in the order of tens of thousands. Much work has been done trying to create a fully peer-to-peer model to support this kind of application, in order to minimize the maintenance cost of its infra-structure, but critical questions remain. Examples of the problems relative to peer-to-peer MMOG support systems are: vulnerability to cheating, overload of the upload links of the peers and difficulty to maintain consistency of the simulation among the participants. In this work, it is proposed the utilization of geographically distributed lower-cost nodes, working as a distributed server to the game. The distribution model and some related works are also presented. To address the communication cost imposed to the servers, we specify a novel refinement to the area of interest technique, significantly reducing the necessary bandwidth. Simulations have been made with ns-2, comparing different area of interest algorithms. The results show that our approach achieves the least bandwidth utilization, with a 33.10% maximum traffic reduction and 33.58% average traffic reduction, when compared to other area of interest algorithms. Besides, in a distributed MMOG server architecture, with heterogeneous resources, the server nodes may become easily overloaded by the high demand from the players for state updates. In this work, we also propose a load balancing scheme, which considers the network traffic as the load to balance between the servers, and it has the following main objectives: allocate load on the servers proportionally to the power of each one of them and reduce as much as possible the overhead introduced by the distribution itself. It is is divided in three phases: local selection of servers, balancing and refinement. Four algorithms were proposed: ProGReGA, ProGReGA-KH, ProGReGA-KF and BFBCT. From these, ProGReGA has proved to be the best for overhead reduction and ProGReGA-KF is the most suited for reducing player migrations between servers.

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vii, 124 p. / Despite the rise in participation and economic importance of online games as a media phenomenon, ever-growing virtual worlds that seemingly exist as "third places" for social interaction and relationship formation, there is little research on the experiences of gamers with harassment, discrimination, and hate speech. Though changes in the industry serve as evidence of shifting attitudes about female, GLBTQ, and non-white gamers, harassment and use of hate speech based on sex and sexual orientation continue to flourish unchecked in online games. This study explores the prevalence of homophobia and sexism in online games as expressed through "griefing" behavior used to police competitive spaces traditionally dominated by white, heterosexual men. This thesis employs qualitative research methods to illuminate the persisting homophobia, sexism, and racism as experienced by gamers in online console and PC games. / Committee in charge: Carol Stabile, Chair; Pat Curtin, Member; Gabriella Martinez, Member

<p>Purpose/Aim: The aim of the paper is to find out if there is a correlation between playing MMORPGs and having better skills in using multi-channel communication.</p><p>Material/Method: A media-skill test was conducted in the internet testing the participants’ ability to respond to targets in three different channels and media at the same time. The results of the study where used for statistical comparisons of the different groups of participants sorted according to their media use.</p><p>Main results: People who use the internet more and who play computer games, especially MMORPGs, have a better Multi-Media Multi-Channel Communication Literacy. There is fast learning visible for people with a use of the respective medium of up to five hours a week. Playing makes you better, not playing a lot.</p>

Purpose/Aim: The aim of the paper is to find out if there is a correlation between playing MMORPGs and having better skills in using multi-channel communication. Material/Method: A media-skill test was conducted in the internet testing the participants’ ability to respond to targets in three different channels and media at the same time. The results of the study where used for statistical comparisons of the different groups of participants sorted according to their media use. Main results: People who use the internet more and who play computer games, especially MMORPGs, have a better Multi-Media Multi-Channel Communication Literacy. There is fast learning visible for people with a use of the respective medium of up to five hours a week. Playing makes you better, not playing a lot.

To adolescents, online game provides a rich playground for developing competence in leadership, coordination, teamwork, and cooperation. Adopting the perspective of positive psychology and social cognitive theory, this research investigates how factors such as personal and social factors may impact adolescents' learning outcomes and subjective will-being. The results show that game efficacy, adolescents' game attitudes, and social influences are important factors that influence adolescents' online game behavior. Moreover, playing online games may improve adolescents' psychological affects and learning, which in turn enhance players' subjective well-being. These results provide a new perspective to game researchers, teachers and parents and can help game manufactures and government in designing games and making policies.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Recently, there has been significant research focus on Peer-to-Peer (P2P) Massively Multi-user Virtual Environments (MMVEs). A number of architectures have been presented in the literature to implement the P2P approach. One aspect that has not received sufficient attention in these architectures is state management and state persistency in P2P MMVEs. This work presents and simulates a novel state management and persistency architecture, called Pithos. In order to design the architecture, an investigation is performed into state consistency architectures, into which the state management and persistency architecture should fit. A novel generic state consistency model is proposed that encapsulated all state consistency models reviewed. The requirements for state management and persistency architectures, identified during the review of state consistency models, are used to review state management and persistency architectures currently receiving research attention. Identifying some deficiencies present in current designs, such as lack of fairness, responsiveness and scalability, a novel state management and persistency architecture, called Pithos, is designed. Pithos is a reliable, responsive, secure, fair and scalable distributed storage system, ideally suited to P2P MMVEs. Pithos is implemented in Oversim, which runs on the Omnet++ network simulator. An evaluation of Pithos is performed to verify that it satisfies the identified requirements. It is found that the reliability of Pithos depends heavily on object lifetimes. If an object lives longer on average, retrieval requests are more reliable. An investigation is performed into the factors influencing object lifetime. A novel Markov chain model is proposed which allows for the prediction of objects lifetimes in any finite sized network, for a given amount of redundancy, node lifetime characteristics and object repair rate. / AFRIKAANSE OPSOMMING: Onlangs is daar ’n beduidende navorsingsfokus op Eweknie Massiewe Multi-gebruiker Virtuele Omgewings (MMVOs). ’n Aantal argitekture is in die literatuur beskikbaar wat die eweknie benadering voorstel. Een aspek wat nie voldoende aandag ontvang in hierdie argitekture nie is toestandsbestuur en toestandsvolharding in eweknie MMVOs. Hierdie werk ontwerp en simuleer ’n nuwe toestandsbestuur- en toestandsvolhardingargitektuur genaamd Pithos. Ten einde die argitektuur te ontwerp is ’n ondersoek uitgevoer in toestandskonsekwentheidargitekture, waarin die toestandsbestuur- en toestandsvolhardingargitektuur moet pas. ’n Nuwe generiese toestandskonsekwentheidargitektuur word voorgestel wat alle hersiene toestandskonsekwentheid argitekture vervat. Die vereistes vir die toestandsbestuur- en toestandsvolhardingargitekture, geidentifiseer tydens die hersiening van die toestandskonsekwentheidargitekture, word gebruik om toestandsbestuuren toestandsvolhardingargitekture te hersien wat tans navorsingsaandag geniet. Identifisering van sekere leemtes teenwoordig in die huidige ontwerpe, soos ’n gebrek aan regverdigheid, responsiwiteit en skaleerbaarheid, lei tot die ontwerp van ’n nuwe toestandsbestuur- en toestandsvolhardingargitektuur wat Pithos genoem word. Pithos is ’n betroubare, responsiewe, veilige, regverdige en skaleerbare verspreide stoorstelsel, ideaal geskik is vir eweknie MMVOs. Pithos word geïmplementeer in Oversim, wat loop op die Omnet++ netwerk simulator. ’n Evaluering van Pithos word uitgevoer om te verifieer dat dit voldoen aan die geïdentifiseerde behoeftes. Daar is gevind dat die betroubaarheid van Pithos afhang van die objek leeftyd. As ’n objek gemiddeld langer leef, dan is herwinning versoeke meer betroubaar. ’n Ondersoek word uitgevoer na die faktore wat die objek leeftyd beïnvloed. ’n Nuwe Markov ketting model word voorgestel wat voorsiening maak vir die voorspelling van objek leeftye in eindige grootte netwerke, vir gegewe hoeveelhede van oortolligheid, nodus leeftyd eienskappe en objek herstelkoers.

<p>Purpose/Aim: The aim of this paper is to study how guild leaders in World of Warcraft (WOW) and leaders of real life organizations compare in terms of tasks, every-day experiences, environment, responsibilities and motivation. This comparison is used to build a new theory describing leadership in Massively Multiplayer Online Role Playing Games (MMORPGs).</p><p>Material/Method: The paper uses the grounded theory approach to build a new theory. 12 interviews were conducted, six with WOW guild leaders and six with leaders of real life organizations. The Four Capacities Framework and the Leadership Grid were used to analyze and compare the results of the interviews.</p><p>Main results: Leadership in MMORPGs is as complex and challenging as real life leadership with the difference that it stresses the internal relationships of the organization very much while neglecting outside relations to a big extend. Guild leadership is in many ways similar to real life leadership as both require long term political decisions, policy setting and good work in the field of human resources. However, it stresses the ability to build working social relationships and to motivate using only digital communication. Some aspects of real life leadership like customer orientation and an organizational instance over the leader like an owner or share holders that the leader is responsible to are not existent.</p>

<p>This dissertation is a study of social interaction in virtual worlds and virtual world design. A virtual world is a synchronous, multi-user system that offers a persistent spatial environment for iconically represented participants. Together, these form an example of social interaction design. I have applied an arena perspective on my object of study, meaning that I focus on these socio-technical systems as places.</p><p>I have investigated the persistent qualities of social interaction in virtual worlds. What I have found is that virtual worlds are as real as the physical world. They are filled with real people interacting with each other evoking real emotions and leading to real consequences. There are no fixed boundaries between the virtual and physical arenas that make up a participant’s lifeworld.</p><p>I have found that participants in virtual worlds are not anonymous and bodiless actors on a level playing field. Participants construct everything needed to create social structures such as identities and status symbols. The qualities of social interaction in virtual worlds cannot be measured against physical interaction. Doing so conceals the qualities of virtual interaction. Through the concepts of levity and proximity, I offer an alternative measure that better captures the unique properties of the medium. Levity is related to the use of avatars and the displacement into a virtual context and manifests itself as a kind of lightness in the way participants approach the interaction. Proximity is my term for the transformation of social distances that takes place in virtual worlds. While participants perceive that they are in the same place despite being physically separated, the technology can also create barriers separating participants from their physical surroundings. The gap between the participant and her avatar is also of social significance.</p><p>As a theoretical foundation for design, I have used Michael Heim’s writings and practices as a base for a phenomenologically grounded approach, which provides an alternative to the dominating perspectives of architecture and engineering. Based on an explorative design project and the earlier mentioned findings regarding social interaction, I have formulated a model for virtual world design called interacture. This model takes the interaction between participants as the fundamental building material and the starting point of the design process. From there, layers of function and structure are added, all the time balancing the design between fantasy and realism.</p><p>I have explored the possibilities of using ethnographic studies as the foundation for a participant centered design approach. I have aimed for an inside view of my object of study both as an ethnographer and as a designer. One outcome of this approach is that I have come to understand virtual worlds not just as places but also as processes where the experience of participating can change drastically over time as the participant reaches new stages in the process.</p><p>In conclusion, the method of integrating ethnography with design and the understanding of social interaction as the fundamental building material is woven into a general approach to the study and design of socio-technical systems called social interaction design.</p>