Enhancing trustability in MMOGs environments

Massively Multiplayer Online Games (MMOGs; e.g., World of Warcraft), virtual worlds (VW; e.g., Second Life), social networks (e.g., Facebook) strongly demand for more autonomic, security, and trust mechanisms in a way similar to humans do in the real life world. As known, this is a difficult matter because trusting in humans and organizations depends on the perception and experience of each individual, which is difficult to quantify or measure. In fact, these societal environments lack trust mechanisms similar to those involved in humans-to-human interactions. Besides, interactions mediated by compute devices are constantly evolving, requiring trust mechanisms that keep the pace with the developments and assess risk situations. In VW/MMOGs, it is widely recognized that users develop trust relationships from their in-world interactions with others. However, these trust relationships end up not being represented in the data structures (or databases) of such virtual worlds, though they sometimes appear associated to reputation and recommendation systems. In addition, as far as we know, the user is not provided with a personal trust tool to sustain his/her decision making while he/she interacts with other users in the virtual or game world. In order to solve this problem, as well as those mentioned above, we propose herein a formal representation of these personal trust relationships, which are based on avataravatar interactions. The leading idea is to provide each avatar-impersonated player with a personal trust tool that follows a distributed trust model, i.e., the trust data is distributed over the societal network of a given VW/MMOG. Representing, manipulating, and inferring trust from the user/player point of view certainly is a grand challenge. When someone meets an unknown individual, the question is “Can I trust him/her or not?”. It is clear that this requires the user to have access to a representation of trust about others, but, unless we are using an open source VW/MMOG, it is difficult —not to say unfeasible— to get access to such data. Even, in an open source system, a number of users may refuse to pass information about its friends, acquaintances, or others. Putting together its own data and gathered data obtained from others, the avatar-impersonated player should be able to come across a trust result about its current trustee. For the trust assessment method used in this thesis, we use subjective logic operators and graph search algorithms to undertake such trust inference about the trustee. The proposed trust inference system has been validated using a number of OpenSimulator (opensimulator.org) scenarios, which showed an accuracy increase in evaluating trustability of avatars. Summing up, our proposal aims thus to introduce a trust theory for virtual worlds, its trust assessment metrics (e.g., subjective logic) and trust discovery methods (e.g., graph search methods), on an individual basis, rather than based on usual centralized reputation systems. In particular, and unlike other trust discovery methods, our methods run at interactive rates.MMOGs (Massively Multiplayer Online Games, como por exemplo, World of Warcraft), mundos virtuais (VW, como por exemplo, o Second Life) e redes sociais (como por exemplo, Facebook) necessitam de mecanismos de confiança mais autónomos, capazes de assegurar a segurança e a confiança de uma forma semelhante à que os seres humanos utilizam na vida real. Como se sabe, esta não é uma questão fácil. Porque confiar em seres humanos e ou organizações depende da percepção e da experiência de cada indivíduo, o que é difícil de quantificar ou medir à partida. Na verdade, esses ambientes sociais carecem dos mecanismos de confiança presentes em interacções humanas presenciais. Além disso, as interacções mediadas por dispositivos computacionais estão em constante evolução, necessitando de mecanismos de confiança adequados ao ritmo da evolução para avaliar situações de risco. Em VW/MMOGs, é amplamente reconhecido que os utilizadores desenvolvem relações de confiança a partir das suas interacções no mundo com outros. No entanto, essas relações de confiança acabam por não ser representadas nas estruturas de dados (ou bases de dados) do VW/MMOG específico, embora às vezes apareçam associados à reputação e a sistemas de reputação. Além disso, tanto quanto sabemos, ao utilizador não lhe é facultado nenhum mecanismo que suporte uma ferramenta de confiança individual para sustentar o seu processo de tomada de decisão, enquanto ele interage com outros utilizadores no mundo virtual ou jogo. A fim de resolver este problema, bem como os mencionados acima, propomos nesta tese uma representação formal para essas relações de confiança pessoal, baseada em interacções avatar-avatar. A ideia principal é fornecer a cada jogador representado por um avatar uma ferramenta de confiança pessoal que segue um modelo de confiança distribuída, ou seja, os dados de confiança são distribuídos através da rede social de um determinado VW/MMOG. Representar, manipular e inferir a confiança do ponto de utilizador/jogador, é certamente um grande desafio. Quando alguém encontra um indivíduo desconhecido, a pergunta é “Posso confiar ou não nele?”. É claro que isto requer que o utilizador tenha acesso a uma representação de confiança sobre os outros, mas, a menos que possamos usar uma plataforma VW/MMOG de código aberto, é difícil — para não dizer impossível — obter acesso aos dados gerados pelos utilizadores. Mesmo em sistemas de código aberto, um número de utilizadores pode recusar partilhar informações sobre seus amigos, conhecidos, ou sobre outros. Ao juntar seus próprios dados com os dados obtidos de outros, o utilizador/jogador representado por um avatar deve ser capaz de produzir uma avaliação de confiança sobre o utilizador/jogador com o qual se encontra a interagir. Relativamente ao método de avaliação de confiança empregue nesta tese, utilizamos lógica subjectiva para a representação da confiança, e também operadores lógicos da lógica subjectiva juntamente com algoritmos de procura em grafos para empreender o processo de inferência da confiança relativamente a outro utilizador. O sistema de inferência de confiança proposto foi validado através de um número de cenários Open-Simulator (opensimulator.org), que mostrou um aumento na precisão na avaliação da confiança de avatares. Resumindo, a nossa proposta visa, assim, introduzir uma teoria de confiança para mundos virtuais, conjuntamente com métricas de avaliação de confiança (por exemplo, a lógica subjectiva) e em métodos de procura de caminhos de confiança (com por exemplo, através de métodos de pesquisa em grafos), partindo de uma base individual, em vez de se basear em sistemas habituais de reputação centralizados. Em particular, e ao contrário de outros métodos de determinação do grau de confiança, os nossos métodos são executados em tempo real

Solving key design issues for massively multiplayer online games on peer-to-peer architectures

Massively Multiplayer Online Games (MMOGs) are increasing in both popularity and scale on the Internet and are predominantly implemented by Client/Server architectures. While such a classical approach to distributed system design offers many benefits, it suffers from significant technical and commercial drawbacks, primarily reliability and scalability costs. This realisation has sparked recent research interest in adapting MMOGs to Peer-to-Peer (P2P) architectures. This thesis identifies six key design issues to be addressed by P2P MMOGs, namely interest management, event dissemination, task sharing, state persistency, cheating mitigation, and incentive mechanisms. Design alternatives for each issue are systematically compared, and their interrelationships discussed. How well representative P2P MMOG architectures fulfil the design criteria is also evaluated. It is argued that although P2P MMOG architectures are developing rapidly, their support for task sharing and incentive mechanisms still need to be improved. The design of a novel framework for P2P MMOGs, Mediator, is presented. It employs a self-organising super-peer network over a P2P overlay infrastructure, and addresses the six design issues in an integrated system. The Mediator framework is extensible, as it supports flexible policy plug-ins and can accommodate the introduction of new superpeer roles. Key components of this framework have been implemented and evaluated with a simulated P2P MMOG. As the Mediator framework relies on super-peers for computational and administrative tasks, membership management is crucial, e.g. to allow the system to recover from super-peer failures. A new technology for this, namely Membership-Aware Multicast with Bushiness Optimisation (MAMBO), has been designed, implemented and evaluated. It reuses the communication structure of a tree-based application-level multicast to track group membership efficiently. Evaluation of a demonstration application shows i that MAMBO is able to quickly detect and handle peers joining and leaving. Compared to a conventional supervision architecture, MAMBO is more scalable, and yet incurs less communication overheads. Besides MMOGs, MAMBO is suitable for other P2P applications, such as collaborative computing and multimedia streaming. This thesis also presents the design, implementation and evaluation of a novel task mapping infrastructure for heterogeneous P2P environments, Deadline-Driven Auctions (DDA). DDA is primarily designed to support NPC host allocation in P2P MMOGs, and specifically in the Mediator framework. However, it can also support the sharing of computational and interactive tasks with various deadlines in general P2P applications. Experimental and analytical results demonstrate that DDA efficiently allocates computing resources for large numbers of real-time NPC tasks in a simulated P2P MMOG with approximately 1000 players. Furthermore, DDA supports gaming interactivity by keeping the communication latency among NPC hosts and ordinary players low. It also supports flexible matchmaking policies, and can motivate application participants to contribute resources to the system

A spatial publish subscribe overlay for massively multiuser virtual environments

Proceedings of the International Conference on Electronics and Information Engineering, 2010, v. 2, p. 314-318Peer-to-peer (P2P) architectures have become popular for designing scalable virtual environments (VEs) in recent years. However, one question that remains is whether a single overlay can be flexible enough to support different types of VEs. We present S-VON, a P2P overlay that attempts this goal by providing spatial publish / subscribe (SPS) services. Besides flexibility, S-VON also aims to be practical and efficient by utilizing super-peers and considering the physical topology (i.e., network distance) to reduce latencies. Our simulations show that super-peers provide a unique design space where both bandwidth usage and latencies can be effectively reduced, such that even a crowded Second Life region can be hosted with residential ADSL. © 2010 IEEE.published_or_final_versio

A Network-Agnostic and Cheat-Resistant Framework for Multiplayer Online Games

"Video games are kids' stuff" may be still in the minds of many people. But the video games industry is far beyond its infancy and has already grown into a multi-billion dollar business. The NPD Group reports that in 2007 the revenues generated in the U.S. with video game soft- and hardware for consoles and personal computers reached a total of 18.8 billion dollars, a 40 percent increase over 2006. According to PricewaterhouseCoopers, the global sales will even surpass those of the music industry within the next years. With the success of the Internet, online games are a constantly increasing part of these sales. According to DFC Intelligence, the worldwide online game market will grow to over 13 billion dollars in 2011. The probably most successful online game genre today is that of the so-called Massively Multiplayer Online Games (MMOGs). This kind of games provides vast virtual worlds, where thousands of players can meet and interact simultaneously. Most of these worlds are persistent, i.e. they may be online for years. They are hosted on Internet servers which are online 24/7 and players can join and leave the game whenever they like to. The persistence of the game world allows for long-term development of virtual avatars with individual characteristics and possessions. The leader of the MMOG market today is Blizzard Entertainment with the title World of Warcraft. In the beginning of 2008, World of Warcraft had 10 million subscribers (each paying up to 15 dollars per month) and a market share of 62 percent. Developing todays video games is a complex and cost-intensive task and multiplayer online functionality has a significant share in this. In 2008, the first video game hit the 100 million dollar mark for development costs. In addition to that, publishers of online games need to provide the necessary services to allow their customers to play the game over the Internet. Traditionally, most online games and nearly all MMOGs are built relying on the Client/Server architecture. The client software runs on the player's computers and shows only an audio-visual representation of the game world. It accepts commands issued by the player and transmits them to the server. Processing the commands and managing the state of the game is completely done on the server-side. Thus, to be able to handle hundreds or thousands of players simultaneously, large amounts of computing power and network bandwidth are required. Additionally, the service requires a large staff for server maintenance, software updates, billing and customer services. The provision of the World of Warcraft service did cost about 200 million dollars since its launch in November 2004. In addition to the effort of maintaining a multiplayer online game service after its launch there arises another challenge: keeping the game free of cheaters. A cheater may be defined as a user that performs an action that gives an advantage over his opponents that is considered unfair by the game developer. One must be aware that cheating is a major concern in multiplayer games as it seriously affects the game experience of honest players. Especially for subscription-based online games this is fatal, since customers will cancel their subscriptions if the experience doesn't meet their expectations. Game publishers usually do not hesitate to close the accounts of players that they believe to have cheated. For example, in 2006 Blizzard Entertainment announced in their forums that they have banned 59,000 players from World of Warcraft within a single month

Reputation mechanism for e-commerce in virtual reality environments

The interest in 3D technology and virtual reality (VR) is growing both from academia and industry, promoting the quick development of virtual marketplaces (VMs) (i.e. e-commerce systems in VR environments). VMs have inherited trust problems, e.g. sellers may advertise a perfect deal but doesn’t deliver the promised service or product at the end. In view of this, we propose a five-sense feedback oriented reputation mechanism (supported by 3D technology and VR) particularly for VMs. The user study confirms that users prefer VMs with our reputation mechanism over those with traditional ones. In our reputation mechanism, five-sense feedback is objective and buyers can use it directly in their reputation evaluation of target sellers. However, for the scenarios where buyers only provide subjective ratings, we apply the approach of subjectivity alignment for reputation computation (SARC), where ratings provided by one buyer can then be aligned (converted) for another buyer according to the two buyers’ subjectivity. Evaluation results indicate that SARC can more accurately model sellers’ reputation than the state-of-the-art approaches.Institute of Asian Consumer Insight ; U.S. Army Research Laboratory ; TÜBİTAKpre-prin

Reputation mechanism for e-commerce in virtual reality environments

The interest in 3D technology and virtual reality (VR) is growing both from academia and industry, promoting the quick development of virtual marketplaces (VMs) (i.e. e-commerce systems in VR environments). VMs have inherited trust problems, e.g. sellers may advertise a perfect deal but doesn’t deliver the promised service or product at the end. In view of this, we propose a five-sense feedback oriented reputation mechanism (supported by 3D technology and VR) particularly for VMs. The user study confirms that users prefer VMs with our reputation mechanism over those with traditional ones. In our reputation mechanism, five-sense feedback is objective and buyers can use it directly in their reputation evaluation of target sellers. However, for the scenarios where buyers only provide subjective ratings, we apply the approach of subjectivity alignment for reputation computation (SARC), where ratings provided by one buyer can then be aligned (converted) for another buyer according to the two buyers’ subjectivity. Evaluation results indicate that SARC can more accurately model sellers’ reputation than the state-of-the-art approaches.Institute of Asian Consumer Insight ; U.S. Army Research Laboratory ; TÜBİTAKpre-prin

Peer-to-peer update dissemination in browser-based networked virtual environments.

PhD ThesisNetworked Virtual Environments (NVEs) have always imposed strict requirements on architectures for update dissemination (UD). Clients must maintain views that are as synchronous and consistent as possible in order to achieve a level of user experience that is tolerable for the user. In recent times, the web browser has become a viable platform on which to deploy these NVEs. Doing so adds another layer of challenges however. There is a distinct need for systems that adapt to these constraints and exploit the characteristics of this new context to achieve reliably high consistency between users for a range of use cases. A promising approach is to carry forward the rich body of past research in peer-to-peer (P2P) networks and apply this to the problem of UD in NVEs under the constraints of a web browser. Making NVEs scalable through P2P networks is not a new concept, however previous work has always been either too specific to a certain kind of NVE, or made performance trade-offs that especially cannot work in a browser context. Furthermore, in previous work on P2P NVEs, UD has always taken the backseat compared to object management and distributed neighbour selection. The evaluation of these UD systems have as a result been one-dimensional and overly simplifying. In this work, we begin by surveying past UD solutions and evaluation methodologies. We then capture NVE, browser, and network constraints, aided by the analysis of a rich dataset of NVE network traces that we have collected, and draw out key observations and challenges to develop the requirements for a feasible UD system. From there, we illustrate the design and implementation of our P2P UD system for NVEs in great detail, augmenting our system with novel architectural insights from the Software-Defined Networking (SDN) space. Finally, we evaluate our system under a range of workloads, test environments, and performance metrics to demonstrate that we have overcome these challenges, as well as compare our method to other existing methods, which we have also implemented and tested. We hope that our contributions in research and resources (such as our taxonomies, NVE analysis, UD system, browser library, workload datasets, and a benchmarking framework) bring more structure as well as research and development opportunities to a relatively niche sub-field

Peer-to-peer network architecture for massive online gaming

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2014.Virtual worlds and massive multiplayer online games are amongst the most popular applications on the Internet. In order to host these applications a reliable architecture is required. It is essential for the architecture to handle high user loads, maintain a complex game state, promptly respond to game interactions, and prevent cheating, amongst other properties. Many of today’s Massive Multiplayer Online Games (MMOG) use client-server architectures to provide multiplayer service. Clients (players) send their actions to a server. The latter calculates the game state and publishes the information to the clients. Although the client-server architecture has been widely adopted in the past for MMOG, it suffers from many limitations. First, applications based on a client-server architecture are difficult to support and maintain given the dynamic user base of online games. Such architectures do not easily scale (or handle heavy loads). Also, the server constitutes a single point of failure. We argue that peer-to-peer architectures can provide better support for MMOG. Peer-to-peer architectures can enable the user base to scale to a large number. They also limit disruptions experienced by players due to other nodes failing. This research designs and implements a peer-to-peer architecture for MMOG. The peer-to-peer architecture aims at reducing message latency over the network and on the application layer. We refine the communication between nodes in the architecture to reduce network latency by using SPDY, a protocol designed to reduce web page load time. For the application layer, an event-driven paradigm was used to process messages. Through user load simulation, we show that our peer-to-peer design is able to process and reliably deliver messages in a timely manner. Furthermore, by distributing the work conducted by a game server, our research shows that a peer-to-peer architecture responds quicker to requests compared to client-server models