Scalable Resource and QoS Brokering Mechanisms for Massively Multiplayer Online Games

Multiplayer online games have become an increasingly integral part of online entertainment. With advances in social media, the number of players of these games is increasing at a very rapid rate, which in some cases has been observed to be exponential. This is when resource becomes a concern. In this thesis, I investigated several challenges in developing and maintaining multiplayer games such as hotspots, genrespeci c limitations, unpredictable quality of service and rigidity in resource availability. I showed that these issues can be solved by adopting mechanisms for separation of resource concerns from functional concerns and coordination of resources. To support resource coordination, I divided the ownership of resources among three partiesgame owner, resource owner and game player. I developed the CyberOrgs-MMOG API, which supports Massively Multiplayer Online Game (MMOG) platforms capable of resource sharing among multiple peers, through mechanisms for acquiring these resources dynamically. I showed that dynamic acquisition of resources can solve the resource questions mentioned above. The API was evaluated using a 2D game with up to 250 simulated players. I also showed, how the game's responsiveness can be dynamically adjusted in a scalable way. This thesis presents the design and implementation of the CyberOrgs-MMOG API, interfaces provided to the interacting agents representing di erent parties. I integrated a 2D multiplayer game with the API and evaluated the mechanisms supported by the API

Passage à l'échelle pour les mondes virtuels

Virtual worlds attract millions of users and these popular applications --supported by gigantic data centers with myriads of processors-- are routinely accessed. However, surprisingly, virtual worlds are still unable to host simultaneously more than a few hundred users in the same contiguous space.The main contribution of the thesis is Kiwano, a distributed system enabling an unlimited number of avatars to simultaneously evolve and interact in a contiguous virtual space. In Kiwano we employ the Delaunay triangulation to provide each avatar with a constant number of neighbors independently of their density or distribution. The avatar-to-avatar interactions and related computations are then bounded, allowing the system to scale. The load is constantly balanced among Kiwano's nodes which adapt and take in charge sets of avatars according to their geographic proximity. The optimal number of avatars per CPU and the performances of our system have been evaluated simulating tens of thousands of avatars connecting to a Kiwano instance running across several data centers, with results well beyond the current state-of-the-art.We also propose Kwery, a distributed spatial index capable to scale dynamic objects of virtual worlds. Kwery performs efficient reverse geolocation queries on large numbers of moving objects updating their position at arbitrary high frequencies. We use a distributed spatial index on top of a self-adaptive tree structure. Each node of the system hosts and answers queries on a group of objects in a zone, which is the minimal axis-aligned rectangle. They are chosen based on their proximity and the load of the node. Spatial queries are then answered only by the nodes with meaningful zones, that is, where the node's zone intersects the query zone.Kiwano has been successfully implemented for HybridEarth, a mixed reality world, Manycraft, our scalable multiplayer Minecraft map, and discussed for OneSim, a distributed Second Life architecture. By handling avatars separately, we show interoperability between these virtual worlds.With Kiwano and Kwery we provide the first massively distributed and self-adaptive solutions for virtual worlds suitable to run in the cloud. The results, in terms of number of avatars per CPU, exceed by orders of magnitude the performances of current state-of-the-art implementations. This indicates Kiwano to be a cost effective solution for the industry. The open API for our first implementation is available at \url{http://kiwano.li}.La réalité mixe, les jeux en ligne massivement multijoueur (MMOGs), les mondes virtuels et le cyberespace sont des concepts extrêmement attractifs. Mais leur déploiement à large échelle reste difficile et il est en conséquence souvent évité.La contribution principale de la thèse réside dans le système distribué Kiwano, qui permet à un nombre illimité d'avatars de peupler et d'interagir simultanément dans un même monde contigu. Dans Kiwano nous utilisons la triangulation de Delaunay pour fournir à chaque avatar un nombre constant de voisins en moyenne, indépendamment de leur densité ou distribution géographique. Le nombre d'interactions entre les avatars et les calculs inhérents sont bornés, ce qui permet le passage à l'échelle du système.La charge est repartie sur plusieurs machines qui regroupent sur un même nœud les avatars voisins de façon contiguë dans le graphe de Delaunay. L'équilibrage de la charge se fait de manière contiguë et dynamique, en suivant la philosophie des réseaux pair-à-pair (peer-to-peer overlays). Cependant ce principe est adapté au contexte de l'informatique dématérialisée (cloud computing).Le nombre optimal d'avatars par CPU et les performances de notre système ont été évalués en simulant des dizaines de milliers d'avatars connectés à la même instance de Kiwano tournant à travers plusieurs centres de traitement de données.Nous proposons également trois applications concrètes qui utilisent Kiwano : Manycraft est une architecture distribuée capable de supporter un nombre arbitrairement grand d'utilisateurs cohabitant dans le même espace Minecraft, OneSim, qui permet à un nombre illimité d'usagers d'être ensemble dans la même région de Second Life et HybridEarth, un monde en réalité mixte où avatars et personnes physiques sont présents et interagissent dans un même espace: la Terre

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 comparative study of the effect of collaborative problem solving in a massively multiplayer online game (MMOG) on individual achievement

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Dynamic Load Balancing for Massively Multiplayer Online Games

In recent years, there has been an important growth of online gaming. Today’s Massively Multiplayer Online Games (MMOGs) can contain millions of synchronous players scattered across the world and participating with each other within a single shared game. Traditional Client/Server architectures of MMOGs exhibit different problems in scalability, reliability, and latency, as well as the cost of adding new servers when demand is too high. P2P architecture provides considerable support for scalability of MMOGs. It also achieves good response times by supporting direct connections between players. This thesis proposes a novel hybrid Peer-to-Peer architecture for MMOGs and a new dynamic load balancing for massively multiplayer online games (MMOGs) based this hybrid Peer-to-Peer architecture. We have divided the game world space into several regions. Each region in the game world space is controlled and managed by using both a super-peer and a clone-super-peer. The region's super-peer is responsible for distributing the game update among the players inside the region, as well as managing the game communications between the players. However, the clone-super-peer is responsible for controlling the players' migration from one region to another, in addition to be the super-peer of the region when the super-peer leaves the game. In this thesis, we have designed and simulated a static and dynamic Area of Interest Management (AoIM) for MMOGs based on both architectures hybrid P2P and client-server with the possibility of players to move from one region to another. In this thesis also, we have designed and evaluated the static and dynamic load balancing for MMOGs based on hybrid P2P architecture. We have used OPNET Modeler 18.0 to simulate and evaluate the proposed system, especially standard applications, custom applications, TDMA and RX Group. Our dynamic load balancer is responsible for distributing the load among the regions in the game world space. The position of the load balancer is located between the game server and the regions. The results, following extensive experiments, show that low delay and higher traffic communication can be achieved using both of hybrid P2P architecture, static and dynamic AoIM, dynamic load balancing for MMOGs based on hybrid P2P system

Models, methods, and tools for developing MMOG backends on commodity clouds

Online multiplayer games have grown to unprecedented scales, attracting millions of players worldwide. The revenue from this industry has already eclipsed well-established entertainment industries like music and films and is expected to continue its rapid growth in the future. Massively Multiplayer Online Games (MMOGs) have also been extensively used in research studies and education, further motivating the need to improve their development process. The development of resource-intensive, distributed, real-time applications like MMOG backends involves a variety of challenges. Past research has primarily focused on the development and deployment of MMOG backends on dedicated infrastructures such as on-premise data centers and private clouds, which provide more flexibility but are expensive and hard to set up and maintain. A limited set of works has also focused on utilizing the Infrastructure-as-a-Service (IaaS) layer of public clouds to deploy MMOG backends. These clouds can offer various advantages like a lower barrier to entry, a larger set of resources, etc. but lack resource elasticity, standardization, and focus on development effort, from which MMOG backends can greatly benefit. Meanwhile, other research has also focused on solving various problems related to consistency, performance, and scalability. Despite major advancements in these areas, there is no standardized development methodology to facilitate these features and assimilate the development of MMOG backends on commodity clouds. This thesis is motivated by the results of a systematic mapping study that identifies a gap in research, evident from the fact that only a handful of studies have explored the possibility of utilizing serverless environments within commodity clouds to host these types of backends. These studies are mostly vision papers and do not provide any novel contributions in terms of methods of development or detailed analyses of how such systems could be developed. Using the knowledge gathered from this mapping study, several hypotheses are proposed and a set of technical challenges is identified, guiding the development of a new methodology. The peculiarities of MMOG backends have so far constrained their development and deployment on commodity clouds despite rapid advancements in technology. To explore whether such environments are viable options, a feasibility study is conducted with a minimalistic MMOG prototype to evaluate a limited set of public clouds in terms of hosting MMOG backends. Foli lowing encouraging results from this study, this thesis first motivates toward and then presents a set of models, methods, and tools with which scalable MMOG backends can be developed for and deployed on commodity clouds. These are encapsulated into a software development framework called Athlos which allows software engineers to leverage the proposed development methodology to rapidly create MMOG backend prototypes that utilize the resources of these clouds to attain scalable states and runtimes. The proposed approach is based on a dynamic model which aims to abstract the data requirements and relationships of many types of MMOGs. Based on this model, several methods are outlined that aim to solve various problems and challenges related to the development of MMOG backends, mainly in terms of performance and scalability. Using a modular software architecture, and standardization in common development areas, the proposed framework aims to improve and expedite the development process leading to higher-quality MMOG backends and a lower time to market. The models and methods proposed in this approach can be utilized through various tools during the development lifecycle. The proposed development framework is evaluated qualitatively and quantitatively. The thesis presents three case study MMOG backend prototypes that validate the suitability of the proposed approach. These case studies also provide a proof of concept and are subsequently used to further evaluate the framework. The propositions in this thesis are assessed with respect to the performance, scalability, development effort, and code maintainability of MMOG backends developed using the Athlos framework, using a variety of methods such as small and large-scale simulations and more targeted experimental setups. The results of these experiments uncover useful information about the behavior of MMOG backends. In addition, they provide evidence that MMOG backends developed using the proposed methodology and hosted on serverless environments can: (a) support a very high number of simultaneous players under a given latency threshold, (b) elastically scale both in terms of processing power and memory capacity and (c) significantly reduce the amount of development effort. The results also show that this methodology can accelerate the development of high-performance, distributed, real-time applications like MMOG backends, while also exposing the limitations of Athlos in terms of code maintainability. Finally, the thesis provides a reflection on the research objectives, considerations on the hypotheses and technical challenges, and outlines plans for future work in this domain

Distributed virtual environment scalability and security

Distributed virtual environments (DVEs) have been an active area of research and engineering for more than 20 years. The most widely deployed DVEs are network games such as Quake, Halo, and World of Warcraft (WoW), with millions of users and billions of dollars in annual revenue. Deployed DVEs remain expensive centralized implementations despite significant research outlining ways to distribute DVE workloads. This dissertation shows previous DVE research evaluations are inconsistent with deployed DVE needs. Assumptions about avatar movement and proximity - fundamental scale factors - do not match WoW’s workload, and likely the workload of other deployed DVEs. Alternate workload models are explored and preliminary conclusions presented. Using realistic workloads it is shown that a fully decentralized DVE cannot be deployed to today’s consumers, regardless of its overhead. Residential broadband speeds are improving, and this limitation will eventually disappear. When it does, appropriate security mechanisms will be a fundamental requirement for technology adoption. A trusted auditing system (“Carbon”) is presented which has good security, scalability, and resource characteristics for decentralized DVEs. When performing exhaustive auditing, Carbon adds 27% network overhead to a decentralized DVE with a WoW-like workload. This resource consumption can be reduced significantly, depending upon the DVE’s risk tolerance. Finally, the Pairwise Random Protocol (PRP) is described. PRP enables adversaries to fairly resolve probabilistic activities, an ability missing from most decentralized DVE security proposals. Thus, this dissertations contribution is to address two of the obstacles for deploying research on decentralized DVE architectures. First, lack of evidence that research results apply to existing DVEs. Second, the lack of security systems combining appropriate security guarantees with acceptable overhead