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

Deadline-Driven Auctions for NPC Host Allocation on P2P MMOGs.

We present the design, implementation and evaluation of Deadline-Driven Auctions (DDAs), a novel task-mapping infrastructure for heterogeneous distributed environments. DDA is primarily designed for hosting Non-Player Characters (NPCs) in P2P Massively Multiplayer Online Games (MMOGs). Experimental and analytical results demonstrate that DDA provides four significant advantages. It is self-organising: the infrastructure is automatically managed. It efficiently allocates computing resources for large numbers (1000s) of real-time NPC tasks. It supports gaming interactivity by minimising communication latency between NPC hosts. Finally, it supports flexible matchmaking policies, and a friendly incentive policy establishes a cooperative economic model to motivate participants to contribute resources

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

A MAP for the library portal: through the labyrinth of online information sources

In as little as 25 years, online information provision has been transformed. This has largely been uncontrolled, yet the resources now available offer rich returns for the data-hungry end user. Increasingly, many users require their information immediately and really do not care where it is stored. Such demands, coupled with librarians’ natural tendency to apply order, have led to the development of library portals which aim to solve the problems arising from trying to navigate this labyrinth of information. The MAP portal is one such product. Using the NISO OpenURL standard, MAP offers three main elements – contextual linking via WebBridge, one step “multi” searching using MetaFind and resource authentication through Web Access Management (WAM). Use of this portal at the University of Exeter Library has made a considerable, positive impact on the recent use of online full-text systems and services and the experiences undoubtedly point to a strong future for such interfaces everywhere

Design Issues for Peer-to-Peer Massively Multiplayer Online Games.

Massively Multiplayer Online Games (MMOGs) are increasing in both popularity and scale, and while classical Client/Server (C/S) architectures convey some benefits, they suffer from significant technical and commercial drawbacks. This realisation has sparked intensive research interest in adapting MMOGs to Peer-to-Peer (P2P) architectures. This paper articulates a comprehensive set of six design issues to be addressed by P2P MMOGs, namely Interest Management (IM), game event dissemination, Non-Player Character (NPC) host allocation, game state persistency, cheating mitigation and incentive mechanisms. Design alternatives for each issue are systematically compared, and their interrelationships discussed. We further evaluate how well representative P2P MMOG architectures fulfil the design criteria

Public Libraries and the Internet 2006

Examines the capability of public libraries to provide and sustain public access Internet services and resources that meet community needs, including serving as the first choice for content, resources, services, and technology infrastructure

Comparação de uma versão Cliente-Servidor com uma versão Peer-to-Peer para o jogo WebRun

O negócio dos jogos online está em constante expansão. Se pensarmos que neste preciso momento se encontram ligados milhões de jogadores a um qualquer jogo online, rapidamente percebemos a dimensão e potencialidade deste mercado. São jogos cada vez mais complexos e elaborados, de maneira fidelizar os jogadores atuais, mantendo-os motivados, e a angariar potenciais jogadores. Essa motivação tem a ver não só com a atratividade do jogo mas também com a qualidade de serviço que o jogo oferece. A maioria dos jogos online segue um modelo cliente-servidor, uma arquitetura que facilita o desenvolvimento e o controlo do jogo, nomeadamente em termos de evitar a utilização indevida por jogadores mal-intencionados. Esta arquitetura tem, no entanto, problemas em termos de escalabilidade. Com o aumento do número de utilizadores, a qualidade do serviço diminui do ponto de vista dos jogadores. Nesta dissertação propomos como alternativa a utilização de uma arquitetura peer-to-peer para um jogo que permite promover a atividade física e que inicialmente foi desenvolvido como cliente-servidor: o jogo WebRun. Apresenta-se um estudo do desempenho das duas versões do jogo quando o número de jogadores aumenta. Os resultados obtidos mostram que a arquitetura peer-to-peer permite aumentar significativamente a escalabilidade do jogo, sendo uma alternativa promissora para áreas em que o problema da fraude no jogo não seja crítico.The business of online gaming is constantly expanding. If we think that in this precise moment there are millions of players linked to any online game, we quickly realized the power of this market. These games are more and more complex and have elaborated sceneries, in order to keep motivated the current players and captivate new potential players. This motivation has to do with not only the attractiveness of the game but also with the quality of service that the game offers. Most online games follow a Client/Server architecture that facilitates the development and control of the game, for example, in terms of preventing improper use by malicious players. This architecture has, however, problems in terms of scalability. When the number of users increases, decreases the quality of service from the viewpoint of the players. In this thesis we propose as alternative the use of Peer-to-Peer architecture for a game that promotes physical activity and that was initially developed as Client/Server: the WebRun game. It presents a study of the performance of two versions of the game when the number of players increases. The results show that the Peer-to-Peer architecture significantly increases the scalability of the game, being a promising alternative for areas where the fraud problem is not critical

Communication technology and education

Probably as far back as people can remember, education has drawn on communication technologies, either to teach students how to use them effectively or to make use of those technologies in the educational process itself. In the former instance, the educational sector typically follows a cultural valuation that regards a given technology as so essential that people cannot leave its use or teaching to chance—reading and writing provide the clearest examples here, with schools teaching both the mechanics of writing and reading (forming or deciphering letters, spelling properly, adhering to a common grammar, and so on) and the composition of texts, arguments, expositions, explanations, essays, etc. In the latter instance, schools use communication technology to provide information or to connect with their students: again, books provide an historical example as does educational television more recently. A great deal of existing research in pedagogy, learning theory, and classroom management examines how learning with technology occurs and how to measure its impact (Jonassen, 2004). Similarly, a great deal of writing addresses the practical issues of making the best use of communication in or for the classroom. This review will not address the learning theory or the pedagogy, except indirectly as it appears in other studies; it will focus instead specifically on the communication technology—a very wide field— and how educators incorporate the various means of communication in the schooling of a younger generation. These typically occur in two ways: distance education and supplemental education. Distance education refers to the use of communication technology to reach students who cannot or do not physically attend a school. Supplemental education refers to the use of communication technology to supplement face-toface or in-school programs. Looking at the recent past (the last 10 years or so), this review will examine published studies discussing communication in or for schools as well as some more accessible online materials describing current work.

Statistics for electronic resources

Includes bibliographical references (leaves 67-74).Electronic resources represent a large portion of many libraries' information resources in the current climate of hybrid libraries where print and electronic formats coexist. Since the dramatic uptake of electronic resources in libraries during the 1990's the topic of usage statistics has been on librarians' lips. The expectations that librarians had of being able to compare resources based on usage statistics were soon dashed as it became apparent that electronic resource providers were not measuring usage uniformly. Given the initial disappointments that librarians had in terms of electronic resource usage statistics the author set out to find the reasons why librarians were keeping statistics for electronic resources, which statistics they were keeping for electronic resources, and what were the issues and concerns with regard to statistics for electronic resources. To get an international answer to these questions a literature review was undertaken. The South African point of view was sought through an e-mail survey that was sent out to the 23 South African academic libraries that form the South African National Library and Information Consortium (SANLiC). A 65% response rate was recorded. The international and South African answers to the three questions were very similar. The study found that the reasons why librarians keep electronic resources statistics were to "assess the value of different online products/services"; to "make better-informed purchasing decisions"; to "plan infrastructure and allocation of resources"; and to "support internal marketing and promotion of library services". The study also found that the statistics that librarians were keeping are: sessions, searches, documents downloaded, turnaways, location of use, number of electronic resources, expenditure and virtual visits. The number of virtual visits was kept by international libraries but no South African libraries reported keeping this information. The concerns that were raised by both international and South African libraries were found to be about: the continued lack of standardisation; the time-consuming nature of data collection; the reliability of the usage data; the fact that the data need to be looked at in context; the management of the data; and how to count electronic resources. Clear definitions of the latter are essential. A concern raised in South Africa but not in the international literature is that there exists a lack of understanding amongst some South African librarians of the basic concepts of electronic resources usage statistics. The author concludes with a suggestion that the CHELSA Measures for Quality be implemented so that librarians can see that the collection of usage data for electronic resources has some purpose. Once this is in place one or more training events under the auspices of SANLiC should be organised in order to train librarians in the best practice of electronic resource usage statistics

Service-Oriented Ad Hoc Grid Computing

Subject of this thesis are the design and implementation of an ad hoc Grid infrastructure. The vision of an ad hoc Grid further evolves conventional service-oriented Grid systems into a more robust, more flexible and more usable environment that is still standards compliant and interoperable with other Grid systems. A lot of work in current Grid middleware systems is focused on providing transparent access to high performance computing (HPC) resources (e.g. clusters) in virtual organizations spanning multiple institutions. The ad hoc Grid vision presented in this thesis exceeds this view in combining classical Grid components with more flexible components and usage models, allowing to form an environment combining dedicated HPC-resources with a large number of personal computers forming a "Desktop Grid". Three examples from medical research, media research and mechanical engineering are presented as application scenarios for a service-oriented ad hoc Grid infrastructure. These sample applications are also used to derive requirements for the runtime environment as well as development tools for such an ad hoc Grid environment. These requirements form the basis for the design and implementation of the Marburg ad hoc Grid Environment (MAGE) and the Grid Development Tools for Eclipse (GDT). MAGE is an implementation of a WSRF-compliant Grid middleware, that satisfies the criteria for an ad hoc Grid middleware presented in the introduction to this thesis. GDT extends the popular Eclipse integrated development environment by components that support application development both for traditional service-oriented Grid middleware systems as well as ad hoc Grid infrastructures such as MAGE. These development tools represent the first fully model driven approach to Grid service development integrated with infrastructure management components in service-oriented Grid computing. This thesis is concluded by a quantitative discussion of the performance overhead imposed by the presented extensions to a service-oriented Grid middleware as well as a discussion of the qualitative improvements gained by the overall solution. The conclusion of this thesis also gives an outlook on future developments and areas for further research. One of these qualitative improvements is "hot deployment" the ability to install and remove Grid services in a running node without interrupt to other active services on the same node. Hot deployment has been introduced as a novelty in service-oriented Grid systems as a result of the research conducted for this thesis. It extends service-oriented Grid computing with a new paradigm, making installation of individual application components a functional aspect of the application. This thesis further explores the idea of using peer-to-peer (P2P networking for Grid computing by combining a general purpose P2P framework with a standard compliant Grid middleware. In previous work the application of P2P systems has been limited to replica location and use of P2P index structures for discovery purposes. The work presented in this thesis also uses P2P networking to realize seamless communication accross network barriers. Even though the web service standards have been designed for the internet, the two-way communication requirement introduced by the WSRF-standards and particularly the notification pattern is not well supported by the web service standards. This defficiency can be answered by mechanisms that are part of such general purpose P2P communication frameworks. Existing security infrastructures for Grid systems focus on protection of data during transmission and access control to individual resources or the overall Grid environment. This thesis focuses on security issues within a single node of a dynamically changing service-oriented Grid environment. To counter the security threads arising from the new capabilities of an ad hoc Grid, a number of novel isolation solutions are presented. These solutions address security issues and isolation on a fine-grained level providing a range of applicable basic mechanisms for isolation, ranging from lightweight system call interposition to complete para-virtualization of the operating systems