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

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

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

온라인 게임과 컨텐트 공유 네트워크 분석을 통한 온라인 군집 현상의 이해

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 2. 권태경.Quantification of collective human behavior and understanding the group characteristics in the Internet is important in user behavior studies since people tend to gather together and form groups due to their inherent nature. On the Internet, people are also often forming a group for a specific purpose such as i) an online group in games (e.g., MMORPGs) to experience various social interactions with other players or accomplish a difficult quest with teammates or ii) a swarm in peer-to-peer network to share a content to utilize a higher download rate with an availability. To this end, we studied the two most well-known major applications in the Internet that people are actively using with different purposesi) MMORPGs and ii) BitTorrent. In this dissertation, we analyze the i) group activities of users in Aion, one of the largest MMORPGs, based on the records of the activities of 94,497 users and ii) crowd phenomena of BitTorrent. First, in a case study of Aion, we focus on (i) how social interactions within a group differ from the ones across groups, (ii) what makes a group rise, sustain, or fall, (iii) how group members join and leave a group, and (iv) what makes a group end. We first find that structural patterns of social interactions within a group are more likely to be close-knit and reciprocative than the ones across groups.We also observe that members in a rising group (i.e., the number of members increases) are more cohesive, and communicate with more evenly within the group than the ones in other groups. Our analysis further reveals that if a group is not cohesive, not actively communicating, or not evenly communicating among members, members of the group tend to leave. Second, we investigate what kinds of crowd phenomena of content exist and why different patterns of crowd phenomena appears and how we can exploit content crowd phenomena considering the content category, publisher, and population of content in BitTorrent. To this end,We conduct comprehensive measurements on content locality in one of the largest BitTorrent portals: The Pirate Bay. In particular, we focus on (i) how content is consumed from spatial and temporal perspectives, (ii) what makes content be consumed with disparity in spatial and temporal domains, and (iii) how we can exploit the content locality. We find that content consumption in real swarms is 4.56 times and 1.46 times skewed in spatial (country) and temporal (time) domains, respectively. We observe that a cultural factor (e.g., language) mainly affects spatial locality of content. Not only the time-sensitivity of content but also the publishing purpose affects temporal locality of content.We reveal that spatial locality of content iii rarely changes on a daily basis (microscopic level), but there is notably spatial spread of content consumption over the years (macroscopic level). Based on the observation, we conduct simulations to show that bundling and caching can exploit the content locality.Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Crowd Phenomena in Massively Multi-player Online Role-Playing Games (MMORPGs) . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Crowd Phenomena in BitTorrent . . . . . . . . . . . . . . . . . . . 3 II. RelatedWork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1 Crowd Phenomena in MMORPGs . . . . . . . . . . . . . . . . . . 6 2.1.1 Social Interactions in MMORPGs . . . . . . . . . . . . . . 6 2.1.2 Group Activities in MMORPGs . . . . . . . . . . . . . . . 7 2.1.3 Group Activities in Other Online Services . . . . . . . . . . 7 2.2 Crowd Phenomena (Locality) in BitTorrent . . . . . . . . . . . . . 8 2.2.1 Peer Localization . . . . . . . . . . . . . . . . . . . . . . . 8 2.2.2 Crowd Phenomena in BitTorrent . . . . . . . . . . . . . . . 9 2.2.3 Locality in Other Domains . . . . . . . . . . . . . . . . . . 10 III. Group Activities in Online Social Game . . . . . . . . . . . . . . . . 11 3.1 Aion overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.1.1 Game Features . . . . . . . . . . . . . . . . . . . . . . . . 11 3.1.2 Datasets . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.2 Group Affiliation . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 v 3.2.1 How prevalent are group activities in Aion? . . . . . . . . . 14 3.2.2 Effect of Joining a Group . . . . . . . . . . . . . . . . . . . 16 3.2.3 Social Interactions Within a Group . . . . . . . . . . . . . . 16 3.3 Group Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.3.1 Group Cohesion . . . . . . . . . . . . . . . . . . . . . . . 20 3.3.2 Group Diversity . . . . . . . . . . . . . . . . . . . . . . . . 24 3.3.3 Group Locality . . . . . . . . . . . . . . . . . . . . . . . . 28 3.3.4 Survival Rate . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.3.5 Dichotomy in Stable Groups . . . . . . . . . . . . . . . . . 32 3.4 Group Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3.4.1 Properties of the Group Network . . . . . . . . . . . . . . . 36 3.4.2 Structural Holes . . . . . . . . . . . . . . . . . . . . . . . 38 3.5 Implications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.5.1 Why people leave groups? . . . . . . . . . . . . . . . . . . 40 3.5.2 Why a group ends? . . . . . . . . . . . . . . . . . . . . . . 42 IV. Crowd phenomena of BitTorrent in Spatial and Temporal Perspective 46 4.1 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 4.1.1 Discovering Swarm Topology . . . . . . . . . . . . . . . . 46 4.1.2 Dataset . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 4.1.3 Representativeness . . . . . . . . . . . . . . . . . . . . . . 49 4.2 Spatial Locality . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 4.2.1 Locality Metrics . . . . . . . . . . . . . . . . . . . . . . . 51 4.2.2 Swarm, Community, and Neighbor . . . . . . . . . . . . . 53 vi 4.2.3 Content Categories, Publishers, and Popularity . . . . . . . 55 4.2.4 Spatial Locality Over Time . . . . . . . . . . . . . . . . . . 58 4.3 Temporal Locality . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 4.3.1 Existence of Temporal Locality . . . . . . . . . . . . . . . 61 4.3.2 Categories, Publishers, and Popularity . . . . . . . . . . . . 63 4.3.3 Temporal Usage Trends . . . . . . . . . . . . . . . . . . . 68 4.4 How to Exploit Locality . . . . . . . . . . . . . . . . . . . . . . . 70 V. Summary & Future Work . . . . . . . . . . . . . . . . . . . . . . . . 74 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76Docto

Understanding human-machine networks: A cross-disciplinary survey

© 2017 ACM. In the current hyperconnected era, modern Information and Communication Technology (ICT) systems form sophisticated networks where not only do people interact with other people, but also machines take an increasingly visible and participatory role. Such Human-Machine Networks (HMNs) are embedded in the daily lives of people, both for personal and professional use. They can have a significant impact by producing synergy and innovations. The challenge in designing successful HMNs is that they cannot be developed and implemented in the same manner as networks of machines nodes alone, or following a wholly human-centric view of the network. The problem requires an interdisciplinary approach. Here, we review current research of relevance to HMNs across many disciplines. Extending the previous theoretical concepts of sociotechnical systems, actor-network theory, cyber-physical-social systems, and social machines, we concentrate on the interactions among humans and between humans and machines. We identify eight types of HMNs: public-resource computing, crowdsourcing, web search engines, crowdsensing, online markets, social media, multiplayer online games and virtual worlds, and mass collaboration. We systematically select literature on each of these types and review it with a focus on implications for designing HMNs. Moreover, we discuss risks associated with HMNs and identify emerging design and development trends

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

Data Storage and Dissemination in Pervasive Edge Computing Environments

Nowadays, smart mobile devices generate huge amounts of data in all sorts of gatherings. Much of that data has localized and ephemeral interest, but can be of great use if shared among co-located devices. However, mobile devices often experience poor connectivity, leading to availability issues if application storage and logic are fully delegated to a remote cloud infrastructure. In turn, the edge computing paradigm pushes computations and storage beyond the data center, closer to end-user devices where data is generated and consumed. Hence, enabling the execution of certain components of edge-enabled systems directly and cooperatively on edge devices. This thesis focuses on the design and evaluation of resilient and efficient data storage and dissemination solutions for pervasive edge computing environments, operating with or without access to the network infrastructure. In line with this dichotomy, our goal can be divided into two specific scenarios. The first one is related to the absence of network infrastructure and the provision of a transient data storage and dissemination system for networks of co-located mobile devices. The second one relates with the existence of network infrastructure access and the corresponding edge computing capabilities. First, the thesis presents time-aware reactive storage (TARS), a reactive data storage and dissemination model with intrinsic time-awareness, that exploits synergies between the storage substrate and the publish/subscribe paradigm, and allows queries within a specific time scope. Next, it describes in more detail: i) Thyme, a data storage and dis- semination system for wireless edge environments, implementing TARS; ii) Parsley, a flexible and resilient group-based distributed hash table with preemptive peer relocation and a dynamic data sharding mechanism; and iii) Thyme GardenBed, a framework for data storage and dissemination across multi-region edge networks, that makes use of both device-to-device and edge interactions. The developed solutions present low overheads, while providing adequate response times for interactive usage and low energy consumption, proving to be practical in a variety of situations. They also display good load balancing and fault tolerance properties.Resumo Hoje em dia, os dispositivos móveis inteligentes geram grandes quantidades de dados em todos os tipos de aglomerações de pessoas. Muitos desses dados têm interesse loca- lizado e efêmero, mas podem ser de grande utilidade se partilhados entre dispositivos co-localizados. No entanto, os dispositivos móveis muitas vezes experienciam fraca co- nectividade, levando a problemas de disponibilidade se o armazenamento e a lógica das aplicações forem totalmente delegados numa infraestrutura remota na nuvem. Por sua vez, o paradigma de computação na periferia da rede leva as computações e o armazena- mento para além dos centros de dados, para mais perto dos dispositivos dos utilizadores finais onde os dados são gerados e consumidos. Assim, permitindo a execução de certos componentes de sistemas direta e cooperativamente em dispositivos na periferia da rede. Esta tese foca-se no desenho e avaliação de soluções resilientes e eficientes para arma- zenamento e disseminação de dados em ambientes pervasivos de computação na periferia da rede, operando com ou sem acesso à infraestrutura de rede. Em linha com esta dico- tomia, o nosso objetivo pode ser dividido em dois cenários específicos. O primeiro está relacionado com a ausência de infraestrutura de rede e o fornecimento de um sistema efêmero de armazenamento e disseminação de dados para redes de dispositivos móveis co-localizados. O segundo diz respeito à existência de acesso à infraestrutura de rede e aos recursos de computação na periferia da rede correspondentes. Primeiramente, a tese apresenta armazenamento reativo ciente do tempo (ARCT), um modelo reativo de armazenamento e disseminação de dados com percepção intrínseca do tempo, que explora sinergias entre o substrato de armazenamento e o paradigma pu- blicação/subscrição, e permite consultas num escopo de tempo específico. De seguida, descreve em mais detalhe: i) Thyme, um sistema de armazenamento e disseminação de dados para ambientes sem fios na periferia da rede, que implementa ARCT; ii) Pars- ley, uma tabela de dispersão distribuída flexível e resiliente baseada em grupos, com realocação preventiva de nós e um mecanismo de particionamento dinâmico de dados; e iii) Thyme GardenBed, um sistema para armazenamento e disseminação de dados em redes multi-regionais na periferia da rede, que faz uso de interações entre dispositivos e com a periferia da rede. As soluções desenvolvidas apresentam baixos custos, proporcionando tempos de res- posta adequados para uso interativo e baixo consumo de energia, demonstrando serem práticas nas mais diversas situações. Estas soluções também exibem boas propriedades de balanceamento de carga e tolerância a faltas

A perennial simulation framework for integrated crisis management studies

Ph.DDOCTOR OF PHILOSOPH

AI in Learning: Designing the Future

AI (Artificial Intelligence) is predicted to radically change teaching and learning in both schools and industry causing radical disruption of work. AI can support well-being initiatives and lifelong learning but educational institutions and companies need to take the changing technology into account. Moving towards AI supported by digital tools requires a dramatic shift in the concept of learning, expertise and the businesses built off of it. Based on the latest research on AI and how it is changing learning and education, this book will focus on the enormous opportunities to expand educational settings with AI for learning in and beyond the traditional classroom. This open access book also introduces ethical challenges related to learning and education, while connecting human learning and machine learning. This book will be of use to a variety of readers, including researchers, AI users, companies and policy makers