5 research outputs found

    Vitruvian: costruzione di reti P2P per Distributed Virtual Enviroment mediante Gossip

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    Gli ambienti virtuali distribuiti (Distributed Virtual Environment) sono applicazioni che consentono di effettuare simulazioni di mondi virtuali nei quali interagiscono migliaia di utenti contemporaneamente. La popolarità dei DVE si è largamente diffusa sopratutto grazie ai giochi virtuali di massa (MMORPG - Massively Multiplayer Online Role Playing Game). Il paradigma predominante per l'architettura di un MMORPG è il modello client-server. Una valida alternativa a tale modello è costruire un'applicazione MMORPG supportata un overlay P2P, la cui caratteristica principale consiste nel permettere ai client partecipanti di auto-organizzarsi, consentendo quindi la creazione di un sistema in grado di scalare dinamicamente in base al numero di giocatori. Questa tesi presenta un algoritmo di gossip completamente originale il cui obiettivo è reperire gli oggetti dal DVE

    Cheating Prevention in Peer-to-Peer-based Massively Multiuser Virtual Environments

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    Massively multiuser virtual environments (MMVEs) have become an increasingly popular Internet application in recent years. Until now, they are all based on client/server technology. Due to its inherent lack of scalability, realizing MMVEs based on peer-to-peer technology has received a lot of interest. From the perspective of the operator, using peer-to-peer technology raises additional challenges: the lack of trust in peers and their unreliability. The simulation of the virtual environment is governed by certain rules specified by the operator. These rules state what actions can be taken by users in the virtual environment and how the state of the environment changes based on these actions. Since MMVEs are very often competitive environments, some people will cheat and try to break the rules to get an unfair advantage over others. Using a central server performing the simulation of the virtual environment, the operator can ensure only allowed actions can be performed and the state of the environment evolves according to the rules. In a peer-to-peer setting, the operator has no control over the peers so they might not behave as implemented by the operator. Furthermore, a central server is inherently more reliable than a peer which could fail at any time so data might be lost. This thesis presents the design of a storage performing a distributed simulation of a virtual environment. It uses a deterministic event-based simulation to calculate the state of the virtual environment only based on the actions of its users. There are multiple replicated simulations using a voting mechanism to overcome the influence of malicious peers trying to tamper with the state of the environment as long as the number of malicious peers does not reach a critical threshold. Replication of data also ensures data is not lost when peers fail. The storage is based on a peer-to-peer overlay allowing peers to exchange messages to store and retrieve data. It creates a Delaunay graph structure matching the way the data in the virtual environment is distributed among the peers. A self-stabilizing algorithm keeps the structure intact as peers join and leave the network. Additional routing tables allow peers to retrieve stored replicas independently on short, disjoint paths reducing the influence of malicious peers on the retrieval of data. A redundant filling algorithm prevents malicious peers from tampering with these routing tables to get more messages routed their way

    AOI-cast by Compass Routing in Delaunay Based DVE Overlays

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    This paper presents a AOI cast strategy for P2P Distributed Environments which is exploited to notify the position updates of a peer P, i.e. its heartbeats, to all the peers located in its Area of Interest. An algorithm for the construction of a spanning tree covering all the peers is presented. The algorithm exploits the properties of Delaunay Triangulations to reduce the traffic load on the P2P overlay. The paper presents a set of formal results which hold when the AOI is a circular area and the root of the tree is at the center of the area. The algorithm is then refined to take into account possible inconsistencies among the local views of the peers due to the latency of the underlying network. A set of experimental results are presented

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

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    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
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