Optimal configuration of active and backup servers for augmented reality cooperative games

Interactive applications as online games and mobile devices have become more and more popular in recent years. From their combination, new and interesting cooperative services could be generated. For instance, gamers endowed with Augmented Reality (AR) visors connected as wireless nodes in an ad-hoc network, can interact with each other while immersed in the game. To enable this vision, we discuss here a hybrid architecture enabling game play in ad-hoc mode instead of the traditional client-server setting. In our architecture, one of the player nodes also acts as the server of the game, whereas other backup server nodes are ready to become active servers in case of disconnection of the network i.e. due to low energy level of the currently active server. This allows to have a longer gaming session before incurring in disconnections or energy exhaustion. In this context, the server election strategy with the aim of maximizing network lifetime is not so straightforward. To this end, we have hence analyzed this issue through a Mixed Integer Linear Programming (MILP) model and both numerical and simulation-based analysis shows that the backup servers solution fulfills its design objective

A novel scalable hybrid architecture for MMOG

We present a novel MMOG Hybrid P2P architecture and detail its key components, topology and protocols. We highlight the main components which lie at the heart of the proposed solution, and their roles, and describe the methods of tackling the key scenarios which are faced by the architecture during gameplay. For each role, we discuss the interactions that exist between them and describe the protocols that will be used for inter-role communication to perform the atomic actions necessary for maintaining the consistency and responsiveness of an MMOG such as peer addition, peer removal, group transfer, object change persistency and many more. We conclude the chapter with a comparison of the architecture against several existing P2P MMOG frameworks, discussing the differences which exist between them and how the novel Hybrid-P2P architecture we propose aims to address their flaws

Re-engineering jake2 to work on a grid using the GridGain Middleware

With the advent of Massively Multiplayer Online Games (MMOGs), engineers and designers of games came across with many questions that needed to be answered such as, for example, "how to allow a large amount of clients to play simultaneously on the same server?", "how to guarantee a good quality of service (QoS) to a great number of clients?", "how many resources will be necessary?", "how to optimize these resources to the maximum?". A possible answer to these questions relies on the usage of grid computing. Taking into account the parallel and distributed nature of grid computing, we can say that grid computing allows for more scalability in terms of a growing number of players, guarantees shorter communication time between clients and servers, and allows for a better resource management and usage (e.g., memory, CPU, core balancing usage, etc.) than the traditional serial computing model. However, the main focus of this thesis is not about grid computing. Instead, this thesis describes the re-engineering process of an existing multiplayer computer game, called Jake2, by transforming it into a MMOG, which is then put to run on a grid

Scalability and availability for massively multiplayer online games

International audienceMMOGs (Massively Multiplayer Online Games) are getting ever more popular, but current game server architectures do not scale with the number of players. Instead of addressing the issue, the most common workaround in the industry is to use multiple distinct and non communicating game servers. After a brief overview of existing game server architectures and methods to distribute server load, this position paper outlines another kind of architecture that should scale and discusses the difficulty of evaluating game platforms on a large scale

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

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

Netzwerkdienste für Massively Multiplayer Online Games

In dieser Arbeit präsentieren wir das Design und die Umsetzung von drei Netzwerkdiensten für Massively Multiplayer Online Games. Der erste Dienst stellt eine integrierte Sprachkommunikation für Online-Spiele dar. Dabei basiert das Design auf einer hybriden Architektur, die für das Aushandeln der Verbindungen einen zentralen Server verwendet, die Audiodaten jedoch von Peer zu Peer überträgt. Dieses Vorgehen ermöglicht es, die Verbindungen basierend auf Spielereignissen aufzubauen, ohne dabei zentrale Ressourcen für das Übertragen der Audioströme zu verbrauchen. Der zweite Dienst ist ein Ansatz für eine Overlay-Netzwerkstruktur. Das Hauptziel bei der Entwicklung war es, hohe Echtzeit- und Skalierbarkeitsanforderungen zu erfüllen. Daher wird ein unstrukturiertes Peer-to-Peer-Netzwerk mit einem dynamischen Verbindungschema verwendet. Der dritte Dienst kann für den Leistungsvergleich von Peer-to-Peer-Gaming-Overlays eingesetzt werden. Er beeinhaltet das Festlegen der Methodik, die Definition von Metriken, die Generierung von realistischer Last und die Implementierung einer vollständigen Evaluationsplattform

Structures and Algorithms for Peer-to-Peer Cooperation

Peer-to-peer overlay networks are distributed systems, without any hierarchical organization or centralized control. Peers form self-organizing overlay networks that are on top of the Internet. Both parts of this thesis deal with peer-to-peer overlay networks, the first part with unstructured ones used to build a large scale Networked Virtual Environment. The second part gives insights on how the users of a real life structured peer-to-peer network behave, and how well the proposed algorithms for publishing and retrieving data work. Moreover we analyze the security (holes) in such a system. Networked virtual environments (NVEs), also known as distributed virtual environments, are computer-generated, synthetic worlds that allow simultaneous interactions of multiple participants. Many efforts have been made to allow people to interact in realistic virtual environments, resulting in the recent boom of Massively Multiplayer Online Games. In the first part of the thesis, we present a complete study of an augmented Delaunay-based overlay for peer-to-peer shared virtual worlds. We design an overlay network matching the Delaunay triangulation of the participating peers in a generalized d-dimensional space. Especially, we describe the self-organizing algorithms for peer insertion and deletion. To reduce the delay penalty of overlay routing, we propose to augment each node of the Delaunay-based overlay with a limited number of carefully selected shortcut links creating a small-world. We show that a small number of shortcuts is sufficient to significantly decrease the delay of routing in the space. We present a distributed algorithm for the clustering of peers. The algorithm is dynamic in the sense that whenever a peer joins or leaves the NVE, the clustering will be adapted if necessary by either splitting a cluster or merging clusters. The main idea of the algorithm is to classify links between adjacent peers into short intracluster and long inter-cluster links. In a structured system, the neighbor relationship between peers and data locations is strictly defined. Searching in such systems is therefore determined by the particular network architecture. Among the strictly structured systems, some implement a distributed hash table (DHT) using different data structures. DHTs have been actively studied in the literature and many different proposals have been made on how to organize peers in a DHT. However, very few DHTs have been implemented in real systems and deployed on a large scale. One exception is KAD, a DHT based on Kademlia, which is part of eDonkey, a peer-to-peer file sharing system with several million simultaneous users. In the second part of this thesis we give a detailed background on KAD, the organization of the peers, the search and the publish operations, and we describe our measurement methodology. We have been crawling KAD continuously for more than a year. We obtained information about geographical distribution of peers, session times, peer availability, and peer lifetime. We found that session times are Weibull distributed and show how this information can be exploited to make the publishing mechanism much more efficient. As we have been studying KAD over the course of the last two years we have been both, fascinated and frightened by the possibilities KAD offers. We show that mounting a Sybil attack is very easy in KAD and allows to compromise the privacy of KAD users, to compromise the correct operation of the key lookup and to mount distributed denial-of-service attacks with very little resources