464 research outputs found
A Reusable Component for Communication and Data Synchronization in Mobile Distributed Interactive Applications
In Distributed Interactive Applications (DIA) such as multiplayer games,
where many participants are involved in a same game session and communicate
through a network, they may have an inconsistent view of the virtual world
because of the communication delays across the network. This issue becomes even
more challenging when communicating through a cellular network while executing
the DIA client on a mobile terminal. Consistency maintenance algorithms may be
used to obtain a uniform view of the virtual world. These algorithms are very
complex and hard to program and therefore, the implementation and the future
evolution of the application logic code become difficult. To solve this
problem, we propose an approach where the consistency concerns are handled
separately by a distributed component called a Synchronization Medium, which is
responsible for the communication management as well as the consistency
maintenance. We present the detailed architecture of the Synchronization Medium
and the generic interfaces it offers to DIAs. We evaluate our approach both
qualitatively and quantitatively. We first demonstrate that the Synchronization
Medium is a reusable component through the development of two game
applications, a car racing game and a space war game. A performance evaluation
then shows that the overhead introduced by the Synchronization Medium remains
acceptable.Comment: In Proceedings WCSI 2010, arXiv:1010.233
Distributed game
Dissertação de mestrado em Engenharia InformáticaThe demand for online games has risen over the years, expanding multiplayer support for new and different game
genres. Among them are Massively Multiplayer Online games, one of the most popular and successful game
types in the industry. Nowadays, this industry is thriving, evolving alongside technological advancements and
producing billions in revenue, making it an economic importance. However, as the complexity of these games
grows, so do the challenges they face when constructing them.
This dissertation aims to implement a distributed game, through a proof of concept or an existing game, using a
distributed architecture to acquire knowledge in the construction of such complex systems and the effort involved
in dealing with consistency, maintaining communication infrastructure, and managing data in a distributed way.
It is also intended that this project implements multiple mechanisms capable of autonomously helping manage
and maintain the correct state of the system.
To evaluate the proposed solution, a detailed analysis is carried out with performance benchmark analysis,
stress testing, followed by an examination of its security, scalability, and distribution’s resilience.
Overall, the present research work allowed for a greater understanding of the technologies and approaches
used in constructing a gaming system, establishing a new set of development opportunities to be further investi gated upon the constructed solution.A procura por jogos online aumentou ao longo dos anos, expandindo o suporte multiplayer para novos e diferentes géneros. Entre estes estão os jogos Massively Multiplayer Online, um dos tipos de jogos mais populares e bem-sucedidos na indústria. Atualmente, esta indústria está a prosperar, evoluindo com os avanços tecnológicos e gerando milhares de milhões em receita, tornando-se uma importância económica. Porém, à medida que a complexidade destes jogos aumenta, também aumenta os problemas encontrados durante a sua construção. Esta dissertação tem como objetivo implementar um jogo distribuído, através de uma prova de conceito ou um jogo existente, usando uma arquitetura distribuída a fim de adquirir conhecimento na construção destes sistemas complexos e o esforço envolvido em lidar com consistência, manter a infraestrutura de comunicação e gerir dados de maneira distribuída. Para isto, é pretendido que este projeto também implemente vários mecanismos capazes de, forma autônoma, ajudar a gerir e manter o correto estado do sistema.
Para avaliar o solução proposta, uma análise detalhada é realizada sobre o desempenho, segurança, escalabilidade e resiliência da distribuição do sistema.
De forma geral, o presente trabalho de pesquisa permitiu uma maior compreensão das tecnologias e abordagens utilizadas na construção de um sistema de jogos, estabelecendo um novo conjunto de oportunidades de
desenvolvimento a serem investigadas sobre a solução construída
Referee-based architectures for massively multiplayer online games
Network computer games are played amongst players on different hosts across the Internet. Massively Multiplayer Online Games (MMOG) are network games in which thousands of players participate simultaneously in each instance of the virtual world. Current commercial MMOG use a Client/Server (C/S) architecture in which the server simulates and validates the game, and notifies players about the current game state. While C/S is very popular, it has several limitations: (i) C/S has poor scalability as the server is a bandwidth and processing bottleneck; (ii) all updates must be routed through the server, reducing responsiveness; (iii) players with lower client-to-server delay than their opponents have an unfair advantage as they can respond to game events faster; and (iv) the server is a single point of failure.The Mirrored Server (MS) architecture uses multiple mirrored servers connected via a private network. MS achieves better scalability, responsiveness, fairness, and reliability than C/S; however, as updates are still routed through the mirrored servers the problems are not eliminated. P2P network game architectures allow players to exchange updates directly, maximising scalability, responsiveness, and fairness, while removing the single point of failure. However, P2P games are vulnerable to cheating. Several P2P architectures have been proposed to detect and/or prevent game cheating. Nevertheless, they only address a subset of cheating methods. Further, these solutions require costly distributed validation algorithms that increase game delay and bandwidth, and prevent players with high latency from participating.In this thesis we propose a new cheat classification that reflects the levels in which the cheats occur: game, application, protocol, or infrastructure. We also propose three network game architectures: the Referee Anti-Cheat Scheme (RACS), the Mirrored Referee Anti-Cheat Scheme (MRACS), and the Distributed Referee Anti-Cheat Scheme (DRACS); which maximise game scalability, responsiveness, and fairness, while maintaining cheat detection/prevention equal to that in C/S. Each proposed architecture utilises one or more trusted referees to validate the game simulation - similar to the server in C/S - while allowing players to exchange updates directly - similar to peers in P2P.RACS is a hybrid C/S and P2P architecture that improves C/S by using a referee in the server. RACS allows honest players to exchange updates directly between each other, with a copy sent to the referee for validation. By allowing P2P communication RACS has better responsiveness and fairness than C/S. Further, as the referee is not required to forward updates it has better bandwidth and processing scalability. The RACS protocol could be applied to any existing C/S game. Compared to P2P protocols RACS has lower delay, and allows players with high delay to participate. Like in many P2P architectures, RACS divides time into rounds. We have proposed two efficient solutions to find the optimal round length such that the total system delay is minimised.MRACS combines the RACS and MS architectures. A referee is used at each mirror to validate player updates, while allowing players to exchange updates directly. By using multiple mirrored referees the bandwidth required by each referee, and the player-to mirror delays, are reduced; improving the scalability, responsiveness and fairness of RACS, while removing its single point of failure. Direct communication MRACS improves MS in terms of its responsiveness, fairness, and scalability. To maximise responsiveness, we have defined and solved the Client-to-Mirror Assignment (CMA) problem to assign clients to mirrors such that the total delay is minimised, and no mirror is overloaded. We have proposed two sets of efficient solutions: the optimal J-SA/L-SA and the faster heuristic J-Greedy/L-Greedy to solve CMA.DRACS uses referees distributed to player hosts to minimise the publisher / developer infrastructure, and maximise responsiveness and/or fairness. To prevent colluding players cheating DRACS requires every update to be validated by multiple unaffiliated referees, providing cheat detection / prevention equal to that in C/S. We have formally defined the Referee Selection Problem (RSP) to select a set of referees from the untrusted peers such that responsiveness and/or fairness are maximised, while ensuring the probability of the majority of referees colluding is below a pre-defined threshold. We have proposed two efficient algorithms, SRS-1 and SRS-2, to solve the problem.We have evaluated the performances of RACS, MRACS, and DRACS analytically and using simulations. We have shown analytically that RACS, MRACS and DRACS have cheat detection/prevention equivalent to that in C/S. Our analysis shows that RACS has better scalability and responsiveness than C/S; and that MRACS has better scalability and responsiveness than C/S, RACS, and MS. As there is currently no publicly available traces from MMOG we have constructed artificial and realistic inputs. We have used these inputs on all simulations in this thesis to show the benefits of our proposed architectures and algorithms
Development of a Physics-Aware Dead Reckoning Mechanism for Distributed Interactive Applications
Distributed Interactive Applications (DIAs) are a class of software that allow
geographically remote users to interact within a shared virtual environment.
Many DIAs seek to present a rich and realistic virtual world to users, both on a
visual and behavioural level. A relatively recent addition to virtual environments
(both distributed and single user) to achieve the latter has been the simulation of
realistic physical phenomena between objects in the environment.
However, the application of physics simulation to virtual environments in DIAs
currently lags that of single user environments. This is primarily due to the
unavailability of entity state update mechanisms which can maintain consistency
in such physics-rich environments. The difference is particularly evident in
applications built on a peer-to-peer architecture, as a lack of a single authority
presents additional challenges in synchronising the state of shared objects while
also presenting a responsive simulation.
This thesis proposes a novel state maintenance mechanism for physics-rich
environments in peer-to-peer DIAs composed of two parts: a dynamic authority
scheme for shared objects, and a physics-aware dead reckoning model with an
adaptive error threshold. The first part is intended to place a bound on the
overall inconsistency present in shared objects, while the second is implemented
to minimise the instantaneous inconsistency during users’ interactions with
shared objects. A testbed application is also described, which is used to validate
the performance of the proposed mechanism.
The state maintenance mechanism is implemented for a single type of physicsaware
application, and demonstrates a marked improvement in consistency for
that application. However, several flexible terms are described in its
implementation, as well as their potential relevance to alternative applications.
Finally, it should be noted that the physics-aware dead reckoning model does not
depend on the authority scheme, and can therefore be employed with alternative
authority scheme
A survey on network game cheats and P2P solutions
The increasing popularity of Massively Multiplayer Online Games (MMOG) - games involving thousands of players participating simultaneously in a single virtual world - has highlighted the scalability bottlenecks present in centralised Client/Server (C/S) architectures. Researchers are proposing Peer-to-Peer (P2P) game technologies as a scalable alternative to C/S; however, P2P is more vulnerable to cheating as it decentralises the game state and logic to un-trusted peer machines, rather than using trusted centralised servers. Cheating is a major concern for online games, as a minority of cheaters can potentially ruin the game for all players. In this paper we present a review and classification of known cheats, and provide real-world examples where possible. Further, we discuss counter measures used by C/S game technologies to prevent cheating. Finally, we discuss several P2P architectures designed to prevent cheating, highlighting their strengths and weaknesses
Cheating in networked computer games: a review
The increasing popularity of Massively Multiplayer Online Games (MMOG) - games involving thousands of players participating simultaneously in a single virtual world - has highlighted the scalability bottlenecks present in centralised Client/Server (C/S) architectures. Researchers are proposing Peer-to-Peer (P2P) architectures as a scalable alternative to C/S; however, P2P is more vulnerable to cheating as it decentralises the game state and logic to un-trusted peer machines, rather than using trusted centralised servers. Cheating is a major concern for online games, as a minority of cheaters can potentially ruin the game for all players. In this paper we present a review and classification of known cheats, and provide real-world examples where possible. Further, we discuss counter measures used by C/S architectures to prevent cheating. Finally, we discuss several P2P architectures designed to prevent cheating, highlighting their strengths and weaknesses
A spatial publish subscribe overlay for massively multiuser virtual environments
Proceedings of the International Conference on Electronics and Information Engineering, 2010, v. 2, p. 314-318Peer-to-peer (P2P) architectures have become popular for designing scalable virtual environments (VEs) in recent years. However, one question that remains is whether a single overlay can be flexible enough to support different types of VEs. We present S-VON, a P2P overlay that attempts this goal by providing spatial publish / subscribe (SPS) services. Besides flexibility, S-VON also aims to be practical and efficient by utilizing super-peers and considering the physical topology (i.e., network distance) to reduce latencies. Our simulations show that super-peers provide a unique design space where both bandwidth usage and latencies can be effectively reduced, such that even a crowded Second Life region can be hosted with residential ADSL. © 2010 IEEE.published_or_final_versio
Round length optimisation for P2P network gaming
The Referee Anti-Cheat Scheme (RACS) increases the scalability of Client/Server (C/S) games by allowing clients to exchange updates directly. Further, RACS maintains the security of C/S as the trusted referee (running on the server) is the game authority, simulating all client updates to validate the simulation. In RACS time is divided into rounds, and every player generates one update per round. The round length d is bounded by dmax which is specified by the game developer. The referee may reduce d to increase game responsiveness for players. Existing approaches to adjust d require purely distributed algorithms as they do not have a trusted central authority. These algorithms are slow and use considerable bandwidth. In this paper we propose a delay model for RACS, and two centralised algorithms to calculate d for maximum responsiveness - an optimal brute force approach and an efficient voting algorithm. We use simulation to show that the voting algorithm produces nearly optimal results, and analytical analysis to show that its processing requirements are far lower than the brute force approach
- …