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We present an approach to support massively multi-player games on peer-to-peer overlays. Our approach exploits the fact that players in MMGs display locality of interest, and therefore can form self-organizing groups based on their locations in the virtual world. To this end, we have designed scalable mechanisms to distribute the game state to the participating players and to maintain consistency in the face of node failures. The resulting system dynamically scales with the number of online players. It is more flexible and has a lower deployment cost than centralized games servers. We have implemented a simple game we call SimMud, and experimented with up to 4000 players to demonstrate the applicability of this approach.

Abstract- Multi-hop wireless networks are vul-nerable to free-riders because they require nodes to forward packets for each other. Deployed routing protocolsignore this issue while proposed solutions incorporate complicated mechanisms with the intent of making free-riding impossible. We present Catch, a protocol that falls between these extremes. It achieves nearly the low mech-anism requirements of the former while imposing nearly as effective barriers to free-riding as the latter. Catch ismade possible by novel techniques based on anonymous messages. These techniques enable cooperative nodesto detect nearby free-riders and disconnect them from the rest of the network. Catch has low overhead andis broadly applicable across routing protocols and traffic workloads. We evaluate it on an 802.11 wireless testbedas well as through simulation.

Existing online multiplayer games typically use a client-server model, which introduces added latency as well as a single bottleneck and single point of failure to the game. Distributed multiplayer games minimize latency and remove the bottleneck, but require special synchronization mechanisms to provide a consistent game for all players. Current synchronization methods have been borrowed from distributed military simulations and are not optimized for the requirements of fast-paced multiplayer games. In this paper we present a new synchronization mechanism, trailing state synchronization (TSS), which is designed around the requirements of distributed first-person shooter games. We look at TSS...

In this work-in-progress report we present the general outline of a research project which aims at providing proxy support for networked computer games. The problems of both client-server and fully replicated architectures are discussed and we reason that employing proxy technology, which has been successfully used for other networked applications, is advantageous for this class of applications as well. In particular we describe how a proxy system for networked computer games can help with providing congestion control, achieving robustness, minimizing the impact of network delay and providing fairness.

architectures

Networking forms an essential part of multiplayer computer games. In this paper, we review the techniques developed for improving networking in distributed interactive real-time applications. We present a survey of the relevant literature concentrating on the research done on military simulations, networked virtual environments, and multiplayer computer games. We also discuss on resource management, consistency and responsiveness, and networking on the application level.

A simple yet remarkably powerful tool of selfish and malicious participants in a distributed system is “equivocation”: making conflicting statements to others. We present TrInc, a small, trusted component that combats equivocation in large, distributed systems. Consisting fundamentally of only a non-decreasing counter and a key, TrInc provides a new primitive: unique, once-in-alifetime attestations. We show that TrInc is practical, versatile, and easily applicable to a wide range of distributed systems. Its deployment is viable because it is simple and because its fundamental components—a trusted counter and a key—are already deployed in many new personal computers today. We demonstrate TrInc’s versatility with three detailed case studies: attested append-only memory (A2M), PeerReview, and BitTorrent. We have implemented TrInc and our three case studies using real, currently available trusted hardware. Our evaluation shows that TrInc eliminates most of the trusted storage needed to implement A2M, significantly reduces communication overhead in PeerReview, and solves an open incentives issue in BitTorrent. Microbenchmarks of our TrInc implementation indicate directions for the design of future trusted hardware. 1

Abstract — Multiplayer games become increasingly popular, mostly because they involve interaction among humans. Typically, multiplayer games are organized based on a Client-Server (CS) or a Peer-to-Peer (PP) architecture. In CS, players exchange periodic updates through a central server that is also responsible for resolving any state inconsistencies. In PP, each player communicates with every other player while state inconsistencies are resolved through a distributed agreement protocol. In this paper, we first examine these architectures from two perspectives: bandwidth requirement at the server and players, and latency to resolve any player state inconsistencies. Our results are based on both analysis and experimentation with an open-source game called “BZFlag”. The CS architecture is not scalable with the number of players due to a large bandwidth requirement at the server. The PP architecture, on the other hand, introduces significant overhead for the players, as each player needs to check the consistency between its local state and the state of all other players. We then propose an architecture that combines the merits of CS and PP. In that architecture, called Peer-to-Peer with Central Arbiter (PP-CA), players exchange updates in a peer-topeer manner but without performing consistency checks. The consistency of the game is checked by a central arbiter that receives all updates, but contacts players only when an inconsistency is detected. As a result, the central arbiter has a lower bandwidth requirement than the server of a CS architecture. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page.

Unpredictable network latency is the most challenging problem in multiplayer game networking design.  Latencies can be reduced by using a peer-to-peer rather than a client-server architecture.  However, peer-to-peer architectures raise a whole new set of issues, the most immediate being game state synchronization. The drawbacks of the peer-to-peer architecture are addressed in our game system.  The game system includes 1) a new mirrored-server architecture, 2) a trailing state synchronization protocol and 3) a many-to-many reliable multicast protocol.  As a proof-of-concept, we converted Quake, a client-server game, to our mirrored-server architecture.