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.

The growth in the popularity of interactive network games has increased the importance of a better understanding of the effects of packet loss and latency on user performance. While previous work on network games has studied user tolerance for high latencies and has studied the effects of latency on user performance in real-time strategy games, to the best of our knowledge, there has been no systematic study of the effects of loss and latency on user performance. In this paper we study user performance for Unreal Tournament 2003 (UT2003), a popular first person shooter game, under varying amounts of packet loss and latency. First, we deduced typical real world values of packet loss and latency experienced on the Internet by monitoring numerous operational UT2003 game servers. We then used these deduced values of loss and latency in a controlled networked environment that emulated various conditions of loss and latency, allowing us to monitor UT2003 at the network, application and user levels. We designed maps that isolated the fundamental first person shooter interaction components of movement and shooting, and conducted numerous user studies under controlled network conditions. We find that typical ranges of packet loss have no impact on user performance or on the quality of game play. The levels of latency typical for most UT2003 Internet servers, while sometimes unpleasant, do not significantly affect the outcome of the game. Since most first person shooter games typically consist of generic player actions similar to those that we tested, we believe that these results have broader implications.

Abstract- Quantifying the latency sensitivity of potential customers/players is critical for Internet-based game providers when planning the network placement of their game servers. In early 2001 we placed two Quake 3 servers at different locations on the Internet, and instrumented them to gather median latency information on every player who played over a multimonth period. Comparison of server logfiles showed an active yet distinct player population on each server, and the median latency distributions suggest players actively prefer Quake 3 servers less than 150 to 180 milliseconds from the player's location. Quake 3 is often played as a multiplayer, Internetbased, highly interactive “first person shooter ” game. Although Quake 3 is nowhere near as popular as games such as Halflife:CounterStrike, we believe our results provide a useful ballpark indicator of latency sensitivity for this class of highly interactive online games.

Online gaming is one of the most profitable businesses over the Internet. Among all genres of the online games, the popularity of the MMORPG (Massive Multiplayer Online Role Playing Games) is especially prominent in Asia. Opting for a better understanding of the game traffic and the economic well being of the Internet, we analyze a 1,356-million-packet trace from a sizeable MMORPG, ShenZhou Online. This work is, as far as we know, the first formal analysis on the MMORPG server traces. We find that the MMORPG and FPS (First-Player Shooting) games are similar in that they both generate small packets and require low bandwidths. In particular, the bandwidth requirement of MMORPG is even lower due to the less real-time game play. More distinctive are the strong periodicity, temporal locality, and irregularity observed in the MMORPG traffic. The periodicity is due to a common practice in game implementation, where the game state updates are accumulated within a fixed time window before transmission. The temporal locality in the game traffic is largely due to the game nature where one action leads to another. The irregularity, particular unique in MMORPG traffic, is due to the diversity of game design where the user behavior can be drastically different depending on the quest at hand.

Research into providing different levels of network Quality of Service (QoS) often assumes that there is a large market for QoSsensitive applications that will be fulfilled once QoS-enabled networks have been deployed. Multiplayer networked games are an example of such an application that requires QoS, and hence will only become popular if QoS is made widely available. The prima facie evidence, however, is that games are already popular, in spite of the existing QoS-free best-effort Internet. Networked games may have become popular despite the lack of QoS because players “make do ” with what is available to them. Such popularity is a double-edged sword. It may mean that there is a demand, as yet unfulfilled, from game players for QoS-enabled networks. On the other hand, it may mean that players have become accustomed to playing games without QoS, and therefore might be

Abstract — The concept of superpeer has been introduced to improve the performance of popular P2P applications. A superpeer is a “powerful ” node that acts as a server for a set of clients, and as an equal with respect to other superpeers. By exploiting heterogeneity, the superpeer paradigm can lead to improved efficiency, without compromising the decentralized nature of P2P networks. The main issues in constructing superpeer-based overlays are the selection of superpeers and the association between superpeers and clients. Generally, superpeers are either run voluntarily (without an explicit selection process), or chosen among the “best ” nodes in the network, for example those with the most abundant resources, such as bandwidth or storage. In several contexts, however, shared resources are not the only factor; latency between clients and superpeers may play an important role, for example in online games and IP-Telephony applications. This paper presents SG-2, a novel protocol for building and maintaining proximity-aware superpeer topologies. SG-2 uses a gossip-based protocol to spread messages to nearby nodes and a biology-inspired task allocation mechanism to promote the “best ” nodes to superpeer status. The paper includes extensive simulation experiments to prove the efficiency, scalability and robustness of SG-2. Index Terms — P2P, superpeer, overlay, latency, quality of service.

Massive multiplayer online games (MMOGs) are today the driving factor for the development of distributed interactive applications, and they are increasing in size and complexity. Even a small MMOG supports thousands of players, the biggest support hundreds of thousands of concurrent players. Since they are typically built as strict client-server systems, they suffer from the inherent scalability problem of the architecture. Computing power and bandwidth limitations close to the server limit the possible number of players. Also, the latency of communication between players through the server will be higher than using direct communication. In the paper, we address these issues and investigate improvement options. A typical MMOG consists of a virtual world with a concept of time and space that is similar to the real world. In it, players are represented by avatars. Only subsets of these avatars interact with each other at any given time. This allows us to divide them into groups, and communication among group members becomes a multi-party communication problem. Thus, to reduce resource consumption, we compare the performance of several algorithms for group communication with the current central server approach. We use overlay multicast as the means of providing group communication, and research algorithms for creating shortest path trees, spanning trees, delay-bounded spanning trees and, more specific, applying Steiner tree heuristics. Our experimental results indicate that different approaches are useful to reduce resource consumption while achieving a good perceived quality under varying conditions, such as frequent changes in group membership and the demand for low latency. 1.

The exclusive goal of a Denial of Service (DoS) attack is to significantly degrade a network’s service quality by introducing large or variable delays, excessive losses, and service interruptions. Conversely, the aim of any DoS defense is to neutralize this effect, and to quickly and fully restore service quality to levels acceptable to the users. DoS attacks and defenses have typically been studied by researchers via network simulation and live experiments in isolated testbeds. To objectively evaluate an attack’s impact on network services, its severity and the effectiveness of a potential defense, we need a precise, quantitative and comprehensive DoS impact metrics that are applicable to any test scenario. Current evaluation approaches do not meet these goals. They commonly measure one or a few traffic parameters and determine attack’s impact by comparing parameter value distributions in different tests. These approaches are customized

Multiplayer online games have now become popular with millions across the globe, capturing the attention of both researchers and practitioners. Unfortunately, online games still have to deal with the limitations imposed by some unresolved issues. Interactivity, consistency, fairness, and scalability are the major requirements that need to be addressed efficiently in order to provide an appealing product to a huge number of potential customers worldwide. To answer this demand, we describe a holistic approach that can exploit the semantics of the game to satisfy the aforementioned requirements. We provide extensive and comparative results that demonstrate how our scheme copes efficiently with an elevated level of game traffic.

In this paper, we advocate the problem of reusing Multiplayer Online Game (MOG) in Client-Server (C/S) architecture. The problem is that MOG services cannot continue to be provided because of high maintenance cost for operating game servers. Additionally, it is caused by the decreasing service users who getting tired of the game and game providers who have faced difficulties in collecting charge of the game service. It is important that every user can play MOGs at any time whether game servers of game providers run them or not. We describe a challenging method for solving the problem. Our solution provides a middleware which is inserted under the game applications to switch network architecture from C/S to Peer-to-Peer (P2P). By exploiting this method, the network architecture of MOGs can be easily changed from