Analyzing the effect of tcp and server population on massively multiplayer games

Many Massively Multiplayer Online Role-Playing Games (MMORPGs) use TCP flows for communication between the server and the game clients. The utilization of TCP, which was not initially designed for (soft) real-time services, has many implications for the competing traffic flows. In this paper we present a series of studies which explore the competition between MMORPG and other traffic flows. For that aim, we first extend a source-based traffic model, based on player’s activities during the day, to also incorporate the impact of the number of players sharing a server (server population) on network traffic. Based on real traffic traces, we statistically model the influence of the variation of the server’s player population on the network traffic, depending on the action categories (i.e., types of in-game player behaviour). Using the developed traffic model we prove that while server population only modifies specific action categories, this effect is significant enough to be observed on the overall traffic. We find that TCP Vegas is a good option for competing flows in order not to throttle the MMORPG flows and that TCP SACK is more respectful with game flows than other TCP variants, namely, Tahoe, Reno, and New Reno. Other tests show that MMORPG flows do not significantly reduce their sending window size when competing against UDP flows. Additionally, we study the effect of RTT unfairness between MMORPG flows, showing that it is less important than in the case of network-limited TCP flows

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

Peer-to-peer live video streaming with rateless codes for massively multiplayer online games

International audienc

Architecting Scalability for Massively Multiplayer Online Gaming Experiences

With this article we want to identify the main scalability issues for the development of Massive Multi-Player Online Games. There is no generic architecture to achieve scalability for every problem. We must understand the nature of the problem in order to reach system scalability. Massive Multi-Player Online Games (MMOG) are conceived with the objective of massive use by a potentially geographically dispersed population. In their design we are faced with scalability challenges which are specific to the interactive modalities and the socio-technical scenarios we intend to enable [Fitch 2001]. The emergence of the Internet made possible the development of interactive distributed systems that can be accessed by thousands of users in virtually any part of the world. The scalability issues introduced by such a massive use must be considered in the system design. By scalability we mean the system fit capacity according to his loading charge, for example, accommodates increasing interaction volume, without significant degradation of quality service. It is commonly known that scalability can’t be secured if we only pay attention to some system parts. To achieve scalability in any kind of distributed system we must design all the components to achieve this goal. For example, a system that has high scalability in the simulation and low communication scalability may result in a poor scalable system, globally. To see the scalability problems in a MMOG we must understand the system dynamics and structure and what’s bound for. Looking at the existent types of MMOG – massive multi-player online role playing games, virtual environments, massive multiplayer real time strategy, massive multiplayer online first-person shooter – we can try to generalize some features that allow us to analyze their scalability requisites. Normally, in this kind of games the action takes place in a virtual 3D environment, where thousands of players interact by controlling avatars, allowing real-time interaction between users in simulated virtual worlds. The action environment can be persistent in order to maintain the notion of space and time continuity [wikipedia 2004]. From an analysis of the characteristics of MMOG systems and their usage we can start to identify four main scalability issues: a) simulation capacity that allows for thousands of players to be online in the same virtual world; b) data storage capacity of all the information that is used to represent the virtual worlds and one efficient distribution method for guaranteeing availability when needed; c) reliable and efficient communications for experience coordination and smooth interaction; d) architectural integration enabling system expansibility through new computational, communication and storage resources. Next we will briefly discuss these issues. The simulation component role in MMOG is to process the events that are generated through the player’s interaction or by sub-systems that generate automatic environmental activities (e.g., atmospheric, AI bots). Besides the high event volume that must be processed, the simulation activity has other challenge: the size of the virtual universe data model. Virtual universe action area can have the size of a planet or even a galaxy, which becomes very complex to handle [Rosedale 2003]. As previously referred, the MMOG environments are commonly 3D and very dynamic, being impossible for the clients to keep the virtual world state. So, when a player enters the virtual world must be given to him all the information necessary to animate that world. This information has two different types: data model that represents abstractly the virtual world; and the necessary multimedia elements needed to visual and sonorous animation. Nature and volume size of multimedia information become the main problem of the distribution system [Yu-Shen 1997]. Communication scalability is one of the essential issues in simulated real-time games through Internet. Scalability must be understood not only by the capacity to support communication between a high numbers of players, but also, as the capacity to maintain a communication performance level that doesn’t put at risk the game experience quality. This fact in the MMOG systems is paradigmatic, since there are possible thousand of players interacting with the world objects and moving in the same space. Objects state and players activity must be informed to all players in order to maintain the game integrity/consistency [Smed 2001]. Structural scalability is important to increase the system live span. In order to achieve this requisite the system structure must be designed to enable the addition of new resources. Architectural scalability, through the specification of clear system components that interact in a clear dynamics, through defined protocols, is a pre-requisite for system repairing, actualization and evolution; and must also have the capacity to integrate significantly contribute to the later incorporation of new technologies and devices. At first glance, we would think that to achieve scalability in MMOG implementations we would simply have to work on an architectural design to satisfy all the requisites that have been presented. But that would not be enough. System scalability also emerges from the balance and harmony of the system components. When we are trying to satisfy some requisite, the ideal solution may be in conflict with some other requisite. For example, the best solution for the distribution of static content (such as 3D models, textures and sounds) can jeopardize communication scalability for more immediate real-time events, as their compete for the available bandwidth. The best solution may not be the optimal one for any system component, but the best overall solution for the integrated system, that guarantees an adequate level of quality to the interactive experience. In order to achieve such a balance we have to consider an adequate partitioning of responsibilities for the components and the internal and the external dynamics that are originated

Clouds + Games: A multifaceted approach

The computer game landscape is changing: people play games on multiple computing devices with heterogeneous form-factors, capability, and connectivity. Providing high playability on such devices concurrently is difficult. To enhance the gaming experience, designers could leverage abundant and elastic cloud resources, but current cloud platforms aren't optimized for highly interactive games. Existing studies focus on streaming-based cloud gaming, which is a special case for the more general cloud game architecture. The authors explain how to integrate techniques from the cloud and game research communities into a complete architecture for enhanced online gaming quality. They examine several open issues that appear only when clouds and games are put together. © 2014 IEEE