Applicability of group communication for increased scalability in MMOGs

Massive multiplayer online games (MMOGs) are today the driving factor for the development of distributed interactive applications, and they are increasing in size and complex-ity. 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 limita-tions 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 im-provement options. A typical MMOG consists of a virtual world with a con-cept 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 communica-tion 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 short-est 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

Dynamic Group Membership Management for Distributed Interactive Applications

Abstract—Distributed interactive applications have become increasingly popular, making it important to address their communication needs, where one of the needs is group communication. In this paper, we consider the applications in which it is at any given time possible to divide its users into groups. The group membership changes over time, and the group division is unrelated to the physical proximity. As a way of enabling the group communication in distributed interactive applications, we choose application layer multicast. We use simulation to evaluate several dynamic algorithms for managing overlay multicast trees. They are compared with respect to four metrics that can be relevant for a distributed interactive application. These are total tree cost, diameter, reconfiguration time and stability. We demonstrate algorithms that perform well for these metrics although they do not consider all users during reconfiguration. I

Applicability of group communication for increased scalability in MMOGs

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

Quality of service aware source initiated ad-hoc routing

Mobil Ad-hoc networks (MANETs) are used in a variety of situations ranging from conference meetings to military operations. Among the important challenges facing MANETs is the development of suitable routing protocols. A Routing Protocol must be aware of the diversity in the network if the network is going to perform at its best. The routing protocol should be efficient and able to adapt to rapidly changing topologies. A MANET is applicable to any situation requiring network communication in particular short-lived highly mobile networks. The routing protocol needs mechanisms that handle the mobility such that the communication disruption time is minimized. Specifically, we desire a routing protocol with quality control mechanisms for every important stage in the lifetime of a route. This thesis proposes a Quality of Service (QoS) aware source-initiated ad-hoc routing protocol (QuaSAR) that adds quality control to all the phases of an on-demand routing protocol. QuaSAR gathers statistical information from the network during route discovery, more specifically battery power, signal strength, bandwidth and latency. In particular we use the signal strength to find stronger connected routes. The metrics are associated to the individual route and later used when a route to the destination is picked. QuaSAR includes proactive route maintenance features in addition to the reactive maintenance. The proactive mechanism of QuaSAR makes a Mobile Node (MN) on an active route aware of route critical incidents in progress and notifies the appropriate party of the development. Performance experiments were conducted to test the performance of QuaSAR using ns2 Network Simulator. Results were compared with Dynamic Source Routing (DSR). The following mobility models were used in the experiments: Random Waypoint, Gauss Markov, Manhattan Grid and Reference Point Group Model. We have demonstrated that using signal strength and proactive mechanisms as a means of routing will increase the throughput and the packet delivery ratio. The quality control mechanisms of QuaSAR enhance the performance experienced by MNs by giving it more stable paths thus minimizing the communication disruption time