A New Approach to Multi-User Environments Using Software Distributed Shared Memory

This paper presents an overview of multiuser environments and the application of the Software Distributed Shared Memory (SDSM) model to solve scalability problems in such environments. It also outlines a suggested distributed architecture which addresses the drawbacks of single-server architectures. Games are a very compelling application within the computer community. This led us to choose MultiUser Dungeons (MUDs) to illustrate our distributed architecture. Such a distributed server system is necessary to accomodate the fast-growing interest in interactive networked games. We have implemented our distributed server system using the Java language with a customized communication protocol based on sockets. The result has proven to be more eecient than existing environments written in C or C++, partially due to the hardware and distribution transparency aaorded by Java and our framework. In this paper we discuss the reasoning behind our system design and provide details about our implementation. 1 Overview Human nature involves interaction. One of the tools which helps people to communicate is the computer. Therefore, it is not surprising that, very soon after their introduction in the early 1980s, multi-player environments became very popular in the computer community. The rst MultiUser Dungeon (MUD), developed in 1979 at Essex University by Roy Trubshaw, was just a collection of interconnected rooms where people could \virtually" walk and communicate 1]. Given the distribution of these environments, we can categorize them as early SDSM systems. Early MUDs were highly appealing to the computer community. However, one major drawback of the MUDs was their simple text-based interface. The rst MUDs were entirely based on text channels; users could interact only by typing simple commands to manipulate their characters and the environment. Nowadays, MUDs ooer persistent worlds, competition and/or cooperation between users, 3-D graphics, sound eeects and other features. The addition of these features has increased the appeal of these games, causing the user base to grow extremely large. This has begun to cause serious problems with traditional system designs. Because of their lack of scalability, existing servers can not increase the number of connections to keep up with the increase in size of the user community and still maintain the same quality of service. The peer-to-peer architecture is not applicable to solve this problem, because there is a single centralized virtual environment shared by all the users in such a system. Traditional client-server architectures are also proving to be insuucient, even in the presence of high-bandwidth …