Massively multiplayer online games (MMOGs)




 

Massively multiplayer online games offer an immersive experience whereby very large numbers of users interact through the Internet with a persistent virtual world. Leading examples of such games include Sony’s EverQuest II and EVE Online from the Finnish
company CCP Games. Such worlds have increased significantly in sophistication and now include, complex playing arenas (for example EVE, Online consists of a universe with over 5,000 star systems) and multifarious social and economic systems. The number of players is also rising, with systems able to support over 50,000 simultaneous
online players (and the total number of players perhaps ten times this figure). The engineering of MMOGs represents a major challenge for distributed systems technologies, particularly because of the need for fast response times to preserve the user experience of the game. Other challenges include the real-time propagation of events to the many players and maintaining a consistent view of the shared world. This, therefore, provides an excellent example of the challenges facing modern distributed systems designers.
A number of solutions have been proposed for the design of massively multiplayer online games:
Perhaps surprisingly, the largest online game, EVE Online, utilizes a client-server an architecture where a single copy of the state of the world is maintained on a  
centralized server and accessed by client programs running on players’ consoles or other devices. To support large numbers of clients, the server is a complex the entity in its own right consisting of a cluster architecture featuring hundreds of computer nodes (this client-server approach is discussed in more detail in Section 1.4 and cluster approaches are discussed in Section 1.3.4). The centralized architecture helps significantly in terms of the management of the virtual world and the single copy also eases consistency concerns. The goal is then to ensure fast response through optimizing network protocols and ensuring a rapid response to incoming events. To support this, the load is partitioned by allocating individual ‘star systems’ to particular computers within the cluster, with highly loaded star systems having their own dedicated computer and others sharing a computer.

Incoming events are directed to the right computers within the cluster by keeping track of movement of players between star systems.
Other MMOGs adopt more distributed architectures where the universe is partitioned across a (potentially very large) number of servers that may also be geographically distributed. Users are then dynamically allocated a particular server based on current usage patterns and also the network delays to the server (based on geographical proximity for example). This style of architecture, which
is adopted by EverQuest, is naturally extensible by adding new servers.
Most commercial systems adopt one of the two models presented above, but researchers are also now looking at more radical architectures that are not based on client-server principles but rather adopt completely decentralized approaches based on peer-to-peer technology where every participant contributes resources (storage and processing) to accommodate the game.

 



Frequently Asked Questions

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Ans: The growth of the World Wide Web as a repository of information and knowledge; the development of web search engines such as Google and Yahoo to search this vast repository view more..
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Ans: The task of a web search engine is to index the entire contents of the World Wide Web, encompassing a wide range of information styles including web pages, multimedia sources and (scanned) books view more..
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Ans: the wide range of applications in use today, from relatively localized systems (as found, for example, in a car or aircraft) to globalscale systems involving millions of nodes, from data-centric services to processorintensive tasks, from systems built from very small and relatively primitive sensors to those incorporating powerful computational elements, from embedded systems to ones that support a sophisticated interactive user experience, and so on. view more..
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Ans: The engineering of MMOGs represents a major challenge for distributed systems technologies, particularly because of the need for fast response times to preserve the user experience of the game. view more..
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Ans: a very different style of underlying architecture from the styles mentioned above (for example client-server), and such systems typically employ what is known as distributed event-based systems. view more..
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Ans: the emergence of ubiquitous computing coupled with the desire to support user mobility in distributed systems view more..
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Ans: The Internet is also a very large distributed system. It enables users, wherever they are, to make use of services such as the World Wide Web, email and file transfer. (Indeed, the Web is sometimes incorrectly equated with the Internet.) view more..
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Ans: Technological advances in device miniaturization and wireless networking have led increasingly to the integration of small and portable computing devices into distributed systems. view more..
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Ans: The crucial characteristic of continuous media types is that they include a temporal dimension, and indeed, the integrity of the media type is fundamentally dependent on preserving real-time relationships between elements of a media type. view more..
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Ans: hysical resources such as storage and processing can be made available to networked computers, removing the need to own such resources on their own. At one end of the spectrum, a user may opt for a remote storage facility for file storage requirements view more..
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Ans: In practice, patterns of resource sharing vary widely in their scope and in how closely users work together. At one extreme, a search engine on the Web provides a facility to users throughout the world, users who need never come into contact with one another directly. At the other extreme, in computer-supported cooperative working (CSCW), a group of users who cooperate directly share resources such as documents in a small, closed group. view more..
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Ans: Data types such as integers may be represented in different ways on different sorts of hardware – for example, there are two alternatives for the byte ordering of integers. These differences in representation must be dealt with if messages are to be exchanged between programs running on different hardware view more..
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Ans: the publication of interfaces is only the starting point for adding and extending services in a distributed system. The challenge to designers is to tackle the complexity of distributed systems consisting of many components engineered by different people. view more..
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Ans: a firewall can be used to form a barrier around an intranet, restricting the traffic that can enter and leave, this does not deal with ensuring the appropriate use of resources by users within an intranet, or with the appropriate use of resources in the Internet, that are not protected by firewalls. view more..
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Ans: ly and efficiently at many different scales, ranging from a small intranet to the Internet. A system is described as scalable if it will remain effective when there is a significant increase in the number of resources and the number of users. The number of computers and servers in the Internet has increased dramatically. view more..
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Ans: Failures in a distributed system are partial – that is, some components fail while others continue to function. Therefore the handling of failures is particularly difficult. The following techniques for dealing with failures are discussed throughout the book view more..
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Ans: he process that manages a shared resource could take one client request at a time. But that approach limits throughput. Therefore services and applications generally allow multiple client requests to be processed concurrently. view more..
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Ans: oncealment from the user and the application programmer of the separation of components in a distributed system, so that the system is perceived as a whole rather than as a collection of independent components view more..



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