A virtualization-based approach for zone migration in distributed virtual environments

Best paper award.</p

Design and implementation of distributed interactive virtual environment.

Chan Ming-fei.Thesis (M.Phil.)--Chinese University of Hong Kong, 1999.Includes bibliographical references (leaves 63-66).Abstract --- p.iAcknowledgments --- p.iiiChapter 1 --- Introduction --- p.1Chapter 1.1 --- Challenging Issues --- p.2Chapter 1.2 --- Previous Work --- p.4Chapter 1.3 --- Organization of the Thesis --- p.5Chapter 2 --- Distributed Virtual Environment --- p.6Chapter 2.1 --- Possible Architectures --- p.6Chapter 2.2 --- Representations of Clients as Avatars --- p.7Chapter 2.3 --- Dynamic Membership --- p.9Chapter 3 --- Bandwidth and Computation Reduction Techniques --- p.11Chapter 3.1 --- Network Communication --- p.12Chapter 3.2 --- Dead Reckoning --- p.13Chapter 3.3 --- Message Aggregation --- p.15Chapter 3.3.1 --- Network-Based Aggregation --- p.15Chapter 3.3.2 --- Organization-Based Aggregations --- p.16Chapter 3.3.3 --- Grid-Based Aggregations --- p.16Chapter 3.4 --- Relevance Filtering --- p.17Chapter 3.4.1 --- Entity-Based Filtering --- p.17Chapter 3.4.2 --- Grid-Based Filtering --- p.19Chapter 3.5 --- Quiescent Entities --- p.20Chapter 3.6 --- Spatial Partitioning --- p.21Chapter 3.6.1 --- Necessity of Spatial Partitioning --- p.22Chapter 3.6.2 --- Binary Space Partitioning Tree --- p.23Chapter 3.6.3 --- BSP Tree Construction --- p.23Chapter 4 --- Partitioning Algorithm --- p.25Chapter 4.1 --- Problem Formulation --- p.25Chapter 4.2 --- Exhaustive Partition (EP) Algorithm --- p.28Chapter 4.3 --- Partitioning Algorithm --- p.29Chapter 4.3.1 --- Recursive Bisection Partition (RBP) Algorithm --- p.30Chapter 4.3.2 --- Layering Partitioning (LP) Algorithm --- p.32Chapter 4.3.3 --- Communication Refinement Partitioning (CRP) Algorithm --- p.38Chapter 4.4 --- Parallel Approach --- p.42Chapter 4.5 --- Further Observation --- p.43Chapter 5 --- Experiments --- p.44Chapter 5.1 --- Experiment 1: Small Virtual World --- p.45Chapter 5.2 --- Experiment 2: Large Virtual World --- p.46Chapter 5.3 --- Experiment 3: Moving of Avatars --- p.47Chapter 5.4 --- Experiment 4: Dynamic Joining and Leaving --- p.48Chapter 5.5 --- Experiment 5: Parallel Approach --- p.49Chapter 6 --- Implementation Considerations --- p.55Chapter 6.1 --- Different Environments --- p.55Chapter 6.2 --- Platform --- p.56Chapter 6.3 --- Lessons learned --- p.57Chapter 7 --- Conclusion --- p.59A Simplex Method --- p.60Bibliography --- p.6

Distributed virtual environment scalability and security

Distributed virtual environments (DVEs) have been an active area of research and engineering for more than 20 years. The most widely deployed DVEs are network games such as Quake, Halo, and World of Warcraft (WoW), with millions of users and billions of dollars in annual revenue. Deployed DVEs remain expensive centralized implementations despite significant research outlining ways to distribute DVE workloads. This dissertation shows previous DVE research evaluations are inconsistent with deployed DVE needs. Assumptions about avatar movement and proximity - fundamental scale factors - do not match WoW’s workload, and likely the workload of other deployed DVEs. Alternate workload models are explored and preliminary conclusions presented. Using realistic workloads it is shown that a fully decentralized DVE cannot be deployed to today’s consumers, regardless of its overhead. Residential broadband speeds are improving, and this limitation will eventually disappear. When it does, appropriate security mechanisms will be a fundamental requirement for technology adoption. A trusted auditing system (“Carbon”) is presented which has good security, scalability, and resource characteristics for decentralized DVEs. When performing exhaustive auditing, Carbon adds 27% network overhead to a decentralized DVE with a WoW-like workload. This resource consumption can be reduced significantly, depending upon the DVE’s risk tolerance. Finally, the Pairwise Random Protocol (PRP) is described. PRP enables adversaries to fairly resolve probabilistic activities, an ability missing from most decentralized DVE security proposals. Thus, this dissertations contribution is to address two of the obstacles for deploying research on decentralized DVE architectures. First, lack of evidence that research results apply to existing DVEs. Second, the lack of security systems combining appropriate security guarantees with acceptable overhead

Network architecture for large-scale distributed virtual environments

Distributed Virtual Environments (DVEs) provide 3D graphical computer generated environments with stereo sound, supporting real-time collaboration between potentially large numbers of users distributed around the world. Early DVEs has been used over local area networks (LANs). Recently with the Internet's development into the most common embedding for DVEs these distributed applications have been moved towards an exploiting IP networks. This has brought the scalability challenges into the DVEs evolution. The network bandwidth resource is the more limited resource of the DVE system and to improve the DVE's scalability it is necessary to manage carefully this resource. To achieve the saving in the network bandwidth the different types of the network traffic that is produced by the DVEs have to be considered. DVE applications demand· exchange of the data that forms different types of traffic such as a computer data type, video and audio, and a 3D data type to keep the consistency of the application's state. The problem is that the meeting of the QoS requirements of both control and continuous media traffic already have been covered by the existing research. But QoS for transfer of the 3D information has not really been considered. The 3D DVE geometry traffic is very bursty in nature and places a high demands on the network for short intervals of time due to the quite large size of the 3D models and the DVE application requirements to transmit a 3D data as quick as possible. The main motivation in carrying out the work presented in this thesis is to find a solution to improve the scalability of the DVE applications by a consideration the QoS requirements of the 3D DVE geometrical data type. In this work we are investigating the possibility to decrease the network bandwidth utilization by the 3D DVE traffic using the level of detail (LOD) concept and the active networking approach. The background work of the thesis surveys the DVE applications and the scalability requirements of the DVE systems. It also discusses the active networks and multiresolution representation and progressive transmission of the 3D data. The new active networking approach to the transmission of the 3D geometry data within the DVE systems is proposed in this thesis. This approach enhances the currently applied peer-to-peer DVE architecture by adding to the peer-to-peer multicast neny_ork layer filtering of the 3D flows an application level filtering on the active intermediate nodes. The active router keeps the application level information about the placements of users. This information is used by active routers to prune more detailed 3D data flows (higher LODs) in the multicast tree arches that are linked to the distance DVE participants. The exploration of possible benefits of exploiting the proposed active approach through the comparison with the non-active approach is carried out using the simulation­based performance modelling approach. Complex interactions between participants in DVE application and a large number of analyzed variables indicate that flexible simulation is more appropriate than mathematical modelling. To build a test bed will not be feasible. Results from the evaluation demonstrate that the proposed active approach shows potential benefits to the improvement of the DVE's scalability but the degree of improvement depends on the users' movement pattern. Therefore, other active networking methods to support the 3D DVE geometry transmission may also be required

Heuristics for Client Assignment and Load Balancing Problems in Online Games

Massively multiplayer online games (MMOGs) have been very popular over the past decade. The infrastructure necessary to support a large number of players simultaneously playing these games raises interesting problems to solve. Since the computations involved in solving those problems need to be done while the game is being played, they should not be so expensive that they cause any noticeable slowdown, as this would lead to a poor player perception of the game. Many of the problems in MMOGs are NP-Hard or NP-Complete, therefore we must develop heuristics for those problems without negatively affecting the player experience as a result of excessive computation. In this dissertation, we focus on a few of the problems encountered in MMOGs – the Client Assignment Problem (CAP) and both centralized and distributed load balancing – and develop heuristics for each. For the CAP we investigate how best to assign players to servers while meeting several conditions for satisfactory play, while in load balancing we investigate how best to distribute load among game servers subject to several criteria. In particular, we develop three heuristics - a heuristic for a variant of the CAP called Offline CAP-Z, a heuristic for centralized load balancing called BreakpointLB, and a heuristic for distributed load balancing called PLGR. We develop a simulator to simulate the operations of an MMOG and implement our heuristics to measure performance against adapted heuristics from the literature. We find that in many cases we are able to produce better results than those adapted heuristics, showing promise for implementation into production environments. Further, we believe that these ideas could also be easily adapted to the numerous other problems to solve in MMOGs, and they merit further consideration and augmentation for future research

Distributed real-time physics for scalable and streamed games and simulation

PhD ThesisIn this study, a solution to delivering scalable real-time physics simulations is proposed. Although high performance computing simulations of physics related problems do exist, these are not real-time and do not model the real-time intricate interactions of rigid bodies for visual effect common in video games (favouring accuracy over real-time). As such, this study presents the first approach to real-time delivery of scalable, commercial grade, video game quality physics and is termed Aura Projection (AP). This approach takes the physics engine out of the player’s machine and deploys it across standard cloud based infrastructures. The simulation world is divided into regions that are then allocated to multiple servers. A server maintains the physics for all simulated objects in its region. The contribution of this study is the ability to maintain a scalable simulation by allowing object interaction across region boundaries using predictive migration techniques. AP allows each object to project an aura that is used to determine object migration across servers to ensure seamless physics interactions between objects. AP allows player interaction at any point in real-time (influencing the simulation) in the same manner as any video game. This study measures and evaluates both the scalability of AP and correctness of collisions within AP through experimentation and benchmarking. The experiments show that AP is a solution to scalable real-time physics by measuring computation workload with increasing computation resources. AP also demonstrates that collisions between rigid-bodies can be simulated correctly within a scalable real-time physics simulation, even when rigid-bodies are intersecting server-region boundaries; demonstrated through comparison of a distributed AP simulation to a single, centralised simulation. We believe that AP is the first successful demonstration of scalable real-time physics in an academic setting

Design and implementation of a secure wide-area object middleware

Tanenbaum, A.S. [Promotor]Crispo, C.B. [Copromotor

Solving key design issues for massively multiplayer online games on peer-to-peer architectures

Massively Multiplayer Online Games (MMOGs) are increasing in both popularity and scale on the Internet and are predominantly implemented by Client/Server architectures. While such a classical approach to distributed system design offers many benefits, it suffers from significant technical and commercial drawbacks, primarily reliability and scalability costs. This realisation has sparked recent research interest in adapting MMOGs to Peer-to-Peer (P2P) architectures. This thesis identifies six key design issues to be addressed by P2P MMOGs, namely interest management, event dissemination, task sharing, state persistency, cheating mitigation, and incentive mechanisms. Design alternatives for each issue are systematically compared, and their interrelationships discussed. How well representative P2P MMOG architectures fulfil the design criteria is also evaluated. It is argued that although P2P MMOG architectures are developing rapidly, their support for task sharing and incentive mechanisms still need to be improved. The design of a novel framework for P2P MMOGs, Mediator, is presented. It employs a self-organising super-peer network over a P2P overlay infrastructure, and addresses the six design issues in an integrated system. The Mediator framework is extensible, as it supports flexible policy plug-ins and can accommodate the introduction of new superpeer roles. Key components of this framework have been implemented and evaluated with a simulated P2P MMOG. As the Mediator framework relies on super-peers for computational and administrative tasks, membership management is crucial, e.g. to allow the system to recover from super-peer failures. A new technology for this, namely Membership-Aware Multicast with Bushiness Optimisation (MAMBO), has been designed, implemented and evaluated. It reuses the communication structure of a tree-based application-level multicast to track group membership efficiently. Evaluation of a demonstration application shows i that MAMBO is able to quickly detect and handle peers joining and leaving. Compared to a conventional supervision architecture, MAMBO is more scalable, and yet incurs less communication overheads. Besides MMOGs, MAMBO is suitable for other P2P applications, such as collaborative computing and multimedia streaming. This thesis also presents the design, implementation and evaluation of a novel task mapping infrastructure for heterogeneous P2P environments, Deadline-Driven Auctions (DDA). DDA is primarily designed to support NPC host allocation in P2P MMOGs, and specifically in the Mediator framework. However, it can also support the sharing of computational and interactive tasks with various deadlines in general P2P applications. Experimental and analytical results demonstrate that DDA efficiently allocates computing resources for large numbers of real-time NPC tasks in a simulated P2P MMOG with approximately 1000 players. Furthermore, DDA supports gaming interactivity by keeping the communication latency among NPC hosts and ordinary players low. It also supports flexible matchmaking policies, and can motivate application participants to contribute resources to the system