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Optimal assignment of distributed servers to virtual partitions for the provision of immersive voice communication in massively multiplayer games

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COMPUTER COMMUNICATIONS 2006年第9期29卷 1260-1270页

作者： Nguyen, Cong Duc Safaei, Farzad Boustead, Paul Univ Wollongong Ctr Emerging Networks & Applicat Wollongong NSW 2522 Australia

This paper investigates the assignment of audio mixing operations to a geographically distributed set of servers to provide an immersive voice communication environment for massively multi-player online games. The immersive voice communication service enables each avatar to hear a spatially accurate audio mix of the conversations in its hearing range. There are three primary delivery architectures for this service, namely, peer-to-peer, central server, and distributed servers. We focus on a distributed server architecture, which partitions the virtual world into regions or locales and then assigns the computation associated with the creation of audio scenes for all avatars in each locale to a server. Our aim is to find the optimal way to partition the virtual world into locales and then choose the locale servers in such a way that reduces the total delay perceived by all avatars. We have produced a mathematical formulation for the optimal partitioning and server assignment and developed a heuristics approach based on a graph algorithm. We have developed a simulation environment that creates both the physical world (geographic distribution of participants and the Internet topology model) and the virtual world (distribution of avatars based on different avatar aggregation behaviors). We have solved the problem exactly as well as using the heuristics for a range of simulated virtual and physical worlds. In many cases, the heuristics results were within 5% of the optimal. Our algorithms and simulation study will be of benefit to future immersive voice communication service providers in the design of a cost effective delivery architecture for this service. (C) 2005 Elsevier B.V. All rights reserved.

关键词： networked games immersive voice communication distributed servers server location optimization heuristics

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Computational Time Complexity of Allocation Problem for distributed servers in Real-time Applications 18

Computational Time Complexity of Allocation Problem for Dist...

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18th Asia-Pacific Network Operations and Management Symposium (APNOMS)

作者： Ba, Seydou Kawabata, Akio Chatterjee, Bijoy Chand Oki, Eiji Univ Electrocommun Tokyo Japan

ISBN: (纸本)9784885523045

This paper analyzes the computational time complexity of the allocation problem for data processing functions among multiple users and distributed servers in the distributed processing communication scheme for a real-time network application. In the distributed processing communication scheme, the application is processed on a data processing function in the distributed servers in order to minimize the delay time. We prove that the allocation problem for data processing functions among multiple users and distributed servers is an NP-complete problem.

关键词： distributed servers Network delay NP-complete

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VoD on steroids: Optimized content delivery using distributed video servers over best-effort Internet

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JOURNAL OF PARALLEL AND distributed COMPUTING 2005年第9期65卷 1057-1071页

作者： Barlas, G Amer Univ Sharjah Dept Comp Sci Sch Engn Sharjah U Arab Emirates

This paper addresses the problem of delivering a long-duration continuous media document, typically a movie, over unreliable communication links like the ones that make up the Internet. Packet loss/drop is one of the main problems that plague Internet's use for offering multimedia services. The framework presented here addresses analytically this problem by offering closed-form solutions for partitioning and scheduling the delivery of a document by multiple spatially distributed servers. The goal is to offer uninterrupted playback to clients while minimizing their access-time. The solid mathematical foundation presented, enables the study of multi-server document delivery using unreliable communications for both CBR and VBR media. It is also shown how slow connections that would otherwise prevent the deployment of Movie-on-Demand class services, could be used to offer such services in an optimal manner. The paper also addresses the problem of optimally arranging the available servers. A rigorous simulation study that explores the potential of the proposed approach concludes the paper. Our simulations show a superlinear speedup in access-times and also the robustness of the proposed scheme, capable of handling unknown network conditions by shifting server "load". (c) 2005 Elsevier Inc. All rights reserved.

关键词： distributed servers divisible load video on demand MPEG VBR packet loss

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Centralized versus distributed multimedia servers

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 2000年第8期10卷 1438-1449页

作者： Serpanos, DN Bouloutas, A Univ Crete Dept Comp Sci GR-71110 Iraklion Greece Bank Boston Treasury Dept Boston MA 02110 USA

The organization of multimedia servers is important in the design of low-cost high-performance multimedia application environments. Considering video services as highly demanding applications in a multimedia environment, we analyze and compare centralized and distributed architectures for multimedia video servers. Comparisons are made in terms of the blocking probability of a video clients request, considering as important parameters the input/output capacity of the system and the amount of storage. Through a combination of analytical results and simulations, we conclude that in general a centralized architecture is preferable. The results indicate, however, that in a distributed architecture containing a large number of powerful servers, performance is similar to the centralized architecture under high load conditions, while the blocking probabilities are quite small under light load conditions. Furthermore, centralized and distributed server architectures become equivalent when large amounts of storage are added to the latter or when their input/output capacity is significantly increased. The results indicate that in many practical environments, factors other than performance, such as cost of management, security, and fault tolerance, will influence the choice for the appropriate server configuration.

关键词： centralized servers distributed servers multimedia servers multimedia systems video servers

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RFID Authentication with Un-Traceability and Forward Secrecy in the Partial-distributed-Server Model

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IEICE TRANSACTIONS ON INFORMATION AND SYSTEMS 2015年第4期E98D卷 750-759页

作者： Chien, Hung-Yu Wu, Tzong-Chen Hsu, Chien-Lung Natl Chi Nan Univ Dept Informat Management Puli Township Nantou County Taiwan Natl Taiwan Univ Sci & Technol Dept Informat Management Taipei Taiwan Chang Gung Univ Dept Informat Management Taoyuan Taiwan

Secure authentication of low cost Radio Frequency Identification (RFID) tag with limited resources is a big challenge, especially when we simultaneously consider anonymity, un-traceability, and forward secrecy. The popularity of Internet of Things (IoT) further amplifies this challenge, as we should authenticate these mobile tags in the partial-distributed-server environments. In this paper, we propose an RFID authentication scheme in the partial-distributed-server environments. The proposed scheme owns excellent performance in terms of computational complexity and scalability as well as security properties.

关键词： authentication RFID anonymity distributed servers error correction code

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On choosing a task assignment policy for a distributed server system

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JOURNAL OF PARALLEL AND distributed COMPUTING 1999年第2期59卷 204-228页

作者： Harchol-Balter, M Crovella, ME Murta, CD MIT Comp Sci Lab Cambridge MA 02139 USA Boston Univ Dept Comp Sci Boston MA 02215 USA

We consider a distributed server system in which each host processes tasks in First-Come-First-Served order and each task's service demand is known immediately upon task arrival. We consider four task assignment policies commonly proposed for such distributed server systems: Round Robin: Random;Size-Based. in which all tasks within a given size range are assigned to a particular host: and Dynamic-Least-Work-Remaining. in which a task is assigned to the host with the least outstanding work. Using analysis and simulation, we explore the influence of task size variability on which task assignment policy is best. Surprisingly, we find that not one of the above task assignment policies is best. In particular, we find that when the task sizes are nut highly variable. the Dynamic policy is preferable. However, when task sizes show the degree of variability more characteristic of empirically measured workloads, the size-based policy is the best choice. We use the resulting observations to argue in favor of a specific size-based policy, SITA-E, that shows very good performance for realistic task size distributions. (C) 1999 Academic Press.

关键词： task assignment scheduling heavy-tailed workloads high valiance distributed servers queueing theory

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Performance *** large-scale video streaming services in highly heterogeneous environment

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IEEE TRANSACTIONS ON BROADCASTING 2007年第4期53卷 763-773页

作者： Ho, K. -M. Poon, W. -E Lo, K. -T. Hong Kong Polytech Univ Dept Elect & Informat Engn Kowloon Hong Kong Peoples R China

To support large-scale Video-on-Demand (Vol) services in a heterogeneous network environment, either a replication or layering approach can be deployed to adapt the client bandwidth requirements. With the aid of the broadcasting and caching techniques, it has been proved that the overall performance of the system can be enhanced. In this paper, we explore the impact on the broadcasting schemes coupled with proxy caching and develop an analytical model to evaluate the system performance in a highly heterogeneous network environment. We develop guidelines for resources allocation, transmission strategies as well as caching schemes under different system configurations. The model can assist system designers to study various design options as well as perform system dimensioning. Moreover, a systematic comparison between replication and layering is performed. From the results, it can be seen that the system performance of layering is better. than that of replication when the environment is highly heterogeneous even if the layering overhead is higher than 25%. In addition, it is found that the system blocking probability can be further reduced by exploring the broadcast capability of the network if the proxy server cannot store all the popular videos.

关键词： broadcasting distributed servers layered video media streaming network performance model video-on-demand

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Load sharing in distributed multimedia-on-demand systems

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IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING 2000年第3期12卷 410-428页

作者： Tay, YC Pang, H Natl Univ Singapore Dept Math Singapore 119260 Singapore Kent Ridge Digital Labs Singapore 119613 Singapore

Service providers have begun to offer multimedia-on-demand services to residential estates by installing isolated, small-scale multimedia servers at individual estates. Such an arrangement allows the service providers to operate without relying on a highspeed, large-capacity metropolitan area network, which is still not available in many countries. Unfortunately, installing isolated servers could incur very high server costs, as each server requires spare bandwidth to cope with fluctuations in user demand. In this paper, we explore the feasibility of linking up several small multimedia servers to a (limited-capacity) network, and allowing servers with idle retrieval bandwidth to help out servers that are temporarily overloaded;the goal is to minimize the waiting time for service to begin. We identify four characteristics of load sharing in a distributed multimedia system that differentiate it from load balancing in a conventional distributed system. We then introduce a GWQ load sharing algorithm that fits and exploits these characteristics;it puts all servers' pending requests in a global queue, from which a server with idle capacity obtains additional jobs. The performance of the algorithm is captured by an analytical model, which we validate through simulations. Both the analytical and simulation models show that the algorithm vastly reduces wait times at the servers. The analytical model also provides guidelines for capacity planning. Finally, we propose an enhanced GWQ+L algorithm that allows a server to reclaim active local requests that are being serviced remotely. Simulation experiments indicate that the scheduling decisions of GWQ+L are optimal, in the sense that it enables the distributed servers to approximate the performance of a large centralized server.

关键词： multimedia-on-demand distributed servers load sharing performance modeling

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Task assignment with unknown duration

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JOURNAL OF THE ACM 2002年第2期49卷 260-288页

作者： Harchol-Balter, M Carnegie Mellon Univ Sch Comp Sci Pittsburgh PA 15213 USA

We consider a distributed server system and ask which policy should be used for assigning jobs (tasks) to hosts. In our server, jobs are not preemptible. Also, the job's service demand is not known a priori. We are particularly concerned with the case where the workload is heavy-tailed, as is characteristic of many empirically measured computer workloads. We analyze several natural task assignment policies and propose a new one TAGS (Task Assignment based on Guessing Size). The TAGS algorithm is counterintuitive in many respects, including load unbalancing, non-work-conserving, and,fairness. We find that under heavy-tailed workloads, TAGS can outperform all task assignment policies known to us by several orders of magnitude with respect to both mean response time and mean slowdown, provided the system load is not too high. We also introduce a new practical performance metric for distributed servers called server expansion. Under the server expansion metric, TAGS significantly outperforms all other task assignment policies, regardless of system load.

关键词： clusters contrary behavior distributed servers fairness heavy-tailed workloads high variance job scheduling load balancing load sharing supercomputing task assignment

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Proxy-assisted periodic broadcast for video streaming with multiple servers

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MULTIMEDIA TOOLS AND APPLICATIONS 2008年第3期36卷 243-266页

作者： Kusmierek, Ewa Du, David H. C. Poznan Supercomp & Networking Ctr Poznan Poland Univ Minnesota Digital Technol Ctr Minneapolis MN USA Univ Minnesota Dept Comp Sci & Engn Minneapolis MN USA

Large scale video streaming over the Internet requires a large amount of resources such as server I/O bandwidth and network bandwidth. A number of video delivery techniques can be used to lower these requirements. Periodic broadcast by a central server combined with proxy caching offers a significant reduction of the aggregate network and server I/O bandwidth usage. However, the resources available to a single server are still limited. In this paper we propose a system with multiple geographically distributed servers. The problem of multiple servers for periodic broadcast is quite different from the problem of object location for multiple web servers. Multiple servers offer increased amount of resources and service availability and may potentially allow a further reduction of network bandwidth usage. On the other hand, the benefit of periodic broadcast mostly comes from high demand videos. With multiple servers holding a video, the demand of the video at each server is reduced. Therefore, it is a challenge to use multiple servers efficiently. We first analyze the dependence of the resource requirements on the number and locations of the servers. Based on the character of the function describing such a dependence, we formulate and solve the problem of video location and delivery, in a way that minimizes resource usage. We explore a trade-off between network and I/O bandwidth requirements. We evaluate our proposed solutions through a number of tests.

关键词： video streaming periodic broadcast proxy-caching distributed servers

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