Dynamic Affinity Cluster Allocation in a Shared Disks Cluster

A shared disks (SD) cluster couples multiple computing nodes for high performance transaction processing, and all nodes share a common database at the disk level. In the SD cluster, a front-end router selects a node for an incoming transaction to be executed. An affinity-based routing can increase the buffer hit ratio of each node by clustering transactions referencing similar data to be executed on the same node. However, the affinity-based routing is non-adaptive to the changes of the system load. This means that a specific node would be overloaded if corresponding transactions rush into the system. In this paper, we propose a new transaction routing algorithm, named Dynamic Affinity Cluster Allocation (DACA). DACA can make an optimal balance between the affinity-based routing and indiscriminate sharing of load in the SD cluster. As a result, DACA can increase the buffer hit ratio and reduce the frequency of inter-node buffer invalidations while achieving the dynamic load balancing.     

Adaptive Probabilistic Search Over Unstructured Peer-to-Peer Computing Systems

A challenging problem that confronts unstructured peer-to-peer (P2P) computing systems is how to provide efficient support to locate desired files. This paper addresses this problem by using some quantitative information in the form of probabilistic knowledge. Two types of probabilistic knowledge are considered in this paper: overlap between topics shared in the network and coverage of topics at each individual peer. Based on the probabilistic knowledge, this paper proposes an adaptive probabilistic search algorithm that can efficiently support file locating operation in the unstructured P2P network. Then, an update algorithm is devised to keep the freshness of the probabilistic knowledge of individual peers by taking advantage of feedback from the previous user queries. Finally, some extensive experiments are conducted to evaluate the efficiency and effectiveness of the proposed method. This work is partially supported by the National Natural Science Foundation of China under grant No. 60496325 and 60496327 and MoE Doctorate Subject Program under project No. 20030246023, and this work was done when the first author was visiting University of California at Berkeley.     

An Effective Cache Replacement Algorithm in Transcoding-Enabled Proxies

In this paper, we address the problem of cache replacement for transcoding proxy caching. Transcoding proxy is a proxy that has the functionality of transcoding a multimedia object into an appropriate format or resolution for each client. We first propose an effective cache replacement algorithm for transcoding proxy. In general, when a new object is to be cached, cache replacement algorithms evict some of the cached objects with the least profit to accommodate the new object. Our algorithm takes into account of the inter-relationships among different versions of the same multimedia object, and selects the versions to replace according to their aggregate profit which usually differs from simple summation of their individual profits as assumed in the existing algorithms. It also considers cache consistency, which is not considered in the existing algorithms. We then present a complexity analysis to show the efficiency of our algorithm. Finally, we give extensive simulation results to compare the performance of our algorithm with some existing algorithms. The results show that our algorithm outperforms others in terms of various performance metrics.     

Performance comparison of routing algorithms in wormhole-switched networks

This paper presents, building on the analytical models developed in [A. Shahrabi, M. Ould-Khoua, L. Mackenzie, Performance modelling of broadcast communication in multicomputer networks, International Journal of Parallel, Emergent, and Distributed Systems 20 (1) (2005); A. Shahrabi, M. Ould-Khoua, On the communication latency of wormhole routed interconnection networks, International Journal of Simulation 4 (5–6) (2003) 32–43; A. Shahrabi, L. Mackenzie, M. Ould-Khoua, Modelling of Adaptive Wormhole-Routed Hypercubes in the Presence of Broadcast Traffic, in: N.J. Dimopoulos, K.F. Li (Eds.), Chapter 10 in High Performance Computing Systems And Applications, Kluwer Academic Publishers, Boston, 2002; A. Shahrabi, M. Ould-Khoua, L. Mackenzie, An Analytical Model of Wormhole-Routed Hypercubes under Broadcast Traffic, Performance Evaluation 53 (1) (2003) 23–42; A. Shahrabi, M. Ould-Khoua, L. Mackenzie, Latency of double-tree broadcast in wormhole-routed hypercubes, in: Proceedings of International Conference on Parallel Processing (ICPP’01), IEEE Computer Society, 2001, pp. 401–408] a comparative performance study of adaptive and deterministic routing algorithms in wormhole-switched interconnection networks carrying a broadcast traffic component and investigates the performance vicissitudes of them under a variety of network operating conditions. In contrast to previous works, which have reported superiority of adaptive over deterministic routing especially in high-dimensional networks such as hypercubes, our results show that adaptivity does not necessarily improve network performance even for high-dimensional networks and its superiority starts to deteriorate as the broadcast fraction of generated traffic increases.     

局域网视频专用代理服务器模型的研究

提出了一种基于局域网的视频专用高速缓存代理服务器模型 .描述了该模型的各组成部分 ,阐述了在模型中的视频存储策略及其内部各组件之间的通信协议     

一种增强AODV路由协议安全性的方案

AODV（On-Demand Distance Vector)路由协议简单、控制开销少，但其本身没有任何安全机制。文中提出的简单而有效的安全性增强方案可以很好地融合到AODV协议中。这个方案采用公钥体制对敏感的路由信息进行认证和加密，只有产生路由请求信息RREQ的源节点才能验证这些敏感信息。在一次路径搜索过程中，只需要产生RREP的节点和源节点进行公钥运算，这样就不会过多增加计算开销，比较适合ad hoc网络。     

全光网中静态路由选择和波长分配的分层图算法

提出了一种将路由选择和波长分配结合起来的启发式的路由选择和波长分配(RWA)算法,并通过这一种新的分层图算法和限制光跳距的加权系数来优化全光网的静态路由选择和波长分配,使建立光连接时所需要的波长数达到最少。最后对一些光网络进行了计算机仿真,证明了该算法比以前的算法有更好的性能。     

自组织网中移动用户的路由选择

自组织网（AD HOC）组网灵活简单、成本低、生存能力强，适用于多种应用环境。路由选择是自组织网达成上述目标的重要环节。该介绍并初步探讨了自组织网的几种路由基本协议，重点介绍和分析了AD HOC路由协议与传统路由协议的不同之处重点介绍和分析。     

基于GIS的光接入网主干光缆路由优化模型和算法研究

指出主干光缆路由优化属于多目标规划问题的范畴,构建了其数学模型,并根据实际工程应用将其转化为单目标规划问题进行求解,深入分析了主干光缆路由3种基本结构:星形、线形和环形的特征,指出星形结构的路由优化问题实质上是两点之间的最优路由求解问题,而线形和环形拓扑结构的路由优化问题则属于组合最优化问题,据实际工程中的应用情形和需求,提出了Dijkstra优先队列算法,并基于它设计了主干光缆路由的优化算法,并基于GIS平台,实现了本文提出的模型和算法.     

多媒体网络实时监控平台中实时音频处理方法的研究

本文以作者自行开发的多媒体网络实时监控平台为例；介绍了利用WIN32 API低层音频函数进行实时音频录播及网络传输的方法，并详细论述了在平台上实现网络电话，音频广播等功能所采用的多缓冲机制。