网络通信中四种寻径方式的性能比较及改进

传输延时是网络性能中非常重要的一个因素,但它并不是网络性能的全部,在讨论网络对信息的传播时,还有其它因素需要考虑。因此,如何在一个更广泛的层面上比较存储转发、虚拟直通、线路开关和Wormhole四种"寻径方式"的优劣便成为需要讨论的问题。也正是由于其它因素的引入,提出了多路Wormhole方法,它是一种并行的、具有很好的综合性能的方案。     

网络通信中四种寻径方式的性能比较及改进

传输延时是网络性能中非常重要的一个因素,但它并不是网络性能的全部,在讨论网络对信息的传播时,还有其它因素需要考虑.因此,如何在一个更广泛的层面上比较存储转发、虚拟直通、线路开关和Wormhole四种"寻径方式"的优劣便成为需要讨论的问题.也正是由于其它因素的引入,提出了多路Wormhole方法,它是一种并行的、具有很好的综合性能的方案.     

并行计算机互联网与包寻径算法

并行处理是计算机科学中最富有挑战性的领域之一,而并行计算机互联网和寻径算法则是这个领域中研究力量很集中的基础技术。本文介绍了几种流行的互联网结构和典型的寻径算法,并对各种网络的特性及寻径算法的性能做了分析和评述。     

超立方体互连网络一种简化自适应寻径算法研究

本文讨论了利用变换函数来求解任意当前节点相邻集合类的方法,提出了一种基于Hamming距离节点进行寻径的搜索算法。通过仿真证明了算法能缩短寻径长度,增强网络的容错性。     

基于蚁群算法的对等网络自适应寻径协议

针对现有的蚁群算法在对等网络寻径中,不能根据访问的对等体状况去自适应克隆转发相应数目的蚂蚁,自适应设置克隆蚂蚁的TTL的问题,给出一种面向对等网络的自适应寻径模型,提出一种基于蚁群算法的对等网络自适应寻径协议AARP,描述蚁群在对等网络中自适应的克隆、寻径过程。分析和仿真实验结果表明,AARP能够以较低的寻径开销、较短的寻径时延,实现较高的寻径效率。     

基于总线网络的确定寻径算法剖析

通过建立一个ｎ×ｎ二维总线网络上的消息传递模型,分析了基于总线网络的确定寻径算法性能,得出了任何基于ｎ×ｎ二维总线网络的确定寻径算法都至少需要１．５ｎ步的结论。并由此推广到多维总线网络,得出结点总数为Ｎ的δ维总线网络上的确定寻径算法需要步。     

基于分层式网络环境的流动Agent寻径策略

流动Ａｇｅｎｔ模式是一种新型的分布式计算模式,该文针对一般的流动Ａｇｅｎｔ寻径方式中存在的问题,提出了一种基于分层式网络环境的流动Ａｇｅｎｔ寻径策略,并对其性能进行了定量分析与比较。     

超立方体网络最佳寻径算法研究

基于Hamming距离概念,提出一种新的超立方体网络的寻径算法,这种算法始终以最佳的寻径方式从当前结点到达邻接点并最终到达目的结点。     

k元n—立方体网络的死锁特征剖析

研究死锁形成几率随网络参数的变化规律 ,对于选择合适的寻径算法、改良网络设计方案都具有重要意义 .环形等多种网络都是 k元 n-立方体网络系列的拓扑同构体 .因此 ,k元 n-立方体网络死锁特征的研究结果具有一定的普遍适用性 .本文根据刻画死锁特征的死锁循环密度属性划分死锁类型 .利用死锁类型分析寻径适应性、物理通道、虚拟通道、缓冲区大小 ,消息长度以及缓冲区结构等参数对死锁形成几率的影响     

A*算法在游戏地图寻径中的应用与实现

寻径算法主要解决如何从图中寻找一条从起点到目标点的路径问题。本文分析了网络游戏中地图文件结构,比较了几种地图寻径算法,并重点介绍了一种典型的启发式搜索算法——A算法原理及其在游戏地图寻径中的具体实现方法。该算法简单、快捷,在实际应用中获得了较好的效果。     

分布存储多机系统中的消息传递技术

本文回顾了分布存储多机系统中消息传递技术几十年来的发展，介绍了现阶段消息传递技术的主要研究成果，例如ｗｏｒｍｈｏｌｅ寻径技术，虚通道流控制技术等。最后，对消息传递技术今后的研究方向作出了一些设想。     

Deadlock-free connection-based adaptive routing with dynamic virtual circuits

Virtual circuits (VCs) can reduce routing overheads with irregular topologies and provide support for a mix of quality of service (QoS) requirements. Information about network loads and traffic patterns may be used during circuit establishment to utilize network resources more efficiently than is practical with packet routing. Most VC schemes are static—each established VC remains unchanged until the connection is no longer needed. In contrast, we propose the dynamic virtual circuit (DVC) mechanism, which enables existing circuits to be quickly torn down in order to free up resources needed for other circuits or to re-establish circuits along routes that are better suited for current network conditions. We propose a deadlock avoidance technique, based on unconstrained routing of DVCs combined with a deadlock-free virtual network. We present a correctness proof for the scheme, describe key aspects of its implementation, and present performance evaluation results that explore its potential benefits.     

Minimal fully adaptive wormhole routing on hypercubes

Wormhole routing is an advanced switching technique used in new generation multicomputers. Since such a machine may suffer serious performance degradation under heavy or uneven traffic load, an adaptive routing method is particularly called upon. In minimal fully adaptive routing, the paths between any source and destination pair to be used are exactly all the shortest paths. We propose in this paper a minimal fully adaptive routing algorithm for n-dimensional hypercube with (n+1)/2 virtual channels per physical channel.     

The impact of virtual channel allocation on the performance of deterministic wormhole-routed k-ary n-cubes

Virtual channels yield significant improvement in the performance of wormhole-routed networks as they can greatly reduce message blocking over network resources. K-ary n-cubes with deterministic routing have been widely analysed using analytical modelling tools. Most existing models, however, have either entirely ignored the effects of virtual channel multiplexing or have not considered the impact of virtual channels allocation on message latency. This paper discusses two different organisations of virtual channels in k-ary n-cubes, resulting in two deterministic routing algorithms. It then proposes an analytical model to compute message latency for the two routing algorithms. The proposed model is used in a case study to demonstrate the sensitivity of network latency to the way virtual channels are allocated to messages.     

A generalized greedy routing algorithm for 2-connected graphs

Geometric routing by using virtual locations is an elegant way for solving network routing problems. In its simplest form, greedy routing, a message is simply forwarded to a neighbor that is closer to the destination. One main drawback of this approach is that the coordinates of the virtual locations require Ω(nlogn) bits to represent, which makes this scheme infeasible in some applications.The essence of the geometric routing is the following: When an origin vertex u wants to send a message to a destination vertex w, it forwards the message to a neighbor t, solely based on the location information of u,w and all neighbors of u. In the greedy routing scheme, the decision is based on decreasing distance. For this idea to work, however, the decision needs not be based on decreasing distance. As long as the decision is made locally, this scheme will work fine.In this paper, we introduce a version of greedy routing which we call generalized greedy routing algorithm. Instead of relying on decreasing distance, a generalized greedy routing algorithm uses other criteria to determine routing paths, solely based on local information. We present simple generalized greedy routing algorithms based on st-coordinates (consisting of two integers between 0 and n−1), which are derived from an st-orientation of a 2-connected plane graph. We also generalize this result to arbitrary trees. Both algorithms are natural and simple to be implemented.     

Adaptive wormhole routing in k-ary n-cubes

Distributed memory multiprocessor (DMMP) systems have gained much attention because their performance can be easily scaled up by increasing the number of processor-memory modules. The k-ary n-cube is the most popular interconnection network topology currently used in DMMPs. Wormhole routing is one of the most promising switching technology and has been used in many new generation multicomputers. Wormhole routing makes the communication latency insensitive to the network diameter and reduces the size of the channel buffer of each router. The concept of virtual channels and virtual networks are widely invented for deadlock-free design. A fully adaptive wormhole routing method for k-ary n-cubes has been proposed by Linder in 1991 [10]. Unfortunately, the need of 2^{n − 1} virtual networks makes it unreasonable. In this paper, we propose a virtual network system to support an adaptive, minimal and deadlock free routing in k-ary n-cubes. It uses only four virtual networks but can get a higher degree of adaptability and higher traffic capacity. Simulation results are presented to verify the performance.     

Ad Hoc移动网络多路径研究

在Ad Hoc移动网络中,由于结点的移动性,网络拓扑结构的易变性,路由成为研究的热点和难点。当前AdHoc路由协议一般都是单路径协议。然而由于多路径路由方式可以大大减少路由开销,提高数据传输率,减少网络拥塞,越来越多的研究表明,它将是未来Ad Hoc网络路由的主要方式。本文介绍了几种典型的多路径路由协议,并对这些多路径协议进行评价,对其性能进行比较,然后介绍多路径协议在QoS、能源和安全方面的应用,最后指出未来多路径研究的关键问题。     

二维mesh上的自适应容错路由算法

基于故障块模型提出了二维ｍｅｓｈ上的自适应无死锁容错路由算法。该算法将网络分为两个虚拟网络ＶＩＮ０和ＶＩＮ１。消息根据源与目的节点的相对位置判断进入哪一个虚拟网络。消息在没有遇上故障时经由最短路径路由。算法的容错技术是基于故障环和故障链的概念。最后,将该算法与另一个二维ｍｅｓｈ上的容错路由算法ｆ－ｃｕｂｃ２进行性能比较。     

Compressionless wormhole routing: an analysis for hypercube with virtual channels

Several recent studies have shown that adaptive routing algorithms based on deadlock recovery have superior performance characteristics than those based on deadlock avoidance. Most of these studies, however, have relied on software simulation due to the lack of analytical modelling tools. In an effort towards filling this gap, this paper presents a new analytical model of compressionless routing in wormhole-routed hypercubes. This routing algorithm exploits the tight coupling between wormhole routers for flow control to detect and recover from potential deadlock situations. The advantages of compressionless routing include deadlock-free adaptive routing with no extra virtual channels, simple router design, and order-preserving message transmission. The proposed analytical model computes message latency by determining the message transmission time, blocking delay at each router, multiplexing delay at each network channel, and waiting time in the source before entering the network. The validity of the model is demonstrated by comparing analytical results with those obtained through simulation experiments.     

一种基于迷宫算法的有效FPGA布线方法

在本篇论文中,我们介绍了在标准对称阵列（隔离岛状）现场可编程逻辑阵列结构下的一种基于迷宫布线算法的新型有效布线方法,Pathfinder.实验结果显示,相比普通的迷宫布线法,Pathfinder算法在布线时间上减少了90%.