A Kind of Multistage Interconnection Networks with Multiple Paths

Mltistage Interconnection Networks(MINs)are orten used to provide interconnections in multiprocessor systems.A unique path MIN usually has lower hardware complexity and a simple control algorithm,but it lacks fault tolerance.This paper proposes a kind of multipat MINs,which are obtained by adding auxiliary links at the final stage in Quad Tree(QT) networks so that they can provide more paths between each source-destination pair,and presents their routing algorithm which is both destination tag based and adaptive.Starting with the routing tag for the minimum path between a given source-destination pair,the routing algorithm uses a set of rules to select switches and modify routing tag.In addition to trying the auxiliary link when link0 an link1 are unavilable,link1 will be tried when link0 ys unavailable.This feature distinguishing the proposed routing algorithm form that for QT networks makes better use of all the possible paths between the given source-destination pair.In the end,this paper introduces a performance index,which is called capacity,to compare different kinds of MINs .Comparison shows that the proposed MINs have better capacity than QT networks.     

Designing a Fault-tolerant Fully-Chained Combining Switches Multi-stage Interconnection Network with Disjoint Paths

Multi-stage Interconnection Networks (MINs) are designed to achieve fault-tolerance and collision solving by providing a set of disjoint paths. Ching-Wen Chen and Chung-Ping Chung had proposed a fault-tolerant network called Combining Switches Multi-stage Interconnection Network (CSMIN) and an inaccurate algorithm that provided two correct disjoint paths only for some source-destination pairs. This paper provides a more comprehensive and accurate algorithm that always generate correct routing-tags for two disjoint paths for every source-destination pair in the CSMIN. The 1-fault tolerant CSMIN causes the two disjoint paths to have regular distances at each stage. Moreover, our algorithm backtracks a packet to the previous stage and takes the other disjoint path in the event of a fault or a collision in the network. Furthermore, to eliminate the backtracking penalties of CSMIN, we propose a new design called Fault-tolerant Fully-Chained Combining Switches Multi-stage Interconnection Network (FCSMIN). It has similar characteristics of 1-fault tolerance and two disjoint paths between any source-destination pair, but it can tolerate only one link or switch fault at each stage without backtracking. Our simulation and comparative analysis result shows that FCSMIN has added advantages of destination-tag routing, lower hardware costs, strong reroutability, lower preprocessing overhead, and higher fault-tolerance power in comparison to CSMIN.     

Reliable multistage interconnection network design

High-performance supercomputers generally comprise millions of CPUs in which interconnection networks play an important role to achieve high performance. New design paradigms of dynamic on-chip interconnection network involve a) topology b) synthesis, modeling and evaluation c) quality of service, fault tolerance and reliability d) routing procedures. To construct a dynamic highly fault tolerant interconnection networks requires more disjoint paths from each source-destination node pair at each stage and dynamic rerouting capability to use the various available paths effectively. Fast routing and rerouting strategy is needed to provide reliable performance on switch/link failures. This paper proposes two new architecture designs of fault tolerant interconnection networks named as reliable interconnection networks (RIN-1 and RIN-2). The proposed layouts are multipath multi-stage interconnection networks providing four disjoint paths for all the source-destination node pairs with dynamic rerouting capability. The designs can withstand switch failures in all the stages (including input and output stages) and provide more reliability. Reliability analysis of various MIN architectures is evaluated. On comparing the results with some existing MINs it is evident that the proposed designs provides higher reliability values and fault tolerance.     

多约束最短链路分离路径精确算法

在通信的源和目的间寻找两条(主用和备用)链路分离的QoS路径是提供可靠QoS路由的重要途径.现有求解多约束链路分离路径对(multi-constrained link-disjoint path pair,简称MCLPP)的算法难以保证求得存在于任意网络中的可行解和最优解.为解决这一问题,分析了MCLPP问题最优解的性质,提出了精确算法的设计原则,在此基础上给出了求解MCLPP问题的精确算法(link-disjoint optimal multi-constrained paths algorithm,简称LIDOMPA算法),可对任意网络求解客观存在的多约束最短链路分离路径对.为了降低算法的复杂性,引入了候选最优解、紧缩的约束向量和结构化的路径支配3种关键方法,在保障算法精确性的同时,有效地降低了LIDOMPA的搜索空间.大量的实验结果表明,LIDOMPA的求解能力优于现有算法,同时可以实现较低的算法执行时间开销.     

多约束最短链路分离路径精确算法

在通信的源和目的间寻找两条(主用和备用)链路分离的QoS路径是提供可靠QoS路由的重要途径.现有求解多约束链路分离路径对(multi-constrained link-disjoint path pair,简称MCLPP)的算法难以保证求得存在于任意网络中的可行解和最优解.为解决这一问题,分析了MCLPP问题最优解的性质,提出了精确算法的设计原则,在此基础上给出了求解MCLPP问题的精确算法(link-disjoint optimal multi-constrained paths algorithm,简称LIDOMPA算法),可对任意网络求解客观存在的多约束最短链路分离路径对.为了降低算法的复杂性,引入了候选最优解、紧缩的约束向量和结构化的路径支配3种关键方法,在保障算法精确性的同时,有效地降低了LIDOMPA的搜索空间.大量的实验结果表明,LIDOMPA的求解能力优于现有算法,同时可以实现较低的算法执行时间开销.     

Performance of multistage bus networks for a distributed sharedmemory multiprocessor

A multistage bus network (MEN) is proposed to overcome some of the shortcomings of the conventional multistage interconnection networks (MINs), single bus, and hierarchical bus interconnection networks. The MBN consists of multiple stages of buses connected in a manner similar to the MINs and has the same bandwidth at each stage. A switch in an MBN is similar to that in a MIN switch except that there is a single bus connection instead of a crossbar. MBNs support bidirectional routing and there exists a number of paths between any source and destination pair. The authors develop self routing techniques for the various paths, present an algorithm to route a request along the path with minimum distance, and analyze the probabilities of a packet taking different routes. Further, they derive a performance analysis of a synchronous packet-switched MBN in a distributed shared memory environment and compare the results with those of an equivalent bidirectional MIN (BMIN). Finally, they present the execution time of various applications on the MBN and the BMIN through an execution-driven simulation. They show that the MBN provides similar performance to a BMIN while offering simplicity in hardware and more fault-tolerance than a conventional MIN     

Joint routing, scheduling, and power control for multichannel wireless sensor networks with physical interference

Reliability and real-time requirements bring new challenges to the energy-constrained wireless sensor networks, especially to the industrial wireless sensor networks. Meanwhile, the capacity of wireless sensor networks can be substantially increased by operating on multiple nonoverlapping channels. In this context, new routing, scheduling, and power control algorithms are required to achieve reliable and real-time communications and to fully utilize the increased bandwidth in multichannel wireless sensor networks. In this paper, we develop a distributed and online algorithm that jointly solves multipath routing, link scheduling, and power control problem, which can adapt automatically to the changes in the network topology and offered load. We particularly focus on finding the resource allocation that realizes trade-off among energy consumption, end-to-end delay, and network throughput for multichannel networks with physical interference model. Our algorithm jointly considers 1) delay and energy-aware power control for optimal transmission radius and rate with physical interference model, 2) throughput efficient multipath routing based on the given optimal transmission rate between the given source-destination pairs, and 3) reliable-aware and throughput efficient multichannel maximal link scheduling for time slots and channels based on the designated paths, and the new physical interference model that is updated by the optimal transmission radius. By proving and simulation, we show that our algorithm is provably efficient compared with the optimal centralized and offline algorithm and other comparable algorithms.     

Design of 4-disjoint gamma interconnection network layouts and reliability analysis of gamma interconnection Networks

Multistage interconnection networks (MINs) are widely used for reliable data communication in a tightly coupled large-scale multiprocessor system. High reliability of MINs can be achieved using fault tolerance techniques. The fault tolerance is generally achieved by disjoint paths available through multiple connectivity options. The gamma interconnection network (GIN) is a class of fault tolerant MINs providing alternate paths for source–destination node pairs. Various 2-disjoint and 3-disjoint GIN architectures have been presented in the literature. In this paper, two new designs of 4-disjoint paths multistage interconnection networks, called 4-disjoint gamma interconnection networks (4DGIN-1 and 4DGIN-2) are proposed. The proposed 4DGINs provide four disjoint paths for each source–destination pair and can tolerate three switches/link failures in intermediate interconnection layers. Proposed designs are highly reliable GIN with higher fault-tolerant capability than other gamma networks at low cost. Terminal pair reliabilities of proposed designs and various other 2-disjoint and 3-disjoint GINs are evaluated, analyzed and compared. Reliability values of proposed designs are found higher.     

A new algorithm for virtual path network design in ATM networks

Virtual paths (VPs) in an ATM network form a logical network, called VP network (VPN), over the underlying physical network. VPN allows flexible management of network resources and hence its design is an important issue in designing an ATM network. In this paper, we consider the VPN design problem which is formulated as an optimization problem with the objective of minimizing the switching and transmission cost, and control and management cost. We present here, a two-phase heuristic solution for designing a good VPN for a given traffic demand. The first phase is a routing phase in which a route is found between every node pair in the network. In the second phase, paths are selected as VPs using the set of routes generated in the routing phase. A path is selected as a VP so as to minimize the following parameters: (i) the total number of VPs configured; (ii) the number of VPs carried by a link (load); and (iii) the VP hopcount, the number of VPs that are concatenated to form a virtual channel (VC). We study the performance of the proposed algorithm through extensive simulation on various networks. The results show that the VPN generated by the proposed algorithm is good in minimizing the number of VPs configured, the load on a link, and the VP hopcount. The comparison of the results obtained by the proposed algorithm and that of Ahn et al. [Virtual path layout design in ATM networks, in: Proceedings of IEEE INFCOM’94, Toronto, Ontario, Canada, 1994, pp. 192–200] shows that our algorithm performs better.     

基于NPV广义超立方体最佳容错路由算法

在网络可靠性研究中,设计较好的容错路由策略、尽可能多地记录系统中最优通路信息,一直是一项重要的研究工作.超立方体系统的容错路由算法分为可回溯算法和无回溯算法.一般说来,可回溯算法的优点是容错能力强:只要消息的源节点和目的节点有通路,该算法就能够找到把消息传递到目的地的路径;其缺点是在很多情况下传递路径不能按实际存在的最短路径传递.其代表是深度优先搜索(DFS)算法.无回溯算法是近几年人们比较关注的算法.该算法通过记录各邻接节点的故障信息,给路由算法以启发信息,使消息尽可能按实际存在的最短路径传递.这些算法的共同缺点是只能计算出Hamming距离不超过n的路由.在n维超立方体系统连通图中,如果系统存在大量的故障,不少节点对之间的最短路径大于n,因此,这些算法的容错能力差.提出了一个实例说明采用上述算法将遗失60%的路由信息.另外,由于超立方体的结构严格,实际中的真正超立方体系统不多.事实上,不少的网络系统可转换为具有大量错误节点和错误边的超立方体系统.因此,研究能适应具有大量错误节点和错误边的超立方体系统的容错路由算法是一个很有实际价值的工作.研究探讨了:(1) 定义广义超立方体系统;(2) 在超立方体系统中提出了节点通路向量(NPV)概念及其计算规则;(3) 提出了中转点技术,使得求NPV的计算复杂度降低到O(n);(4) 提出了基于NPV的广义超立方体系统最佳容错路由算法(OFTRS),该算法是一种分布式的和基于相邻节点信息的算法.由于NPV记录了超立方体系统全部最优通路和次最优通路的信息,在具有大量故障的情况下,它不会遗漏任何一条最优通路和次最优通路信息,从而实现了高效的容错路由.在这一点上,它优于其他算法.     

The composite banyan network

A new multipath multistage interconnection network called the composite banyan network is proposed. The network incorporates both the banyan and the reverse banyan networks and is constructed by superimposing the two. The basic building blocks in the composite banyan network are 3×3 switching elements with log₂N stages. A major advantage of the composite banyan network over existing networks with 3×3 SEs is an efficient and fast control algorithm that sets up a path between any source and destination pair. Instead of complex numerical calculations, the network can easily generate a primary routing tag and alternate tags through simple binary operations. Also, the network has a lot of favorable features, including regularity, symmetry, and easy rerouting capability under faults and conflicts. It is shown that at least two totally disjoint paths exist between any source and destination pair, which increase the degree of fault-tolerance. A deterministic permutation routing algorithm is also developed for the 8×8 composite banyan network, Using a simple tabular method, it is shown that the algorithm always finds a set of conflict-free tags     

Routing permutations on baseline networks with node-disjoint paths

Permutation is a frequently-used communication pattern in parallel and distributed computing systems and telecommunication networks. Node-disjoint routing has important applications in guided wave optical interconnects where the optical "crosstalk" between messages passing the same switch should be avoided. In this paper, we consider routing arbitrary permutations on an optical baseline network (or reverse baseline network) with node-disjoint paths. We first prove the equivalence between the set of admissible permutations (or semipermutations) of a baseline network and that of its reverse network based on a step-by-step permutation routing. We then show that an arbitrary permutation can be realized in a baseline network (or a reverse baseline network) with node-disjoint paths in four passes, which beats the existing results [M. Vaez et al., (2000)], [G. Maier et al., (2001)] that a permutation can be realized in an n /spl times/ n banyan network with node-disjoint paths in O(n/sup 1/2/) passes. This represents the currently best-known result for the number of passes required for routing an arbitrary permutation with node-disjoint paths in unique-path multistage networks. Unlike other unique path MINs (such as omega networks or banyan networks), only baseline networks have been found to possess such four-pass routing property. We present routing algorithms in both self-routing style and central-controlled style. Different from the recent work in [Y. Yang et al., (2003)], which also gave a four-pass node-disjoint routing algorithm for permutations, the new algorithm is efficient in transmission time for messages of any length, while the algorithm in [Y. Yang et al., (2003)] can work efficiently only for long messages. Comparisons with previous results demonstrate that routing in a baseline network proposed in this paper could be a better choice for routing permutations due to its lowest hardware cost and near-optimal transmission time.     

Probabilistic quality-aware routing in cognitive radio networks under dynamically varying spectrum opportunities

In this paper, we introduce a probabilistic routing metric that considers the peculiar characteristics of the operating environment of cognitive radio networks (CRNs). This metric captures the dynamic changes in channel availabilities due to the randomness of primary user’s activity and the rich channel diversity due to the fact that a CRN is expected to operate over highly separated frequency channels with different propagation characteristics. Our metric, Probability of Success (PoS), statistically quantifies the chances of a successful cognitive radio (CR) packet transmission over a given channel. Based on the PoS metric, we propose a joint probabilistic routing and channel assignment protocol for multi-hop CRNs that attempts at selecting the path with the maximum probability of success among all possible paths for a given CR source-destination pair. Selecting such a path results in minimizing the number of disruptions to CR packet transmissions, which consequently improves network throughput. Simulation results verify the significant throughput improvement achieved by our protocol compared to reference CRN routing protocols.     

关于实际构造最大带宽路径算法的研究

建立最大带宽路径一直是网络路由研究，尤其是在最近的网络QoS路由研究中的基本问题，在以往的文献中，有人提出了利用修改的Dijkstra算法或修改的Bellman-Ford算法来构建最大带宽路径。该文给出了一个简单的证明，指出了最大生成树与最大带宽路径之间的特殊关系，证明了可以使用修改的Kruskal算法来构建最大带宽路径，文中给出了修改的Kruskal算法，并且与已有的Kijkstra算法作了性能上的比较，尽管从理论上说，Dijstra算法和Kruskal算法的时间复杂度具有同样的阶，但在多种不同网络结构上的模拟测试结果表明，用Kruskal算法构建最大带宽路径的实际运行比Dijkstra算法至少要快3倍，而且在实际上比Dijkstra算法更简单，灵活。     

一种基于扩散机制的LEO卫星网络多径路由协议

提出一种适用于LEO卫星网络的动态多径路由协议——DMRP（Diffusion—based Multi—path Routing Protocol）。协议按需运行,且具有在源、目的之间建立多条路由的能力。按需协议仅当节点发送数据时才启动路由过程,寻找到达目的节点的路由,不要求节点实时维护网络拓扑信息,从而降低了协议运行时间与拓扑存储开销;多径路由则提高了网络的可靠性及协议的健壮性。仿真结果表明,DMRP在协议收敛时间、丢包率等方面都有良好的性能。     

满足指定节点约束的路由算法

在MPLS或GMPLS网络中,路由算法常常需考虑节点约束条件(即用户可能指定一条端到端路径所必须经过的一些中途节点)。对链路代价值为整数的有向无回路网络,文章提出了一种伪多项式时间算法,用于计算满足指定节点约束的最小代价路径。对一般有向网络,文中给出了一种计算时间及空间上限可调的启发式算法。仿真实验结果表明,所给的启发式算法在网络规模变大时明显优于已知的算法。     

Backup path set selection in ad hoc wireless network using link expiration time

Topological changes in mobile ad hoc networks frequently render routing paths unusable. Such recurrent path failures have detrimental effects on quality of service. A suitable technique for eliminating this problem is to use multiple backup paths between the source and the destination in the network. Most of the proposed on-demand routing protocols however, build and rely on single route for each data session. Whenever there is a link disconnection on the active route, the routing protocol must perform a path recovery process. This paper proposes an effective and efficient protocol for backup and disjoint path set in an ad hoc wireless network. This protocol converges into a highly reliable path set very fast with no message exchange overhead. The paths selection according to this algorithm is beneficial for mobile ad hoc networks, since it produces a set of backup paths with much higher reliability. Simulations are conducted to evaluate the performance of our algorithm in terms of route numbers in the path set and its reliability. In order to acquire link reliability estimates, we use link expiration time (LET) between each two nodes.In another experiment, we save the LET of entire links in the ad hoc network during a specific time period, then use them as a data base for predicting the probability of proper operation of links.Links reliability obtains from LET. Prediction is done by using a multi-layer perceptron (MLP) network which is trained with error back-propagation error algorithm. Experimental results show that the MLP net can be a good choice to predict the reliability of the links between the mobile nodes with more accuracy.     

网络编码下不可靠自组织网络高效路由算法

无线自组织网络(wireless ad hoc network)中链路的不可靠性与高丢包率是影响网络性能和应用的主要缺陷.为了优化多跳的不可靠无线网络中完成数据传输所需的数据分组发送次数,提出了融合路径切换思想的基于网络编码的路由协议(network coding routing with path switching,简称NCPS).为了发现潜在的适合网络编码的路径,首先分析并提出了网络中路径可编码与可解码条件;其次对比于传统的最优路径,分析得出了在网络编码下路径切换所能获取的编码收益;最后以优化网络中数据分组发送次数为目标,设计了网络编码下结合路径切换的路由协议.实验结果表明,在不同的网络环境参数下,NCPS能够有效减少网络中的数据发送次数,获取稳定的编码收益.     

弹性光网络中基于频谱连续度的算法研究

针对光网络中可用的波长资源有限、频谱利用率不高的问题,提出了一种基于KSP算法的频谱连续度感知算法（KSPDP）。该方法在路由选择方面,用KSP算法求得源节点和目的节点之间的不同的路径长度,并根据业务请求所需的频谱资源数量,分配不同的路径。在频谱分配方面,算法将感知各链路的频谱连续情况,最大限度减少业务分配的路径上各链路的频谱碎片。仿真结果表明,所提出的算法与传统的最短路径RMSA算法相比,能降低频谱阻塞率,提高频谱资源利用率。     

无线多媒体传感器网络视频流多路径路由算法

无线多媒体传感器网络中的视频流传输,需要提供多样QoS保障.提出一种基于改进蚁群算法多路径路由算法ACMRA(ant colony based multipath routing algorithm),以寻找具有多种优先级路径的路径集,并对重要性不同的视频数据进行相应路径的选择.通过优化网络链路上人工信息素的初始分布,改进后的蚁群算法具有更快的可行路径发现速度及收敛速度.多路径机制的引入提高了网络数据吞吐量与视频传输性能,同时可均衡网络资源,延长网络生命.实验结果表明,算法ACMRA在网络性能、视频传榆性能与网络生命周期方面,较之其他路由算法具有明显优势.