The Flexible Hypercube: A New Fault-Tolerant Architecture for Parallel Computing

This paper presents the new Flexible Hypercube architecture. The Flexible Hypercube is a fault-tolerant network topology that can be constructed for an arbitrary number of nodes and is incrementally expandable. This topology maintains the strong features of the Hypercube while overcoming deficiencies in expandability. It is shown to have strong node connectivity, a small diameter, and to be tolerant of faults. The Flexible Hypercube is a suitable architecture for the design of both tightly coupled parallel systems and distributed systems. Efficient fault-free and fault-tolerant algorithms for message routing and broadcasting are presented for the architecture. The fault-free algorithm guarantees successful routing inO(logN) time, whereNis the number of nodes in the system, and the fault-tolerant algorithm guarantees routing to functioning nodes if a route exists. The fault-free and fault-tolerant broadcasting algorithms have time complexityO(logN), and the fault-tolerant algorithm guarantees success if no two faulty nodes are adjacent and no functioning node is adjacent to two faults.     

Fault-tolerant wormhole routing for hypercube networks

We present an adaptive fault-tolerant wormhole routing algorithm for hypercubes by using 3 virtual networks. The routing algorithm can tolerate at least n−1 faulty nodes and can route a message via a path of length no more than the shortest path plus four. Previous algorithms which achieve the same fault tolerant ability need 5 virtual networks. Simulation results are also given in this paper.     

二维网格中基于最小通路区的自适应和最小容错路由算法

网格结构是并行与分布式处理中最流行的一种网络拓扑结构。在存在故障的情况下，如何设计具有最优性的容错路由算法一直是研究的热，点问题。本文研究了采用故障块模型的二维网格的最小路由问题，提出存在最小通路的一个充分必要条件。基于最小通路区（RMP）的概念，提出一种自适应的最小容错路由算法。如果源节点和目的节点之间存在最小通路区，则在最小通路区中进行自适应最小容错路由；反之，则采用多阶段最小容错路由。主要思想就是在存在故障的情况下，尽量保证路由算法能走最短路径。因为只要求知道每个节点的局部信息，故算法是分布式的。     

A dynamic fault-tolerant message routing algorithm for double-loop networks

Message routing is a fundamental function of a network, and fault-tolerance is an important tool to ensure the quality of service of a network. Assume that the network contains at most one faulty element and the algorithm does not know the faulty element in advance. We present an optimal fault-tolerant message routing algorithm for double-loop networks. We show that sending at most two messages with different routing strategies can ensure that one of the messages will be sent through a shortest path that avoids the faulty element. At each vertex, for any destination, the algorithm needs only constant time and space to determine the next vertex to which the message is to be sent.     

Routing in wormhole-switched clustered networks with applicationsto fault tolerance

This paper presents a novel technique for routing in wormhole-switched multiprocessor interconnection networks with clustered configuration. The network model used here consists of a set of clusters interfaced through a common central network. We assume that the central network and the clusters use independent algorithms to route messages between their internal nodes. A technique for deriving a global routing algorithm based on the local algorithms is presented, which allows the transfer of messages between any pair of nodes in the network. This proposed method is shown to be deadlock-free with two virtual channels. The clustered network model and the proposed routing technique can be used to enhance the fault tolerance capability of existing routing algorithms. In particular, we describe fault-tolerant routing methods for meshes, which can tolerate any arbitrary fault distribution without disabling connected healthy nodes     

A theory of deadlock-free adaptive multicast routing in wormholenetworks

A theory for the design of deadlock-free adaptive routing algorithms for wormhole networks, proposed by the author (1991, 1993), supplies sufficient conditions for an adaptive routing algorithm to be deadlock-free, even when there are cyclic dependencies between channels. Also, two design methodologies were proposed. Multicast communication refers to the delivery of the same message from one source node to an arbitrary number of destination nodes. A tree-like routing scheme is not suitable for hardware-supported multicast in wormhole networks because it produces many headers for each message, drastically increasing the probability of a message being blocked. A path-based multicast routing model was proposed by Lin and Ni (1991) for multicomputers with 2D-mesh and hypercube topologies. In this model, messages are not replicated at intermediate nodes. This paper develops the theoretical background for the design of deadlock-free adaptive multicast routing algorithms. This theory is valid for wormhole networks using the path-based routing model. It is also valid when messages with a single destination and multiple destinations are mixed together. The new channel dependencies produced by messages with several destinations are studied. Also, two theorems are proposed, developing conditions to verify that an adaptive multicast routing algorithm is deadlock-free, even when there are cyclic dependencies between channels. As an example, the multicast routing algorithms of Lin and Ni are extended, so that they can take advantage of the alternative paths offered by the network     

Leapfrog: Optimal Opportunistic Routing in Probabilistically Contacted Delay Tolerant Networks

Delay tolerant networks (DTNs) experience frequent and long lasting network disconnection due to various reasons such as mobility, power management, and scheduling. One primary concern in DTNs is to route messages to keep the end-to-end delivery delay as low as possible. In this paper, we study the single-copy message routing problem and propose an optimal opportunistic routing strategy – Leapfrog Routing – for probabilistically contacted DTNs where nodes encounter or contact in some fixed probabilities. We deduce the iterative computation formulate of minimum expected opportunistic delivery delay from each node to the destination, and discover that under the optimal opportunistic routing strategy, messages would be delivered from high-delay node to low-delay node in the leapfrog manner. Rigorous theoretical analysis shows that such a routing strategy is exactly the optimal among all possible ones. Moreover, we apply the idea of Reverse Dijkstra algorithm to design an algorithm. When a destination is given, this algorithm can determine for each node the routing selection function under the Leapfrog Routing strategy. The computation overhead of this algorithm is only O(n ²) where n is the number of nodes in the network. In addition, through extensive simulations based on real DTN traces, we demonstrate that our algorithm can significantly outperform the previous ones.     

Fault-tolerant routing over shortest node-disjoint paths in hypercubes

This paper presented a routing algorithm that finds n disjoint shortest paths from the source node s to target node d in the n-dimensional hypercube. Fault-tolerant routing over all shortest node-disjoint paths has been investigated to overcome the failure encountered during routing in hypercube networks. In this paper, we proposed an efficient approach to provide fault-tolerant routing which has been investigated on hypercube networks. The proposed approach is based on all shortest node-disjoint paths concept in order to find a fault-free shortest path among several paths provided. The proposed algorithm is a simple uniform distributed algorithm that can tolerate a large number of process failures, while delivering all n messages over optimal-length disjoint paths. However, no distributed algorithm uses acknowledgement messages (acks) for fault tolerance. So, for dealing the faults, acknowledgement messages (acks) are included in the proposed algorithm for routing messages over node-disjoint paths in a hypercube network.     

Depth-first search approach for fault-tolerant routing in hypercubemulticomputers

Using depth-first search, the authors develop and analyze the performance of a routing scheme for hypercube multicomputers in the presence of an arbitrary number of faulty components. They derive an exact expression for the probability of routing messages by way of optimal paths (of length equal to the Hamming distance between the corresponding pair of nodes) from the source node to an obstructed node. The obstructed node is defined as the first node encountered by the message that finds no optimal path to the destination node. It is noted that the probability of routing messages over an optimal path between any two nodes is a special case of the present results and can be obtained by replacing the obstructed node with the destination node. Numerical examples are given to illustrate the results, and they show that, in the presence of component failures, depth-first search routing can route a message to its destination by means of an optimal path with a very high probability     

An efficient hop count routing protocol for wireless ad hoc networks

An efcient hop count route fnding approach for mobile ad hoc network is presented in this paper.It is an adaptive routing protocol that has a tradeof between transmission power and hop count for wireless ad hoc networks.During the route fnding process,the node can dynamically assign transmission power to nodes along the route.The node who has received route request message compares its power with the threshold power value,and then selects a reasonable route according to discriminating algorithms.This algorithm is an efective solution scheme to wireless ad hoc networks through reasonably selected path to reduce network consumption.Simulation results indicate that the proposed protocol can deliver better performances with respect to energy consumption and end-to-end delay.     

局部扭曲立方体单播容错路由算法

在n维局部扭曲立方体存在节点故障的情况下,基于路由能力的概念提出了一种单播容错路由算法,该算法首先寻找最短路径上满足路由能力值要求的邻接节点,其次寻找非最短路径上满足路由能力值要求的邻接节点。这样求得的容错路径首先是最优路径,其次为次优路径。     

移动社会网络中基于社区的消息机会传输策略

移动社会网络是一种由大量具有社会特征的节点组成的机会网络.已有的基于社区的路由算法大多选用社会性最优的节点参与转发,而没有考虑到社区分布对节点移动的影响,将这些算法直接用于移动社会网络中会导致网络资源消耗高、传输成功率低等问题.针对这些问题,提出一种基于社区的消息机会传输算法,在社区间根据节点到目标社区的传输概率选择社区间的最优传输路径,在社区内选择与目标节点相遇概率较高的节点完成社区内传输.仿真实验结果表明,在移动社会网络中,该算法与 Prophet,Spray and Wait 等经典算法相比,提高了消息传输成功率,降低了网络开销.     

Store-and-Forward Multicast Routing on the Mesh

We study the complexity of routing a set of messages with multiple destinations (multicast routing) on an n-node square mesh under the store-and-forward model. A standard argument proves that time is required to route n messages, where each message is generated by a distinct node and at most c messages are to be delivered to any individual node. The obvious approach of simply replicating each message into the appropriate number of unicast (single-destination) messages and routing these independently does not yield an optimal algorithm. We provide both randomized and deterministic algorithms for multicast routing, which use constant-size buffers at each node. The randomized algorithm attains optimal performance, while the deterministic algorithm is slower by a factor of O( log ² n). We also describe an optimal deterministic algorithm that, however, requires large buffers of size O(c). A preliminary version of this paper appeared in Proceedings of the 13th Annual ACM Symposium on Parallel Algorithms and Architectures, Crete, Greece, 2001. This work was supported, in part, by MIUR under project ALGO-NEXT.     

AODV‐RIP: improved security in mobile ad hoc networks through route investigation procedure

Most routing protocols in mobile ad hoc networks (MANETs) place an emphasis on finding paths in dynamic networks without considering security. As a result, there are a number of attacks that can be used to manipulate the routing in MANET. A malicious node that sends a modified control message to an intermediate node can disturb the network using a control message. To solve this problem, we introduce AODV protocol with route investigation procedure (AODV‐RIP). It uses two additional control messages to defeat security attacks that can occur in AODV routing protocol. When an intermediate node that is on the path between the source node and the destination node receives a control message, it sends a Rroute Investigation Request (IREQ) message to the destination node in order to check the reliability of the control message. According to the existence of Route Investigation Reply (IREP), the intermediate node decides whether it transmits the control message to the source node or not. Consequently, the intermediate node that receives the control message confirms that it is using two additive control messages: IREQ and IREP. Through this investigation procedure, the source node can obtain a reliable path for transmitting data packets to an intentional destination node. The simulation results show an improvement in the packet delivery ratio and end‐to‐end delay at the expense of a moderate increase of the control message overhead compared with the current routing protocols. Copyright © 2009 John Wiley & Sons, Ltd.     

Fault-Tolerant Wormhole Routing with 2 Virtual Channels in Meshes

In wormhole meshes, a reliable routing is supposed to be deadlock-free and fault-tolerant. Many routing algorithms are able to tolerate a large number of faults enclosed by rectangular blocks or special convex, none of them, however, is capable of handling two convex fault regions with distance two by using only two virtual networks. In this paper, a fault-tolerant wormhole routing algorithm is presented to tolerate the disjointed convex faulty regions with distance two or no less, which do not contain any nonfaulty nodes and do not prohibit any routing as long as nodes outside faulty regions are connected in the mesh network. The processors＇ overlapping along the boundaries of different fault regions is allowed. The proposed algorithm, which routes the messages by X-Y routing algorithm in fault-free region, can tolerate convex fault-connected regions with only two virtual channels per physical channel, and is deadlock- and livelock-free. The proposed algorithm can be easily extended to adaptive routing.     

一种基于分簇蚁群策略的无线传感器网络路由算法

如何最大化地延长网络的生存时间是无线传感器（WSN）网络研究的核心问题.基于分簇策略,提出一种能量有效的路由算法（EEA）.该算法利用分簇原理减少了参与寻找最优路径的节点数,从而降低了系统的能耗.同时设计一种改进的最优路径评价标准,该标准兼顾了传输路径上各节点的剩余能量和最优路径上总的能量消耗.仿真结果表明,与其他蚁群策略的路由算法（如：基于蚁群算法的路由算法（ARA）和EEAWSN）相比,该算法能在寻找最优路径时避开剩余能量少的节点,使最优路径上各节点的能量呈整体性衰落,从而沿长了网络的寿命.     

Fully adaptive minimal deadlock-free packet routing in hypercubes,meshes, and other networks: algorithms and simulations

This paper deals with the problem of packet-switched routing in parallel machines. Several new routing algorithms for different interconnection networks are presented. While the new techniques apply to a wide variety of networks, routing algorithms will be shown for the hypercube, the two-dimensional mesh, and the shuffle-exchange. Although the new techniques are designed for packet routing, they can be used alternatively for virtual cut-through routing models. The techniques presented for hypercubes and meshes are fully-adaptive and minimal. A fully-adaptive and minimal routing is one in which all possible minimal paths between a source and a destination are of potential use at the time a message is injected into the network. Minimal paths followed by messages ultimately depend on the local congestion encountered in each node of the network. All of the new techniques are completely free of deadlock situations     

Optimal multicast communication in wormhole-routed torus networks

This paper presents efficient algorithms that implement one-to-many, or multicast, communication in wormhole-routed torus networks. By exploiting the properties of the switching technology and the use of virtual channels, a minimum-time multicast algorithm is presented for n-dimensional torus networks that use deterministic, dimension-ordered routing of unicast messages. The algorithm can deliver a multicast message to m-1 destinations in [log₂ m] message-passing steps, while avoiding contention among the constituent unicast messages. Performance results of a simulation study on torus networks with up to 4096 nodes are also given     

具有逻辑路由跳数O(1)的可扩展的分散式查找算法

对等网络中的一个基本问题就是如何高效地进行数据查找．分散式查找是解决这类问题的一种新思路．现有的分散式查找方法在查找时所需的逻辑路由跳数都与网络中的节点数相关(一般为O(logn)，少数为O(n^1/c)．Sifter是一种可扩展、自组织、高容错和高效率的分散式查找算法．在该算法中，单个节点只需维护O(n1／c)个其他节点的链接信息，就能够在O(1)个逻辑路由跳内找到目的数据．该算法适用于网络动态性不大，但是对查找的实时性要求较高的应用．     

在分裂的机会网络中多个消息摆渡的路由设计

针对机会网络中节点分布不规则造成分割的网络区域相隔较远的情况, 提出了一种基于全局消息摆渡和节点中继的多摆渡路由算法（GMF-NRA）。该算法使用一个全局消息摆渡节点和各个区域内的中继节点为运行于区域内部的局部消息摆渡节点中继消息, 共同完成区域间的信息传输。摆渡节点在中继节点处交互区域间的信息, 以至于不再需要摆渡节点之间实现在线协作转发消息。最后, 仿真结果表明GMF-NRA较现有的节点中继算法在网络的平均传输时延和数据交付率方面能获得更好的网络性能。