Optimal routing policy of a stochastic-flow network

Under the assumption that each arc’s capacity of the network is deterministic, the quickest path problem is to find a path sending a given amount of data from the source to the sink such that the transmission time is minimized. However, in many real-life networks such as computer systems, telecommunication systems, etc., the capacity of each arc is stochastic due to failure, maintenance, etc. Such a network is named a stochastic-flow network. Hence, the minimum transmission time is not fixed. We try to evaluate the probability that d units of data can be sent through the stochastic-flow network within the time constraint according to a routing policy. Such a probability is named the system reliability, which is a performance index to measure the system quality. This paper mainly finds the optimal routing policy with highest system reliability. The solution procedure is presented to calculate the system reliability with respect to a routing policy. An efficient algorithm is subsequently proposed to derive the optimal routing policy.     

An efficient and robust design optimisation of multi-state flow network for multiple commodities using generalised reliability evaluation algorithm and edge reduction method

The network of delivering commodities has been an important design problem in our daily lives and many transportation applications. The reliability of delivering commodities from a source node to a sink node in the network is maximised to find the optimal routing. However, the design problem is not simple due to randomly distributed attributes in each path, multiple commodities with variable path capacities and the allowable time constraints for delivery. This paper presents the design optimisation of the multi-state flow network (MSFN) for multiple commodities. We propose an efficient and robust approach to evaluate the system reliability in the MSFN with respect to randomly distributed path attributes and to find the optimal routing subject to the allowable time constraints. The delivery rates of the path segments are evaluated and the minimal-speed arcs are eliminated to reduce the complexity of the MSFN. Accordingly, the correct optimal routing is found and the worst-case reliability is evaluated. The reliability of the optimal routing is at least higher than worst-case measure. Three benchmark examples are utilised to demonstrate the proposed method. The comparisons between the original and the reduced networks show that the proposed method is very efficient.     

Routing policy of stochastic-flow networks under time threshold and budget constraint

The quickest path problem is to find a path which sends a given amount of data from the source to the sink such that the transmission time is minimized. More specifically, the capacity of each arc in the network is assumed to be deterministic. However, in many real-life networks such as computer systems, telecommunication systems, etc., the capacity of each arc is stochastic due to failure, maintenance, etc. Such a network is named as stochastic-flow network. Hence, the minimum transmission time is not a fixed number. The purpose of this paper is to provide a decision procedure for a stochastic-flow network under the time and budget constraints. We try to evaluate the probability that d units of data can be sent through the network under both time threshold and budget according to the routing policy. Such a probability is named the system reliability, which is a performance index to measure the system quality. An efficient algorithm is proposed to derive the optimal routing policy with highest system reliability. The sensitive analysis can be conducted to improve the most important component which increases the system reliability most significantly.     

An artificial neural network approach for routing in distributed computer networks

This paper presents a new approach based on the Hopfield model of artificial neural networks to solve the routing problem in a context of computer network design. The computer networks considered are packet switching networks, modeled as non-oriented graphs where nodes represent servers, hosts or switches, while bi-directional and symmetric arcs represent full duplex communication links. The proposed method is based on a network representation enabling to match each network configuration with a Hopfield neural network in order to find the best path between any node pair by minimizing an energy function. The results show that the time delay derived from flow assignment carried out by this approach is, in most cases, better than those determined using conventional routing heuristics. Therefore, this neural-network approach is suitable to be integrated into an overall topological design process of moderate-speed and high-speed networks subject to quality of service constraints as well as to changes in configuration and link costs.     

一种基于路径跟踪反馈的SDN网络可信传输方案

针对软件定义网络(SDN)中的转发设备存在不可避免的漏洞和后门、缺乏主动监测或被动检查网络行为的机制等问题,提出一种基于路径跟踪反馈的SDN网络可信传输方案,设计基于跟踪反馈的传输路径可信验证机制,依据反馈信息分析节点的可信性,以此评估路径的可信度;同时,提出一种基于路径跟踪反馈的不相交多路径可信路由算法DMTRA-PTF,能够通过路径跟踪反馈和可信评估引导新的路径及时规避恶意交换机节点,构造不相交多路径路由方案以增强SDN网络传输服务的可信性。对比实验结果表明,路径跟踪反馈机制能够以较小的性能代价准确识别恶意交换机,提出的可信路由算法能够以此为后续路由动态规划不相交多条可信路径,有效提升网络整体的可信性。     

Assessment of spare reliability for multi-state computer networks within tolerable packet unreliability

From a quality of service viewpoint, the transmission packet unreliability and transmission time are both critical performance indicators in a computer system when assessing the Internet quality for supervisors and customers. A computer system is usually modelled as a network topology where each branch denotes a transmission medium and each vertex represents a station of servers. Almost every branch has multiple capacities/states due to failure, partial failure, maintenance, etc. This type of network is known as a multi-state computer network (MSCN). This paper proposes an efficient algorithm that computes the system reliability, i.e., the probability that a specified amount of data can be sent through k (k ≥ 2) disjoint minimal paths within both the tolerable packet unreliability and time threshold. Furthermore, two routing schemes are established in advance to indicate the main and spare minimal paths to increase the system reliability (referred to as spare reliability). Thus, the spare reliability can be readily computed according to the routing scheme.     

Implementation of energy efficient circuit design using A* algorithm in embedded network

In wireless sensor network, the routing path plays a prominent role in network resource utilization. Since, the nodes in network are open to physical abuse an effective routing protocol is necessary to improve data reliability in network and to overcome node data link disconnection. In this paper, we propose to implement A*EEDDP (Energy Efficient Distributed Diffusion protocol) to improve data reliability and increase network lifetime. The A* algorithm determines the shortest routing path between source node and destination node. In addition, the routing path determine with respect to parameters such as energy consumed for communication, residual energy of nodes and the time over which the nodes can support the routing path. The combined A*EEDDP implement in testbed and performance evaluate interms of network lifetime, throughput, packet delivery ratio, energy efficiency and end to end delay. The A*EEDDP performs better compared to other algorithm and achieves higher packet delivery ratio of 97%.     

基于节点多样性的域内路由保护算法

已有的路由保护方案都没有考虑网络中节点的重要程度,然而在实际网络中不同节点在网络中的重要程度是不相同的。针对该问题,提出一种基于节点多样性的域内路由保护算法（intra-domain routing protection algorithm based on node diversity,RPBND）。计算节点构造以目的为根的最短路径树（shortest path tree,SPT）,从而保证RPBND算法和目前互联网部署的路由算法的兼容性;在该最短路径树的基础上构造特定结构的有向无环图（directed acyclic graph,DAG）,从而最大化路由可用性。实验结果表明,RPBND极大地提高了路由可用性,降低了故障造成的网络中断时间,为ISP部署域内路由保护方案提供了充分的依据。     

A method to evaluate the routing policy with two minimal paths within time threshold

Two attributes, the capacity and the lead time, are involved in the quickest path problem which finds a path with the minimum transmission time. The capacity of each edge is assumed to be deterministic in this problem. However, in many real-life networks such as computer, telecommunication, logistics networks, etc., each edge should be multistate due to failure, maintenance, etc. Such a network is named a multistate network. Hence, the minimum transmission time through a multistate network is not fixed. We evaluate the system reliability that a specified amount of data can be sent through a pair of minimal paths simultaneously within the time threshold. A solution procedure is first proposed to calculate it. In order to boost the system reliability, the network administrator decides the routing policy in advance to indicate the first and the second priority pairs of minimal paths. The second one will be responsible for the transmission duty if the first one fails. According to the routing policy, the system reliability can be subsequently computed. The case to transmit data through more than two minimal paths can be extended easily.     

System reliability for a multistate flow network with multiple joint minimal paths under time constraint

The uncertainty of transmission time for a multistate flow network is the main issue when the quickest path problem is applied to such a network. A variant of quickest path problem focusing on the probability of complete transmission instead of finding the quickest path is studied in this paper. In transmission process, a congestion phenomenon may happen when there are joint arcs in minimal paths (MPs). That is, the some arcs are shared by some of MPs. Based on Monte Carlo Simulation, an algorithm is developed to assign the flows through MPs for evaluating the system reliability, the probability that the data can be sent within a time constraint. Experiments are performed to verify the approximate system reliability value obtained from the proposed algorithm is close to the real one. Furthermore, the experiments about CPU time of the algorithm and the characteristics of the variants of quickest path problem are also displayed.     

Two-commodity reliability evaluation of a stochastic-flow network with varying capacity weight in terms of minimal paths

A real-life manufacturing system can be modeled as a stochastic-flow network in which nodes stand for the machine stations, and arcs stand for the shipping media. In terms of minimal paths (MPs), this paper presents a stochastic-flow network model with four characteristics: (1) both nodes and arcs have multiple possible capacities, and may fail; (2) each component (arc/node) has both capacity and cost attributes; (3) two-commodity are proceeded; and (4) the capacity weight varies with arcs, nodes, and types of commodity. We study the possibility of two-commodity to be transmitted through this network simultaneously under the budget constraint. Such a possibility is named as the system reliability. The MPs play the role of media to describe the relationship among flow assignments and capacity vectors. Subsequently, a simple algorithm, in terms of MPs, is proposed to evaluate the system reliability. From the capacity management and decision making viewpoints, managers may adopt the system reliability as a performance index to measure the system capacity and finally to determine if it meets the customers’ orders or not.     

A secure alternate path routing in sensor networks

This paper presents a secure alternate path routing in sensor networks. Our alternate path scheme makes the routing protocol resilient in the presence of malicious nodes that launch selective forwarding attacks. SeRINS (a Secure alternate path Routing IN Sensor networks) detects and isolates the compromised nodes, which try to inject inconsistent routing information, from the network by neighbor report system. In neighbor report system, a node’s route advertisement is verified by its surrounding neighbor nodes so that the suspect node is reported to the base station and is excluded from the network. Simulation experiments show that SeRINS is resilient in the presence of several compromised nodes which launch selective forwarding attacks, and robust by excluding the compromised nodes which inject inconsistent routing information from the network.     

An on-demand routing protocol for improving channel use efficiency in multichannel ad hoc networks

In wireless ad hoc networks, end-to-end delivery over network is a critical concern for routing protocols. The capacity of routing protocols is constrained by the intra-flow interference introduced by adjacent nodes on the same path, and inter-flow interference generated by nodes from neighboring paths. In this paper, we develop an on-demand routing protocol M-AODV-R that solves the channel assignment, reuse and routing problem jointly. The proposed channel reuse scheme and channel assignment scheme can enhance channel reuse rate. This cross-layer design approach can significantly improve the performance of multichannel ad hoc networks over existing routing protocols. Simulation results show that the proposed routing M-AODV-R can effectively increase throughput and reduce delay, as compared to AODV protocol.     

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.     

Design of multi-path data routing algorithm based on network reliability

Data routing through an interconnected network is important and this paper addresses the design of a multi-path data routing algorithm based on network reliability. Generally, multiple routes for a given source–terminal pair exist in a data network and the best possible route based on network metrics like hop-count, delay, traffic, queue, etc. is selected by a routing algorithm. Since network reliability incorporates all these metrics, the routing decision based on reliability seems to be the best possible option and a distributed routing algorithm based on the source–terminal (s–t) path reliability has been proposed in this work. Each node in the proposed routing generates an adjacency matrix of a network graph by periodically exchanging connection information with the adjacent nodes and selects multiple routes based on reliability of the paths. We propose an implementation of a two-path routing algorithm that instead of one includes two next-hop nodes in each node’s routing table. An example is given for further illustration of the proposed algorithm.     

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.     

基于离散粒子群算法的动态网络路由重组

寻找最优路由作为动态网络研究的一个重要方面,对于提高网络资源的利用率及可靠性具有现实的应用价值,但无论在理论上还是实际的网络条件下,最优问题一直都是研究难点。针对不同的网络实际条件,提出一种改进的离散粒子群算法来寻找网络中任意两个节点间的最优路由。在以寻找最小路由总延时作为目标函数的情况下,仿真结果显示该算法能较准确地在网络拓扑结构变化的情况下较快地寻找到最优路径,且显示出了比蚁群算法更好的收敛性能,获得了较好的寻优结果。     

Simple algorithms for updating multi-resource allocations in an unreliable flow network

In this paper, algorithms are developed to update the reliability-maximizing resource allocation in an unreliable flow network when either resource demand or the characteristic of the flow network changes. An unreliable flow network consists of nodes, characterized as source nodes, which supply resources of various types, sink nodes, at which resource demand takes place, and intermediate nodes, as well as unreliable directed arcs, which join pairs of nodes and whose capacities have multiple operational states. The network reliability of such an unreliable flow network is the probability that resources can be transmitted successfully from source nodes to sink nodes. With earlier developments on evaluating network reliability and resolving reliability-maximizing resource allocation problems in an unreliable flow network, one may recompute a new resource allocation strategy, when either resource demand or the characteristic of the flow network changes, without incorporating the efforts that have been made in obtaining the existing resource allocation. This study, in contrast, proposes updating, rather than recomputing, alternatives that take advantage of existing minimal path vectors and corresponding flow patterns. Procedural comparisons and numerical examples indicate that the updating schemes would perform better than the recomputing scheme in a large sized flow network that transmits various resource types.     

基于博弈理论的无线传感器网络融合路由

主要研究了无线传感器网络路由路径的链路质量及节点剩余能量对网络整体可靠性及能效的影响,提出了无线传感器网络数据融合可靠路由的博弈论模型。该模型的求解属于NP问题,论文还提出了一种基于节点效用进行路由选择的分布式实现算法。仿真结果表明该算法能提高网络路由路径的可靠度和能效性。     

一种面向WIA-PA网络的节能型路由算法

为解决WIA—PA网络中节点能耗不均的问题,提出一种改进的节能型路由算法。根据网络节点剩余电量情况,选择网络中总体翻余电量较高的路径,将其作为数据转发路径,并充分利用网络中的有源节点,使其尽可能多地转发数据,由此平衡网络中各个节点的电量消耗。实验结果表明,该算法适用于WIA—PA网络环境,可延长网络总体生存时间。