A distributed algorithm of delay-bounded multicast routing formultimedia applications in wide area networks

Multicast routing is to find a tree which is rooted from a source node and contains all multicast destinations. There are two requirements of multicast routing in many multimedia applications: optimal network cost and bounded delay. The network cost of a tree is defined as the sum of the cost of all links in the tree. The bounded delay of a routing tree refers to the feature that the accumulated delay from the source to any destination along the tree shall not exceed a prespecified bound. This paper presents a distributed heuristic algorithm which generates routing trees having a suboptimal network cost under the delay bound constraint. The proposed algorithm is fully distributed, efficient in terms of the number of messages and convergence time, and flexible in dynamic membership changes. A large amount of simulations have been done to show the network cost of the routing trees generated by our algorithm is similar to, or even better than, other existing algorithms     

Energy efficient routing with delay guarantee for sensor networks

The paper presents a routing algorithm that maximizes the lifetime of a sensor network in which all data packets are destined for a single collection node. Lifetime is maximized by adjusting the number of packets traversing each node. The adjustment is carried out by transmitting over alternative routes. The first part of the paper assumes that the worst case delay resulting from energy efficient routing is less than the maximum tolerable value. Ignoring the delay constraint of the network, the routes are selected as the solution to a linear programming (LP) problem in which the objective is to maximize the minimum lifetime of each node. The solution is implemented in a centralized algorithm, and then approximated by an iterative algorithm based on least cost path routing, in which each step is implemented efficiently in a distributed manner. The second part of the paper incorporates delay guarantee into energy efficient routing by constraining the length of the routing paths from each sensor node to the collection node. Simulations reveal that the lifetime of the network increases significantly by optimal routing, and including delay constraint in energy efficient routing improves the network performance since the delay of the network keeps increasing as the delay constraint is relaxed beyond the value at which the optimal lifetime is achieved. Research supported by National Science Foundation under Grant CMS-0408627 and California Department of Transportation. Sinem Coleri Ergen received the BS degree in electrical and electronics engineering from Bilkent University, Ankara, Turkey, in 2000, and the M.S. and Ph.D. degrees in electrical engineering and computer sciences from University of California Berkeley (UCB), in 2002 and 2005. Since January 2006, she has been a postdoctoral researcher in electrical engineering at UCB. Her research interests are in wireless communications and networking with a current focus on energy efficient system design for sensor networks. She is a member of the Sensor Networks for Traffic Monitoring project at UCB. She received Regents Fellowship from University of California Berkeley in 2000. Pravin Varaiya is Nortel Networks Distinguished Professor in the Department of Electrical Engineering and Computer Sciences at the University of California, Berkeley. From 1975 to 1992 he was also Professor of Economics at Berkeley. From 1994 to 1997 he was Director of the California PATH program, a multi-university research program dedicated to the solution of Californias transportation problems. His current research is concerned with communication networks, transportation, and hybrid systems. He has taught at MIT and the Federal University of Rio de Janeiro. Varaiya has held a Guggenheim Fellowship and a Miller Research Professorship. He received an Honorary Doctorate from LInstitut National Polytechnique de Toulouse, and the Field Medal of the IEEE Control Systems Society. He is a Fellow of IEEE and a member of the National Academy of Engineering. He is on the editorial board of several journals, including “Discrete Event Dynamical Systems” and “Transportation Research—C”. He has co-authored three books and more than 250 technical papers. The second edition of “High-Performance Communication Networks” (with Jean Walrand) was published by Morgan-Kaufmann in 2000. “Structure and interpretation of signals and systems" (with Edward Lee) was published by Addison-Wesley in 2003. Varaiya is a member of the Board of Directors of Sensys Networks.     

A Failsafe Distributed Routing Protocol

An algorithm for constructing and adaptively maintaining routing tables in communication networks is presented. The algorithm can be employed in message as well as circuit switching networks, uses distributed computation, provides routing tables that are loop-free for each destination at all times, adapts to changes in network flows, and is completely failsafe. The latter means that after arbitrary failures and additions, the network recovers in finite time in the sense of providing routing paths between all physically connected nodes. For each destination, the routes are independently updated by an update cycle triggered by the destination.     

An Ant-Based Approach for Dynamic RWA in Optical WDM Networks

In this paper, we propose a new ant-based algorithm for the dynamic routing and wavelength assignment (RWA) problem in optical WDM networks under the wavelength continuity constraint. Unlike conventional approaches, which usually require centralized global network information, our new RWA algorithm constructs the routing solution in a distributed manner by means of cooperative ants. To facilitate the ants’ foraging task, we adopt in our algorithm a probabilistic routing table structure for route selection. The new algorithm is highly adaptive in that it always keeps a suitable number of ants in the network to cooperatively explore the network states and continuously update the routing tables, so that the route for a connection request can be determined promptly by the current states of routing tables with only a small setup delay. Some new schemes for path scoring and path searching are also proposed to enhance the performance of our ant-based algorithm. Extensive simulation results upon three typical network topologies indicate that the proposed algorithm has a very good adaptability to traffic variations and it outperforms both the fixed routing algorithm and the promising fixed–alternate routing algorithm in terms of blocking probability. The ability to guarantee both a low blocking probability and a small setup delay makes the new ant-based routing algorithm very attractive for both the optical circuit switching networks and future optical burst switching networks     

基于蚁群算法的无线传感器网络数据聚合路由算法

传感器网络为减少冗余数据的传输耗能。降低延迟,需要在路由过程中采用数据聚合技术。文中采用定向传输方式,在消息路由机制基础上提出了一种基于蚁群算法的数据聚合路由算法。该算法主要思想在于将节点能耗、传输距离与聚合收益3方面作为启发因子,通过一组称为“蚂蚁”的人工代理寻找到达汇聚节点的最优路径。该算法利用蚁群算法的正反馈效应来达到数据汇集的目的,不需要网络节点维护全局信息,因此是一种实现数据聚合在能量与时延上折中的分布式路由算法。理论分析和仿真结果说明了新算法的有效性。     

一种集中调控的分布式服务路径选择算法

在可重构网络多态路由模型中,通常存在多条满足业务需求的服务路径。针对最优服务路径选择问题,该文设计了一种集中调控的分布式服务路径选择算法,各节点根据服务请求中的第1个元能力和目的节点生成路由表,控制器实时监控网络,调控代价过高路径并平衡网络的带宽和负载。性能分析和仿真结果表明,分布式路由表能够生成有效的服务路径,表项规模、收敛时间与元能力个数成正比,在30%的集中调控比例下,路径代价和负载均衡度性能良好,与其他算法相比,对服务请求的响应时延降低约50%。     

Two-stage cut saturation algorithm for designing all-opticalnetworks

We design and optimize the physical topology of all-optical networks. This problem is more challenging than the traditional one for electronic communication networks, because of the wavelength-continuous constraint and it involves routing and wavelength assignment. In this problem, we are given the number of lightpaths required by every node pair and a cost specification, and our objective is to determine a physical topology of minimal cost. We formulate the problem, prove that it is NP-hard, and design an efficient algorithm called two-stage cut saturation algorithm for it. In the first stage, we relax the wavelength-continuous constraint and apply the main idea of the cut saturation method to determine a good initial network. In the second stage, we impose the wavelength-continuous constraint and perform routing and wavelength assignment to establish the specified lightpaths on the initial network. When some lightpaths cannot be established, we apply the main idea of the cut saturation method to optimize the insertion of additional links into the network. Simulation results show the following: (1) the proposed algorithm can efficiently design networks with low costs and high utilization and (2) if wavelength converters are available to support full wavelength conversion, the total cost of the links can be significantly reduced     

Extended bridge algorithms for large networks

A network bridge is a device that operates at the ISO data link level and routes packets across extended networks, commonly composed of multiple local area networks (LANs) and bridges. A set of algorithms that greatly extends the application of the network bridge is presented. This multitree bridge algorithm allows networks of arbitrary topology and capacity to use bridge routing. The reduced broadcast bridge algorithm alleviates the problem of extraneous broadcasting in large networks built from bridges and packet switches. A method for routing to network users who change their location rapidly, as in mobile cellular radio systems, is presented. An algorithm for efficient multicasting in bridges is given. Application of this technology to the broadband integrated services digital network (BISDN) is proposed     

Achieving timely message delivery quality-of-service in fixed and variable connectivity distributed routing networks

Variable connectivity distributed routing networks (VCDRNs) are networks designed with the goal of reliably delivering message traffic even when network connectivity (both routing node to routing node and subscriber to routing node) is continuously and unpredictably changing. A general-purpose point-to-point VCDRN which provides optimum (fewest hop) connectivity in a fixed network and adapts as network topology changes so as to automatically reroute traffic is presented. The routing algorithm includes the multimedia, multidata rate, multierror rate case. It is shown how to design the network to offer a quality-of-service (QoS) in terms of a numerical probability of successful message delivery in a specified time or to adjust the network to provide a users desired QoS on single and multihop paths. This is an important feature to users who want rapid message delivery, even as network topology changes. The case of multiple message priorities is also included. Routing knowledge is distributed by adding path and error rate information to packets as they traverse the network, without adversely impacting QoS. This methodology applies to all routing protocols that employ selective reject retransmission error control. The methodology also presents a means for comparing the performance of candidate protocols in terms of parameters meaningful to the user. While the methods presented herein are applicable to any network they are of particular value to the wireless network with limited bandwidth, high error rates, and variable connectivity, where the user wants message traffic to be delivered as fast as possible in that environment with some prior assurance as to the speed and certainty of delivery.     

An efficient topology reconfiguration algorithm for high speed connection-oriented LANs

This paper deals with the design and performance issues of a protocol, proposed for dynamic topology reconfiguration in high-speed connection-oriented local area networks (LANs). A distributed reconfiguration algorithm is introduced where each network node maintains the minimum-hop-tree connectivity information, corresponding to all the physically reachable network interfaces within the local subnetwork. An incremental and adaptive tree-maintenance strategy is designed for keeping a reconfiguration process isolated from the unaffected parts of the network. A call-by-call routing algorithm, working on top of this reconfiguration protocol, is also proposed with multiple heuristics for optimizing the end-to-end connection hop-count and network load distribution. Simulation results illustrating the correctness and performance of these protocols are included in this paper. Issues regarding a prototype implementation of the presented protocols are also discussed. © 1997 John Wiley & Sons, Ltd.     

A utility-based distributed maximum lifetime routing algorithm for wireless networks

Energy-efficient routing is a critical problem in multihop wireless networks due to the severe power constraint of wireless nodes. Despite its importance and many research efforts toward it, a distributed routing algorithm that maximizes network lifetime is still missing. To address this problem, this paper proposes a novel utility-based nonlinear optimization formulation to the maximum lifetime routing problem. Based on this formulation, a fully distributed localized routing algorithm is further presented, which is proved to converge at the optimal point, where the network lifetime is maximized. Solid theoretical analysis and simulation results are presented to validate the proposed solution.     

Cross Layer Optimized Video Streaming based on IEEE 802.11 Multi-rate over Multi-hop Mobile Ad Hoc Networks

In this paper, we present an effective cross layer optimized video streaming algorithm over multi-hop mobile ad hoc networks. The proposed algorithm selects the most efficient PHY (physical) mode and retransmission limit of WLAN (wireless local area network) multi-rate service at each node in a distributed way. The control parameters of the proposed algorithm (i.e. PHY mode and retransmission limit) are determined based on the available information at application, MAC, and physical layers in order to satisfy the end-to-end delay constraint and maintain packet loss rate in the tolerable range at the receiver. Finally, experimental results are provided to show the performance of the proposed algorithm.     

Providing Fault-Tolerant Ad hoc Routing Service in Adversarial Environments

Most existing designs of ad hoc networks are based on the assumption of non-adversarial environments, where each node in the network is cooperative and well-behaved. When misbehaving nodes exist in the network, the performance of current routing protocols degrades significantly. Since ad hoc networks, consisting of autonomous nodes, are open and distributed in nature, maintaining a fault-free network environment is extremely difficult and expensive. In this paper, we propose a new routing service named best-effort fault-tolerant routing (BFTR). The design goal of BFTR is to provide packet routing service with high delivery ratio and low overhead in presence of misbehaving nodes. Instead of judging whether a path is good or bad, i.e., whether it contains any misbehaving node, BFTR evaluates the routing feasibility of a path by its end-to-end performance (e.g. packet delivery ratio and delay). By continuously observing the routing performance, BFTR dynamically routes packets via the most feasible path. BFTR provides an efficient and uniform solution for a broad range of node misbehaviors with very few security assumptions. The BFTR algorithm is evaluated through both analysis and extensive simulations. The results show that BFTR greatly improves the ad hoc routing performance in the presence of misbehaving nodes.     

Distributed, scalable routing based on vectors of link states

We have present a new method for distributed routing in computer networks and internets using link-state information. Link vector algorithms (LVA) are introduced for the distributed maintenance of routing information in large networks and internets. According to an LVA, each router maintains a subset of the topology that corresponds to adjacent links and those links used by its neighbor routers in their preferred paths to known destinations. Based on that subset of topology information, the router derives its own preferred paths and communicates the corresponding link-state information to its neighbors. An update message contains a vector of updates; each such update specifies a link and its parameters. The LVA can be used for different types of routing. The correctness of the LVA is verified for arbitrary types of routing when correct and deterministic algorithms are used to select preferred paths at each router and each router is able to differentiate old updates from new. The LVA are shown to have better performance than the ideal link-state algorithm based on flooding and the distributed Bellman-Ford algorithm     

An extended least-hop distributed routing algorithm

A routing strategy called NELHNET has been developed for networks with multiprecedence traffic and operating under dynamic traffic and topological conditions. An adaptive distributed algorithm that uses least-hop and least-hop-plus-1 routes in a table of routing vectors, as opposed to the usual table of routing scalars, is described. Current delays are passed backward and forward with the packets to allow development of expected delays to each node via all acceptable routes. The route then selected is the acceptable route with the least expected delay. For speedier recovery, a node returning to service receives the current network status from an adjoining node as soon as the link connecting them is operational. The resultant algorithms show far greater than the marginal improvements originally expected over Arpanet simulations. NELHENET strategies also permit the network to function stably under more heavily loaded conditions than do the Arpanet strategies     

Optical quorum cycles for efficient communication

Many optical networks face heterogeneous communication requests requiring topologies to be efficient and fault tolerant. For efficiency and distributed control, it is common in distributed systems and algorithms to group nodes into intersecting sets referred to as quorum sets. We show efficiency and distributed control can also be accomplished in optical network routing by applying the same established quorum set theory. Cycle-based optical network routing, whether using SONET rings or p-cycles, provides the sufficient reliability in the network. Light-trails forming a cycle allow broadcasts within a cycle to be used for efficient multicasts. Cyclic quorum sets also have all pairs of nodes occurring in one or more quorums, so efficient, arbitrary unicast communication can occur between any two nodes. Efficient broadcasts to all network nodes are possible by a node broadcasting to all quorum cycles to which it belongs (\(O(\sqrt{N})\)). In this paper, we propose applying the distributed efficiency of the quorum sets to routing optical cycles based on light-trails. With this new method of topology construction, unicast and multicast communication requests do not need to be known or even modeled a priori. Additionally, in the presence of network link faults, greater than 99 % average coverage enables the continued operation of nearly all arbitrary unicast and multicast requests in the network. Finally, to further improve the fault coverage, an augmentation to the ECBRA cycle finding algorithm is proposed.     

基于蚂蚁算法的时延受限分布式多播路由研究

本文探讨了在高速包交换计算机网络中,具有端到端时延限制的多播路由问题。提出了一种新颖的基于蚂蚁算法的多播路由优化算法,该算法是完全分布式的。仿真实验表明,用该算法产生的多播路由树的费用比已存在的主要算法更好,并且适应于多播成员数的变化。     

基于ERPMT改进启发式方法的WSN寿命最大化算法

针对传感器节点的电池容量限制导致无线传感网络寿命低的问题,基于容量最大化(CMAX)、线上最大化寿命(OML)两种启发式方法以及高效路由能量管理技术(ERPMT),提出了基于ERPMT改进启发式方法的无线传感网络寿命最大化算法。首先,通过启发式方法初始化每个传感器节点,将节点能量划分为传感器节点起源数据和其它节点数据延迟;然后利用加入的一种优先度量延迟一跳节点的能量消耗;最后,根据路径平均能量为每个路由分配一个优先级,并通过ERPMT实现最终的无线传感网络优化。针对不同分布类型网络寿命的实验验证了本文算法的有效性及可靠性,实验结果表明,相比较为先进的启发式方法CMAX及OML,本文算法明显增大了无线传感网络的覆盖范围,并且大大地延长了网络的寿命。     

多传感器网络系统基于无序估计的分布式信息融合

无线传感器网络的局部节点往融合中心传输信息时,不确定的随机延迟易使得信息无序现象频繁发生,从而导致传统信息融合方法的应用面临诸多难题和挑战。该文以带有任意随机延迟的多传感器同步采样系统为对象,研究无序估计(“Out-Of-Sequence” Estimate, OOSE)信息系统的最优分布式融合问题,最终建立一种新型的通用最优OOSE融合算法。与现有基于集中式框架的无序量测融合方法相比,新算法在融合精度和算法复杂度上均具有显著优势。算法分析和计算机仿真验证了新算法的有效性和优越性。     

Ad Hoc网络中一种随机化分布式QoS路由算法

针对无线移动Ad Hoc网络(Mobile Ad Hoc Network,MANET),采用一种基于随机化分布式QoS路由算法RBAD(Random-Based Distributed QoS Routing Algorithm),该算法依据信道条件和业务量优化分组在多条路径上的路由,及寻找路由和存储路由表的代价,通过对结点排序,达到实现网络平均时延和平均消息复杂度最小的目标。仿真结果表明该算法能够以较小的路由消息开销获得较高的路由成功率,此外,算法具有可扩展性,可以应用于较大规模的Ad Hoc网络。