Joint coverage and link utilization for fast IP local protection

To mitigate the impact of failures, many IP Fast Local Recovery (IPFLR) schemes have been proposed to reroute traffic in the events of failures. However, the existing IPFLR schemes either aimed to find the alternate backup routes to protect failures, or focused on balancing the traffic load routed on the backup routes. Furthermore, in Internet, flows are often managed by shortest path routing, and therefore purely determining the backup routing paths is not sufficient in protecting the error-prone networks. In this paper, we propose a Simulated Annealing based Load balancing and Protection (SALP) scheme to determine link weights for balancing link utilization in the non-failure state and simultaneously construct backup routing tables for protecting any single link failure in IP networks. In our proposed scheme, the two most significant issues, (1) load balancing and (2) coverage, are jointly considered to recover the network operation from single link failures. In the proposed scheme, upon a failure, only the nodes adjacent to a failure are activated to divert affected traffic to backup paths without disturbing regular traffic. Numerical results delineate that the proposed scheme achieves high coverage rate and load balancing at the expense of slightly increasing the entries of backup routing table.     

Design and performance analysis of an inductive QoS routing algorithm

Routing mechanism is key to the success of large-scale, distributed communication and heterogeneous networks. Consequently, computing constrained shortest paths is fundamental to some important network functions such as QoS routing and traffic engineering. The problem of QoS routing with multiple additive constraints is known to be NP-complete but researchers have been designing heuristics and approximation algorithms for multi-constrained paths algorithms to propose pseudo-polynomial time algorithms. This paper introduces a polynomial time approximation quality of service (QoS) routing algorithm and constructs dynamic state-dependent routing policies. The proposed algorithm uses an inductive approach based on trial/error paradigm combined with swarm adaptive approaches to optimize lexicographically various QoS criteria. The originality of our approach is based on the fact that our system is capable to take into account the dynamics of the network where no model of the network dynamics is assumed initially. Our approach samples, estimates, and builds the model of pertinent aspects of the environment which is very important in heterogeneous networks. The algorithm uses a model that combines both a stochastic planned pre-navigation for the exploration phase and a deterministic approach for the backward phase. Multiple paths are searched in parallel to find the K best qualified ones. To improve the overall network performance, a load adaptive balancing policy is defined and depends on a dynamic traffic path probability distribution function. We conducted a performance analysis of the proposed QoS routing algorithm using OPNET based on a platform simulated network. The obtained results demonstrate substantial performance improvements as well as the benefits of learning approaches over networks with dynamically changing traffic.     

Transient chaotic neural network-based disjoint multipath routing for mobile ad-hoc networks

Due to mobility of wireless hosts, routing in mobile ad-hoc networks (MANETs) is a challenging task. Multipath routing is employed to provide reliable communication, load balancing, and improving quality of service of MANETs. Multiple paths are selected to be node-disjoint or link-disjoint to improve transmission reliability. However, selecting an optimal disjoint multipath set is an NP-complete problem. Neural networks are powerful tools for a wide variety of combinatorial optimization problems. In this study, a transient chaotic neural network (TCNN) is presented as multipath routing algorithm in MANETs. Each node in the network can be equipped with a neural network, and all the network nodes can be trained and used to obtain optimal or sub-optimal high reliable disjoint paths. This algorithm can find both node-disjoint and link-disjoint paths with no extra overhead. The simulation results show that the proposed method can find the high reliable disjoint path set in MANETs. In this paper, the performance of the proposed algorithm is compared to the shortest path algorithm, disjoint path set selection protocol algorithm, and Hopfield neural network (HNN)-based model. Experimental results show that the disjoint path set reliability of the proposed algorithm is up to 4.5 times more than the shortest path reliability. Also, the proposed algorithm has better performance in both reliability and the number of paths and shows up to 56% improvement in path set reliability and up to 20% improvement in the number of paths in the path set. The proposed TCNN-based algorithm also selects more reliable paths as compared to HNN-based algorithm in less number of iterations.     

基于拥塞预警与分流传输的AOMDV协议优化

针对AOMDV协议只使用主路径传输数据,导致备用路径未能得到充分利用以及网络负载失衡的问题,本文提出一种LBAOMDV(Load Balanced AOMDV)协议。该协议在AOMDV协议的基础上使用基于路径长度、路径使用次数以及路径状态的分流传输机制在多条路径上同时传输数据以均衡网络负载,当网络中的节点负载过重并通过预先设定的阀值时将触发拥塞预警机制以减少通过该节点的数据流量,从而进一步达到网络负载的动态均衡。     

Development and research of improved model of multipath adaptive routing in computer networks with load balancing

In modern computer networks, loading and bandwidth of communication links are optimized for providing high-quality service of network traffic, new services and technologies. As a rule, for this task the protocols of dynamic routing based on Dijkstra’s algorithm are used. Protocols of multipath routing for ensuring reliability and accuracy of the provided information allow to divide critical traffic and to execute load balancing along several routes at the same time. The purpose of the work is development and research of the improved multipath adaptive routing model in computer networks with load balancing. In this work, we focused on indicator of jitter optimization between the paved paths and a deviation value of reserve routes from an optimal route. Comparison and estimation of the offered algorithm with some existing approaches, and also modeling and analysis on various topologies of computer networks have been carried out.     

面向时间敏感网络的流量调度方法

从高效流量路由调度计算的角度出发,针对时间敏感流量调度中通常存在的计算效率低、迭代收敛慢等问题,提出一种基于最短路径负载均衡与改进遗传算法的流量调度方法。建立网络模型与流量模型并定义时间敏感网络中的流量传输约束,同时利用基于K最短路径的负载均衡路由算法与改进选择算子和交叉变异概率的遗传算法进行路由与调度计算。实验结果表明,该方法能有效缩短时延敏感流量调度任务的完成时间,提高调度计算效率,并加快迭代收敛速度。     

Improving the efficiency of multipath traffic via opportunistic traffic scheduling

Multipath routing, as defined by OSPF extensions and other protocols, enables a network’s traffic to be split among two, or more, possibly disjoint paths. Advantages of multipath vs. unipath routing include load balancing, reduced latency, and improved throughput. However, once the control plane establishes multiple routes, a policy is needed for efficiently splitting traffic among the selected paths. In this paper, we introduce opportunistic multipath scheduling (OMS), a technique for exploiting short-term variations in path quality to minimize delay, while simultaneously ensuring that the splitting rules dictated by the routing protocol are satisfied. We develop a performance model of OMS and derive an asymptotic lower bound on the performance of OMS as a function of path conditions (mean, variance, and Hurst parameter) for self-similar traffic. Finally, we use an extensive simulation-based performance study to evaluate the accuracy of the analytical model, explore the impact of OMS on TCP throughput and performance of real-time traffic, and study the impact of factors such as delayed measurements.     

Multi-path routing versus tree routing for VPN bandwidth provisioning in the hose model

In this paper we study the bandwidth provisioning of VPN service in the hose model with multi-path routing and tree routing. We have investigated the bandwidth efficiency and blocking performance of these two routing schemes. Our study shows that without any restriction on the maximum fraction of traffic on a path (MFTP), multi-path routing often turns out to be single path routing, and only reduces the total bandwidth requirement slightly at rare combination of network topologies and hose parameters. In order to alleviate the overprovisioning problem of the hose model, we propose the concept of sub-provisioning and study the blocking performance using static reduced provisioning. The results show that with full provisioning, the two routing schemes have almost the same blocking performance. However, with sub-provisioning and the variation of the MFTP constraint, multi-path routing is capable of delivering a significant improvement in blocking performance, often better than tree routing by a few orders of magnitude. The improvement is attributed to the multiple alternative paths brought in by the MFTP constraint. With sub-provisioning, the link bandwidth availability becomes the restricting factor in admitting a connection. Having multiple paths, a connection request is able to explore available bandwidth more thoroughly in the network, thus increasing its chances of being admitted. We employ both analytical model and discrete event simulation for the blocking performance study. The analytical model is developed based on the multi-rate reduced load approximation technique and the simulation is carried out using the OPNET simulator. The close agreement between analytical and simulation results indicate the validity of the approach.     

Randomized dynamic route maintenance for adaptive routing in multihop mobile ad hoc networks

Several approaches have been proposed for designing multihop routing protocols in mobile ad hoc networks (MANET). Many of them adopt a method, called flooding, to discover a routing path. Due to the time-varying nature of the route in MANET, the discovered route needs to be dynamically maintained for optimality in terms of traffic load, hop-distance, and resource usage. It is easy to see that flooding incurs significant overhead and hence is inappropriate for the dynamic route maintenance. In this paper we propose a randomized, dynamic route maintenance scheme for adaptive routing in MANET. The scheme makes use of a nomadic control packet (NCP) which travels through the network based on a random walk, and collects its stopovers as a traversal record. The NCP uses the traversal record to probabilistically provide the nodes with clue for routing path updates. From the clue, the nodes can find the routing path update information that is up-to-date and optimal (less-loaded and shorter), thereby adapting to the dynamic network topology and traffic load conditions. We present an analytical model for measuring the effectiveness of NCP in terms of its frequency of visits and probability of finding the clue from the NCP traversal record. The proposed randomized scheme serves as a routing protocol supporting layer and can be easily applied with minimum modifications to the existing on-demand routing protocols such as AODV and DSR. In our experimental study, we modified the AODV protocol to maintain routing paths using NCPs’ traversal record. Simulation results show that NCPs help the routing protocol to notably reduce average end-to-end packet delay with increased route optimality and better control on traffic congestion.     

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.     

一种基于动态负载均衡的路由算法

传统IGP仅基于最短路径算法来为数据流选择传输通路，对数据流的需求以及网络资源的动态变化未加以考虑，因此不具备均衡网络负载的能力。文中通过分析IGP的局限性，提出基于动态负载均衡的DLB-OSPF路由算法。该算法依据数据流的带宽需求和网络资源的使用状况来进行路由选择，并通过有效手段将数据流更合理地分配到能满足传输需求的链路上。经过示例分析表明，该算法不仅能减少网络拥塞，并且提高了网络资源利用率。     

A performance comparison of mobility anchor point selection schemes in Hierarchical Mobile IPv6 networks

Hierarchical Mobile IPv6 (HMIPv6) introduces a mobility anchor point (MAP) that localizes the signaling traffic and hence reduces the handoff latency. In addition to processing binding update messages from mobile nodes (MNs) on behalf of MNs’ home agents (HAs), the MAP performs data traffic tunneling destined to or originated from MNs, both of which will burden the MAP substantially as the network size grows. To provide scalable and robust mobile Internet services to a large number of visiting MNs, multiple MAPs will be deployed. In such an environment, how to select an appropriate MAP has a vital effect on the overall network performance. In this paper, we choose four MAP selection schemes: the furthest MAP selection scheme, the nearest MAP selection scheme, the mobility-based MAP selection scheme, and the adaptive MAP selection scheme. Then, we compare their performances quantitatively in terms of signaling overhead and load balancing. It can be shown that the dynamic schemes (i.e., the mobility-based and the adaptive MAP selection schemes) are better than the static schemes (i.e., the furthest and the nearest MAP selection schemes), since the dynamic schemes can select the serving MAP depending on the MN’s characteristics, e.g., mobility and session activity. In addition, the adaptive MAP selection scheme achieves low implementation overhead and better load balancing compared with the mobility-based MAP selection scheme.     

Load-balanced short-path routing in wireless networks

We study routing algorithms on wireless networks that use only short paths, for minimizing latency, and achieve good load balance, for balancing the energy use. We consider the special case when all the nodes are located in a narrow strip with width at most /spl radic/3/2 /spl ap/ 0.86 times the communication radius. We present algorithms that achieve good performance in terms of both measures simultaneously. In particular, the routing path is at most four times the shortest path length and the maximum load on any node is at most three times that of the most load-balanced algorithm without path-length constraint. In addition, our routing algorithms make routing decisions by only local information and, as a consequence, are more adaptive to topology changes due to dynamic node insertions/deletions or due to mobility.     

改进蚂蚁算法在网络流量平衡中的研究

在分析了当前蚂蚁算法实现网络流量负载重配置的基础上,提出了新的网络链路资源分配策略及改进算法,利用蚂蚁具有找到最短路径及不同种类蚂蚁互相排斥的这一天然特性,很容易在最短路由和链路负载之间取得折中。仿真结果表明,改进的蚂蚁算法对业务请求越是频繁的情况,其负载平衡度和业务到达率越优于其他算法。     

Joint range assignment and routing to conserve energy in wireless ad hoc networks

In wireless ad hoc networks, energy utilization is perhaps the most important issue, since it corresponds directly to the operational network lifetime. Topology Control (TC) is a well-known energy saving technique which tries to assign transmission ranges of nodes to optimize their energy utilization while keeping the network connected. In current TC schemes, the transmission range of each node is mostly accounted as the exclusive estimator for its energy consumption, while ignoring the amount of data it forwards. Especially when such schemes are coupled with the popular shortest path routing, they usually create a highly-loaded area at the center of the network in which nodes deplete their battery very quickly. In this paper, we introduce efficient strategies that take both load and range into account to handle this problem. We first consider the simple strategy in which a proper transmission range is computed for all nodes of the network to optimize their energy utilization under the presence of the shortest path routing. Inspiring from the results of this strategy, we then propose our combined strategy and argue that a combination of circular paths and shortest paths could result in a much better solution. We also provide detailed analytical models to measure the forwarding load and interference of nodes and then corroborate them with simulation results. Using the combined strategy, the achieved improvement in terms of traffic load, interference, and maximum energy consumption is about 50%, as compared with the simple strategy.     

Providing QoS in OSPF based best effort network using load sensitive routing

In an open shortest path first (OSPF) based best effort network, when a packet experiences congestion, the routing subsystem cannot send it through an alternate path. Thus, it fails to provide desired quality of service (QoS) during congestion. In order to provide QoS we have reported three different load sensitive routing (LSR) protocols in [A. Sahoo, An OSPF based load-sensitive QoS routing algorithm using alternate paths, in: IEEE International Conference on Computer Communication Networks, October 2002; A. Tiwari, A. Sahoo, Providing QoS support in OSPF based best effort network, in: IEEE International Conference on Networks, November 2005; A. Tiwari, A. Sahoo, A local coefficient based load sensitive routing protocol for providing QoS, in: IEEE International Conference on Parallel and Distributed Systems, July 2006]. The LSR protocol forwards packets through alternate paths in case of congestion. The number of alternate paths at any node depends on the value of operating parameter or coefficient used for alternate path calculation. Though the basic protocol in these cases was the same, the methods of choosing operating parameter were different. We referred to these three methods as LSR [A. Sahoo, An OSPF based load-sensitive QoS routing algorithm using alternate paths, in: IEEE International Conference on Computer Communication Networks, October 2002], E-LSR [A. Tiwari, A. Sahoo, Providing QoS support in OSPF based best effort network, in: IEEE International Conference on Networks, November 2005] and L-LSR [A. Tiwari, A. Sahoo, A local coefficient based load sensitive routing protocol for providing QoS, in: IEEE International Conference on Parallel and Distributed Systems, July 2006] coefficient methods. In this paper, we present the LSR protocol along with the three coefficient calculation methods pointing out the reason for going from one method to the next. The main strength of our LSR protocol is that it provides loop free alternate paths in the event of congestion and can interwork with routers running vanilla OSPF protocol. We show through simulation that the LSR protocol based on any of the three different coefficient calculation methods performs much better than OSPF and that out of the three methods proposed by us, L-LSR performs the best.     

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.     

On the optimality of field-line routing in massively dense wireless multi-hop networks

We consider the load balancing problem in large wireless multi-hop networks by applying the continuum approximation. The task is to find routes, geometric curves, such that the maximal traffic load in the network is minimized. In finite fixed networks, multi-path routes generally yield a lower congestion and thus allow higher throughput. In contrast, we show that in dense wireless multi-hop networks, the optimal load balancing can be achieved by a destination based single-path routing referred to as field-line routing. This is because any routing can be transformed to the corresponding field-line routing with the same or better performance, by using as paths, the field lines of the so-called destination flow associated with the original routing. The concepts are illustrated with two examples. In the case of a unit disk with unit traffic, the maximal load of 0.389 of a multi-path routing system is reduced to 0.343 by using the field-line routing. Similar improvements are also demonstrated for the unit square.     

基于MPLS流量工程的负载均衡策略

本文讨论了当前网络所面临的负载不均衡问题和传统的基于IP目的地址的逐跳式路由算法在解决不均衡问题的局限性,并提出了解决此问题的一种可行方案：基于流量工程的负载均衡策略,通过对经过关键链路的路径调整,从而达到负载均衡的目的。     

一种SRIO网络负载均衡最短路径路由算法

在串行RapidIO传输过程中,路由选路算法是影响传输性能的重要因素之一。针对串行高速输入-输出(SRIO)网络深度优先搜索分配路径非最优问题,提出一种负载均衡最短路径路由算法。通过广度优先搜索对SRIO网络中的节点进行枚举并建立网络拓扑信息,以路由跳数定义路由的成本,根据改进Floyd-WarShall算法计算并保存交换节点间的K最短路径。给出预期负载的概念和链路上的路由路径数量来定义链路的负载,采用负载均衡算法从K最短路径中进行选路,建立SRIO网络最短路径约束的负载均衡路由。实验结果表明,与深度遍历路由算法、最小跳数算法相比,该算法在网络传输平均跳数、链路平均负载和链路负载均衡方面有更好的表现,能够有效提升SRIO路由网络的稳定性。