基于SDN分级分域架构的QoS约束路由算法

传统分布式的网络架构制约路由算法的创新,软件定义网络的出现为路由算法的优化提供了新思路。已有研究中,启发式算法广泛应用于服务质量路由,但由于计算复杂度高而无法在大型网络中应用。而其他算法均存在不同程度的问题,要么复杂度较高,要么算法性能较差,如最短路径算法。基于 SDN 分级分域架构,提出了 LC-LD 路由算法,综合时延条件和代价度量约束并在计算复杂度和算法性能之间保持平衡。仿真分析表明,LC-LD路由算法在有较低的计算复杂度的同时还有较高的服务质量路由选路性能。     

基于QoS的单播源路由算法研究

保证服务质量的QoS路由是网络中解决QoS问题的一项关键技术,QoS路由的主要目标是为接入的业务选择满足服务质量要求的传输路径,同时保证全网资源的有效利用。围绕度量参数选择问题、寻路问题这两个方面,给出了一个基于源地址的单播QoS次优解路由算法,并对其正确性进行了证明。     

时延和时延差别受限的最大带宽多播路由分布式算法

本文采用反映网络实时特性的可用带宽代替代价作为第一度量，提出一种基于最大可用带宽路径且满足时延和时延差别约束的QoS实时多播路由分布式启发算法，该算法具有多项式复杂性，并通过分析得到每路径时延和二约束度量之间的关系，有效降低涉及时延和时延差别此类问题的复杂性。仿真实验证明，该算法具有较好的带宽性能。     

Designing Connection Oriented Networks for Multi-Domain Path Resilience

A challenge in network management and control is the ability to account for multi-domain requirements in the network planning process. Especially in Connection Oriented Networks where multi-domain path finding is a critical issue, networks need to be designed in such a manner as to restrict the possibility of erroneous inter-domain path selection. In this paper we propose per-domain topology design considerations that would leverage accurate disjoint path computations in a multi-domain environment, covering requirements of end-to-end path resiliency. In multi-domain environments state information between domains is heavily aggregated, hiding internal topology details dictated by scalability concerns, but also by restrictive domain administration policies for privacy, and security. Disjoint path finding is strongly affected by the aggregation techniques, since they do not provide information on path overlap. To handle this issue we introduce a metric, the Overlap Factor (OF), that quantifies path overlap in domains. The OF can be passed as an additional parameter of the inter-domain information exchange model to evaluate disjoint end-to-end paths. Alternatively, if domains were appropriately designed, this additional parameter might not be needed in evaluating resilient pairs of inter-domain paths. We based our recommended topology design algorithm on exploiting locally known OF values within the context of Genetic Algorithms. Extensive simulations confirm that domains designed using our proposed algorithm, result into accurate multi-domain disjoint path identification, with a high success ratio compared to networks that are designed without inter-domain considerations.     

基于多个QoS约束的路径选择算法

寻找同时满足多个独立的QoS 约束的路径是一个NP 完全问题。提出一种解决多约束路径问题的有效算法———多约束最小跳路径算法( MHMCA) , 该算法首先利用Bellman-Ford 最短路径算法进行标记, 并删除图中的无用链路, 在简化后的图中使用基于堆栈的深度优先搜索算法寻找所有满足约束的最小跳可行路径。最坏情况下, 算法的时间复杂度为O( n3) 。仿真结果表明, 该算法寻找具有最小跳可行路径的成功率高, 接近于最优算法。     

Complexity and design of QoS routing algorithms in wireless mesh networks

Quality of service (QoS) provisioning in wireless mesh networks (WMNs) is an open issue to support emerging multimedia services. In this paper, we study the problem of QoS provisioning in terms of end-to-end bandwidth allocation in WMNs. It is challenging due to interferences in the networks. We consider widely used interference models and show that except a few special cases, the problem of finding a feasible path is NP-complete under the models. We propose a k-shortest path based algorithmic framework to solve this problem. We also consider the problem of optimizing network performance by on-line dynamic routing, and adapt commonly used conventional QoS routing metrics to be used in WMNs. We find the optimal solutions for these problems through formulating them as optimization models. A model is developed to check the existence of a feasible path and another to find the optimal path for a demand; moreover, an on-line optimal QoS routing algorithm is developed. Comparing the algorithms implemented by the proposed framework with the optimization models shows that our solution can find existing feasible paths with high probability, efficiently optimizes path lengths, and has a comparable performance to the optimal QoS routing algorithm. Furthermore, our results show that contrary to wireline networks, minimizing resource consumption should be preferred over load distribution even in lightly loaded WMNs.     

A new scalable multicast routing algorithm for interactive real-time applications

Quality of service (QoS) provisioning generally assumes more than one QoS measure that implies that QoS routing can be categorized as an instance of routing subject to multiple constraints: delay jitter, bandwidth, cost, etc. We study the problem of constructing multicast trees to meet the QoS requirements of real-time interactive applications where it is necessary to provide bounded delays and bounded delay variation among the source and all destinations while keeping overall cost of the multicast tree low. The main contribution of our work is a new strategy for constructing multiconstrained multicast trees. We first derive mathematically a new delay-variation estimation scheme and prove its efficiency. Thereafter, we propose a simple and competitive (in terms of running time) heuristic algorithm, for delay and delay variation constrained routing problem based on the proposed delay-variation estimation scheme and using the Extended Prim-Dijkstra tradeoffs’ algorithm. Our contribution also extends previous works in providing some properties and analyses of delay bounded paths satisfying delay variation constraints. Extensive simulation results show that our algorithm outperforms DVDMR in terms of multicast delay variation with the same time complexity as DVDMR.     

Precomputation for intra-domain QoS routing

Quality-of-service routing (QoSR), seeking to find a feasible path with multiple constraints, is an NP-complete problem. We propose a novel precomputation approach to multi-constrained intra-domain QoS routing (PMCP). It is assumed that a router maintains the link state information of the entire domain. PMCP cares each QoS weight to several degrees, and computes a number of QoS coefficients uniformly distributed in the multi-dimensional QoS metric space. Based on each coefficient, a linear QoS function is constructed to convert the multiple QoS metrics to a single QoS value. We then create a shortest path tree with respect to the QoS value by Dijkstra’s algorithm. Finally, according to the multiple coefficients, different shortest path trees are calculated to compose the QoS routing table. We analyze linear QoS functions in the QoS metric space, and give a mathematical model to determine the feasibility of a QoS request in the space. After PMCP is introduced, we analyze its computational complexity and present a method of QoS routing table lookup. Extensive simulations evaluate the performance of the proposed algorithm and present a comparative study.     

基于局部信息的时延和时延差约束的组播路由

组播通信是从一个源节点同时向网络中的多个目的节点发送分组的通信服务,它一般提供一个以上的端到端的服务约束,实际的路由算法在应用时可以受到多重约束,解决这类问题的组播路由算法是NP完全的。在研究了构建组播树的相关算法后,提出了一种新的时延和时延差约束的低代价组播路由算法-DDVMC。该算法采用基于贪婪策略的Dijkstra最小生成树算法,利用局部信息来构建低代价组播树,很好地平衡了树的代价、时延和时延差。仿真表明,该算法能正确地构造出满足约束的组播树,同时还具有较低的代价和计算复杂度。     

无线mesh网络多路径QoS路由研究*

基于TDMA提出了一种多路径路由算法。该路由算法是利用两个节点间多条并行的路径作为一个QoS请求的路线。而这多条路径的带宽总和能够满足QoS的带宽要求。通过仿真实验结果证明了该算法相比SPR能明显提高路由的请求成功率。     

基于应用层流量优化的中继路径选择方案

基于网络层路由协议的缺省单一路径难以满足高带宽应用的端到端传输需求,多径传输是一种有效方式。在基于应用层中继的多径传输系统的基础上,提出基于应用层流量优化的中继路径选择方案：借助于应用层流量优化机制,提出中继路径选择过程中遵循的规则,提出基于运营商定义域的最优中继路径生成算法,为数据传输分配优质的中继路径,同时在运营商定义域之间以及中继服务转发器之间保持负载均衡。仿真结果表明,提出的方案在选择优质中继路径方面具有较优性能,同时能够灵活地均衡运营商定义域之间的负载。     

Path approximation for multi-hop wireless routing under application-based accuracy constraints

Provisioning of rich routing building blocks to mobile ad hoc networking applications has been of high interest. Several MANET applications need flexibility in describing paths their traffic will follow. To accommodate this need, previous work has proposed several viable routing schemes such as Dynamic Source Routing (DSR) and Trajectory-Based Routing (TBR). However, tradeoffs involved in the interaction of these routing schemes and the application-specific requirements have not been explored. Especially, techniques to help the application to do the right routing choices are much needed. In this paper, we consider techniques that minimize routing protocol state costs under application-based constraints. We study the constraint of “accuracy” of the application’s desired route, as this constraint provides a range of choices to the applications. As a crucial part of this concept, we investigate the tradeoff between the size of packet headers (needed to store end-to-end paths) and the network state (needed to store routing tables). We, then, apply the concept to the case of TBR with application-based accuracy constraints in obeying a given trajectory. We begin with simple discrete models to clarify the tradeoff between the packet header size and the network state. We show that the problem of accurate approximation of a trajectory (a.k.a. an application-specific end-to-end path) with the objective of minimizing the cost incurred due to header size and network state is difficult to solve optimally. We design an exhaustive search method as well as a genetic algorithm to find the optimum solution. We also develop heuristics solving this problem with smaller computational complexity and illustrate their performance. Finally, we explore ways of customizing our trajectory approximation framework for power-scarce or memory-scarce networking scenarios.     

基于多条件约束的无线传感器网络QoS路径选择算法

多约束QoS路径选择是无线多媒体传感器网络亟待解决的关键问题,已被证明是NP全问题。分析了有线传感器网络使用的多项式时间和伪多项式时间启发式路径选择算法存在着计算复杂度高的特点,不适合无线多媒体传感器网。提出了一种基于改进的模拟退火的多约束QoS路径选择算法,选取控制参数T的衰减函数和控制参数T的终值Tf这两个重要参数进行优化,构造出更精细的冷却进度表。分析表明该算法是一种高效的路径选择算法,在不牺牲算法复杂度的情况下,能够提高最终解的质量。     

一个快速的时延有界低代价多播路由算法

基于ＱｏＳ的多播路由算法需要在满足每个个体ＱｏＳ需求的同时,又能高效管理网络资源,提出了一种满足端端时延限制的低代价多播路由算法。算法使用一个修改的Ｓｔｅｉｎｅｒ树近似算法先构建时延有界的低代价多播树,再通过最小时延路径与其它尚不在多播树的且结点相连。     

QoS-based routing algorithms for ATM networks

This paper presents a planned routing algorithm (PRA) and a hierarchical routing algorithm (HRA) for ATM networks. The PRA can establish the multicast tree with the presence of bandwidth and delay constraints. The HRA can be compliant with the PNNI specification from the ATM Forum. It uses an adaptive and iterative path search approach and takes advantage of the PNNI hierarchical network structure to reduce path computation complexity and maximize network throughput. The performances of the PRA and HRA are evaluated by simulations. The simulation results show that the PRA can provide the best performance while the complexity is acceptable and the HRA can reduce processing time and improve network utilization, and both are suited for QoS requirements of ATM networks’ routing.     

多约束服务质量路由中的路径压缩算法

多约束服务质量路由是一种能够支持灵活的服务质量控制的有效方案.然而在多约束的环境下,从一个源节点到一个目的节点可能存在多条路径,因而必须相应地增大路由表容量.由于当前路由表的规模已相当庞大,尤其是在高速核心网中,因此,为了在QoS路由表中存储更少的路径信息,需要首先进行路径压缩.文章以解决最优路径压缩问题(OPR)为目标,力图在尽量减小路由表存储规模的同时使路由成功率最大化.为了实现这个目标,文中提出了两个基于贡献区域的算法:增量贡献算法和改进的增量贡献算法.这两个算法从一个大的多约束路径集合中依次计算出具有最大贡献区域的积的路径,最后得到一个小的结果路径集合.大量模拟实验表明,这两个算法能够以较低的运算复杂度获得令人满意的路由成功率.     

An ant based multi constraints QoS aware service selection algorithm in Wireless Mesh Networks

Over the years, multihop Wireless Mesh Networks (WMNs) are providing cost effective services to the end users such as Video on demand (VoD), Voice over IP (VoIP), and Video conferencing in an efficient manner. Most of these services require an efficient service selection mechanism that can provide Quality of Service (QoS) in presence of various constraints such as delay, jitter, and service availability. In presence of these constraints, multi-constraint QoS aware service selection in WMNs is an NP-hard problem. In this paper, we propose an ant colony based multi constraints QoS aware service selection (QSS) algorithm. In the proposed algorithm, ants are launched from source node. The best path is chosen based upon the defined cost effective (CE) metric in presence of constraints. The constraints are chosen both from network and user perspectives. The goodness of the chosen path is determined by the CE metric. Moreover, ants are not launched randomly from the source node. They are launched based upon the guided search evaluation (GSE) criterion. This criterion is also used if the two paths have the same CE metric. The simulation results show that the proposed algorithm is more effective than the earlier improved ant colony QoS routing algorithm (IAQR) algorithm with respect to convergence, end-to-end delay (jitter), and service availability. Specifically, the service availability increases by 35–50% in the proposed QoS aware scheme compared to IAQR algorithm.     

MPLS流量工程K路径标号算法

针对多协议标签交换流量工程(MPLS-TE)提出一种有带宽保证的K路径标号算法(KPLA),该算法利用扩展标号算法计算出K条最短路径,综合考虑了链路关键度和链路最大剩余带宽的影响,进一步结合预计算和在线计算减少计算复杂度.该算法目的是避免忽视重要的非关键链路和避免选择过长的路径,提供有效的QoS保证.仿真结果表明该算法路由拒绝率低,延迟小,吞吐量大,计算速度快,是一种高效快捷的动态路由算法.     

The performance of a hybrid routing intelligent algorithm in a mobile ad hoc network

End-to-end delay, power consumption, and communication cost are some of the most important metrics in a mobile ad hoc network (MANET) when routing from a source to a destination. Recent approaches using the swarm intelligence (SI) technique proved that the local interaction of several simple agents to meet a global goal has a significant impact on MANET routing. In this work, a hybrid routing intelligent algorithm that has an ant colony optimisation (ACO) algorithm and particle swarm optimisation (PSO) is used to improve the various metrics in MANET routing. The ACO algorithm uses mobile agents as ants to identify the most feasible and best path in a network. Additionally, the ACO algorithm helps to locate paths between two nodes in a network and provides input to the PSO technique, which is a metaheuristic approach in SI. The PSO finds the best solution for a particle’s position and velocity and minimises cost, power, and end-to-end delay. This hybrid routing intelligent algorithm has an improved performance when compared with the simple ACO algorithm in terms of delay, power consumption, and communication cost.     

无线网状网服务质量路由研究

无线网状网允许系统同时使用多个正交信道,以达到提高网络性能的目的.但是干扰问题仍然存在.基于TDMA提出了一种没有干扰的系统模型.基于这种模型,一种启发式的路径带宽计算方法被提出.将这个算法和AODV路由协议相结合,可以建立一条满足服务质量的最短路由.通过仿真实验结果证明了该路由协议相比SPR能明显提高QoS路由的请求成功率.