基于资源共享的MPLS组播网络中的路径恢复

MPLS组播网络能快速有效地传输数据,其中的路径恢复机制确保提供持续的网络服务。该文提出了一种基于资源共享的MPLS组播网络中的路径恢复方案,该方案在每条链路的入口处保存一个链路资源使用数据库,使用基于共享资源且提供带宽保证的备份路径计算方法来预先建立备份路径,能优化网络资源的利用并减少切换时延。     

GMPLS based OBS网络中链路管理协议的应用*

GMPLS虽然是通用多协议标签交换,但是并不是支持所有的交换方式。由于光突发交换方式信令与数据分离,以及数据的多信道选择等特性,这些特性与传统的链路管理协议[1]的结构和功能非常相似,因此在将GMPLS作为OBS传输网络控制面时,最需要修改的协议就是链路管理协议。首次将链路管理协议中流量工程链路绑定与OBS的数据信道调度关联起来,提高了网络的可扩展性和安全性,支持流量工程,并通过OPNET仿真数据验证了对多媒体业务流恢复性能的改善。     

Dynamic Fuzzy Controlled RWA Algorithm for IP/GMPLS over WDM Networks

This paper proposes a dynamic RWA scheme using fuzzy logic control on IP/GMPLS over WDM networks to achieve the best quality of network transmission. The proposed algorithm dynamically allocates network resources and reserves partial bandwidth based on the current network status, which includes the request bandwidth, average utilization for each wavelength and its coefficient of variance (C.V.) of data traffic, to determine whether the connection can be set up. Five fuzzy sets for request bandwidth, average rate and C.V. of data traffic are used to divide the variable space: very large (LP), large (SP), normal (ZE), small (SN), and very small (LN). Setting the fuzzy limit is a key part in the proposed algorithm. The simulation of scenarios in this paper has two steps. In the first step, the adaptive fuzzy limits are evaluated based on average transmission cost pertaining to ten network statuses. The second step is to compare the proposed algorithm with periodic measurement of traffic (PMT) in ATM networks in six network situations to show that the proposed FC-RWA algorithm can provide better network transmission.     

基于多条件约束的网络信息传输路径动态选择

针对传统网络信息传输路径动态选择速率低的问题,提出基于多条件约束的网络信息传输路径动态选择。笔者在原有技术基础上增加传输路径时延和丢失率两个参数条件,约束传输路径动态选择,建立新的传输路径动态选择模型,利用Qos算法将模型通过线性整数规划方式对其求解。经实例验证,该方法能够快速地选择出距离短、时延最低且丢失率较低。     

Dynamic Multicast in Overlay Networks with Linear Capacity Constraints

In a peer-to-peer overlay network, the phenomenon of multiple overlay links sharing bottleneck physical links leads to correlation of overlay link capacities. We are able to more accurately model the overlay by incorporating these linear capacity constraints (LCCs). We formulate the problem of maximizing bandwidth in overlay multicast using our LCC model. We show that finding a maximum bandwidth multicast tree in an overlay network with LCC is NP-complete. Therefore, an efficient heuristics algorithm is designed to solve the problem. Extensive simulations show that our algorithm is able to construct multicast trees that are optimal or extremely close to optimal, with significantly higher bandwidth than trees formed in overlays with no LCC. Furthermore, we develop a fully distributed algorithm for obtaining near-optimal multicast trees, by means of gossip-based algorithms and a restricted but inherently distributed class of LCC (node-based LCC). We demonstrate that the distributed algorithm converges quickly to the centralized optimal and is highly scalable.     

具备QoS保证的WDM网络中多路径路由问题

针对WDM网络中波长和路由分配(RWA)问题,提出了一种具有QoS保证的多路径路由的新方法。通过为中间节点路由器提供多条可选路径来转发分组数据,可以有效地解决WDM网络中分组数据阻塞的问题,从而可以更好地提供QoS保证。文中也给出了计算机仿真结果,并对仿真结果进行了分析和比较。     

一个有效的延迟费用受限的多路径算法

在集成网络中,服务质量(QoS)的一个重要方面是寻找满足端到端约束的可行路径,从而有效利用网络资源。考虑端到端的延迟约束和传输费用,对宽度优先算法(BFS)进行扩展,提出了满足延迟约束多路径算法K_DCP,并对其进行改进,得到多路径算法K_EDCP。仿真结果显示,两种算法性能良好。     

一种快捷的MPLS网络负载均衡动态路由算法

针对MPLS网络引入了一种快捷的有带宽保证的负载均衡动态路由算法（FDRA）,该算法通过提出预期负载的概念和链路上的剩余容量来定义链路的成本,然后采用以链路成本为基础的最短路径算法选路,使得网络快捷地建立尽可能多的有带宽保证的路由,并且使这些路由均衡地通过网络。在与其他算法相比较中,该算法在业务请求拒绝率和重路由性能方面有更好的表现,特别是路由的建立时间快捷。     

DiffServ/MPLS网络中最小化抢占的路由算法

在支持具有不同优先级和不同QoS需求的多业务网络中,抢占是带宽分配和管理的有效策略,但同时也对网络造成了振荡。在路径选择策略中引入抢占信息可最小化重路由,提高网络的稳定性。论文给出了最小化抢占的路由问题的数学规划模型。在此基础上提出了简单的启发式算法以运用于大型实际网络。策略是将路径选择和连接建立过程有效地结合起来,对现有的MPLS信令协议仅做了少许扩展。仿真证明该算法能达到抢占最小化的优化目标,有效地提高网络性能。     

多约束QoS动态多播路由算法

YAM和QoSMIC是支持QoS动态多播路由算法,允许多播组成员动态地加入/退出,同时为接收方提供多个可选择的多播接入路径,以满足不同应用的QoS需求。该文在分析这些算法的基础上,研讨了具有延迟、延迟抖动、带宽和代价等多约束QoS的多播路由问题,描述了一种适应于研究QoS多播路由的网络模型,提出了一种具有多约束QoS的动态多播路由算法(MQDMR),MQDMR试图有效地减少生成多约束QoS的多播树的开销。在MQDMR中,一个多播组成员能动态地加入/退出一个多播会晤,且不干扰现有的多播树。仿真实验结果表明,MQDMR比YAM和QoSMIC具有较小的延时和较少的代价。     

Dynamic Shortest Path Monitoring in Spatial Networks

With the increasing availability of real-time traffic information, dynamic spatial networks are pervasive nowadays and path planning in dynamic spatial networks becomes an important issue. In this light, we propose and investigate a novel problem of dynamically monitoring shortest paths in spatial networks (DSPM query). When a traveler aims to a destination, his/her shortest path to the destination may change due to two reasons: 1) the travel costs of some edges have been updated and 2) the traveler deviates from the pre-planned path. Our target is to accelerate the shortest path computing in dynamic spatial networks, and we believe that this study may be useful in many mobile applications, such as route planning and recommendation, car navigation and tracking, and location-based services in general. This problem is challenging due to two reasons: 1) how to maintain and reuse the existing computation results to accelerate the following computations, and 2) how to prune the search space effectively. To overcome these challenges, filter-and-refinement paradigm is adopted. We maintain an expansion tree and define a pair of upper and lower bounds to prune the search space. A series of optimization techniques are developed to accelerate the shortest path computing. The performance of the developed methods is studied in extensive experiments based on real spatial data.     

TRIDENT: An automated approach to traffic engineering in IP/MPLS over ASON/GMPLS networks

This paper addresses the problem of designing a capacity management/traffic engineering procedure for an IP/MPLS over ASON/GMPLS scenario. We suggest TRIDENT, a procedure whose main goal is to dynamically provide the bandwidth required to transport through an ASON the MPLS–LSPs already established at the IP/MPLS client network. TRIDENT relies on automatically triggering demands to set up or tear down the ASON switched connections, and it is based on monitoring and predicting the offered traffic at the interfaces between the IP (MPLS) and the ASON layers. TRIDENT allows providing automatic Bandwidth on Demand (BoD) and it counteracts potential congestion at the client network. Its merits are evaluated by simulation results and it has also been experimentally tested.     

处理动态优化问题中控制变量路径约束的方法

目前国际上对动态优化问题中的状态变量路径约束已有一些研究,但专门处理控制变量路径约束的方法却鲜见报道. 本文首先介绍两种分别基于三角函数变换、约束算子截断来处理控制变量路径约束的方法,然后提出一种基于光滑化的二次罚函数方法. 光滑化罚函数方法不仅能够处理控制变量路径约束,而且还能同时处理关于状态变量的路径约束. 最后使用目前流行的控制变量参数化 (Control variable parameterization, CVP)策略对最终获得的、不再含控制变量路径约束的动态优化问题求解. 实例测试一展现了三种方法各自的特点;实例测试二表明了光滑罚函数方法的有效性和优越性.     

具有QoS保证的MPLS网络生存性策略*

概述了保证QoS的MPLS网络生存性中各种保护和恢复策略,包括它们对QoS的不同要求、算法思想、应用领域、各自的优缺点等.将MPLS网络生存性与DiffServ模型结合起来,针对不同的业务要求选出不同的保证QoS的生存性方法.     

基于Ad Hoc多QoS约束的多播路由协议

针对移动Ad Hoc网络特点，研讨了Ad Hoc网络中其有多QoS约束的多播路由问题，其中主要包含延迟、延迟抖动、带宽、代价等QoS约束。描述了一种适应于研究Ad Hoc网络QoS多播路由的网络模型，提出了Ad Hoc网络中一种具有多QoS约束的多播路由协议。给出了MQAP的路由实现过程，进行了正确性证明和复杂性分析。仿真实验结果表明，MQAP为Ad Hoc网络多QoS约束多播路由提供了一种新的有效途径。     

区间非线性路径约束的动态优化问题求解

本文研究路径约束中含有区间参数形式的动态优化问题,提出了一种新的非线性路径约束的确定化描述形式,和采用惩罚函数法的求解算法。对于转化后的极大极小优化命题,论文提出采用Lagrangian多项式加权和的方法得到有限维的确定性优化求解形式。该算法可有效地描述和求解不确定参数动态优化问题。     

A Pareto-based hybrid multiobjective evolutionary approach for constrained multipath traffic engineering optimization in MPLS/GMPLS networks

This paper proposes a hybrid evolutionary algorithm for solving the constrained multipath traffic engineering problem in MPLS (Multi-Protocol Label Switching) network and its extended architecture GMPLS (Generalized MPLS). Multipath traffic engineering is gaining more importance in contemporary networks. It aims to satisfy the requirements of emerging network applications while optimizing the network performance and the utilization of the available resources within the network. A formulation of this problem as a multiobjective constrained mixed-integer program, which is known to be NP-hard, is first extended. Then, we develop a hybrid heuristic algorithm based on combining linear programming with a devised Pareto-based genetic algorithm for approximating the optimal Pareto curve. A numerical example is adopted from the literature to evaluate and compare the performance of six variations of the proposed heuristic. We study the statistical significance of the results using Kruskal–Wallis nonparametric test. We also compare the results of the heuristic approach with the lexicographic weighted Chebyshev method using a variety of performance metrics.     

A Smooth Path Tracking Algorithm for Wheeled Mobile Robots with Dynamic Constraints

In order to avoid wheel slippage or mechanical damage during the mobile robot navigation, it is necessary tosmoothly change driving velocity or direction of the mobile robot. This means that dynamic constraints of the mobile robotshould be considered in the design of path tracking algorithm. In the study, a path tracking problem is formulated asfollowing a virtual target vehicle which is assumed to move exactly along the path with specified velocity. The drivingvelocity control law is designed basing on bang-bang control considering the acceleration bounds of driving wheels. Thesteering control law is designed by combining the bang-bang control with an intermediate path called the landing curve whichguides the robot to smoothly land on the virtual target's tangential line. The curvature and convergence analyses providesufficient stability conditions for the proposed path tracking controller. A series of path tracking simulations and experimentsconducted for a two-wheel driven mobile robot show the validity of the proposed algorithm.     

主动队列管理下大时滞网络路径拥塞控制算法

与传统的无线网络相比,大时滞网络对路径拥塞环境下的无线通道交换具有较高的要求.为此提出主动队列管理下大时滞网络路径拥塞控制算法.首先利用主动队列管理算法对相邻路由节点网络路径的拥塞情况展开预测,进而分析网络路由节点的队列状态;然后以优化后续节点队列、传输距离以及传输方向为目的,从路径概率选择、分组丢弃函数、WSN蚁群路...