一种基于MPLS流量工程的QoS保证路由算法

随着因特网流量的快速增加和对服务质量要求的不断提高,基于MPLS流量工程的QoS路由算法成为业界研究的重点。文章介绍了MPLS流量工程的工作机制和原理,在传统的Dijkstra算法的基础之上,提出了一种新颖的基于遗传优化的QoS保证的路由选择算法,同时配置一批LSP,并克服了一条一条配置时的先占先优的“顶端优势”。最后的仿真实验说明了算法在优化网络资源、平衡网络负载中是有效的和实用的。     

一种基于SRLG条件失败概率限制的保护算法

研究了IP／MPLSover WDM网中，如何建立两条共享风险链路组(SRLG)分离的标记交换(LSP)问题，提出一种新的基于SRLG条件失败概率限制的保护算法。该算法寻找SRLG条件失败概率最小的最短路径作为工作通路的保护通路，既能最大限度地保护用户业务的可靠性要求，同时又能够有效降低全网LSP建立请求的阻塞率。     

MPLS TE中一种新的路径选择算法

目前,MPLS TE的实现多使用CSPF算法选择路径,然而此算法没有考虑建立LSP时的抢占特性,因此可能会导致其它业务不必要的中断.对CSPF算法的这种缺陷进行了研究,提出了COPF算法,该算法在选择路径时,尽量减少被抢占的LSP的数量,使已建立的LSP受影响程度最小,从而选择一条使业务中断最少的路径建立LSP.在网络空闲时,COPF算法也尽量选择合理的路径使业务流量均衡分布.     

一种MPLS流量工程动态路由选择算法

MPLS网络中,允许在网络的入口和出口之间建立多条LSP来分担流量。MPLSTE的关键问题是LSP的分布优化问题针对这一特性,本文提出一种基于遗传算法的求解方法,仿真结果表明,该算法是有效且切实可行的。     

DS-TE网络中改进的LSP抢占算法

Min_BW算法在优化被抢占移动交换路径(LSP)的优先级时,存在被抢占LSP个数多和优先级高的问题.为此,提出DS-TE网络中改进的LSP抢占算法(I_Min_BW),全面考虑可能被抢占的LSP组中LSP的个数、LSP的最高优先级以及LSP的优先级总和.实验结果表明,该算法抢占的LSP组中最高优先级小于等于Min_B...     

层次化服务流程向可执行BPEL转换的方法

基于人工智能规划的服务组合算法得到的组合方案是一种层次化服务流程（layered service process, LSP）,由服务之间的数据流（而非传统块结构流程中的控制结构）加以驱动执行。为使该类服务流程能在业务
　　过程执行语言（business process execution language,BPEL）引擎上直接执行,研究了将LSP转换为BPEL的方法,追求BPEL执行效率的优化。给出了LSP的形式化模型,分析了将LSP转换为BPEL的3种策略（完全拆分、按层拆分、按块拆分）,定性对比了三者之间的性能优劣。针对按块拆分策略,提出了9条规则用于对LSP的拆分,提出了块拆分算法和块合并算法。通过一个LSP案例对转换过程进行了演示,并通过实验证实了该转换方法可以获得比其他转换策略性能更好的BPEL。     

生产批量计划问题的RCWW算法验证研究

Wagner-Whitin( WW)算法是经典的、求解生产批量计划((Lot-sizing Planning,LSP)问题的最优启发式算法,对于中小规模问题可以有效求得产品的最优生产量。随机累加WW(Randomized Cumulative WW,RCWW)算法是改进了的WW算法,适用于求解具有一般生产结构的、多层级LSP问题。RCWW算法的求解效果已经得到了验证。根据RCWW算法的求解思想,通过采用C语言进行编码实现算法流程。通过对具有一般生产结构LSP问题的标准算例进行求解,验证了RCWW算法的求解效果,发现了原文献的错误,证明了作者对RCW W算法的正确理解。     

网络平滑算法在流量工程中的应用

流量工程是当前IP网络解决QoS问题的关键技术之一。然而目前实现流量工程的LSP分布算法一般只对网络资源的利用率进行优化，可能导致网络负载的不平衡。文中引入网络负载平滑度的概念，定义了链路代价函数。针对当前主要的LSP分布算法“带宽．跳数算法”在网络负载平滑度方面的不足，提出由代价函数控制的网络平滑算法，并对算法进行了分析，最后给出相应的实验结果和结论。     

MPLS的基于最小干涉的负载均衡算法研究

当MPLS网络中的业务流请求存在时间上的先后顺序时,选择一个高效的路由算法使得已存在的业务流的LSP对后续业务流的LSP路由影响最小变得很重要.在分析了常用的几种QoS保障的算法基础上,提出了一种基于最小干涉的负载均衡算法.该算法解决了MPLS网络中所有"入口/出口对"之间的业务流相互干扰的问题,为后续业务流路由预留了必要的"关键链路".     

MPLS中的工作路由和后备路由确定算法

为提高网络资源的利用率,在基于Local故障恢复方案的前提下,提出了一种路由算法,这种算法在确定工作LSP的同时也确定好后备LSP,并使工作路由和后备路由带宽之和最小。     

基于MPLS-DiffServ的LSP动态抢占算法研究

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。基于普通的LSP路由方案,提出了一个动态的LSP抢占算法——Min_Prec算法:总是首先抢占最低优先级的LSP;在同一个优先级别内最优化被抢占的带宽和LSP数目。最后,通过引入一个抢占策略对于路由过程的反馈机制,减少抢占引起的重路由,增强网络稳定性。仿真结果验证了算法的有效性、优越性。     

Path selection with preemption and re-routing control for multi-protocol label switching networks

Multi Protocol Label Switching (MPLS) networks enhance the services of conventional best-effort IP networks by providing end-to-end Quality of Service (QoS) guaranteed Label Switched Paths (LSP) between customer sites. The LSP has to be set up in advance before carrying the traffic. Contention for network resources may happen if many LSPs try to use a common network link with limited bandwidth. In this paper, we investigate the problem of providing services to high priority LSPs whereby existing LSPs with lower priority may be preempted. The consequent interruption of the services of preempted LSPs would detrimentally affect users’ perception on the QoS provided. Therefore, the preemption strategies may incorporate additional re-routing mechanisms to provide alternative paths for the LSPs which are to-be-preempted so that their services remain unaffected. A newly arrived high priority LSP in an MPLS network may find M possible paths between its source and destination. It may select the shortest path which may trigger preemption or choose a longer path which however utilizes more resources. We begin by formulating preemption strategies with global re-routing. Our investigations include the effects of routing of high priority LSPs on the shortest path and its alternative paths. We show that by persistently routing the high priority LSP on the shortest path, more preempted LSPs can be re-routed which would reduce the negative effects of preemption. However, as excessive re-routing may degrade the network performance as well, a re-routing control strategy is proposed to constrain the length of these re-routed paths. Finally, a decentralized preemption strategy with local re-routing is also presented to approximate the performance of the proposed strategy with significantly lower control overheads. Simulations show that with this approach, high priority LSPs can gain better access to network resources while simultaneously ensuring that, as compared to the existing preemption strategies, the network throughput and the ongoing connection services are not adversely affected.     

基于双种群遗传算法的MPLS流量工程研究

针对因特网流量的快速增加和对服务质量要求的不断提高,为避免网络数据流过大造成拥塞问题,利用MPLS流量工程的路由算法成为业界研究的重点。介绍了MPLS流量工程的工作机制,并提出了数学模型。MPLS流量工程的关键问题是LSP的分布优化问题,针对这一问题的Np-hard特性,提出一种基于双种群策略的遗传算法求解方法,算法采用自然数编码来提高搜索效率。算法中,两个子种群周期性地交流最优染色体,进一步提高了性能。仿真实验表明,提出的算法能有效提高搜索速度,增加获得最优解的概率。     

Policy-Based Grooming in Optical Networks

This work presents a discussion about policies and architecture to aggregate Internet Protocol/Multiprotocol Label Switching (IP/MPLS) traffics within lightpaths. The scenario is that of IP/MPLS client networks over an optical network. It is well known that aggregating lower traffic flows (e.g., packet-based LSPs—Label Switched Path) within higher traffic flows (e.g., lambda-based LSPs) is considered an effective way to maximize the use of the optical network resources. In this work, the policies are divided into two groups. The first one, which solely considers the class of the flow (High Priority—HP or Low Priority—LP), consists of simple policies meant to aggregate packet-based LSPs within lightpaths. In this group, the policies we have defined intend to reduce the optical network overhead to remove and reroute LP LSPs. The second group presents more sophisticated policies taking into account the possibility of having to deal with further transport faults. In this case, the grooming is better planned and the defined policies tend to reduce the negative impact when a failure is detected in the optical transport network. Our approach has been implemented to validate the policies and the results for each group are showed and discussed.     

MPLS流量工程最小冲突路径算法

优化网络资源利用是Internet流量工程的重要目标之一.最小冲突路由机制通过利用多协议标记交换(MPLS)网络中的源-目的(SD)节点对信息,在为业务流请求选择标记交换路径(LSP)时,尽可能避免当前请求与将来请求之间的冲突,实现网络资源的合理利用.作者基于最小冲突机制,提出一种新颖的最小冲突路径算法(LIP).LIP通过简单的最短路径算法定位关键链路,并将链路剩余容量、节点对之间的冲突和竞争结合起来定义链路权重,在实现网络资源高效利用的同时,降低了算法的计算复杂度.实验结果进一步验证,相对于以往算法,LIP在请求带宽拒绝率、网络带宽接收量和LSP平均路径长度等方面都比较理想.     

New MPLS network management techniques based on adaptive learning

The combined use of the differentiated services (DiffServ) and multiprotocol label switching (MPLS) technologies is envisioned to provide guaranteed quality of service (QoS) for multimedia traffic in IP networks, while effectively using network resources. These networks need to be managed adaptively to cope with the changing network conditions and provide satisfactory QoS. An efficient strategy is to map the traffic from different DiffServ classes of service on separate label switched paths (LSPs), which leads to distinct layers of MPLS networks corresponding to each DiffServ class. In this paper, three aspects of the management of such a layered MPLS network are discussed. In particular, an optimal technique for the setup of LSPs, capacity allocation of the LSPs and LSP routing are presented. The presented techniques are based on measurement of the network state to adapt the network configuration to changing traffic conditions.