PLS流量工程故障恢复路径算法

提出一种适合MPLS保护切换和再路由--备份路径预有效恢复机制的备份路径优化算法.该算法引入故障说明,针对指定的保护对象计算恢复路径,同时,对链路的带宽进行分割,在链路可用带宽中指定备份路径可用带宽.通过算法优化,备份路径可以充分利用工作路径上的资源,降低带宽资源消耗,在保证网络提供连续服务能力的同时,提高网络资源的利用率,优化网络的运行性能.     

支持多故障恢复的MPLS快速重路由

分析了传统MPLS快速重路由应对多故障环境的不足,提出一种支持MPLS域并发多故障时快速恢复的重路由策略.通过有限洪泛故障信息,使本地修复的节点掌握有限范围内节点、链路的可用性信息,并通过建立主,从备份路径,保证MPLS层有效的恢复及较快的切换速度.理论分析及实验结果表明了该方法的可行性和有效性.     

基于MPLS的分布式快速重路由算法

在分析现有MPLS快速重路由算法基础上提出了一种分布式的MPLS快速重路由算法,并给出了算法描述.算法通过划分自治域并行预先建立备份路径,从而降低了原来算法中对整个拓扑预先建立备份路径的复杂度.仿真试验表明该算法在丢包率、重路由成功率上比现有算法有较好的性能.     

无线传感器网络中一种节省资源的快速重路由算法

因其特殊的需求和应用,无线自组传感器网络对信息采集、处理和传输等技术有着特殊的要求.基于选播路由策略,本文提出一种节省能耗和带宽资源的快速重路由算法(RFR)以应用于无线传感器网络的网络通信.使用选播技术,RFR算法可在原有有效传输路径基础上快速重路由,从而降低路由恢复时间,提高路由恢复成功概率.同时,算法通过限制参与重路由的节点数目,减少因重路由而消耗的能量和带宽资源,延长网络的生存周期,并提高网络性能.仿真算例验证RFR算法应用于无线传感器网络的有效性、较优性.     

MPLS VPN动态路径管理算法*

针对标签交换路径的设计与维护问题,提出基于故障恢复模型的MPLS VPN动态路径管理算法。该算法在备份路径设计准则的基础上,测试全连通MPLS VPN中备份路径可用性的条件,利用快速备份路径构造算法,在多故障发生时,自动地构造满足客户故障恢复需求的VPN路径,从而使VPN业务受干扰程度最小。     

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。     

一种基于MPLS网络的快速故障恢复算法

现有的MPLS故障恢复方案存在不同的性能问题:Makam方案需要提前建立备份路径,浪费了大量网络资源;简单动态方案动态建立备份路径,资源利用率高,但是需要等待路由表收敛,恢复时间长,造成大量丢包.针对这些不足,提出了一种基于MPLS网络的快速故障恢复算法MBFR.MBFR算法在故障发生以后建立备份路径,但是不需要等待路由表收敛,只需根据PIL中信源树和当前故障信息就可以快速计算出备份路径,既不浪费网络资源,又缩小了恢复时间.仿真实验结果验证了MBFR算法的优越性.     

基于MPLS网络的选播QoS路由算法

提出一种基于MPLS网络且保证QoS的选播路由算法。使用链路状态路由协议,找到一条从发出请求的客户到服务器方向上最小跳数的最优路径,该路径能满足选播服务带宽要求。使用度量为路径逆向(服务器到客户)上的链路带宽值,通过约束路由的标记分发协议,建立一条从服务器到客户方向的标记交换路径,并预留资源。仿真结果表明,在传输服务数据流时,该算法的时延及丢包率性能良好,能在一定程度上平衡服务器的负载。     

基于MPLS流量工程的重路由算法研究

概述了MPLS的流量工程和故障恢复机制。在区分服务网络环境中,描述了一种基于集中模型的多故障的重路由算法。采用以优先级属性划分LSP的策略,将带宽作为主要需求参数,满足了不同LSP的QoS要求。其实现是基于MPLS流量工程的约束路由的最优化方程。模拟示例分析验证了算法的可行性和优越性。     

基于CDMA-over-TDMA的多路带宽预留算法

讨论了在进行有QoS保证的路由选择的研究中所遇到的一些问题,并提出了一种新的带宽预留的路由选择算法MBR。MBR算法把路由选择分为两个阶段：路由发现和带宽预留。在路由发现阶段,算法首先寻找多条到达目的节点的路径,然后在带宽预留阶段,对寻找到的路径进行带宽预留,最后由目的节点决定使用哪些路径进行传输。由于MBR算法是采用同时寻找多条路径来进行带宽预留,因此它与其它带宽预留算法相比,具有更高的成功率。     

A New Fast Backup Method for Bidirectional Multicast Traffic in MPLS Networks: Control Plane Procedures and Evaluation by Simulations

Bidirectional multicast mechanisms are used to support multi-point to multi-point (MP2MP) traffic such as video-conferencing. These mechanisms are deployed today in multi-protocol label switching (MPLS) networks using the connectionless mode in which traffic engineering (TE) features such as bandwidth reservation and fast reroute in case of link and/or node failure are not defined. Indeed, TE procedures are defined in MPLS for unicast and multicast point-to-multipoint (P2MP) traffic only. Hence, MP2MP traffic that requires TE procedures is carried out using a full mesh of P2P or P2MP paths. Similarly, a full mesh of P2P and P2MP backup paths should be predefined in order to fast reroute traffic in case of a node failure. This leads to a major scalability problem since MPLS TE paths incur heavy overhead burden on MPLS nodes (CPU and memory). In this paper, we emphasize on fast reroute procedures using MP2MP TE paths. In particular, we define the control plane procedures that should be established. In addition, we present a simulation study that demonstrates the scalability amelioration when using MP2MP TE paths for fast rerouting instead of full mesh P2P and/or P2MP paths.     

PLR-based heuristic for backup path computation in MPLS networks

To ensure service continuity in networks, local protection pre-configuring the backup paths is preferred to global protection. Under the practical hypothesis of single physical failures in the network, the backup paths which protect against different logical failure risks (node, link and shared risk link group (SRLG)) cannot be active at the same time. Thus, sharing bandwidth between such backup paths is crucial to increase the bandwidth availability.In this article, we focus on the optimal on-line distributed computation of the bandwidth-guaranteed backup paths in MPLS networks. As the requests for connection establishment and release arrive dynamically without knowledge of future arrivals, we choose to use the on-line mode to avoid LSP reconfigurations. We also selected a distributed computation to offer scalability and decrease the LSP setup time. Finally, the optimization of bandwidth utilization can be achieved thanks to the flexibility of the path choice offered by MPLS and to the bandwidth sharing.For a good bandwidth sharing, the backup path computation entities (BPCEs) require the knowledge and maintenance of a great quantity of bandwidth information (e.g. non aggregated link information or per path information) which is undesirable in distributed environments. To get around this problem, we propose here a PLR (point of local repair)-based heuristic (PLRH) which aggregates and noticeably decreases the size of the bandwidth information advertised in the network while offering a high bandwidth sharing. PLRH permits an efficient computation of backup paths. It is scalable, easy to be deployed and balances equitably computations on the network nodes.Simulations show that with the transmission of a small quantity of aggregated information per link, the ratio of rejected backup paths is low and close to the optimum.     

A survey of IP and multiprotocol label switching fast reroute schemes

One of the desirable features of any network is its ability to keep services running despite a link or node failure. This ability is usually referred to as network resilience and has become a key demand from service providers. Resilient networks recover from a failure by repairing themselves automatically by diverting traffic from the failed part of the network to another portion of the network. This traffic diversion process should be fast enough to ensure that the interruption of service due to a link or node failure is either unnoticeable or as small as possible. The new path taken by a diverted traffic can be computed at the time a failure occurs through a procedure called rerouting. Alternatively the path can be computed before a failure occurs through a procedure called fast reroute. Much attention is currently being paid to fast reroute because service providers who are used to the 50-ms failure recovery time associated with SONET networks are demanding the same feature from IP and MPLS networks. While this requirement can easily be met in SONET because it operates at the physical layer, it is not easily met in IP and MPLS networks that operate above the physical layer. However, over the last few years, several schemes have been proposed for accomplishing 50-ms fast reroutes for IP and MPLS networks. The purpose of this paper is to provide a survey of the IP fast reroute and MPLS fast reroute schemes that have been proposed.     

Dynamic Path Management with Resilience Constraints under Multiple Link Failures in MPLS/GMPLS Networks

Most previous research on MPLS/GMPLS recovery management has focused on efficient routing or signaling methods from single failures. However, multiple simultaneous failures may occur in large-scale complex virtual paths of MPLS/GMPLS networks. In this paper, we present a dynamic MPLS/GMPLS path management strategy in which the path recovery mechanism can rapidly find an optimal backup path which satisfies the resilience constraints under multiple link failure occurrences. We derived the conditions to test the existence of resilience-guaranteed backup path, and developed a decomposition theorem and backup path construction algorithm for the fast restoration of resilience-guaranteed backup paths, for the primary path with an arbitrary configuration. Finally, simulation results are presented to evaluate the performance of the proposed approach.     

基于MPLS的带宽保证的N-to-1保护方法

提出了一个基于MPLS的带宽保证的N-to-1保护方法，它采用了基于约束的最短路径的选路思想，提出了动态和静态保护方案．该方案充分利用了MPLS所具有的ER-LSP和CR-LSP的优点，和MPLS特有的保护机制，具有重路由快，分组丢失率低，数据包逆序少的特点．它既能提供普通数据链路的保护，也适合用于VoIP和VOD传输的骨干链路．它能极大地提高传统IP网络的故障恢复能力．本文对算法的实现进行了详细的描述．并对所提出的算法进行了部分仿真．     

MPLS故障恢复机制及其仿真研究

对MPLS故障恢复机制进行了研究,分析了各种恢复机制在恢复时机、恢复拓扑、恢复效率、备份路径资源耗费等方面的性能.对NS2进行扩展,设计和实现了支持MPLS故障恢复机制的仿真组件,包括故障检测、故障通告和故障切换功能.故障恢复仿真组件提供了基本MPLS恢复能力,支持多种故障恢复机制,为深入研究MPLS故障恢复方法、优化MPLS恢复算法提供了试验平台.     

Using Shared Risk Link Groups to enhance backup path computation

To cope quickly with all types of failure risks (link, node and Shared Risk Link Group (SRLG)), each router detecting a failure on an outgoing interface activates locally all the backup paths protecting the primary paths which traverse the failed interface. With the observation that upon a SRLG failure, some active backup paths are inoperative and do not really participate to the recovery (since they do not receive any traffic flow), we propose a new algorithm (SRLG structure exploitation algorithm or SSEA) exploiting the SRLG structures to enhance the admission control and improve the protection rate.With our algorithm, more flexibility is provided for the backup path selection since a backup path which protects against the failure of a link belonging to a SRLG does not systematically bypass all the links of that SRLG. Moreover, our algorithm permits to save more bandwidth because it does not allocate the bandwidth for the inoperative backup paths even if they are activated.Simulations show that our algorithm SSEA decreases the ratio of rejected backup paths and, it reduces in distributed environments the average number of messages sent to manage the bandwidth information necessary for the backup path computation.