基于着色树优化的网络并发链路故障快速恢复方法

为了实现网络并发链路故障的快速恢复,提出一种基于改进人工鱼群算法着色树优化的故障快速恢复方法.首先从备份拓扑构造、着色树生成及流量转发三个方面分析整体恢复方案,在此基础上,建立着色树的生成模型并利用人工鱼群算法对其进行优化以进一步提高其性能,引入变异操作有效解决寻优陷入局部僵局的问题.仿真实验表明,该恢复方案不仅提高了网络在并发链路失效情况下的故障恢复能力,同时在恢复路径及路由备份方面也具有较强的性能.     

QoS路由中链路状态更新机制的研究

针对QOSPF中频繁洪泛而导致的通信开销过大问题，把组播有源树引入洪泛的链路状态更新中，利用链路状态更新中LSA的确认机制建立链路状态更新树，提出了FBLT方案和在部分链路失效情况下的IFBLT方案，并证明了FBLT和IFBLT方案相对于纯洪泛方式减少了链路状态更新造成的通信开销，在规模较大的网络中尤其明显。     

一种基于流聚合与拥塞避免的SDN快速故障恢复方案

针对主动式故障恢复方案会忽略备份路径的TCAM存储资源消耗和故障恢复后的拥塞问题，提出一种基于流聚合与拥塞避免的SDN快速故障恢复方案FACAR。FACAR是一种具有拥塞感知、低存储开销的主动式快速故障恢复方案，将通过同一链路的流视作一个或几个聚合流，并为这些聚合流提前配置保护路径。将FACAR方案形式化表示为一个整数线性规划问题，然后提出一种基于贪心的启发式算法ILP-FACAR以求解最少配置备份转发规则的数量。实验结果表明，FACAR可以满足单链路故障后的快速恢复需求，而且相比于其他故障恢复方法，FACAR可以保证在故障恢复后的网络中无链路拥塞问题，且大大减少了备份流规则的TCAM资源消耗。     

SpaceWire冗余网络故障检测恢复技术实现

为提高SapceWire网络可靠性,基于SpaceWire-D提出了一种应用于SpaceWire冗余网络的故障检测恢复技术。网络节点通过比较主、备份端口收到的时间码来判断链路故障状态,在确认主链路发生故障后,节点自动启用备份端口工作。通过引入时间码抖动容限参数,提高了节点对故障判断的准确性,避免了故障误判。测试结果表明,即使故障链路未与节点直接连接,节点也能够在一个时间槽长度内检测到链路故障并自动切换至备份链路。此技术保证了网络故障情况下的数据正确传输,提高了SpaceWire网络的可靠性,是一种稳定可靠的故障检测恢复技术。     

基于拥塞及内存感知的SD-WAN故障恢复

在软件定义广域网(SD-WAN)中, 链路故障会导致大量丢包, 严重时会引起部分网络瘫痪. 现有的流量工程方法通过在数据平面提前安装备份路径能够加快故障恢复过程, 但在资源受限的情况下难以适应各种网络故障情况, 从而使恢复后的网络性能下降. 为了保证网络在故障恢复之后的性能并减少备份资源的消耗, 本文提出一种基于拥塞及内存感知的主动式故障恢复方案(CAMA), 不仅能够将受影响数据流进行快速重定向, 还能实现负载均衡避免恢复后潜在的链路拥塞. 实验结果表明, 与已有方案相比, CAMA能有效利用备份资源, 在负载均衡上有较好的性能, 且仅需少量备份规则即可覆盖所有单链路故障情况.     

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。     

高校多出口网络下基于GRE隧道模式的链路虚拟备份策略路由研究

分析了目前高校教育科研网链路冗余备份方法的不足,利用现有高校多出口网络,通过使用GRE隧道模式建立一条虚拟冗余备份链路的方法,提出了一种校园网多出口网络下基于GRE隧道模式的链路虚拟冗余备份的路由策略方案。     

一种基于GEO/MEO星层组网的卫星网络抗毁路由研究

提出一种新的基于GEO/MEO星层组网的抗毁路由算法（DRRA）,基于分群管理、群首备份、链路冗余、链路修补的星座结构.在基于卫星移动的动态卫星网络中,在数据包路由抗毁、数据包路由最短延时等方面具有优势.这主要在于：①在充分考虑该卫星网络结构特点的基础上采用卫星分群管理和群首备份机制,以减少网络中冗余信息的流动和对特定中心节点的依赖;②在充分考虑卫星网络运行环境复杂与恶劣的基础上采用星间链路冗余、星间链路修补方案,以降低网络中星间链路失效和/或卫星节点失效对整个卫星网络通信性能的影响.     

E-2DMesh网络中链路失效模型的可靠性分析

提出了基于子网的E-2DMesh网络结构在存在链路故障情况下的状态转移模型。通过马尔科夫链过程建立了具有单向链路的E-2DMesh网络的可靠性模型,并分别对链路失效独立和链路失效相关条件下的网络可靠性进行了分析。运用概率分析的方法,通过组合模型计算出了较大规模的E-2DMesh网络的可靠性。通过对模型的仿真表明,链路失效相关时的网络可靠性要比链路失效独立时的网络可靠性低。     

基于关键网络状态的域内路由可用性研究

业界通常采用路由保护方案来提高域内路由可用性.然而已有的路由保护方案存在下面两个方面的问题:a)没有考虑网络中链路的失效概率,同等对待网络中所有的链路,事实上在互联网中,不同链路的失效概率是不同的,因此应该在路由保护方案中考虑链路的失效概率;b)将保护链路的数量作为设计目标,事实上方面某些链路出错的概率非常低,保护这些链路反而会增加开销,而另一方面某些链路出错的概率非常高,需要重点保护这些链路.因此应该将路由可用性作为路由保护方案的设计目标.针对上述两个问题,提出了一种基于关键网络状态的域内路由保护方案(RPBCNS),该算法首先通过链路失效概率计算出所有的关键网络状态,然后在每种关键网络状态下计算节点对之间相应的路径,保证节点对之间路径的多样性,从而使得尽可能多的节点对满足路由可用性需求.仿真实验将RPBCNS算法与主流算法ECMP、DC、path splicing分别在三个真实网络中进行对比,在网络可用性和节点对可用性满足率上RPBCNS的性能明显优于其他三种算法.仿真结果表明,RP-BCNS不仅具有较高的网络可用性,并且能够使得尽可能多的节点对满足路由可用性目标,更符合实时应用的实际需求.     

Comparison of two path restoration schemes in self-healing networks

The state-independent (SI) and state-dependent (SD) path restoration schemes for self-healing networks are studied in this paper. The integer programming (IP) formulations for the spare capacity allocation and restoration flow assignment are first presented. Based on the optimal IP solutions, the SI and SD restoration schemes are then compared quantitatively in terms of spare capacity requirement (SCR), restoration time, VPI (virtual path identifier) redundancy (in ATM) and nodal storage capacity requirement. The comparison is based on spare optimization, single link failure scenario and 100% restoration. The SCR is also compared under single node failure scenario. It is observed that using group VP (virtual path) restoration (for either SI or SD) can substantially reduce the restoration time with only a small increase in spare capacity cost. Further, the SI restoration seems better than the SD restoration for the cases we have studied, at least in spare optimization, as its implementation is relatively easier and the difference in SCR between SI and SD is not significant. The economies of scale in transmission facility cost is also investigated in the paper.     

An improved scheme for self-healing in ATM networks

Broadband networks based on ATM technology can carry a large volume of data and can support diverse services like audio, video, and data uniformly. The reliability and availability levels provided by such networks should be very high. Self-healing is an elegant concept in this direction to provide highly reliable networks. A self-healing network can detect failures such as link/node failures and reroute the failed connections automatically using distributed control mechanisms. In this paper, we consider link and node failures including the VP terminating nodes unlike Kawamura and Tokizawa (Self-healing in ATM networks based on virtual path concept, IEEE Journal on Selected Areas in Communications 12 (1) (1994) 120–127). We present here an improved scheme for self-healing in ATM networks based on the concept of backup VPs. The problems we address are: (i) self-healing scheme; and (ii) backup VP routing. Two issues are addressed in the self-healing scheme: (i) backup VP activation protocol; and (ii) dynamic backup VP routing. We propose a new backup VP activation protocol which uses a VC packing strategy which allows the fast and prioritized restoration of critical VCs that were carried by failed VPs. We also propose a distributed dynamic backup VP routing algorithm which reduces the resource contention that may occur when multiple source–destination pairs contend for the routes simultaneously. The objective of the backup VP routing problem is to find a backup VP for each of the working VPs so that the cost of providing the backup is minimized. We propose a heuristic based solution for the backup VP routing problem using the concept of minimum cost shortest paths. We conducted simulation experiments to evaluate the performance of the proposed schemes. The results show that the proposed schemes are effective. Comparison of the results with those of the earlier schemes (R. Kawamura, I. Tokizawa, Self-healing in ATM networks based on virtual path concept, IEEE Journal on Selected Areas in Communications 12 (1) (1994) 120–127; C.J. Hou, Design of a fast restoration mechanism for virtual path-based ATM networks, Proceedings of IEEE INFOCOM’97, Kobe, Japan, April 1997) shows that the proposed schemes perform better.     

ATM网络中基于VC、VP层的综合恢复框架

生存性是当前ATM网络中亟待解决的问题。文章针对目前恢复机制的缺点,提出了基于VC、VP层的综合恢复框架。在该框架下引入生存重要性加权恢复率,来表征各种不同服务要求下网络的生存性;提出了三种新的综合恢复机制,分析了各种恢复机制的适用条件。模拟结果显示该框架能够灵活地提供关键服务的优先恢复,有效地提高了整个网络的生存能力。     

网络化控制系统改进事件触发机制与L∞控制协同设计研究

文章研究了网络诱导延时和外部干扰约束下,网络化控制系统的改进事件触发机制与 控制协同设计策略。为了克服相对(绝对)事件触发机制在系统接近(远离)平衡点运行时数据发送率较高的局限,文章提出了综合利用状态相关信息和状态无关信息的改进事件触发机制,其能够在系统整体运行期间获得较低数据发送率。然后,建立了同时刻画事件触发机制和网络诱导延时影响的闭环时滞系统模型,得到了系统最终有界稳定的充分条件,给出了事件触发机制与控制器的协同设计方法,比要求控制器预先给定的两步设计方法更方便。最后,仿真验证了所提方法的有效性。     

Oracle数据库恢复管理器研究及应用

介绍了ORACLE数据库恢复管理器的功能特点及进行数据库备份恢复的过程，探讨了RMAN备份恢复机理，以及如何应用到实际系统中，提高了数据库备份恢复有效性，优化数据库性能，加强了整个计算机应用系统的可靠性，     

基于与状态无关的激活集的包含派生谓词的规划问题求解

派生谓词是PDDL2．2语言的新特性之一。在2004年的规划大赛IPC-4上，许多规划系统都无法求解包含派生谓词的两个标准竞赛问题。在经典规划中，派生谓词是指不受领域动作直接影响的谓词，它们在当前状态下的真值是在封闭世界假设中由某些基本谓词通过领域公理推导出来的。本文提出一种新的方法来求解包含派生谓词的规划问题，即用与状态无关的激活集来取代派生谓词用于放宽式规划中。     

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。     

State-independent uncertainty relations and entanglement detection

The uncertainty relation is one of the key ingredients of quantum theory. Despite the great efforts devoted to this subject, most of the variance-based uncertainty relations are state-dependent and suffering from the triviality problem of zero lower bounds. Here we develop a method to get uncertainty relations with state-independent lower bounds. The method works by exploring the eigenvalues of a Hermitian matrix composed by Bloch vectors of incompatible observables and is applicable for both pure and mixed states and for arbitrary number of N-dimensional observables. The uncertainty relation for the incompatible observables can be explained by geometric relations related to the parallel postulate and the inequalities in Horn’s conjecture on Hermitian matrix sum. Practical entanglement criteria are also presented based on the derived uncertainty relations.     

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.     

A Kushner approach for small random perturbations of the Duffing-van der Pol system

The stochastic version of the Duffing-van der Pol system (SDvdP), which assumes the structure of a non-linear stochastic differential equation, is an appealing and a standard case from the stochastic systems’ point of view, since it involves linear and non-linear vector fields, i.e. system non-linearities, state-independent and state-dependent stochastic accelerations. This paper discusses and explores the efficacy of three non-linear filters, which are developed using the Kushner equation, for the stochastic differential system of concern here. This paper introduces the notion of a qualitative analysis to decide a structure of the observation equation for non-linear stochastic filtering as well.