一种域间效能优先的二阶段控制器均衡部署策略

当前的软件定义网络多控制器部署问题研究，大多针对控制网络中面向南向接口的控制域内时延、可靠性和负载均衡等指标进行优化，而对面向东西向接口的控制网络域间时延以及控制器本身的可靠性统筹考虑较少。然而，东西向接口中控制网络域间时延和控制器可靠性等因素对网络域间信息传输效率和服务质量有着关键影响。针对该问题，首先分析了控制器域间效能对软件定义网络整体性能及相关因素的影响；其次，建立了以域间平均时延、域内平均时延、控制器可靠性度量、控制路径可靠性和负载均衡度为参数，以控制器域间效能和控制网络综合性能为目标的控制器部署优化评价模型；最后，采用反向学习机制对标准麻雀搜索算法进行改进，提出一种域间效能优先的二阶段控制器部署策略，在确保控制器域间效能最大的情况下，增强了解空间的全局搜索能力，得出了控制器部署的全局非劣最优解集。仿真结果表明，所提的部署策略既有效降低了软件定义网络的控制时延，也增强了控制网络的可靠性，在保证软件定义网络域间效能的情况下，对网络整体性能表现具有较为明显的提升作用。     

容错计算机网络综合可用性建模与仿真分析

在充分分析现有UMS容错计算机网络可靠性分析技术的基础上,针对容错计算机网络可靠性分析中存在的问题,从容错网络系统的特点出发,对计算机网络系统的典型的容错设备可用性建模、网络流量对网络可用性的影响、计算机网络综合可用性评价进行了研究。在容错计算机网络设备可用性建模的过程中,首先分析了软硬件故障相关性系统的特点,采用基于随机Petri网的可靠性分析方法解决了复杂设备难以进行可靠性建模的问题。通过分析影响网络可用性的因素,建立了基于网络性能的综合可用性模型,与现有的网络可靠性评价指标相比,其评价指标反映的信息更加的全面和科学。这对于建设高可用性网络具有较大的指导意义。     

随机供求下的道路服务水平可靠性

目前对路网可靠性的研究主要集中在连通可靠性、行程时间可靠性和容量可靠性三个方面,但这些可靠性指标均不能综合反映路网的性能.为此本文从交通供给和交通需求随机性分析入手,借鉴可靠性理论,从出行者个体和网络管理者的角度出发,提出了服务水平可靠性的概念,拓展了现有的路网可靠性评价指标.通过将路段容量和交通需求简化为离散随机变量,基于路网最可能状态生成算法,建立了路段及路网服务水平可靠性计算的近似算法,最后在一简单网络上进行了计算分析.     

高可靠性软件定义航空光信息网络的控制器分布优化策略

针对未来航空光信息网络中控制平面的可扩展性问题,基于软件定义网络思想,提出了软件定义航空光信息网络的网络架构,研究了软件定义航空光信息网络控制器部署策略。以网络节点及链路中断概率为参量,以航空网络的全网可靠性为优化目标,建立基于网络可靠性的整数规划模型;提出融合人工免疫策略、小生境思想和改进遗传算法的混合优化算法,获得控制器部署的最佳部署方案。仿真结果表明,基于可靠性的整数规划模型可实现对软件定义航空信息网络中的控制器部署问题准确建模,为实现控制器最优化部署提供了依据。     

蒙特卡罗方法在网络性能仿真中的应用

在节点和链路不可靠的复杂情况下,为了对网络性能进行有效评估,将蒙特卡罗(MC)方法引入网络可靠性模型求解,获得了较边界法更准确的结果.其优点在于只要得出部分网络常量,就可直接为网络可靠性计算提供基础,即使极端情况下该方法也能获得网络可靠性的紧致上下界(即剩余连通可靠度).仿真结果表明了方法的有效性,且评估概率的相对误差很小.     

无人机集群系统弹性研究

为提升无人机集群(unmanned aerial vehicle swarm, UAVS)应对恶劣天气、人为干扰、组件故障等扰动的能力,借鉴复杂网络弹性理念,对UAVS扰动场景进行建模，提出了UAVS弹性的概念与内涵,通过与鲁棒性、可靠性、抗毁性等指标对比,阐述了弹性指标对于研究UAVS系统特性的意义;分析UAVS性能变化曲线和选取指标,刻画了弹性定量指标,从而提出了UAVS系统弹性评估方法;从吸收扰动和恢复两方面,提出了UAVS系统弹性的优化策略。最后,展望UAVS系统弹性未来研究的发展趋势。     

基于加速退化数据的可靠性评估技术综述

随着加速退化试验技术的不断进步,加速退化数据日趋复杂,可靠性评估理论和方法需要不断完善和发展。可靠性建模与统计分析是可靠性评估的两大核心问题,从这两方面对基于加速退化数据的可靠性评估技术进行综述,重点阐述了性能退化建模、加速退化建模、失效机理一致性辨识等关键问题,提炼了基于加速因子不变原则进行加速退化数据可靠性评估的新思路,展望了未来的研究重点和发展前景。研究工作对完善加速退化数据可靠性评估理论和方法,提高评估准确性具有一定的指导意义。     

通信网络可靠性指标的新定义及计算方法

为了从网络的宏观角度更全面地评估通信可靠性能,新定义了一套把网络拓扑连通性与传输容量有机地综合在一起的通信网可靠性指标———归一化容量加权可靠性指标,并从网络设计的主观和客观角度以及兼容传统指标等方面阐述了新定义指标的合理性与全面性。为了利于用新指标分析实际问题,研究出一套新指标的计算方法。从路由寻找到不交化网络状态及其对应容量的计算,所有运算过程都实现了易于程序化分析的代数化计算,并论证了算法每个环节的正确性。通过典型算例详述了新指标的计算方法,并以新指标作为参考扼要地介绍了提高网络可靠性方法。     

网络安全研究中的建模环境分析与实现

提出网络建模环境的形式化描述,据此将网络模型划分为三种虚拟度,并结合网络安全研究特点提出了具备三种虚拟度的高保真建模概念。在网络模拟器NS2基础上实现了一个原型系统,并阐述和分析了其结构、实现与性能,还给出一个支持真实攻击包的蠕虫模型实例。最后分别对若干问题和未来工作进行了总结与展望。     

面向软件定义航空集群机载网络的更新策略

软件定义网络（software-defined networking，SDN）的出现为突破机载网络在航空集群作战应用背景下存在的性能瓶颈提供了全新的思路。针对航空集群机载网络的更新问题，提出适用于软件定义架构下航空集群机载网络的更新策略——可靠性增强的两阶段提交更新策略（reliability-enhenced two-phase commit，RE-TPC）。首先设计最高可靠性算法以及多路径算法搜索下发指令消息的高可靠路径。然后引入基于ACK（acknowledge）消息的确认机制和ACK消息高效融合传输机制，进一步提升网络更新过程的可靠性和实时性。仿真结果表明，与已有经典网络更新策略相比，所提更新策略能够有效提高更新的可靠性，同时更新持续时间更低、开销更小。     

覆盖网对域间路由可靠性的影响研究

覆盖网可以利用终端间的多路径路由提升Internet路由的性能和可靠性。如何选取高质量的覆盖网路径,并且准确地对其进行性能评估是有待解决的核心问题。对此,首先提出一种对覆盖网路由的评估方法,该方法从路由可靠性角度进行分析,运用可靠度(RD)这一指标,从多条覆盖网路径的分离度、长度、质量等方面进行综合评估。在此基础上,提出基于广度优先遍历队列(BFSQ)的分布式的启发式算法优化覆盖网多路径的选择。仿真结果表明该算法可以通过少量底层拓扑信息的获取,达到有效提升多路径覆盖网路由可靠性及性能的目的。     

System reliability of assured accuracy rate for multi-state computer networks from service level agreements viewpoint

From the viewpoint of service level agreements, the transmission accuracy rate is one of critical performance indicators to assess internet quality for system managers and customers. Under the assumption that each arc＇s capacity is deterministic, the quickest path problem is to find a path sending a specific of data such that the transmission time is minimized. However, in many real-life networks such as computer networks, each arc has stochastic capacity, lead time and accuracy rate. Such a network is named a multi-state computer network. Under both assured accuracy rate and time constraints, we extend the quickest path problem to compute the probability that d units of data can be sent through multiple minimal paths simultaneously. Such a probability named system reliability is a performance indicator to provide to managers for understanding the ability of system and improvement. An efficient algorithm is proposed to evaluate the system reliability in terms of the approach of minimal paths.     

基于拓扑的不相交路径抗毁性评估方法

为了能够定量地计算出通信网络的抗毁性,以网状全连通网络作为参考基准,定义了基于拓扑的不相交路径抗毁性评估指标,以及节点和链路重要性评估指标,并配套研究了不相交路径的计算方法。计算被考核网络与全连通网络节点间不相交路径数的比重,得到抗毁性指标。通过计算各节点及链路失效后抗毁性变化的大小,得到网络元素重要性评估指标。阐述了计算方法的正确性,并给出时间及空间复杂度。通过算例分析并且与基于最短路径的评估方法进行对比,论证了不相交路径抗毁性评估指标和计算方法更加合理,更能体现出实际通信网络性能。     

网络系统可靠度的BDD算法

ＢＤＤ是布尔函数的图形表示形式。提出了采用ＢＤＤ方法求解网络系统的不交化最小路集,从而直接计算网络系统的可靠度。算法为网络系统的可靠性分析提供了一种新的途径。最后给出了一个算例。     

Performance Improvement of NCSs Under Complex Network via Concurrent Paths

Different from the single paths between controllers and plants of networked control systems(NCSs), the complex network provides widespread links and brings plenty of paths from the controller side to the plant side. Benefit from this advantage, a novel data transmission dispatching strategy is proposed. When the direct path can not satisfy the condition of system demand, neither stability nor performance, some specified paths compose a concurrent-path to transmit the control signal concurrently. Firstly, the networked control systems(NCSs) are expressed by the switched systems model with the constant network-induced delay, and the network communication is described as a packet-loss process. Secondly, taking system's exponential decay rate as its performance indicator, the relationship between control signal transmission paths and system performance is quantitatively given by considering packet losses as the compound poisson process and the alternating renewal process. Then, due to that different combination of paths induces the different statistical properties of packet losses, the approach to find an appropriate concurrent-path is proposed concerning two mutually constrained factors, the system performance demand and the utilization of network resources. After the theoretical analysis, a distributed communication platform based on peer-to-peer(P2P) network technology is designed and implemented to realize the concurrent-path transmission on internet. Finally, the practical experiment on the platform demonstrates the validity and effectiveness of proposed approach.     

Estimated and exact system reliabilities of a maintainable computer network

This paper presents an algorithm to evaluate estimated and exact system reliabilities for a computer network in the cloud computing environment. From the quality of service (QOS) viewpoint, the computer network should be maintained when falling to a specific state such that it cannot afford enough capacity to satisfy demand. Moreover, the transmission time should be concerned as well. Thus, the data can be sent through several disjoint minimal paths simultaneously to shorten the transmission time. Under the maintenance budget B and time constraint T, we evaluate the system reliability that d units of data can be sent from the cloud to the client through multiple paths. Two procedures are integrated in the proposed algorithm-an estimation procedure for estimated system reliability and an adjusting procedure utilizing the branch-and-bound approach for exact system reliability. Subsequently, the estimated system reliability with lower bound and upper bound, and exact system reliability are computed by applying the recursive sum of disjoint products (RSDP) algorithm.     

基于有效状态空间的多状态网络可靠性评估

鉴于应用d-最小割(路)集计算多状态网络可靠度精确值的算法中基于最小割(路)集求解d-最小割(路)集及容斥原理的复杂性,提出一种不需要d-最小割(路)集计算网络可靠度精确值的算法.该算法按一定规则分割状态空间,在此基础上生成有效状态空间,通过迭代计算直接获得可靠度精确值;同时通过删除边的无效状态、对最小割集进行分组,有效减小计算量;通过有序树执行该算法简单、易操作.实例表明算法的计算结果是正确的,且计算量较小,证明了其正确性和有效性,但同时也表明算法所需存储空间较大.     

Shortest Path Routing Algorithm Based on Chaotic Neural Network

A shortest path routing algorithm based on transient chaotic neural network is proposed in this paper. Gam-pared with previous models adopting Hopfield neural network, this algorithm has a higher ability to overcome the local minimum, and achieves a better performance. By introducing a special post-processing technique for the output matrixes, our algorithm can obtain an optimal solution with a high probability even for the paths that need more hops in large-size networks.     

Application reliability for communication networks and its analysis method

The network reliability is difficult to be evaluated because of the complex relationship among the network components.It can be quite different for different users running different applications on the same network.This paper proposes a new concept and a model of application reliability.Different from the existing models that ignores the effects of applications,the proposed application reliability model considers the effects of different applications on the network performance and different types of network faults and makes the analysis of network components relationship possible.This paper also provides a method to evaluate the application reliability when the data flow satisfies Markov properties.Finally,a case study is presented to illustrate the proposed network reliability model and the analysis method.     

有限需求量的网络路径优选研究

“有限需求量的网络路径优选”是一种比较特殊的费用流问题。本文描述并分析有限需求量的网络路径优选问题,建立路径优选的最短时间非线性模型,该模型考虑把物资发送到相应路径的时间。在有限需求条件下,给出n条独立路径的优选定理。借助于该定理和最小费用最大流算法,提出有限需求量的网络路径优选算法,并用示例作算法验证。