Byzantine agreement in the presence of mixed faults on processorsand links

In early stage, the Byzantine agreement (BA) problem was studied with single faults on processors in either a fully connected network or a nonfully connected network. Subsequently, the single fault assumption was extended to mixed faults (also referred to as hybrid fault model) on processors. For the case of both processor and link failures, the problem has been examined in a fully connected network with a single faulty type, namely an arbitrary fault. To release the limitations of a fully connected network and a single faulty type, the problem is reconsidered in a general network. The processors and links in such a network can both be subjected to different types of fault simultaneously. The proposed protocol uses the minimum number of message exchanges and can tolerate the maximum number of allowable faulty components to make each fault-free processor reach an agreement     

一种基于无效链路的分布式故障诊断一致性协议

故障诊断一致性(fault diagnosis agreement,FDA)是高可靠容错分布式系统的性能和完整性的重要保障.目前,大部分FDA协议还是只考虑单一故障组件的简单网络,而对于实际的分布式应用、故障节点和故障链路并存的系统假设更加有意义.但是,在此假设下,对恶意(拜占庭故障)组件的诊断是不可能满足FDA的.为此,首先提出了一种无效链路(invalid link)故障模型,可以更加准确地描述恶意组件的故障行为对系统的影响,有效提高故障诊断的覆盖率.在此模型基础上,提出了一个基于证据的故障诊断协议--PLFDA,可以同时对恶意节点和恶意链路进行检测和定位,并且能够满足故障诊断一致性要求.     

Minimum cost multiple multicast network coding with quantized rates

In this paper, we consider multiple multicast sessions with intra-session network coding where rates over all links are integer multiples of a basic rate. Although having quantized rates over communication links is quite common, conventional minimum cost network coding problem cannot generally result in quantized solutions. In this research, the problem of finding minimum cost transmission for multiple multicast sessions with network coding is addressed. It is assumed that the rate of coded packet injection at every link of each session takes quantized values. First, this problem is formulated as a mixed integer linear programming problem, and then it is proved that this problem is strongly NP-hard on general graphs. In order to obtain an exact solution for the problem, an effective and efficient scheme based on Benders decomposition is developed. Using this scheme the problem is decomposed into a master integer programming problem and several linear programming sub-problems. The efficiency of the proposed scheme is subsequently evaluated by numerical results on random networks.     

The incremental agreement

To achieve reliable distributed systems, the fault-tolerance must be studied. One of the most important problems of fault-tolerance issues lies in the Byzantine Agreement (BA) problem. The primary issue surrounding BA is that fault-free processors must obtain common agreement even in cases where faults persist. In this field, the fault diagnosis protocol has been proposed so that each fault-free processor detects/locates a common set of faulty processors. However, in this study, the incremental agreement is invoked to make each processor able to agreement upon executing the fault diagnosis protocol using minimal rounds of message exchange in the presence of dual failure characteristics of processors.     

Human-like fault diagnosis using a neural network implementation of plausibility and relevance

In real systems, fault diagnosis is performed by a human diagnostician, and it encounters complex knowledge associations, both for normal and faulty behaviour of the target system. The human diagnostician relies on deep knowledge about the structure and the behaviour of the system, along with shallow knowledge on fault-to-manifestation patterns acquired from practice. This paper proposes a general approach to embed deep and shallow knowledge in neural network models for fault diagnosis by abduction, using neural sites for logical aggregation of manifestations and faults. All types of abduction problems were considered. The abduction proceeds by plausibility and relevance criteria multiply applied. The neural network implements plausibility by feed-forward links between manifestations and faults, and relevance by competition links between faults. Abduction by plausibility and relevance is also used for decision on the next best test along the diagnostic refinement. A case study on an installation in a rolling mill plant is presented.     

基于双线性对的卫星网络密钥协商协议

提出一种基于双线性对的卫星网络密钥协商协议,分析卫星网络的特点,给出协议实现过程。对协议的安全性分析表明,该协议不存在密钥托管问题,能抵御主动攻击,会话密钥协商满足不可控性。对协议的性能分析表明,该协议能提高会话密钥协商效率,满足实际的卫星网络密钥协商需求。     

Calibrating embedded protocols on asynchronous systems

Embedding is a method of projecting one topology into another. In one-to-one node embedding, paths in the target topology correspond to links in the original topology. A protocol running on the original topology can be modified to be executed on a target topology by means of embedding. However, if the protocol is tolerant to a number of faults - faults that affect the data but not the code of a distributed protocol executed by the nodes in a distributed systems - then the adapted protocol will not have the fault tolerance property preserved, due to the fact that links in the original topology can be embedded into paths of length greater than one: faults at the intermediate nodes on such paths are not accounted for in the protocol. We propose a communication protocol in the target topology that preserves the fault tolerance characteristics of any protocol designed for the original topology, namely by our mechanism the modification preserves fault tolerance.     

Grouping Byzantine Agreement

The reliability of the distributed system has always been an important topic of research. Byzantine Agreement (BA) protocol, which allows the fault-free processors to agree on a common value, is one of the most fundamental problems studied in a distributed system. In previous works, the problem was visited in a fully connected network or an unfully connected network with fallible processors. In this paper, the BA problem is reexamined in a group-oriented network, which has the feature of grouping, and the network topology does not have to be fully connected. We also enlarge the fault tolerant capability by allowing dormant faults and malicious faults (also called as the dual failure mode) to exist in a group-oriented network simultaneously. The proposed protocol is more efficient than the traditional BA protocols and can tolerate the maximum number of tolerable faulty processors.     

Fault detection and accommodation of a class of nonlinear systems with unknown multiple time-delayed faults

This paper investigates a fault detection and accommodation (FDA) problem of a class of nonlinear time-delay systems in the presence of unknown multiple time-delayed faults. Compared with existing literature, a main contribution of this paper is to design a time-delay independent FDA scheme, namely, the exact information on time delays is not required to implement the proposed FDA scheme. Under the assumption that the magnitude and occurrence time of multiple faults are unknown, we first design a delay-independent fault detection scheme with a detection threshold for time-delay systems and analyze the fault detectability. Then, an approximation-based fault accommodation design activated after the detection of the first fault is presented for compensating multiple faults. The robustness of the fault detection scheme and asymptotic stability of the tracking error are established through Lyapunov stability analysis. A simulation example is used to illustrate the proposed FDA scheme.     

MPLS流量工程仿真

在通信网络中,负载不均衡或部分网络失效常常会引起网络拥塞问题,导致业务的服务质量下降.相对于传统的动态路由协议解决此类问题所具有的局限性,MPLS流量工程是解决问题的一种有效途径.在计算机网络仿真平台上,设计了动态路由协议和MPLS流量工程仿真实例,通过运行仿真,获取了它们的网络性能及业务服务质量数据.通过对仿真结果进行比较和分析,可以看出,MPLS流量工程通过更为灵活的方式在多条链路上实现负载分担,可以改进网络资源利用率,当链路或节点失效时,能够提供快速的恢复机制.     

Hybrid Control for Connectivity Preserving Flocking

In this technical note, we address the combined problem of motion and network topology control in a group of mobile agents with common objective the flocking behavior of the group. Instead of assuming network connectivity, we enforce it by means of distributed topology control that decides on both deletion and creation of communication links between agents, adapting the network to the group's spatial distribution. With this protocol ensuring network connectivity, a decentralized motion controller aligns agent velocity vectors and regulates inter-agent distances to maintain existing network links. The stability of the flocking controller is established in continuous time by means of an observability argument on a quadratic form of the graph Laplacian that exploits the time delay between link deletion and creation caused by the topology control protocol, which induces a dwell time between network switches.      

一个适于结构健康监测的WSN能量高效动态路由协议一个适于结构健康监测的WSN能量高效动态路由协议

针对结构健康监测无线传感器网络应用中,网络生命期不足的问题,提出一种低占空比网络下能量高效动态路由协议EEDRP(Energy Efficient Dynamic Routing Protocol),该协议利用邻居节点剩余能量和链路质量动态确定转发集,通过基于转发集活动时隙预测的数据包重传机制,解决了因链路不可靠导致数据传输失败问题.最后,通过仿真对协议进行了验证,结果表明:该协议在保证数据收集低延迟和可靠性前提下,有效延长了网络生命期,满足结构健康监测应用要求.     

一种轻量级基于证书的认证密钥协商方案

认证密钥协议对于在公共网络上安全通信至关重要,它使通信方能够在恶意攻击者当前安全地设置共享会话密钥.基于证书的密码学(CBC)很好地解决了传统公钥密码体制中的证书撤销问题、基于身份的密码体制中的密钥托管问题和无证书密码体制中安全信道建立困难问题.现有的基于证书认证密钥协商方案大多都采用了昂贵的双线性配对,不适合计算资源有限的移动设备.本文设计了一种轻量级的基于证书的AKA协议,该协议用假名技术实现用户身份匿名.该协议提供了前向保密,抵抗中间人攻击,重放攻击等安全性分析.与以往基于证书的AKA协议相比,该协议在计算效率上具有明显的优势.     

移动自组网中跨域两方认证密钥协商协议研究

针对基于身份的移动自组网认证密钥协商协议中,会话两方属于不同私钥生成中心（PKG）的情况,利用双线性对的性质和椭圆曲线离散对数问题,提出了一种跨域两方认证密钥协商协议,并采用应用pi演算和ProVerif自动化验证工具对其安全属性进行形式化分析。分析结果表明,提出的协议实现了保密性、身份认证性以及密钥一致性确认,同时又具有较好的性能,非常适用于资源有限的移动自组网。     

基于故障传播模型与监督学习的电力通信网络故障定位

针对电力通信网络中的故障定位问题,分析了一种网络设备或链路故障引发的大范围连通片故障告警情形,提出一种基于故障传播模型和监督分类学习方法的故障定位算法。首先使用改进的故障传播模型求得初步定位结果,用最少的故障数目解释当前告警;然后通过故障源-故障告警向量分解将故障定位问题转化为监督分类问题,定位告警区域内部故障;最后加入猜测的故障设备和故障链路完善定位结果以提高定位准确率。模拟结果表明提出的故障定位算法的故障检测率达到84%~95%,具有较高的故障定位可靠性。     

高速因特网中含卫星单向链路的路由研究

由于多数卫星地面站只具有接收能力而形成了单向链路,无法应用现有的路由协议.为了解决含有卫星单向链路的路由问题,首先针对卫星直播系统的拓扑结构建立了网络模型,并在简化模型的基础上提出了基于环路发现的链路状态路由算法和一种基于服务器的协议--SERP(sever-based routing protocol).通过证明路由算法的收敛性,并利用Network Simulator工具对协议进行仿真的结果,得出SERP的正确性和具有协议开销小的特点,可用以支持在高速因特网中集成宽带卫星网络的动态路由.     

正则化FDA的核化及与SVM的比较研究*

无论是Fisher判别分析（FDA）还是基于核的FDA（KFDA）,在小样本情况下都会面临矩阵的病态问题,正则化技术是解决该问题的有效途径。为了便于研究正则化FDA与支持向量机（SVM）的关系,推导了一种正则化FDA的核化算法。将约束优化问题转换为对偶的优化问题,得到了与SVM相似的形式,分析了该核化算法与SVM的联系。针对Tenessee-Eastman(TE)过程的故障诊断结果表明,正则化KFDA的诊断效果明显好于LS-SVM。     

The anatomy study of consensus agreement in MANETs

Reliability is an important research topic of distributed systems. To achieve fault-tolerance in the distributed systems, healthy processors need to reach a common agreement before performing certain special tasks, even if faults exist in many circumstances. This problem is called as the Byzantine Agreement (BA) problem and it must be addressed. In general, the traditional BA problem is solved in well-defined networks. However, the MANETs (Mobile Ad-hoc Network) are increasing in popularity and its network topology is dynamic in nature. In this paper, the BA problem is re-examined in MANETs. Our protocol uses the minimum number of message exchanges to reach an agreement within the distributed system while tolerating the maximum number of faulty processors in MANETs.     

A new solution for the Byzantine agreement problem

Reliability is an important research topic in distributed computing systems consisting of a large number of processors. To achieve reliability, the fault-tolerance scheme of the distributed computing system must be revised. This kind of problem is known as a Byzantine agreement (BA) problem. It requires all fault-free processors to agree on a common value, even if some components are corrupt. Consequently, there have been significant studies of this agreement problem in distributed systems. However, the traditional BA protocols focus on running ⌊(n−1)/3⌋+1 rounds of message exchange continuously to make each fault-free processor reach an agreement. In other words, since having a large number of messages results in a large protocol overhead, those protocols are inefficient and unreasonable, especially for some network environments which have large number of processors. In this study, we propose a novel and efficient protocol to reduce the number of messages. Our protocol can collect, compare and replace the received values to find the reliable processors and replace the values sent by the unreliable processors. Subsequently, each processor can agree on a common value through three rounds of message exchange. Furthermore, the proposed protocol can use the minimum number of messages to tolerate the maximum number of faulty components in a distributed system.     

Ad Hoc网络中一种组密钥协商协议

移动Ad Hoc网络是一种新型的移动多跳无线网络。在网络中构建组密钥协商协议时应尽量减少节点的资源开销。该文提出一种新的多层组密钥协商协议,MTKA-ECC协议。该协议在多层组模型结构上,采用椭圆曲线密码体制实施密钥协商和分配,使得节点在密钥协商过程中具有低计算开销与低通信开销的优势。与GDH, TGDH组密钥协商协议相比,该协议有效地降低了节点在密钥协商过程中的计算和通信开销,适用于移动Ad Hoc网络。