生存能力技术及其实现案例研究

生存能力技术谋求增强系统在面临攻击、失效等灾难情况下仍能继续提供服务的能力。本文提出了以多样化分布式动态备份技术和主动漂移机制为手段，以被保护目标的机动性和隐蔽性为目的的生存能力技术模型。提出了多样化体系理论及其实现案例，基于该理论设计并实现了自适应TOM方法。最后通过模拟和测试探讨了生存能力的评价方法，并验证了本文的结果。     

Integrated Survivability Strategies of IP／GMPLS／Opticai Multi——layer Network

In last decade,due to that the popularity of the internet, data--central traffic kept growing, some emerging networking requirements have been posed on the today‘s telecommunication networks,especially in the area of network survivability. Obviously, as a key networking problem, network reliability will be more and more important. The integration of different technologies such as ATM, SDH, and WDM in multilayer transport networks raises many questions regarding the coordination of the individual network layers.This problem is referred as multilayer network survivability. The integrated multilayer network survivability is investingated as well as the representation of an interworking strategy between different single layer survivability schemes in IP via generalized multiprotocol label switching over ootical netwnrk     

近年西方国家通信网发展动态

首先说明西方国家通信网近年发展变迁情况，然后对IP与WDM的结合使用、光数据网的发展、密集波分多路的应用和光网中通路的保护4个主要方面作了具体说明。     

基于本地缓存的弹性分组环保护机制

本文提出一种基于本地缓存的弹性分组环保护倒换机制(WrapProtectionBasedOnLocalBuffers,简称WP-LB)。其主要思想是当环路上任何位于源节点和故障区域之间的中间节点接收到含有故障信息的控制信令后,就不再向下游转发数据分组,而是在本地缓存这些数据。等到保护通路建立好之后,再把缓存的数据分组经过保护通路发送给目的节点。分析计算表明,与原有的保护倒换(WrapProtection,简称WP)机制相比,WP-LB机制不仅提高带宽利用率,减少平均时延,并且还能避免数据包的丢失和失序。     

求通信网生存能力的一种分裂二叉树算法

本文研究了布尔代数方法在通信网生存能力分析中的应用，提出了一种求布尔代数式不交化变换的分裂二叉树算法，与现有的同类算法相比，该算法具有结构清晰、执行效率高、易于实现等优点。     

Dynamic Survivability in WDM Mesh Networks Under Dynamic Traffic

Network survivability is a crucial requirement in WDM mesh networks. In this paper, we systematically consider the problem of dynamic survivability with dynamic single link failure in WDM networks under dynamic traffic demands. Specifically, we investigate various protection schemes, such as dedicated path protection (DPP), shared path protection (SPP), dedicated link protection (DLP), shared link protection (SLP), and two restoration schemes, path restoration (PR) and link restoration (LR). Moreover, two new shared protection methods are proposed, i.e., SRLG-based shared link protection (SRLG-SLP) and SRLG-based shared path protection (SRLG-SPP). The SRLG (shared risk link group) constraint defines the availability of protection resources to a working path, which requires that any two working paths sharing the same risk of failure (or in the same SRLG) cannot share the same protection resources. Furthermore, in our study, we consider a more practical dynamic single-link failure model, in which the link-failure-interarrival time and link-failure-holding time are considered as two independent parameters. Based on this link-failure model, extensive simulations are done to analyze and compare the dynamic survivable performance of various protection and restoration schemes. Resource utilization, protection efficiency, restoration efficiency, and service disruption ratio are employed as survivable performance metrics versus traffic load, link-failure frequency, and link-failure reparation time to evaluate the survivable performance. Many meaningful results are given. In addition, we show that the developed SRLG-SLP and SRLG-SPP protection schemes perform very well in terms of protection efficiency and service disruption ratio, while sacrificing some performance in terms of resource utilization.     

服务自组织途径的信息系统生存性增强

在组件冗余备份的前提条件下,提出一种基于连接迁移技术的服务自组织方法。该方法根据服务处理流程将系统组件分解为通信组件、服务分发组件、数据存储组件;备份组件将其生存性信息实时发送给工作组件,并获取最新服务状态列表,当某一组件生存性最高时,根据组件的功能及其在体系结构中的位置,通过多种连接迁移技术进行服务自组织。利用仿真实验验证了生存性计算的有效性;并通过在网络环境中搭建一个Web服务器证明:在攻击情况下该方法可以有效提高稳态和瞬时的服务可生存性。     

Survivability-oriented optimal node density for randomly deployed wireless sensor networks

The survivability is usually critical for wireless sensor networks,which are often deployed in the unattended harsh environment.Lots of technical schemes to improve the survivability depend on the redundant resources of the sensor networks.The amount of resources is usually determined by the node density during the deployment phase.For the random deployment and random node failures,the quantitative relation between the survivability and the node density is studied.Based on the conditional survivability,the node density to meet the required survivability level is presented.Finally,the survivability for unpredictable failures and the optimal node density to maximize the price–performance ratio are also discussed.     

On the Survivability of Self-repairing Control System for a Hybrid Underwater Vehicle

A hybrid remotely operated underwater vehicle （HROV） capable of working to the full ocean depth has been developed. In order for the vehicle to achieve a certain survivability level, a self-repairing control system （SRCS） has been designed. It consists of two basic technologies, fault diagnosis and isolation （FDI） and reconfigurable control. For F＇DI, a model-based hierarchical fault diagnosis system is designed for the HROV. Then, control strategies which reconfigure the control system at intervals according to information from the FDI system are presented. Combining the two technologies, it can obtain the fundamental frame of SRCS for the HROV. Considering the hazardous underwater environment at the limiting depth and the hybrid operating modes, an assessment of the HROV＇ s survivability is vitally needed before it enters operational service. This paper presents a new definition of survivability for underwater vehicles and develops a simple survivability model for the SRCS. As a result of survivability assessment for the SRCS, we are able to figure out the survivability of SRCS and make further optimization about it. The methodology developed herein is also applicable to other types of underwater vehicles.     

FTP服务漂移技术的研究及实现

基于服务漂移必须包含的3类状态——初始状态、活动状态和完成状态,提出服务漂移的体系结构,分析服务漂移的实现过程。面临威胁事件时,服务漂移技术能主动或被动地漂移到备份节点,以适应威胁,决定是否漂移。服务漂移对用户是透明的,用户感觉不到服务器的变化。服务飘移只对服务状态进行漂移,可以减少传输数据量、缩短漂移时间。以FTP服务为例实现了服务漂移的原型。