MPLS宽带网络技术及其标准化新进展

一、引言多协议标签交换(MPLS),是IETF综合选路和交换问题研究工作组提出的一项IP领域的新技术。多协议不仅是指MPLS可支持多种网络层协议(如 IP、IPX等),而且MPLS可运行于多种链路层技术(如 ATM、FR、Ethernet、LAN等)之上。但由于MPLS的产生源于对IPOA技术的改进,因此MPLS的网络层主要针对IP协议。MPLS采用集成模型,将第三层的IP选路和寻址功能与第二层的高速数据交换相结合,兼备了硬件交换和现有选路方式的优势。当分组进入MPLS网络时,首先由入口路由器为分组划分转发等价类(FEC),然后利用标签分发协议(LDP)和路由协议(如OSPF、IGRP等)为FEC建立起标签交换路径,在分组头部插入标签信息;在网络内部,标签交换路由器(LSR)只需依据分组所携     

一种基于OSPF扩展的预计算QoS路由算法研究

在一个MPLS域,LSPs的建立需要QoS路由协议分发QoS相关的信息和执行QoS路径选择,但是传统的OSPF不支持QoS路由。本文提出并详细讨论了一种0SPF-QoSR路由机制,它是对OSPF路由协议的扩展,基于网络的动态可用带宽资源和流的QoS请求来决定流的QoS LSPs。仿真证明,该机制在丢包率、链路利用率、延时方面的性能优于只考虑最短路径的OSPF。     

OSPF动态路由协议的研究

OSPF已成为目前Internet广域网和Internet企业网采用最多,应用最广泛的路由协议之一。如果没有高效的路由算法,路由器的效率将大打折扣。该文详细研究了OSPF路由协议的工作机制,介绍并改进了OSPF路由算法,最后给出了实例。     

基于OSPF服务器的网络拓扑发现

OSPF是一种链路状态路由协议，其分组中含有网络拓扑信息。运行一台OSPF服务器。像路由器一样在网络中收集OSPF分组，便能通过这些路由分组快速准确可靠地发现网络拓扑。描述了OSPF服务器的设计思路，并利用隧道技术有效解决了OSPF服务器在部署上的问题。在实验中OSPF服务器取得了良好的效果。     

基于OSPF协议的路由器安全防范

路由器组网过程中,OSPF协议是比较常用的一种网络协议,但因为OSPF路由协议在设计时本身的一些缺陷及安全考虑上的不足,导致该协议容易遭受黑客的攻击。本文在对OSPF路由协议研究的基础上,对其一些漏洞进行了分析,并提出了一些建议及配置,以巩固和加强OSPF协议的安全性。     

拟态防御体系OSPF协议研究及分析

网络空间拟态防御技术是一种基于动态异构冗余的新型主动防御技术，通过引入多个异构冗余的执行体，增强广义鲁棒性，通过对多个执行体的策略或者周期性调度，对外呈现特征的不确定性变化，增强安全性。路由协议安全是网络安全的重要组成部分，OSPF协议作为网络空间中部署最广泛、实现最复杂的路由协议，如何实现各异构执行体OSPF协议功能的等价，是支持拟态防御的网络设备亟需解决的问题。首先，科学阐述了拟态防御的设计思想，详细描述了支持拟态防御的路由器的体系结构，论述了OSPF协议在拟态防御体系结构中的处理方法，通过引入OSPF协议代理实现各异构执行体OSPF协议功能的等价，在支持拟态防御的路由器原型样机中验证了该方法的可行性和高性能。最后，结合几种经典的OSPF路由攻击产生的路由器安全风险进行了具体说明及实验验证，实验表明该方法能够有效提高其应对OSPF网络攻击的能力。     

小知识

MPLS路由器介绍 MPLS的核心思想是转发基于标记交换的范例应用,这种标记交换能和不同的控制模块组合。每个控制模块负责分配和分布一组标签,也负责维护其他相关的控制信息。例如,一个MPLS路由器可能包括: (1)一个unicast路由模块,它用常规的IP路由协议(OSPF、EnhancedIGRP等等)建立路由表,把标签分配     

GMPLS技术研究

GMPLS是MPLS的扩展,旨在解决多种组网技术的流量工程问题。为了探讨当前应用GMPLS时存在的问题及其解决方案,分析了GMPLS架构及研究现状,通过对MPLS协议应用于光纤网时存在的问题的分析,得出了GMPLS协议MPLS协议的改进点。指出了GMPLS中亟待解决的问题并提出了自己的见解。     

OSPF路由协议上的服务质量扩展

首先介绍了OSPF中的链路状态广播机制，提出了链路状态广播为实现QoS所需的改进；然后介绍和比较了几种路径选择算法，通过对其效率和计算复杂度的分析，为QoS路由选择出合适的算法；最后提出QoS路由扩展的体系结构，使得这一体系结构对现有的OSPF协议产生最小的影响。     

适用于移动MPLS的改进RSVP协议研究

首先提出了一种改进的资源预留协议,能够保证基于分级移动的移动MPLS在切换过程中连续的集中服务质量。阐述了该改进协议的工作过程,证明了它能很好地适应移动MPLS,并能保证对移动MPLS在切换后的新路径进行快速的资源预留,从而保障业务的集中服务质量。最后,给出仿真结果并进行分析。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.