Managing QoS for Multimedia Applications in the Differentiated Services Environment

The overall quality of network connections has a significant impact on the performance of networked applications. As a result, Quality-of-Service (QoS) management for networked multimedia applications over IP is a significant and immediate challenge. While differentiated services (DiffServ) provide a sense of resource allocation and QoS, they do not guarantee QoS. This paper presents the design, implementation and evaluation of a content-aware bandwidth broker (CABB) that manages QoS for multimedia applications in a DiffServ environment. CABB allocates network resources to multimedia flows based on client requirements, the adaptability of the application, and its tolerance to network level parameters such as bandwidth, delay, and latency. It has been implemented and evaluated using the NS-2 simulator toolkit. Evaluations show that CABB improves network resource allocations and increases overall throughput. Furthermore multimedia application flows are better managed and controlled, improving perceived QoS and avoiding possible congestion at core routers.     

Internet综合服务模型和分类服务模型

文章介绍了未来Ｉｎｔｅｒｎｅｔ中存在的两种服务模型,综合服务（Ｉｎｔ－Ｓｅｒｖ）和分类服务（Ｄｉｆｆ—Ｓｅｒｖ）,并对它们进行了评价。     

提供IP Qos保障的区分服务系统模型及算法

主要介绍了提供IPQos的区分服务(DifferentiatedServices)体系。DS系统在IETF中正在经历一个热烈讨论和规范的过程。很有可能成为为下一代INTERNET提供Qos保障的框架体系。该文深入阐述了DS系统进行通讯速率管理和资源分配的原理和算法,并举出了相应的例子。文章认为,将流量调节和资源分配单元分离是DS系统优于其它Qos保障系统的重要原因。这使得DS系统具有极佳的可扩展性。随着性能更好的调度算法的出现,DS系统的性能可以得到进一步的提高。     

Heterogeneous CPU Services Using Differentiated Admission Control

We present an adaptive rate-controlled scheduler for heterogeneous applications running on general purpose computers. Our scheduler can effectively support diverse application requirements. It employs uniform rate-based sharing. Application heterogeneity is satisfied by partitioning CPU capacity into service classes, each with a different criterion for admission control. As a result, we are able to provide at once guaranteed performance, flexible allocation of rates with excellent scalability and intermediate service classes offering tradeoffs between reserved rate utilization and the strength of guarantees. Our scheduler has been implemented in Solaris 2.5.1. It runs existing applications without modifications. We present experimental results showing the scalability, efficiency, guaranteed performance, and overload performance aspects of our scheduler. We demonstrate the importance of priority inheritance implemented in our scheduler for stable system performance.     

基于QoS域代理在移动无线互联网中区分服务的设计与实现

随着用户数和应用业务的快速发展,对新一代Internet的服务质量提出了更高的要求。然而,在Internet中引入无线接入方式使得提供QoS面临更大挑战。文章基于区分服务(DiffServ)框架结构,并结合移动管理协议———移动IP(MobileIP)协议来研究和解决如何在新一代移动无线互联网中提供QoS控制。同时在每个自治域中引入一个新的概念———QoS域代理(QoSDomainAgent,QDA),并利用QDA进行资源管理并参与和移动主机/用户(MobileHost,MH)或其它QDA进行动态SLS的协商,同时采用组播方式把QDA中的QoSSLS内容信息传输给域内的每一个第一跳和边界路由节点。通过对相关协议和功能进行必要的修改和扩充,从而有效地解决了MH和网络的动态服务级别协议(SLA)的协商和在MobileIP切换中各入口节点动态建立SLS的问题,同时可以有效减少信令交互,节省无线资源和减少移动终端的电池消耗,并且有利于MH在域内漫游时进行无缝切换。最后给出作者的结论及进一步的研究内容。     

基于分类服务的下一代互联网体系结构的实现

随着互联网应用的增长,目前提供尽力服务的互联网体系结构越来越不能满足这些新的服务要求。通过设计出一种新的路由器缓冲区管理策略,探讨一种基于分类服务的新一代互联网体系结构的实现方式。     

Monitoring Edge-to-Edge Traffic Aggregates in Differentiated Services Networks

Differentiated Services (DiffServ), which are currently being standardized in the IETF DiffServ working group, is a solution that can provide different qualities of service to different network users. DiffServ aggregates network packets at edge routers and forwards the aggregated packets to core routers with different priorities. In this paper, we propose methods using the SNMP framework for monitoring edge-to-edge traffic aggregates in a DiffServ domain, which consists of a set of DiffServ-enabled routers. In order to manage each DiffServ router, we have analyzed the DiffServ MIB and instrumented it in the router. Further, we propose monitoring behaviors of edge-to-edge traffic aggregates by combining topology and performance information from MIB II and DiffServ MIB. Construction procedures and graphical representation of the edge-to-edge traffic aggregates are explained in detail. We also extend our efforts to implement a DiffServ domain monitoring system that monitors a set of DiffServ-enabled routers and traffic aggregates between every edge router pair. We believe that the proposed monitoring methods can serve as useful building blocks for managing DiffServ networks.     

基于支持向量机的Internet流量分类研究

准确的网络流量分类是众多网络研究工作的基础,也一直是网络测量领域的研究热点.近年来,利用机器学习方法处理流量分类问题成为了该领域一个新兴的研究方向.在目前研究中应用较多的是朴素贝叶斯(naive Bayes,NB)及其改进算法.这些方法具有实现简单、分类高效的特点.但该方法过分依赖于样本空间的分布,具有内在的不稳定性.因此,提出一种基于支持向量机(sulbport vector machine,SVM)的流量分类方法.该方法利用非线性变换和结构风险最小化(structural risk minimization,SRM)原则将流量分类问题转化为二次寻优问题,具有良好的分类准确率和稳定性.在理论分析的基础上,通过在实际网络流集合上与朴素贝叶斯算法的对比实验,可以看出使用支持向量机方法处理流量分类问题,具有以下3个优势:1)网络流属性不必满足条件独立假设,无须进行属性过滤;2)能够在先验知识相对不足的情况下,仍保持较高的分类准确率;3)不依赖于样本空间的分布,具有较好的分类稳定性.     

基于遗传算法的IP网流量优化算法

流量工程通过对IP网流量的优化以更有效利用网络资源。现有研究的一个重要方向是把流量工程问题用线性规划建模,并利用传统的Simplex算法求得最优解,文章提出了一种基于遗传算法的求解方法,从一组随机选取的解(染色体)出发,经过交叉、突变等基因进化操作和多代的选择,最终达到预先设定的适应度准则;给出仿真结果和相关讨论;显示该文算法在运算量,处理动态流量需求等方面有较好的应用前景。     

物联网在智能交通领域的应用

介绍了我国的交通现状:随着家用汽车数量急剧增加,城市交通拥堵现象尤为突出,城市交通管理效率低下。物联网技术的到来为智能交通的发展带来了新的动力。列举了国外先进的智能交通技术及其发展状况,分析了我国发展智能交通的应用领域,得出了发展智能交通的瓶颈所在,探讨了我国智能交通的发展与展望。     

Definition and Performance Evaluation of Network Services Deployed Over a Differentiated Services Network

A vital requirement for next generation IP networks is the provision of services with differentiated behavior and characteristics. The basic reason for that is the need to provide Quality of Service (QoS) to the different types of user traffic produced by applications that are different in nature and behavior, analogously to the IP network services. The Differentiated Services (DiffServ) paradigm is still one of the major outcomes of the research community toward the provision of QoS to individual customer needs and applications. This paper addresses the definition and deployment of specific network services in a DiffServ environment. We reuse and extend the fundamental concepts of the Expedited Forwarding and Assured Forwarding per hop behaviors in order to define four new network services, apart from the well known Best Effort one, which introduce a specific traffic handling implementation along with an Admission Control methodology. These are analyzed and simulated in the paper in order to evaluate their performance and confirm the correctness of their fundamental principles.     

Managing Highly Dynamic Services Using Extended Temporal Network Information Models

The management of Highly Dynamic Services implies the necessity for fast reconfiguration and provisioning. One important feature for this management is its supporting information model able to capture both temporal and aggregate information. Such a model is proposed in this paper. More specifically, we address the management of Dynamic Virtual Private Networks (DVPNs) as a special case of highly dynamic services.     

GPRS中QoS管理机制研究

通用无线分组业务 (GPRS)中服务质量 (Qo S)管理机制是当前 GPRS研究的热点 ,它包含四大部分 :业务源特性描述、整形与监管 (Shaping/Policing)、调度 (Scheduling)和接纳控制 (CAC) ,其中 CAC是核心 .本文对每一部分的机理和实现算法进行了描述 ,且给出了相应的试验方案 ,包括业务源选择和仿真语义、分组类型和比率的定义 .     

Managing QoS in Multimedia Services

We present a case study of multimedia servicedelivery in the World Wide Web environment. Our systemis founded on the notion of end-to-endQuality-of-Service (QoS) management. We outline our viewof an integrated management frame and explain how ourQoS management architecture fits into this framework. Wethen describe our object-oriented multimedia deliverysystem based on CORBA and Java. We discuss some issues of stream delivery and managementwith reference to our own experiences.     

Ajax式富客户端在学习管理系统的应用研究

目前在一些门户网站已经广泛应用的富客户端技术能有效改变网络学习系统交互界面上存在的问题。使用开源的Ajax4JSF组件按照JSF框架构建的富客户端学习管理系统利用Ajax的异步交互模式优化了用户的交互界面。经loadrunner等工具测试显示能有效的降低服务器负载,快速相应用户需求。因此满足学习者在网络学习中的心理需求。     

区分服务网络中双窗口TCP协议的性能分析与研究

提出一种分析模型，用于计算区分服务网络中双窗口TCP的性能，并清楚揭示了TCP流预订带宽、数据分组的丢失率以及TCP连接的往返时延(RTT)对确保服务性能的影响．仿真实验验证了该数学模型的有效性．同时仿真结果也表明。双窗口TCP机制能在较大程度上解决带宽保证和剩余带宽的公平分配问题，并且性能不受网络环境变化的影响．     

Two different approaches for providing QoS in the Internet backbone

This paper compares two different approaches for providing QoS in the Internet backbone. The first, denoted as simple approach, is a simple method of Admission Control performed by a weighted-fair-queuing scheduler. This approach guarantees QoS with a suitable overprovisioning of transmission resources. The second approach, denoted as basic statistical approach, is a full-featured statistical framework, based on the central limit approximation, for estimating the delay bound violation probability associated to each traffic class, given the offered traffic and the schedulers’ configuration. Both approaches adopt the dual-leaky-bucket (p, r, b) regulated traffic model in order to characterize the aggregate traffic flows. At first, we analyze the characteristics of both approaches in order to point out the respective pros and cons. Then, we propose an enhanced version of the basic statistical approach, the enhanced statistical approach. Our novel approach, as opposed to the basic statistical approach, performs a joint optimization of the regulator’s parameters and of the network capacity instead of a separate optimization. Our study shows that the enhanced statistical approach outperforms both the basic statistical approach and the simple approach and offers the highest potential for a better utilization of transmission resources. The basic and the enhanced statistical approaches assume that traffic is Gaussian. The simple approach has looser constraints on the statistical behavior of traffic, but it requires overprovisioning of transmission resources to guarantee the required QoS in terms of packet delay and loss.     

Priority shaping of source traffic in ATM B-ISDN

A source traffic shaper based on prediction of the behaviour of the ATM B-ISDN access policer is discussed. Using this approach, it is possible, within a policed virtual circuit, to reduce both loss and delay of the high-priority cells at the expense of delay of the low-priority cells. The priority-based traffic shaping is beneficial for sources generating cell streams with differing service requirements, e.g. multimedia sources.     

互连网上私有资源的安全防范

该文首先讨论了当前Ｉｎｔｅｒｎｅｔ上保护私有资源的各种技术及其存在的问题，经此基础上，提出了复旦校园网防御系统的设计与实现，并对该系统进行了全面的分析。