园区网中QoS解决方案的研究

随着网络技术的发展,网络用户的增多以及各种大型实时的多媒体应用在园区网上实施,园区网在大学、公司和医院等企事业单位的生产和发展过程中发挥着越来越重要的作用,同时网络应用对网络服务的QoS提出更高的要求。本文介绍在园区网实施QoS方案的主要策略;分析DiffServ模型,DiffServ通过对园区网中的通信数据包进行分类和策略控制来达到调节网络资源的目的;探讨区分服务模型的实现,从而实现园区网的QoS保证。     

基于H.323协议的实时多媒体网络系统中QoS的保证与实现

H．323是国际电信联盟标准部(ITU-T)制定且全球普遍接受的关于多媒体通讯的标准之一。本文主要对因特网上H．323实时多媒体通信进行研究，着重分析影响实时多媒体网络系统中QoS服务质量保证的因素，提出实现实时多媒体网络系统中QoS服务质量的具体措施和方法。区分服务(Diff-Serv)模型具灵活性，可扩展性和简单易于实现的特点，是实现对实时多媒体网络系统中服务质量QoS的可取的技术。     

DiffServ和MPLS相结合的流量工程机制

MPLSTE对传统的流量工程进行扩展,实现端到端的QoS保证,但是以流量中继为服务粒度。对流量缺乏区分服务的能力。DifIServ模型提供了区分服务,但是缺乏端到端的QoS有效路由策略。通过将MPLSTE的有效路由策略和DiffServ的区分服务相结合,引入区分服务感知的流量工程．运用带宽约束模型,在网络中实现端到端区分服务的QoS保证。     

IPv6下DiffServ在Linux中的设计与实现

QoS的研究目标是有效地为用户提供端到端的服务质量控制或保证,而IPv6不仅有效地解决了网络地址危机的问题,而且为提升网络服务质量(QoS)提供了更好的支持。剖析区分服务模型的数据流分类和PHB实现预定义标识流,同时分析Linux内核中的流控制机制。在Linux平台上利用流量控制工具集TC,对物理网络设备绑定CBQ队列、在队列上建立分类、为每个分类建立路由的过滤器,从而实现不同类数据流的区分和带宽保证。并对现有的队列、分类、过滤器和路由进行监视。实现表明,测试平台运行稳定,可以为QoS研究提供一个开发式的测试环境。     

认知网络中基于服务信息的队列管理算法

通过感知网络外部环境,认知网络能够自主地调节并分配网络资源,从而保证网络服务的正常运行。当发生网络拥塞时,当前普遍应用的主动队列管理算法只能从数据层面对数据包进行丢弃,不具备服务QoS对底层队列的调控。本文针对以上问题,提出了一种综合服务等级以及服务传输特点的队列管理算法,引入了服务对数据队列的参与调节模型,保证了在网络拥塞环境下特定服务的服务质量。使用Matlab对算法进行仿真,表明该算法在发生网络拥塞时,能够依据服务等级和服务传输特点对数据队列进行调节,从数据层面体现了服务层面的优先策略,从而保证了高级别服务的服务质量。     

IPv6下DiffServ在Linux中的设计与实现

QoS的研究目标是有效地为用户提供端到端的服务质量控制或保证,而IPv6不仅有效地解决了网络地址危机的问题,而且为提升网络服务质量(QoS)提供了更好的支持.剖析区分服务模型的数据流分类和PHB实现预定义标识流,同时分析Linux内核中的流控制机制.在Linux平台上利用流量控制工具集TC,对物理网络设备绑定CBQ队列、在队列上建立分类、为每个分类建立路由的过滤器,从而实现不同类数据流的区分和带宽保证.并对现有的队列、分类、过滤器和路由进行监视.实现表明,测试平台运行稳定,可以为QoS研究提供一个开发式的测试环境.     

Linux上QoS保证及编程接口的设计

目前的因特网服务并没有提供服务质量（QoS）。随着一些实时的多媒体应用的增加和ATM等具有端到端的服务质量保障的链路技术的出现,需要在IP层上实现QoS的保证。主要讨论Linux的内核中提供的QoS的功能,以及如何在此基础上设计用户编程的接口。     

业务驱动的无线多媒体传感器网络跨层优化

由于无线多媒体传感器网络链路动态变化、节点移动、带宽和能量受限等特点,传统的分层协议及其局部优化很难保证整个网络性能最优。为实现无线传感器网络中多媒体业务保障服务质量(QoS),提出一种基于业务驱动和自反馈机制的无线多媒体传感器网络跨层优化策略。该策略按照保证QoS等级最高业务服务质量原则,自适应优化网络协议栈各层参数,并将优化后参数反馈给相应网络协议层,实现保证QoS的网络资源优化,仿真结果表明,该方法在综合物理层误码率和链路层数据帧丢失率的情况下,与传统网络分层协义相比,提高多媒体信息传输质量方面有一定优越性。     

IP网络设备中的QoS实现技术

随着IP网络的不断扩大和网络承载业务的不断增加,网络运营商在网络QoS方面的要求在不断提高,由最初的尽力而为和无需QoS保证的网络服务质量要求,逐渐演变到要求运营商提供严格端到端QoS的服务质量保证。本文主要是在基于MPLS的DiffServ网络中,在数据经过IP网络设备时,对QoS实现过程进行分析,并且对比分析了目前QoS在IP网络上实现的几种主要技术,着重对基于MPLS的DiffServ模型网络的DS域边界设备LER和域内设备LSR的QoS实现过程,包括用户识别、流分类、队列调度和拥塞控制等做了全面的论述。     

一种支持多媒体实时通信的动态QoS管理机制

多媒体实时通信其实时性强，数据量大的特点对服务质量QoS提出了很高的要求，本文根据多媒体实时传输的特点，在研究现有服务质量控制方法的基础上，提出了一种源端，接收端和网络三方协商的端到端的动态QoS管理机制。     

一种细粒度的区分服务及QoS映射优化研究

针对传统区分服务模型服务等级分类有限,结合策略管理的优势,提出了基于策略的细粒度区分服务概念,给出了不同类型区分服务的通用描述形式,提出了基于遗传算法的细粒度服务优化算法.当系统资源不足以满足多媒体流的传输要求或者用户需要细粒度的区分服务质量时,通过启用遗传算法对PHB进行组合优化,能够在较少的代数内求得满足用户QoS要求的最优解,实验表明该算法可行.     

IntServ与DiffServ结合实现端到端的QoS

本文从网络发展从当前的Best-Effort到QoS的必然趋势出发,介绍了两种主要的QoS控制机制:IntServ和DiffServ体系结构,并通过对两者的不同特点的分析,对两种体系结构的有机结合提出初步的模块设计,并做出展望分析。     

一种区分服务网络的设计与实现

给出了DiffServ网络的一种设计与实现，提出了一种有效的资源管理模型。在该模型中，存在一个带宽代理(Bandwidth Broker)同步多个边界节点的接纳控制，负责区分服务网络之间的SLA(Server Level Agreement)协商，进行路由器配置；边界节点使用RSVP协议为集聚流预留资源；RSVP使用预计算QoS路由寻找路径。整个模型不仅综合了已有资源管理方案的优点，而且保持了区分服务网络的可扩展性。     

Assured end-to-end QoS through adaptive marking in multi-domain differentiated services networks

The issue of resource management in multi-domain Differentiated Services (DiffServ) networks has attracted a lot of attention from researchers who have proposed various provisioning, adaptive marking and admission control schemes. In this paper, we propose a Reinforcement Learning-based Adaptive Marking (RLAM) approach for providing assured end-to-end quality of service (QoS) in the form of end-to-end delay and throughput assurances, while minimizing packet transmission cost since ‘expensive’ Per Hop Behaviors like Expedited Forwarding (EF) are used only when necessary. The proposed scheme tries to satisfy per flow end-to-end QoS through control action,s which act on flow aggregates in the core of the network. Using an ns2 simulation of a multi-domain DiffServ network with multimedia traffic, the RLAM scheme is shown to be effective in significantly lowering packet transmission costs without sacrificing end-to-end QoS, when compared to the commonly used static marking scheme.     

Quality of Service Networking for High Performance Grid Applications

This paper reports on different efforts to provide quality of service (QoS) Networking to Grid applications done in the context of the MB-NG, GRS and DataTAG EU projects. These are leading edge network research projects involving more that 50 researchers in the UK, Europe and North America, concerned with the development and testing of protocols and standards for the next generation of high speed networks. We have implemented and tested the Differentiated Services Architecture (DiffServ) in a multi-domain, 2.5 Gbits/s network (the first such deployment) defining appropriate Service Level Agreements (SLAs) to be used between administrative domains to guarantee end-to-end Quality of Service. We characterised several hardware implementations of DiffServ and concluded on their appropriateness for several network scenarios. Since current and future Grid applications will have to use modified mechanisms of congestion control we have evaluated old and new TCP implementations over a Differentiated Services Networks. These quality of service tests have also included innovative MPLS (Multi-Protocol Label Switching) experiments to establish guaranteed bandwidth connections to Grid applications in a fast and efficient way. We have also developed a software based bandwidth broker architecture for Grids based on IETF standards which allows applications to transparently request dynamic and advanced reservations and implemented it in a real experimental network. We finally report on experiences delivering Quality of Service networking to high performance applications like Particle Physics data transfer and High Performance Computation. This includes quantitative results on the performance improvements that QoS brought to real data transfers in the context of High Performance Computing.     

An end-to-end QoS control model for enhanced internet

This paper describes an end-to-end QoS(Quality of Serviece) control model for distributed multimedia computing on enhanced Internet,and gives the design and implementation of this model including hosts and routers.The architecture,the mathematical definition about QoS parameters,and the mapping between Integrated Service(IS)and Differentiated Service(DS) are discussed in this paper,The simulation shows that this model can improve the performance of audio streams when it is used in IPhone system.     

Web server QoS models: applying scheduling rules from production planning

Most web servers, in practical use, use a queuing policy based on the Best Effort model, which employs the first-in-first-out (FIFO) scheduling rule to prioritize web requests in a single queue. This model does not provide Quality of Service (QoS). In the Differentiated Services (DiffServ) model, separate queues are introduced to differentiate QoS for separate web requests with different priorities. This paper presents web server QoS models that use a single queue, along with scheduling rules from production planning in the manufacturing domain, to differentiate QoS for classes of web service requests with different priorities. These scheduling rules are Weighted Shortest Processing Time (WSPT), Apparent Tardiness Cost (ATC), and Earliest Due Date. We conduct simulation experiments and compare the QoS performance of these scheduling rules with the FIFO scheme used in the basic Best Effort model with only one queue, and the basic DiffServ model with two separate queues. Simulation results demonstrate better QoS performance using WSPT and ATC, especially when requested services exceed the capacity of a web server.     

A distributed-request-based CDMA CAC for DiffServ multimedia services in wireless cellular mobile networks

In this paper, a distributed-request-based CDMA DiffServ (differentiated service) call admission control (CAC) scheme is proposed to provide various multimedia services seamlessly in wireless mobile Internet. Conventional CDMA CAC schemes cannot fully support DiffServ QoS (Quality of Service) and seamless handoff due to lack of consideration on service priority and seamless mobility. Therefore, in order to achieve QoS guarantee for each service class, seamless fast-handoff, and high utilization of the scarce wireless resource, we define a code assignment policy and an adaptive access permission scheme taking each user’s service priority and mobility into consideration. For that purpose, in the proposed scheme, the DQRUMA/CDMA is combined with the new code assignment scheme and the adaptive access permission probability (APP). Numerical examples show that the forced termination ratio of handoff calls is guaranteed to be much less than the blocking ratio of new calls for a seamless fast-handoff while proposed scheme provides QoS guarantee for each service class efficiently.     

Joint source coding and packet classification for real-time video transmission over differentiated services networks

Differentiated Services (DiffServ) is one of the leading architectures for providing quality of service in the Internet. We propose a scheme for real-time video transmission over a DiffServ network that jointly considers video source coding, packet classification, and error concealment within a framework of cost-distortion optimization. The selections of encoding parameters and packet classification are both used to manage end-to-end delay variations and packet losses within the network. We present two dual formulations of the proposed scheme: the minimum distortion problem, in which the objective is to minimize the end-to-end distortion subject to cost and delay constraints, and the minimum cost problem, which minimizes the total cost subject to end-to-end distortion and delay constraints. A solution to these problems using Lagrangian relaxation and dynamic programming is given. Simulation results demonstrate the advantage of jointly adapting the source coding and packet classification in DiffServ networks.