区分服务网络队列调度策略的研究与仿真

针对目前几种DiffServ(Differentiated Service)网络队列调度算法进行研究,提出一种动态队列调度策略来提高队列转发效率。通过动态调整队列权值实现队列的动态管理,从而改进网络资源的利用效率,改善DiffServ网络QoS。利用NS2模拟动态队列调度算法,实验表明动态队列调度算法有效地提高了区分服务网络的队列转发效率。     

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.     

面向无线视频传输的内容感知AQM算法研究

区分服务（DiffServ,Differentiated Services）在各种保障技术中能更好地满足视频流对服务的要求。在区分服务网络中,常用的主动队列管理算法由于对视频重要数据保护强度的不足,不能很好地满足用户的QoS的需求。针对H.264/MPEG-4视频编码的特性,在现有算法WRED的基础上,通过改变平均队长的计算方法,进一步加强对重要数据的保护能力,以提高视频传输的质量,同时,还考虑了延时对视频传输的影响,提出了超时早检测机制,避免了无效视频数据传输占用宝贵的网络资源。仿真结果显示该算法在原有算法的基础上进一步提高了视频传输质量。     

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.     

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。     

A measurement-based approach for dynamic QoS adaptation in DiffServ networks

This paper presents a practical approach to managing multimedia traffic in DiffServ network, using network monitoring feedback and control. We exploit the flexibility of multimedia traffic and process network level parameters to adapt the traffic according to the current state of the network. The latter is determined based on reports sent by bandwidth monitors installed on each node of a DiffServ Domain. The bandwidth monitors interact with a policy server which, depending on the network state, decides the policy(ies) that should be enforced by the DiffServ network. The implementation of the selected policies typically leads to accepting, remarking, or dropping the multimedia traffic entering the network. Multimedia streams may be assigned different levels of QoS, as interpreted by the marker at the DiffServ edge router and marked according to network state. To achieve such dynamic QoS adaptation for multimedia applications, we have implemented and evaluated a policy-based management system. Performance evaluation shows that multimedia applications adapt better to network conditions using our approach.     

Multi-channel live streaming in service overlay network

Service overlay network (SON) provides an effective means to deploy quality of service (QoS)-guaranteed live streaming over today’s Internet. A major challenge in designing such a network is dealing with resource sharing among multiple channels. To achieve the best overall QoS in SON, we devise a new multi-channel live streaming scheme. First, we propose a multi-tree construction algorithm by infrastructure-based overlay multicast. The algorithm employs pre-allocated session degree constraints in overlay nodes to reserve resources for multiple channels, and constructs multiple trees by considering the total resource utilization of overlay nodes. Second, we propose a tree-aware queue scheduling algorithm to reduce the overlay processing delay in view of the entire overlay network. Scheduling priority is identified to trade off session priority with node location in different trees. From simulation and experimental results, the scheme achieves a differentiated control among different sessions, provides load balancing among overlay nodes, and improves the delay performance on SON.     

DiffServ网络中接纳控制方法的研究

深入分析了DiffServ网络中接纳控制方法的缺点,提出了一种新的接纳控制方法.该方法将边界和内部接纳控制分开进行.边界接纳控制时,采用边界区分服务策略,根据流对QoS不同要求,将流分为两类区别对待,不但提高了网络资源利用率,而且保证了流的服务质量;内部接纳挖制时,采用了基于路径的方法,大大提高了网络接纳控制的效率.     

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。     

基于多队列切换的SDN拥塞控制

由于传统网络缺乏对转发队列的直接控制,并且难以保证链路利用率和服务质量(QoS),针对这一问题,本文提出基于多队列的SDN拥塞控制算法。该算法对链路数据流量设置多个阈值,当某一链路流量突增达到设定阈值时,控制器立即启动相应的拥塞控制机制。根据数据流的优先级,自适应增加高优先级队列的带宽,适当减小低优先级数据队列的带宽,保障高优先级数据顺利传送。实验结果表明,该方法能有效减少网络拥塞,优化数据流的QoS。     

实时多媒体服务端到端QoS解决方案

区分服务（Diif-Serv）模型其主要是通过实时多媒体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,从而实现对实时多媒体服务端到端服务质量QoS。如何时多媒体网络系统中的不同的信息流进行正确的区分服务．然后对不同类别采取不同的服务策略和拥塞管理,从而对网络资源进行有效配置,是实现实时多媒体服务端到端服务质量QoS的关键步骤。文章重点对实时多媒体信息如何进行分类及相应的服务策略和拥塞管理进行时比研究,提出实现端到端QoS服务质量的具体措施和解决方案。并在Cisco思科路由器和交换机建立的DiffSeFV网络环境中进行验证,实验结果表明。对实时多媒体信息进行合理的分类及采用相应服务策略．能很好地实现实时多媒体信息流端到端的服务质量QoS。最后阐述了Diffsenr区分服务存在的问题和未来的发展趋势。     

基于IP网络的自适应QoS管理方案研究

目前实时音频、视频多媒体应用已经开始进入IP网络,但还有许多问题没有得到很好地解决,其中一个关键问题是多媒体服务的QoS问题、TCP／IP协议本身只提供一种“Best-effort”级别的服务,对QoS支持很少,“Best-effort”级别的服务往往会导致实时应用出现延迟抖动、分组丢失率高,从而极大的影响了实时应用的运行效果,因此必须研究可行的、高效的基于IP网络的QoS控制机制。IP网络QoS已成为分布式多媒体和网络通信的重要研究热点和难点课题。本文在IEＴＦ Intserv与Diffserv相结合的体系结构基础上,提出了一种适用于IP网络的自适应QoS管理框架,与Intserv或Diffserv模型不同的是,该QoS管理框架引入优先级节和自适应概念,QoS俦权处理采用基于多媒体优先级节的算法,在传输控制上采用了自适应QoS控制算法。它在应用层上完成,因此独立于底层网络协议。本文首先讨论了基本概念和函数,然后提出一种基于优先级节的自适应QoS管理框架和优先级调度流程。提出一种基于IP的自适应QoS协商机制,基本思想是基于RSVP（资源预留协议）。在提出QoS请求时进行QoS映射,然后启动适应性函数和资源管理函数进行协商,直到获得一组在当前资源状况下最佳的QoS指标。最后,本文还讨论了此方案的有效性并在自行开发的实验平台GUT上进行的QoS实验。实验表明应用该方法可以根据网络当前状态自适应地整多媒体实时应用的QoS需求。     

Modeling and performance analysis for IPv6 traffic with multiple QoS classes

This paper focuses on the modeling and performance analysis for IPv6 traffic with multi-class QoS in virtual private networks (VPN). The multi-class QoS is implemented on differentiated service basis using priority scheme of 4 bits defined in the packet header of IPv6. A VPN-enabled IP router is modeled as a tandem queuing system in which each output link consists of two parallel priority output queues. The high-priority queue is used to carry the delay sensitive traffic while the low-priority queue is used to carry the delay insensitive traffic. On the other hand, multiple thresholds are implemented in each queue, respectively, for packet loss priority control. The performance analysis is done using fluid flow techniques. The numerical results obtained from the analysis show that the differentiated service based on the priority schemes defined in IPv6 is able to effectively satisfy the multi-class QoS requirement for supporting multimedia services in VPN. The performance trade-off between the delay sensitive traffic and delay insensitive traffic in terms of traffic throughput, packet loss probability and end-to-end delay in VPN networks is presented.     

基于Difserv协议的IP拥塞控制策略

此文在IP QoS的研究领域内，讨论了IP广域骨干网上区分服务（DiffServ)体系协议的IP拥塞控制策略。首先分析了IP拥塞程度的几个等级，其次归纳了DiffServ体系协议中4种标准化的PHB逐跳行为，然后构建了4种优先级队列结构，并以此为基础，讨论和分析了相对应的IP拥塞控制机制，并认真分析了其机制所采用的算法。     

区分服务中每跳行为的一种实现方案

区分服务体系结构 (简称DiffServ) ,作为一种互联网服务质量的解决方案 ,具有较好的可扩展性和健壮性。DiffServ中 ,其每跳行为 (PHB)的实现是关键。该文提出的PHB实现方案主要包括 :①采用类似最大队长和最小分配共享的DiffServ缓冲分配策略 ,进行队列间的缓冲区分配 ;②选用交错方式的RIOC策略进行队列管理 ;③使用一种新的调度算法———PRI/FWRR ,来进行队列调度。并通过计算机仿真说明 ,该方案能够满足DiffServ中各类PHB的特性要求     

基于MPLS实现IPv6网络QoS的新机制

通过分析IPv6的QoS特性以及DiffServ和MPLS技术,提出了在MPLS平台下通过TC字段实现IPv6网络QoS的新机制。该机制简化了网络结构设计,更容易提供端到端的QoS。试验结果表明,新机制可以充分利用网络资源,优化网络性能。     

一种基于区分服务的嵌套队列调度算法

现有队列调度算法只能满足某一种特定类型业务流量的服务质量(QoS)需求,无法广泛支持多种类型业务流量。为此,提出一种基于区分服务的嵌套队列调度算法。将现有队列调度算法通过嵌套模型进行组合,并根据该嵌套模型进行队列调度,从而为多种类型业务流量提供均衡的QoS保障。仿真结果表明,该算法能够满足不同类型业务流量的QoS需求,其各项性能指标所达效果与最优效果的差距较小,并且在多种类型业务流量的支持方面比现有队列调度算法表现更好。     

保障QoS的实时Linux系统设计

为了在综合业务网络中保障实时多媒体业务的服务质量(QoS),设计了软实时Linux系统。系统中将网络接受中断的推后执行工作校由工作队列来执行,而非传统的由网络接受软中断处理。工作队列是Linux2.6内核的进程调度机制,对实时多媒体任务和数据任务实施不同的优先级调度,以保证实时多媒体任务的优先处理而不是尽力而为(BestEffort),保障其服务质量。通过简单的测试证明本系统运行稳定,能够保障实时多媒体业务的服务质量,尤其对解决延迟抖动问题有明显的效果。     

基于区分服务的无线多媒体传感器网络QoS路由协议*

针对无线多媒体传感器网络数据量大且不同业务传输的QoS约束不同的特点,提出了一种数据融合的区分服务的QoS路由算法（DF-DSQR）。该算法在兴趣泛洪期间建立实时（RT）和尽力而为（BE）业务两类梯度,采用优先级排队模型对两类业务的传输进行分级处理,并采用数据融合转发机制,为RT业务和BE业务提供了保证QoS的路由路径。仿真结果表明,该算法既能保证实时业务低时延的要求,又能保证尽力而为业务的QoS要求,均衡了网络能耗,延长了网络生存期。     

一种基于QoS的多维资源近似最优分配算法

分布式多媒体应用需要同时使用多种系统资源来保证用户的ＱｏＳ要求,如何在竞争资源的应用之间合理分配资源,使得在满足用户ＱｏＳ要求的基础上资源的利用率最高成为一个急需解决的问题,针对分布式多媒体应用的特性提出了一种基于ＱｏＳ的多维资源近似最优分配方法,该方法能显著地降低资源最优分配问题中的计算复杂度,并获得近似最优的资源分配方案。