多业务流量预测动态带宽分配方法

静态带宽资源分配方法或基于业务分类的动态带宽分配方法等很难适应业务流特性,无法保证各级业务的服务质量。设计了流量预测及带宽分配模型,给出了流量预测计算方法,提出多业务流量预测动态带宽分配方法（MSTPDBA）,该方法基于业务预测流量的大小进行可用带宽的重新分配。仿真实验证明了MSTPDBA的有效性,能控制不同业务的时延,并提高了系统带宽资源的利用率。     

IEEE 802.11e协议HCCA机制下的QoS研究

分析了IEEE 802.11e协议HCCA信道接入机制下的简单带宽调度算法对多媒体业务的QoS支持情况,指出其不足并在其基础上进行了改进,提出了一种基于业务等级的带宽调度算法E-HCCA（Enhanced HCCA）。E-HCCA对不同优先等级业务的数据在带宽分配上采用不同的策略,在优先保证各个节点CBR业务的基础上,根据节点的VBR流量动态平均分配剩余带宽。相比较简单调度算法,E-HCCA算法更好地支持了多用户下的语音业务流和视频业务流,降低了分组时延,增加了系统吞吐率。     

无线Mesh网络中基于业务价值的组播带宽分配方案

高延迟及低效益是无线Mesh网络中开展流媒体业务面临的主要问题。为解决该问题,首先赋予组播业务价值,该值反映了业务的网络优先级及效益优先级,并提出一个基于组播价值优先级的组播带宽分配方案。该方案第一阶段实施基于价值优先级的不区分业务类型的静态分配,通过对高价值业务的优先调度,实现了组播价值最大化及带宽效益最大化。在拥塞时,实施第二阶段的基于业务带宽需求调整及抢占的动态分配,保证了低时延约束业务的服务质量。仿真与常见算法的比较表明,所提出的方案在保证业务网络服务质量的同时,能实现带宽效益最大化。     

利用组播及QoS技术对IPTV网络进行优化

主要阐述了有关IPTV网络业务、组播协议、Qos协议和OPNET网络仿真软件的有关基础知识,同时阐述了在业务承载网中的IPTV网络的发展现状,研究IPTV可能出现的网络传输拥塞时的缺点,提出基于组播和QoS技术的IPTV承载网络组网方案。重点阐述了OPNET的模型层次与构建方式,并提出了OPNET网络模拟仿真的具体步骤,通过OPNET软件进行模拟仿真实验,仿真中,按照数据业务、IP语音业务、IPTV服务等三个类型,分别对网络发射数量、终端接收数据流量、网络时延值和网络抖动数值等进行测试仿真,同时对所收集的网络状态信息进行数据分析。通过仿真实验,可以发现在IPTV网络中使用Qos及组播,有效减轻业务网的流量负荷,减少传输时延,提高网络系统稳定性,从而保证了相关服务的顺利进行。     

ACR下的IPTV频道快速切换方法

通过研究大规模汇聚路由器(ACR)网络结构特点和IPTV业务的组播组切换步骤,提出一种ACR下的先复制、后鉴权的频道快速切换方法,减小了频道切换时延,提升了用户体验。该方法通过各部分时延的相互覆盖,并行处理切换步骤,达到了缩短总时延的目的,形成频道快速切换。由仿真得到的各关键参数的分布图显示,与传统的频道切换方法相比,所述方法进一步减小了频道切换时延,得到了很好的效果,同时不需要增加任何额外带宽和设备复杂度。     

基于队列时延检测的链路可用带宽流量调度方法

为有效提高链路带宽资源的利用率和减小数据传输时延,首先分析了链路中数据传输时延的特点,提出一种基于队列时延检测的链路可用带宽流量调度方法,该方法研究了在调度流量与可用带宽之间在各种不同情况下的数据传输时延变化趋势,保证了该方法较好的全局完整性。通过仿真实验证明,该方法有较好的流量调度能力,能有效地控制各链路的流量,改善链路时间响应特性和提高链路带宽利用率。     

WLAN与EPON融合接入网上行带宽分配算法

为了提高带宽的利用率,提出一种WLAN与EPON融合接入网上行带宽分配算法。该算法将无线终端接入的业务分为不同的服务等级,以实现不同业务Qo S保证。首先,ONU-AP给各个无线终端STA分配带宽,采用IEEE 802.11E协议的简单调度算法给语音业务和一般数据业务分配带宽,利用视频流的平均速率估算视频业务的传输带宽。其次,光线路终端OLT给各个ONU-AP分配带宽,OLT根据语音业务速率和当前视频业务流量分别估算语音、视频业务在下一个轮询周期的带宽,并将剩余带宽在重负载终端中二次分配,最后给一般数据业务分配带宽。通过仿真实验,结果表明:与传统算法相比,该算法的网络时延和丢包率明显降低,实现了带宽资源的合理分配。     

WiMAX接入技术在IPTV系统中的应用研究

在分析IPTV接入网的要求和WiMAX技术优势的基础上,提出了WiMAX应用于IPTV的系统模型,并具体分析了系统流程;针对IPTV业务下行数据量比较大的特点,提出了适合IPTV业务特点的下行链路实时调度(DLRTS)算法,该算法的主要目的在于降低实时业务的时延,从而保证IPTV的服务质量(QoS)。仿真结果表明,与常用的轮叫调度(Round R0bin)算法相比,本文算法在实时业务的时延和吞吐量两方面的性能都有明显提高,可很好地支持IPTV业务。     

基于WiMAX的实时业务带宽优化调度策略

WiMAX是一项无线城域网(WMAN)技术,支持实时与非实时等多种业务,SS可以向BS动态申请所需求的带宽,由IEEE 802.16协议定义.但协议中没有具体定义实时服务QoS所需要的带宽调度策略.因此,如何高效地分配使用带宽,成为一个亟需解决的问题.本文提出一种自适应的实时轮询业务带宽分配策略,SS依据当前带宽需求和以往的实际分配带宽,提前预测实时业务数据包所需求的确切带宽.文中给出了数学分析模型和仿真.仿真结果表明,与传统的带宽分配机制和其他自适应算法相比,该自适应的带宽分配算法能更好地改善系统性能,提高吞吐量,减少时延和减少缓冲区需求.     

基于Richards模型的数据中心骨干网络带宽分配策略

针对数据中心间骨干网络中存在大量突发性强的小流而难以实时跟随流量变化对其进行带宽分配的问题,提出了基于Richards种群生长模型的数据中心骨干网络带宽分配策略(RBA)。该策略采用闭环反馈控制系统实时分配带宽,以基于Richards曲线设计链路的反馈控制因子作为此系统的反馈量,可对突发流量做出平滑响应,并根据时延敏感性的不同,采用不同的异速生长参数得到不同的流量速率增长曲线,以满足时延敏感流量的QoS需求。在Mininet平台上进行了实验仿真并与典型的带宽分配策略进行了对比,结果表明RBA不但可对突发流量提供较高的带宽分配效率,还确保了各流对带宽资源竞争的公平性。     

A lexicographically fair allocation of discrete bandwidth for multirate multicast traffics

Fair bandwidth allocation is an important issue in the multicast network to serve each multicast traffic at a fair rate commensurate with the receiver's capabilities and the capacity of the path of the traffic. Lexicographically fair bandwidth layer allocation problem is considered and formulated as a nonlinear integer programming problem. A nonincreasing convex function of the bandwidth layers of the virtual sessions is employed to maximize the bandwidth of each virtual session from the smallest.To solve the fairness problem a genetic algorithm (GA) is developed based on the fitness function, ranking selection and the shift crossover. Outstanding performance is obtained by the proposed GA in various multicast networks. The effectiveness of the GA becomes more powerful as the network size increases.     

OpenIPTV: a comprehensive SDN-based IPTV service framework

IPTV is an emerging TV content delivery service that should guarantee Quality of Service (QoS) to deliver television contents over IP for their customers. However, providing such QoS regarding service level agreements (SLA) requires frequent service monitoring and adaptive configuration mechanisms. Nowadays, Software Defined Networks (SDNs) provide capabilities to deploy and manage networks dynamically and can maintain QoS. In this paper, a novel IPTV service framework (OpenIPTV) is proposed, which utilizes SDN as an underlying technology for providing QoS for IPTV customers in a shared backbone network. OpenIPTV is implemented in a well-known OpenDayLight controller and strictly followed a modular design for the sake of efficiency. OpenIPTV comprises all service requirements such as resource monitoring, channel changing, multicast group managing and dynamic QoS multicast traffic engineering. The performance of OpenIPTV is evaluated under different scenarios and experimental results confirmed the effectiveness of the proposed framework in terms of QoS metrics. Furthermore, experimental results show that OpenIPTV is a feasible and practical solution to deliver IPTV services with high level of QoS over SDN.     

LGRR: A new packet scheduling algorithm for differentiated services packet-switched networks

Since Quality of Service (QoS) support is a mandatory requirement in the next-generation networking, each router in a packet-switched network must provide a better service to higher-priority packets under any situation such as congestion. We propose in this paper the loan-grant based Round Robin (LGRR) packet scheduler for use in each output port of a router in a DiffServ network. LGRR is a frame-based scheduler to pass traffic streams according to their class types and to their immediate upstream source routers. It uses a loan-grant scheme so that a higher priority traffic stream can be processed quickly by requesting a bandwidth loan from the scheduler. To control the amount of transmitted bits from each stream and to prevent malicious abuse, the bandwidth loan must be paid back from the quantum values acquired in future. LGRR gives a fair opportunity to different traffic streams to access to the network bandwidth. It performs better than MDRR+, MDRR++, and OCGRR in handling traffic under both normal and bursty traffic, but it also gives a better loss and delay performance to the higher-priority traffic when traffic load is very high.     

Bandwidth guaranteed multicast scheduling for virtual output queued packet switches

Multicast enables efficient data transmission from one source to multiple destinations, and has been playing an important role in Internet multimedia applications. Although several multicast scheduling schemes for packet switches have been proposed in the literature, they usually aim to achieve only short multicast latency and high throughput without considering bandwidth guarantees. However, fair bandwidth allocation is critical for the quality of service (QoS) of the network, and is necessary to support multicast applications requiring guaranteed performance services, such as online audio and video streaming. This paper addresses the issue of bandwidth guaranteed multicast scheduling on virtual output queued (VOQ) switches. We propose the Credit based Multicast Fair scheduling (CMF) algorithm, which aims at achieving not only short multicast latency but also fair bandwidth allocation. CMF uses a credit based strategy to guarantee the reserved bandwidth of an input port on each output port of the switch. It keeps track of the difference between the reserved bandwidth and actually received bandwidth, and minimizes the difference to ensure fairness. Moreover, in order to fully utilize the multicast capability provided by the switch, CMF lets a multicast packet simultaneously send transmission requests to multiple output ports. In this way, a multicast packet has more chances to be delivered to multiple destination output ports in the same time slot and thus to achieve short multicast latency. Extensive simulations are conducted to evaluate the performance of CMF, and the results demonstrate that CMF achieves the two design goals: fair bandwidth allocation and short multicast latency.     

An FEC scheme combined with weighted scheduling to reduce multicast packet loss in IPTV over PON

Congestion is one of the most important challenges in optical networks. In a Passive Optical Network (PON), the Optical Line Terminal (OLT) is a bottleneck and congestion prone. In this paper, a framework is proposed with Forward Error Correction (FEC) at the IP layer combined with Weighted Round Robin (WRR) at the scheduling level to overcome packet-loss due to congestion in the OLT in order to achieve efficient video multicasting over PON. In the FEC scheme, Reed-Solomon (RS(n,k)) with erasure coding is used, where (n−k) erroneous symbols per n symbol blocks can be corrected. In our framework, an Internet Protocol TeleVision (IPTV) service provider uses the mentioned RS coding and generates redundant packets from regular IPTV packets in such a way that an Optical Network Unit (ONU) can recover lost packets from received packets, thus resulting in a better video quality. Simulation results show that using the proposed framework, an ONU can recover many lost packets and achieve better video quality under different traffic loads for its users. For instance, the proposed method can reduce packet loss rate by almost 55% and 10% under traffic load 0.9, respectively, compared with the Round Robin (RR) and WRR methods under symmetric traffic load. When High Receivers Queue (HRQ) traffic (i.e., traffic received by many users) is twice Low Receivers Queue (LRQ) traffic (i.e., traffic received by a small number of users), this reduction is almost 86% and 30% under traffic load 0.9. Finally, when LRQ traffic is twice HRQ traffic, the reduction in packet loss rate is almost 70% and 91% at traffic load 0.5.     

Fair and efficient packet scheduling using Elastic Round Robin

Parallel systems are increasingly being used in multiuser environments with the interconnection network shared by several users at the same time. Fairness is an intuitively desirable property in the allocation of bandwidth available on a link among traffic flows of different users that share the link. Strict fairness in traffic scheduling can improve the isolation between users, offer a more predictable performance and improve performance by eliminating some bottlenecks. This paper presents a simple, fair, efficient, and easily implementable scheduling discipline, called Elastic Round Robin (ERR), designed to satisfy the unique needs of wormhole switching, which is popular in interconnection networks of parallel systems. In spite of the constraints of wormhole switching imposed on the design, ERR is also suitable for use in Internet routers and has better fairness and performance characteristics than previously known scheduling algorithms of comparable efficiency, including Deficit Round Robin and Surplus Round Robin. In this paper, we prove that ERR is efficient, with a per-packet work complexity of O(1). We analytically derive the relative fairness bound of ERR, a popular metric used to measure fairness. We also derive the bound on the start-up latency experienced by a new flow that arrives at an ERR scheduler. Finally, this paper presents simulation results comparing the fairness and performance characteristics of ERR with other scheduling disciplines of comparable efficiency     

一种适合在无线传感网络中传输实时业务的区分服务方案

本文在我们建立的基于Directed Diffusion（DD）的无线传感器网络模型的基础上，提出一种针对实时业务传输的区分服务方案，称为轮询路径调度算法（Round Robin Path Scheduling，RRPS）。通过泛洪建立路径能量瓶颈梯度及跳数梯度，并根据这两个梯度的组合，将源节点（Source node）和观测节点（Sink node）之间的中继节点（Intermedlate node）优化成多条路径。根据网络的资源状况为不同等级的业务分配不同的路径：为实时业务分配延时小的路径组，同时轮流切换该组中的路径，以达到局部负载均衡；剩余的路径组为尽力而为业务提供服务，并以轮询方式选择路径，以均衡网络能耗。实验结果表明，RRPS能支持传感器网络中同时传输不同服务等级的业务，降低实时业务的端对端延时和延时抖动，并使网络生存期得到提高。     

高速路由器中一种有效的组播交换排队机制

许多Internet新业务产生的网络流量都属于组播类型．高速路由器中组播交换队列设计是解决组播数据在复杂网络中有效传输的关键问题之一．理想情况下,为保证服务的公平性及有效性,不应该在排队和调度时对组播和单播人为地进行区分．在二者共存的情况下,如何进行公平地排队、交换是亟待解决的问题．基于共享存储交换结构,提出了一种有效的组播交换队列设计方案,同时提供了相应的与组播比例和平均扇出相关的缓存管理机制和队列调度算法．仿真结果表明,与在Cisco高端路由器中广泛应用的ESLIP设计方案相比,在输入负载大于80％的重负载环境中,该系统能够获得更低的平均时延和更小的系统丢包率．     

基于ECN的单播流与多播流间带宽共享算法

An ECN-based implementing bandwidth-sharing algorithm for unicast and multicast flows is presented.The algorithm uses a bandwidth allocation strategy to give an incentive to multicast flows in bandwidth allocation according to algorithm of the number of receivers, and to assure the unicast flows get their bandwidth shares fairly.Provided best-effort networks, an ECN-based congestion control algorithm is used to implement differentiated service in bandwidth allocation between unicast flows and multicast flows. In implementation, we solve the problems such asreceiver‘s number estimation, the RTT estimation and compromise between convergence and stability.The simulation results show that the algorithm can implement bandwidth sharing for TCP flows and multicast flows. Atthe same time, the algorithm not only allocates more bandwidth to multicast flows, but promises TCP flows to get their fair bandwidth share.