【作者】 汪学舜；

【导师】 余少华；

【作者基本信息】 华中科技大学 ， 计算机应用技术， 2011， 博士

【摘要】 光纤接入是下一代网络中的主要组成,能提供高速大容量传输,而流媒体是将来IP网络的主要应用,由于流媒体数据的传输有着特别的需求,需要对现有基于IP流的网络,实施适当的QoS保证。流媒体在网络中传输时,通过网络接入层交换设备进入网络,然后在网络中传输,因此需要在接入层交换设备和传输网络中,根据其传输特点,分别实施有效的QoS控制。光纤接入网中针对流媒体的QoS保证一直是业界的热点问题,本文围绕光纤接入网络中拥塞控制和波长带宽分配的关键技术取得了如下成果：(1)提出了一种基于E-Model传输级别的动态门限控制算法(EDTA),实现光纤接入交换设备实施有效地缓存管理策略和拥塞控制策略,将交换设备的缓存管理分为全局门限控制和队列门限控制两部分。全局门限控制通过判断不同的传输场景,进行门限控制,保证不同传输场景下的传输性能。队列门限控制则基于E-Model传输级别参数,进行门限的划分和调整,保证流媒体的传输质量。另外,该算法在流媒体数据流传输过程中检测和跟踪其时延,在转发分组数据前,根据容忍时延阀值,丢弃超时数据包,减少不必要的带宽浪费,并且对所到达的数据流按照累积时延进行优先级分类。理论分析和实验结果表明,该算法能有效改善流媒体的传输性能,对交换设备的缓存资源进行有效控制,并提高网络流媒体传输质量。本文基于E-Model传输级别的动态门限控制算法已在交换容量为384Gbps/768Gbps的机架式汇聚交换机平台(支持IPv4/IPv6双栈)上实现并得到验证,并在2011年1月第1期的《计算机研究与发展》、在2010年7月第7期的《计算机科学》和国际会议SPIE 2009发表相关论文。(2)提出了基于门限的动态带宽分配算法,实现以太无源光网络(EPON)中共享上行带宽的公平和有效分配,该算法根据一个轮循周期中接收光网络单元(ONU)数据的速率,判断当前状态处于高负载状态还是低负载状态,进而自适应地调整光线路终端(OLT)接收ONU发送数据的门限值。高负载时,该算法能延长轮循周期并减少空闲信道周期,从而提高网络吞吐量；低负载时,该算法能减短轮循周期而加快数据的转发。对ONU授权带宽时,根据ONU的带宽请求和门限值进行分配。另外文中实现了三种基于反馈控制理论的白适应调整门限方法并分析其优缺点。在10G EPON系统中实验表明相比其他算法,该算法能减少平均包时延,提高网络吞吐量。在光纤通信技术和网络国家重点实验室(武汉邮电科学研究院)开放基金资助项目“下一代光接入关键技术和系统研究”项目中的10G EPON的OLT系统上验证了基于门限的EPON动态带宽分配。该算法即将发表在《软件学报》上,另在2011年1月第1期的《重庆大学学报》(英文版)发表相关论文。(3)提出了基于欧氏距离的高效用ONU带宽分配算法,实现波分多路无源光网络技术(WDM PON)中ONU授权调度,该算法采用调度理论的方法来解决授权调度问题。将授权调度和波长分配进行结合,并将其形式化为矩形Packing问题,采用拟人的策略,为WDM EPON中ONU授权调度问题的快速求解提供了一种高效的启发式算法。进一步模拟实验表明,提出的算法可以减少平均包时延,提高网络带宽利用率,表明算法对授权调度的有效性。该算法即将发表在《通信学报》上。(4)提出了一种新的光纤接入网络中组播聚合的双邻域查找算法,该算法用于解决光纤接入网中聚合组播问题。使得生成的聚合树数量满足波长约束的前提下,带宽浪费比率尽可能的小。定义了一种新的优先聚合规则以生成初始解；定义了两种新的邻域结构,使邻域查找具有更高效率；提出了跳跃策略以跳出局部最优解并且将查找引向有希望的方向。模拟实验表明,该算法可有效进行组播组的聚合,有效地减少网络中的组播树数量,而且对不同的应用场景都能获得较好的性能。已在国际会议WiCOM 2009、CiSE 2009等上发表相关论文。本文申请了《适用于多媒体数据传输门限缓存管理方法》和《一种新型以太无源光网络动态带宽分配方法》两项发明专利,共发表论文16篇,其中以第一作者发表论文13篇。EDTA算法在吉林、茂名等多个工程应用中,有效的解决了由于各种攻击造成的网络流媒体传输不稳定问题,基于门限的动态带宽分配算法在10G EPONOLT产品An5516-01B中高效地实现了动态带宽分配。另外,与其相关的科研项目通过了专家组的验收,获得好评。更多还原

【Abstract】 It is widely believed that media service will be one of the major applications in future IP networks, and IP over optical networks will be a major component of the next generation IP network because optical fiber access networks can provide high-speed and large-capacity transmission. But media service have their own characteristic, they need quality of service(QoS) in transmission. Media data may be introduced into network by optical access devices, then be transmitted in network. So it need to support quality of service in these devices according to media service characteristic.The QoS is stille an hot topic with great challenge in optical fiber access networks. In order to guarantee the transmission quality of medium traffic in optical fiber access networks, our thesis focus on the key technologies of the researches on bandwidth allocation and congestion control. The major contributions of this thesis are as follows:(1)This paper proposes a novel dynamic threshold algorithm at media traffic level for shared buffer packet switches, known as Dual-dynamic Threshold Algorithm based on E-Model(EDTA). The EDTA strategies for buffer management and congestion control strategy are applied in exchanging devices for flow medium in optical fiber access networks, such as switches and routers. EDTA divides buffer management of switch into two parts:the global threshold strategy and the queue threshold strategy. The global threshold strategy controls the shared buffer by a whole threshold through judging different traffic scenarios to ensure good transmission performance in all situations. The queue threshold strategy decides and adjusts output queue threshold based on E-Model traffic levels, which transforms several medium service quality effecting parameters into users’ psychological factors, thus guarantees the quality of flow medium data. On the other hand, EDTA improves the QoS of multimedia stream in network by detecting and discarding these packets that accumulated delay exceeds multimedia stream’s delay tolerance so as to maintain high bandwidth utilization. All kinds of packets are firstly classified into queues according to their own priorities which calculated by accumulative delay. Experimental results show that the proposed algorithm (EDTA) can improve the traffic performance for flow media more effectively, achieve better quality of network flow medium transmission, comparing with those algorithms using traditional control. And it is suitable to be used in any network condition and can improve the utilization of the network resources. The EDTA algorithms and schemes have been implemented and available on a 384/768Gbps switch. The idea of EDTA has been published in Journal of Computer Research and Development, Computer Science and in proceedings of the International Society for Optical Engineering.(2)A dynamic bandwidth allocation algorithm based on gate threshold was proposed to provide efficient and fair utilization of the Ethernet passive optical networks (EPON) upstream bandwidth and support QoS requirements of different traffic classes. The algorithm uses optical network unit (ONU) data-receiving rate to decide whether the current state is at high payload or at low payload, and further adjust optical line terminal (OLT) receiving data gate threshold from ONU. At high payload state, it lengthens polling cycle, shortens channel idle time and increases network throughput; at low payload state, it shortens polling cycle and increases data transmission. The algorithm decided the data-receiving rate from the ONU according to the ONU data-sending response rate and the gate threshold; implemented three methods to adaptive adjust the gate threshold, and analyzed these methods’characteristic. Experiments show this algorithm can decrease average packet delay and increase network throughput in 10G EPON. The algorithm for EPON system have been implemented on a 10G EPON OLT designed for the project "Research on key technology and system of next generation optical access" of Open Foundation of State Key Laboratory of Optical Communication Technologies and Networks(Wuhan Research Institute of Posts & Telecommunications). The idea will be published in Journal of Software, and has been published in Journal of Chongqing University(English Edition).(3)The authors propose the so-called high utility ONU grant scheduling policy based on Euclidian distance by the quasi-human strategy to solve ONU grant scheduling techniques for wavelength division multiplexed Ethernet passive optical networks (WDM EPONs), and take a scheduling theoretic approach to solving the grant scheduling problem. After formulate the joint grant scheduling and wavelength assignment problem as the rectangles packing problem, An effective heuristic algorithm is present, and the solution to the joint grant scheduling and wavelength assignment problem for WDM EPON can be obtained quickly by applying this algorithm. Simulation experiments show the grant scheduling algorithm can decrease average packet delay and increase network utilization. Results indicate that improvements may be obtained in the network performance. The idea will be published in Journal of Communication.(4)A new double local search algorithm(DLSA) for solving the multicast aggregation tree in networks is presented. It is aggregate multicast tree for wavelengths bandwidth allocation in medium data transmitting by multicast in optical fiber networks. The objective of this kind of multicast aggregation algorithm is minimizing the bandwidth wastage ratio subject to the constraints that the number of wavelength affects the aggregation results. A new priority aggregate rule based on the greedy strategy is proposed to generate initial solution, and proposed a new concept of neighborhood structure which is based on greedy strategy. DLSA search effectively in two kind neighborhood structures, and some off-trap strategies are proposed to jump from local optimal solution and carry the search to the feasible areas in promising directions. Simulation experiments show the double local search algorithm can aggregate multiple multicast group, and decrease the amount of aggregation multicast tree, and the results indicate that improvements may be obtained in different network condition. The idea of DLSA has been published in proceedings of the 5th international Conference on Wireless Communications, Networking and Mobile Computing and 2009 International Conference on Computational Intelligence and Software Engineering.The paper has applied for two patents, one is "Threshold of Buffer Management Strategy for Transmission Quality of Medium Traffic", and the other is "A Novel Dynamically Bandwidth Assignment Method for Ethernet Passive Optical Network". The author has written 16 papers about this paper. The first and the second innovation item have applied in some scientific research projects, and these projects and their measurement had been checked and accepted.更多还原