基于TCP/IP协议的网络负载均衡软件的设计与实现

随着以太网技术的发展,用户对业务的实效性和QoS的需求也越来越高。要解决这类问题,首先需要面对网络上传输的信息内容与传输链路协调管理的问题。特别是当网络传输大量的不同级别、不同需求的数据,一旦重要数据长时间延时或所需传输链路带宽不足甚至被占用或突然中断,将会造成极大的损失。针对多WAN口接入、网络负载均衡的运用,首先对传输的数据信息分类,然后根据所获取的每个WAN口链路状态数据,对传输的数据按比例进行分段并通过不同的计算机端口发送,最后通过不同的链路进行传输。     

光纤链路的自动交换设计

针对当前光纤链路交换的特点,提出了一种光纤链路的自动交换技术,该技术利用程序控制发送光纤链路旋转,实现与其它光纤链路的对接,完成光纤链路的自动化交换,为全光网的实现提供了另一种途径。     

基于OBS的分布并行海量地形数据服务系统

海量地形数据的存储与管理是大规模地形实时漫游系统的关键。该文提出一种基于对象存储的分布式并行地形数据服务系统(DPTSS),采用自治的存储对象存储和管理地形块数据,实现了控制路径和数据路径分离。通过元数据集群提供高效率和高可用的元数据服务,以及基于对象的存储集群实现并行的地形数据块传输服务,提供高吞吐率和高带宽的地形数据服务。对比实验表明,DPTSS在较低的TCO情况下能提供高性能的地形数据服务。     

以太网通道技术的实现与应用简

采用太网通道技术来增加链路间的带宽,并且实现链路间数据骨干线路热备份,保证数据网络的不间断服务,实现负载均衡;结合cisco设备在交换机间捆绑两条或多条链路配置形成以太网通道;通道形成后链路间带宽明显增加;链路部分故障中断,交换机重新学习,建立新的物理链路继续通信;故障排除后交换机会自动恢复通告。     

基于多链路聚合的无线实时视频传输系统

无线实时视频传输已成为当前通信领域发展的热点,但当前的无线通信技术提供的带宽尚无法满足高码率的实时视频传输的需求.针对这一问题,设计并开发一个基于多链路聚合技术的无线实时视频传输系统.该系统通过聚合多链路带宽,对各链路运用TFRC速率控制,有效地提高数据传输速率和稳定性,同时采用提早丢弃和关键帧优先发送等实时性优化策略,获得更好的视频传输质量.     

基于三层卫星网络的星间链路性能分析

星间链路性能分析是建立星间通信的基础。以包含GEO卫星、IGSO卫星和MEO卫星的三层卫星网络为例,仿真了三层卫星网络层间卫星星间距离的变化范围。在设定星间传输体制、链路参数、传输损耗等条件下,分别分析了该三层卫星网络的GEO-IGSO、GEO-MEO和IGSO-MEO三种链路在Ka频段和激光频段的性能。结果表明,在Ka频段,0.5m天线仅需5W的发射功率,可以满足2Mb/s以上的星间数据传输率;激光频段仅需0.5W的发射功率,直径0.25m的天线,可以达到2Gb/s以上的星间数据传输率,激光链路更有利于星间链路性能的提高。研究结果在未来三层卫星网络建立星间链路时,为卫星的发射功率、天线直径和星间链路数据传输速率等方面的选择提供了参考。     

ChattyGraph:面向异构多协处理器的高可扩展图计算系统

现阶段,随着数据规模扩大化和结构多样化的趋势日益凸现,如何利用现代链路内链的异构多协处理器为大规模数据处理提供实时、可靠的并行运行时环境,已经成为高性能以及数据库领域的研究热点.利用多协处理器(GPU)设备的现代服务器(multi-GPU server)硬件架构环境,已经成为分析大规模、非规则性图数据的首选高性能平台.现有研究工作基于Multi-GPU服务器架构设计的图计算系统和算法(如广度优先遍历和最短路径算法),整体性能已显著优于多核CPU计算环境.然而,这类图计算系统中,多GPU协处理器间的图分块数据传输性能受限于PCI-E总线带宽和局部延迟,导致通过增加GPU设备数量无法达到整体系统性能的类线性增长趋势,甚至会出现严重的时延抖动,进而已无法满足大规模图并行计算系统的高可扩展性要求.经过一系列基准实验验证发现,现有系统存在如下两类缺陷:(1)现代GPU设备间数据通路的硬件架构发展日益更新(如NVLink-V1,NVLink-V2),其链路带宽和延迟得到大幅改进,然而现有系统受限于PCI-E总线进行数据分块通信,无法充分利用现代GPU链路资源(包括链路拓扑、连通性和路由);(2)在...     

Performance of a Scalable Multimedia Server with Shared-Storage Clusters

The existing SCSI parallel bus has been widely used in various multimedia applications. However, due to the unfair bus accesses the SCSI bus may not be able to fully utilize the potential aggregate throughput of disks. The number of disks that can be attached to the SCSI bus is limited, and link level fault tolerance is not provided. The serial storage interfaces such as Serial Storage Architecture (SSA) provide high data bandwidth, fair accesses, long transmission distance between adjacent devices (disks or hosts) and link level fault tolerance. The fairness algorithm of SSA ensures a fraction of data bandwidth to be allocated to each device. In this paper we would like to know whether SSA is a better alternative in supporting continuous media than SCSI. The scalability of a multimedia server is very important since the storage requirement may grow incrementally as more contents are created and stored. SSA in a shared-storage cluster environment also supports concurrent accesses by different hosts as long as their access paths are not overlapped. This feature is called spatial reuse. Therefore, the effective bandwidth over an SSA can be higher than the raw data bandwidth and the spatial reuse feature is critical to the scalability of a multimedia server. This feature is also included in FC-AL3 with a new mode called Multiple Circuit Mode (MCM). Using MCM, all devices can transfer data simultaneously without collision. In this paper we have investigated the scalability of shared-stroage clusters over an SSA environment.     

一个网格应用程序监测系统的实现

并行程序在运行过程中会受到外部运行环境的干扰而出现错误,并行程序调试可以帮助用户发现并排除程序中存在的错误。只有对程序的运行进行监测才能获得调试数据,并对监测到的数据进行分析,以达到调试程序的目的。网格计算的提出推动了并行计算的发展,越来越多的应用程序在网格环境中运行。该文从以上两点出发,开发了一个网格应用程序的监测系统,可以用以调试网格上的应用程序。     

基于病毒-抗体免疫博弈的WSN链路稳定算法

为解决超宽带无线传感器网络(WSN)存在的链路稳定性较差、数据传输遇阻等问题,提出一种基于病毒-抗体免疫博弈机制的超宽带WSN链路稳定算法.对节点所在区域进行均匀分割,通过设计覆盖划分方法并结合距离及剩余能量因素来优化分割区域,从而降低链路抖动概率.引入免疫算法,根据链路-节点之间的抗体特性来构建病毒-抗体免疫博弈机制,以优化节点及链路聚类效果,并通过病毒-抗体训练改善节点与链路间的数据交互特性,从而提升链路质量及区域传输性能.基于能量-跳数均衡方法,设计多参数判定机制,评估区域节点与sink节点的链路连通性能,提高算法的链路拥塞控制能力.在此基础上,利用PSK预发射方法的频域正交特性,对区域节点逐个设定发射频率,最大限度地降低因频率干涉而导致的链路抖动现象.仿真结果表明,与LEACH、LMS-A算法相比,该算法链路稳定性更高,网络稳定运行时间更长,拥塞发生频率更低.     

光纤传输设计中的距离计算

光纤通信系统性能受光纤带宽及其传输损耗的影响,而光纤的传输损耗特性是决定光纤网络传输距离、传输稳定性和可靠性的最重要因素之一。针对上述问题,文章在对光：纤链路损耗进行分析的的基础上,给出了光纤传输距离计算的方法。     

Modeling and analysis of nano-sized GMRs based on Co,NiFe and Ni materials

Magnetic simulation method is introduced to analyze giant magnetoresistances(GMRs)in nanoscale for nano-sized biosensors.A spin valve model with special gridding corresponding to the exchange interaction length is proposed to study the influence of easy axes,exchange coefcients,pinning fields and feature widths on magnetization reversals and hysteresis characteristics of nano-sized GMRs with diferent pinned layer and free layer materials of Co,NiFe and Ni.The switching field is found to be almost linear with the pinning field and decrease with the absolute exchange coefcients and the feature widths for the nano-sized GMRs.The increase rate of each depends on the spin valve stacks.Further investigations into variations of the magnetization distribution reveal that the initial magnetization distribution and the magnetization reversal mode depend greatly on easy axes and materials The dependence on easy axes based mainly on the magnetocrystalline anisotropy is illustrated in detail.     

Fairness performance of dynamic weights in the ATM ABR service

Traditional schemes fail to achieve fair distribution of bandwidth among available bit rate connections. In this paper, a new scheme called Active Fairness is proposed which substantially improves fairness in bandwidth allocation. Contrary to one set of weights used in traditional schemes, Active Fairness maintains two sets of weights at each link. The first set is the same as that used in traditional schemes, which represents the relative bandwidth allocation desired out of the available bandwidth at the link. If these weights are used directly in bandwidth allocation, the actual proportion of the bandwidth utilized by an individual connection can deviate substantially due to factors such as the number of links traversed by the connection, its round-trip propagation delay, etc. In order to take into account these factors, another set of weights (dynamic in nature) is derived at each link, which is used in bandwidth allocation. Active Fairness achieves significant fairness improvement which is demonstrated through simulations involving bursty background traffic, network bottlenecks, dynamic VC mixes and different fairness definitions.     

Will new fiber technology quench the thirst for bandwidth?

The worldwide demand for bandwidth is soaring, driven by increasing Internet usage. To meet this demand, telephone companies are working on ways to implement dense wavelength division multiplexing, a technology designed to wring more bandwidth out of fiber-optic cable     

基于QoE感知的中继卫星带宽资源分配方法研究

为改善数据中继卫星的带宽分配对负载传输效率的影响，提出了一种基于用户体验质量QoE感知的中继卫星带宽资源分配方法。考虑到空间信息网络高动态链路情况下传输的可靠性，建立基于多个静止同步轨道卫星协同接入模型，研究了低轨道用户卫星进行多路数据上传的优势特点。通过设置链路效能函数，其将用户QoE满意度量化为链路反馈和链路成本，并用库恩塔克方法求解，实现最大化系统效能和带宽公平分配。研究结果表明，与Load-Balancing和Best-SNR-First方法相比，该方法不仅保证了用户QoE满意度，还提升了网络的接入性能。     

改进的遗传算法无线视频传感器网络协作路由技术研究

提出了适用于无线视频传感器网络的基于能量感知的跨层交互多路径协作路由技术.该技术首先采用了基于视频传感器节点感知距离的遗传优化算法,预测传输视频数据的能耗和剩余能量,结合无线信道质量和视频编码算法建立一种跨层协同的工作体系,优化节点传输视频数据的能耗、时延和带宽等因素;然后建立应用层、网络层和物理层跨层协同工作体系.仿真实验和数学分析表明,该技术不仅能够较好地满足视频传感器网络应用业务的多样性QoS数据传输性能需求,而且可以充分利用视频传感器网络受限的计算、存储能力和能量等资源.     

Increasing multicast transmission rate with localized multipath in software-defined networks

Network layer multicast is a highly efficient oneto- many transmission mode. Data rates supported by different group members may differ if these members are located in different network environments. Currently there are roughly two types of methods solving the problem, one is limiting the data rate so that every group member can sustain transmissions, and the other is building multiple trees to increase the provision of network bandwidth. The former is inefficient in bandwidth usage, and the latter adds too many states in the network, which is a serious problem in Software-Defined Networks. In this paper, we propose to build localized extra path(s) for each bottleneck link in the tree. By providing extra bandwidth to reinforce the bottleneck links, the overall data rate is increased. As extra paths are only built in small areas around the bottleneck links, the number of states added in the network is restrained to be as small as possible. Experiments on Mininet verify the effectiveness of our solution.     

一种测量任意链路可用带宽的方法

可用带宽测量对于网络行为分析、网络服务质量(quality of service,简称QoS)的验证等有很重要的作用.现有可用带宽测量工作主要集中在端到端路径可用带宽测量,仅提供路径上承压链路(tight link)的信息,而不能提供其他关键链路的信息.为此,提出一种新颖的链路可用带宽测量算法LinkPPQ(trains of pairs of packet-quartets used to measure available bandwidth of arbitrary links),它采用由四探测分组结构对构成的探测序列,能够测量网络中任意链路的可用带宽,并跟踪该链路上背景流的变化.在仿真环境和实际网络环境下研究了LinkPPQ 的性能.仿真结果表明,在几种不同背景流场景下,对于具有单狭窄链路的路径和具有多狭窄链路的路径,LinkPPQ 都能够对各个链路的可用带宽进行有效的测量.绝大多数情况下测量误差小于30%,且具有较好的测量平稳性.实验网的实验结果也表明,LinkPPQ 可以准确测量以下几种情况下的链路的可用带宽:a) 从容量为10Mbps 的链路准确地测量一条100Mbps 链路的可用带宽;b) 准确测量容量10 倍于紧邻其后狭窄链路的容量的链路的可用带宽;c) 准确测量具有多狭窄链路的路径上各狭窄链路的可用带宽.     

Signal strength based routing for power saving in mobile ad hoc networks

The transmission bandwidth between two nodes in mobile ad hoc networks is important in terms of power consumption. However, the bandwidth between two nodes is always treated the same, regardless of what the distance is between the two nodes. If a node equips a GPS device to determine the distance between two nodes, the hardware cost and the power consumption increase. In this paper, we propose using a bandwidth-based power-aware routing protocol with signal detection instead of using GPS devices to determine the distance. In our proposed routing protocol, we use the received signal variation to predict the transmission bandwidth and the lifetime of a link. Accordingly, the possible amount of data that can be transmitted and the remaining power of nodes in the path after data transmission can be predicted. By predicting the possible amount of data that can be transmitted and the remaining power of nodes after data transmission, we can design a bandwidth-based power-aware routing protocol that has power efficiency and that prolongs network lifetime. In our simulation, we compare our proposed routing protocol with two signal-based routing protocols, SSA and ABR, and a power-aware routing protocol, MMBCR, in terms of the throughput, the average transmission bandwidth, the number of rerouting paths, the path lifetime, the power consumed when a byte is transmitted, and the network lifetime (the ratio of active nodes).     

CbRouter:一种利用交叉开关旁路的双向链路片上网络路由器

片上互连网络为多核体系结构提供了高效的通信支持。目前的片上网络通常采用单向传输链路,链路资源利用率较低。为了实现链路带宽资源高效分配、进而高效利用链路带宽资源,提出了一种新的双向链路调度算法,并设计了一种支持此算法的双向链路路由器。这种新型的路由器结构能够在不影响路由原有数据通道条件下,提供一条旁路数据通道来快速传输数据。实验结果表明,应用该双向链路路由器可使Mesh网络饱和吞吐率和链路平均利用率分别得到最大83.3%和24.53%的提升。