支持未来网络创新的可编程虚拟化路由器技术

未来互联网体系结构、协议、算法需要在试验网络中进行评估与验证。可编程虚拟化路由器是构建未来互联网试验床的核心设备。由可编程虚拟化路由器构建的试验床可以在一个物理网络上构建多个独立虚拟网络,实现不同体系结构并行实验验证。相比传统路由器,可编程虚拟化路由器需要具备虚拟化与灵活可编程的特点。文章给出一种支持未来网络创新的可编程虚拟化路由器平台——PEARL。PEARL具有可编程、虚拟化隔离与高性能的特点,可满足未来互联网试验床建设要求。     

虚拟CPU负载预测算法性能评估

准确的虚拟CPU负载预测是提高虚拟机CPU调度性能的重要前提,然而,虚拟机操作系统环境下,虚拟CPU负载预测方法需要尽可能简单、有效.针对虚拟机CPU调度应用场景,以实际CPU负载为研究对象,选取五种简单的时间序列预测算法,详细评估其虚拟CPU负载预测性能,为虚拟机CPU调度的实现提供了研究基础.结果表明,平均移动法、...     

一种改进的光突发交换调度算法研究

数据信道调度是OBS核心路由器的关键技术之一,文章对数据信道的几种调度算法进行了分析.在此基础上,介绍了一种改进的波长调度算法.网络仿真结果表明,该算法可以有效改善网络性能.     

制播网IP化方案探究及演进

本文分析了目前制播网IP化边缘调度和核心调度的几种方案,并研究一种基于通用交换机实现无压缩媒体流无阻塞调度的实现方法。同时探讨交换机和路由器混合组网的可能性,在得到路由器制播网优势特性的同时,降低整体成本。以SDN集中管控方式实现IP媒体流的无阻塞、逐流调度,为中小型演播室、转播车、外场制播等应用场景提供一种新的IP信号调度交换组网方案。     

面向虚拟路由器的基于历史转发开销的资源调度算法

通过研究以Xen为代表的虚拟工具中资源调度算法,得知它们无法保证虚拟路由器中资源共享的公平性。该文提出一种基于历史转发开销的资源调度算法,用来确保路由器实例占用资源的公平性,尤其物理平台的输入/输出(I/O)资源。该算法通过统计路由器实例最近的报文转发开销来计算出路由器实例调度的优先级,确保平均吞吐量较低的路由器实例获得被调度的机会。同时,该算法通过设置优先级计算公式中处理延迟的值,达到对延迟敏感强的路由器实例的支持,以及通过预测报文处理时间决定待处理报文是否丢弃,避免不必要的系统开销。通过实验测试,相对于Credit算法,该文算法在确保虚拟路由器资源共享的公平性方面存在明显优势,并且能为延迟敏感的路由器实例提供支持。     

一种支持多优先级的高速Crossbar调度算法

现有支持多优先级的高速Crossbar调度算法需要交互的控制信息较多,控制信息的传输时间已成为调度算法性能提高的主要瓶颈.为提高Crossbar调度的性能,本文提出一种新的支持多优先级的高速Crossbar调度算法p-iDRR,该算法具有硬件实现简单、控制信息量少、高速和可扩展性强等优点.仿真结果表明,p-iDRR具有良好的吞吐量、时延性能,适用于高速、多端口、大容量的路由器.     

用于DiffServ的核心无状态的虚拟时钟调度算法

提出了一种同时满足对资源进行分配要求和具有良好的可扩展性要求的包调度算法。通过一个基于虚拟时钟的 FIFO 队列来达到公平队列中多个队列的效果,即在不同的流间实现资源的公平分配;同时,由于在核心路由器维持的是一个 FIFO 队列,因此无需进行每流状态的管理和对收到的数据包执行按流分类的工作,这样较之公平队列算法大大地降低了在核心路由器的系统开销,从而满足可扩展性的要求。     

基于双向共享树的MPLS多播流聚合算法

可扩展性是影响多播在MPLS网络大规模使用的主要问题,为解决该问题提出了一种基于双向共享树的多播流聚合算法.它根据节点之间的关系计算多播流的可聚合度,然后将标记边缘路由器聚类生成共享树的叶子节点集,并由树管理服务器计算双向共享树的拓扑结构,最后将可聚合度大于指定阈值的多播流汇聚到树中.实验结果表明,该算法可以大幅缩小MPLS标记的占用,简化中间节点的处理过程,减少路由器的转发状态,大大提高了MPLS多播的可扩展性.     

片上网络调度算法相关研究

随着半导体集成工艺的发展,单个芯片上集成的IP核数目急剧增加,片上网络(NoC)成为未来取代总线设计的新模式。调度算法作为NoC研究的关键问题之一,对整个网络的传输性能起着重要的作用。本文对片上网络虚信道路由器调度算法的相关研究进展进行了总结,首先从路由器结构特点出发,介绍了几种典型的NoC仲裁器和调度器实例,总结相应的算法设计思想。再对NoC常用路由器调度算法进行了分类介绍,详细分析了各种调度算法的相关特性。最后,探讨了NoC路由器调度算法的研究方向。     

一种支持带宽预约的crossbar调度算法

由于受到存储器带宽的限制,目前宽带路由器一般采用输入缓冲的crossbar交换开关.支持带宽预约的开关调度算法对保证路由器的服务质量(QoS-Qualityof Service)十分重要.本文介绍一种支持带宽预约的crossbar交换开关调度算法——CISP(Configurable Input Serial Polling).该算法不但支持确保服务,而且硬件实现简单.     

基于可编程硬件的虚拟路由器数据平面设计与实现

未来网络体系结构创新和验证亟需建设虚拟化网络实验平台,虚拟路由器作为其中的核心组网设备,其结构和性能决定了实验平台的灵活性和承载能力.本文提出基于并行流水线的虚拟路由器数据平面结构,结合并行包分类和异步多指针轮询调度机制,在同一物理底层上实现了多个相互隔离的并行异构路由器.本设计在可编程硬件上进行了原型实现,并结合商用及软件路由器在真实的网络环境中部署、测试与实验.实验结果表明与传统单流水线结构相比,本设计能以更高灵活性和并行性支持异构的路由器实例独立运行;在逻辑资源开销和延时特性未显著增加的情况下,并行虚拟路由器可以达到与硬件可比的线速转发能力.     

Congestion Detection in the European Internet

In this paper we present a study about the utilization of one-way delay measurements to detect and characterize network congestion in the european Internet. The experiments have been made using the ETOMIC platform that allows one-way delay measurement with high precision timestamps. We have found a peculiar router behaviour in which the bottleneck is not the available bandwidth but it is the packet processing power of the router (backplane and CPU constraints). This router has been characterized with several network parameters. Some of them are the dependency of this limitation with the input data rate in packets per second, the size of burst packet losses measured in packets or time and the absence of specific scheduling algorithms in the router that could affect to larger flows.     

Deficit round-robin scheduling for input-queued switches

We address the problem of fair scheduling of packets in Internet routers with input-queued switches. The goal is to ensure that packets of different flows leave a router in proportion to their reservations under heavy traffic. First, we examine the problem when fair queuing is applied only at output link of a router, and verify that this approach is ineffective. Second, we propose a flow-based iterative deficit-round-robin (iDRR) fair scheduling algorithm for the crossbar switch that supports fair bandwidth distribution among flows, and achieves asymptotically 100% throughput under uniform traffic. Since the flow-based algorithm is hard to implement in hardware, we finally propose a port-based version of iDRR (called iPDRR) and describe its hardware implementation.     

分级调度算法在路由交换机上的应用

本文提出了一种两级的分级调度模型,着重研究其算法的具体实现,并分析算法在路由交换机中的应用。分级调度算法的引入,保证在现有Internet体系结构下、best-effort服务能很好地与有QoS要求的实时服务相结合,仿真实验证明该发级调度算法可行有效。     

Comparative study of two CPU router time management algorithms in cellular IP networks

Providing good quality of service (QoS) in cellular IP networks is an important requirement for performance improvement of the cellular IP network. Resource reservation is one of the methods used in achieving this goal and is proven to be effective. The main resources to be reserved in a cellular IP network are bandwidth, buffer and central processing unit (CPU) cycles. Router CPU cycle is the time taken by the router to process the packet of the flow before forwarding it to the next router (hop). This paper proposes a model for CPU cycle optimization of routers for real‐time flows in a cellular IP network. The model applies both genetic algorithm (GA) and particle swarm optimization (PSO) as soft computing tools to optimize the CPU cycles and reduces the flow processing time at each router in the route taken by a flow. Simulation experiments illustrate a comparative study of the model.     

Resource prediction and management in active networks

Active networks provide a programmable user–network interface that supports dynamic modification of the network's behavior. Network nodes, in addition to forwarding packets, perform customized computation on the messages flowing through them. Resources in an active network mainly consist of CPU and bandwidth. The inherent unpredictability of processing times of active packet poses a significant challenge in CPU scheduling. It has been identified that prior estimation of the resource requirements of a packet is very difficult since it is platform dependent and also depends on processing load at the time of execution, operating system scheduling, etc. An efficient allocation is required for the optimal utilization of resources. In this paper, resources are estimated using prediction techniques such as single exponential smoothing (SES), adaptive‐response‐rate single exponential smoothing (ARRSES) and Holt's two‐parameter estimation models. The estimated results agreed most with the actual requirements. The estimation models were compared with model criteria. An algorithm was also designed for the allocation of resources. Effectiveness of the algorithm was measured through simulation and achieved almost perfect fairness for all flows and also provided much superior delay guarantees under a highly dynamic environment. Copyright © 2008 John Wiley & Sons, Ltd.     

基于 ForCES的转发件中Xscale层的研究和实现

为了改进目前IP路由器的可扩展性和灵活性等特点,研究基于开放可编程的新一代路由器架构.介绍了控制和转发相分离的ForCES协议框架和Intel IXA结构,提出了一种基于网络处理器IXP2400并支持ForCES协议的开放可编程的路由器框架.详细地分析了转发件中Xscale层的设计和实现.在此基础上设计了相应的测试平台,实验结果表明了这种路由器框架的可行性.     

基于虚拟分割机制的多服务交换路由器的研究

本文提出了一处基于虚拟分割机制的可编程多服务器由器实现结构：PVSMR，并对它的三个层面的主要构成及其关键技术进行了深入研究。PVSMR基于一种有效而灵活的资源虚拟分割算法，它能够提供与多类应用相适应的、灵活的报文处理和转发控制能力。     

Processing the new world of interactive media

Trimedia is a family of programmable multimedia processors from the Trimedia product group of Philips Semiconductors. This architecture is based upon a high-performances VLIW CPU core. TM-1000 is the first product from a family of multimedia processors based upon the Trimedia architecture. TM-1000 is designed to concurrently process video, audio, graphics, and communication data. TM-1000 consists of a high-performance VLIW-based CPU core, large instruction and data caches, main memory interface, and video, audio and communication related peripherals. TM-1000 is a multimedia system on a chip: high-quality video and audio applications can be implemented in TM-1000 using high-level languages such as “C” and “C++”. The authors mainly focus on the VLIW CPU architecture