TD-LTE系统帧配置方法的研究

针对TD-LTE无线网络规划中时隙规划的需要,对TD-LTE小区帧配置方法进行了研究.首先归纳总结了TD-LTE系统吞吐量计算方法,通过仿真,验证了TD-LTE帧配置对系统容量的影响.然后研究了TD-LTE单业务小区的帧配置方法,设计建立了基于帧结构的TD-LTE小区业务吞吐量仿真平台,并对单业务小区的用户平均吞吐量进行了仿真分析,给出了部分单业务小区的最佳帧配置建议.最后,仿真分析了多业务小区的用户平均吞吐量,给出了部分混合业务下小区的最佳帧配置建议.     

基于IP突发信源模型数据包的定量计算研究

本文以IP突发信源on/off模型的单IP业务源的数据包生成特性分析为基础,以队列缓冲配置和IP数据包丢失率、排队时延的计算为主要研究对象,通过对多业务源排队系统的IP数据包排队时延进行深入的综合分析,得出了一些新的QoS定量计算解析式,这些解析式可用于计算IP交换路由器QoS参数.     

未来光网络中的交换路由器

IP业务的爆炸式增长与DWDM技术的突飞猛进为新的WDM网络直接承载IP业务创造了条件。光交换和交换路由器的发展提供一种集成了智能IP路由技术和大容量光交换网络的交换路由器模型。这种交换路由器支持高QoS保证 ,简化了光核心网络结构 ,是近期光联网的理想解决方案     

未来光网络中的交换路由器

IP业务的爆炸式增长与DWDM技术的突飞猛进为新的WDM网络直接承载IP业务创造了条件,光交换和交换路由器的发展提供一种集成了智能IP路由技术和大容量光交换网络的交换路由器模型。这种交换路由器支持高QoS保证,简化了光核心网络结构,是近期光联网的理想解决方案。     

基于IP突发信源模型数据包的定量计算研究

本文以IP突发信源on／off模型的单IP业务源的数据包生成特性分析为基础，以队列缓冲配置和IP数据包丢失率、排队时延的计算为主要研究对象，通过对多业务源排队系统的IP数据包排队时延进行深入的综合分析，得出了一些新的QoS定量计算解析式，这些解析式可用于计算IP交换路由器QoS参数．     

高速路由转发引擎的关键技术与实现

给出一种分段式高速IP路由查表算法。若采用50ns的动态存储器,该方法可以在小于100ns内完成一次最长匹配路由查找,并且具有快速的路由表项更新。这种分段式高速IP由查表算法在国家863计划重大课题核心路由器－OmniRouter880的研制中得到了工程实现应用。机要验收测试表明,该算法具有2．5G线速率的转发能力,能够有效支持每秒1000条路由更新的路由抖动。工程实现证明,分段式高速IP路由查表算法对设计高速骨干路由器的转发引擎,具有重要的指导意义。     

SoC中的IP核同步设计方法

基于对IP核复用的集成效率考虑,针对片上系统的设计特点构造了一种新型的IP核模型.该模型包括用于描述IP核的延迟信息的时序接口模块、多时钟域适应的再同步接口模块和IP功能描述模块.然后给出了该模型在片上系统中的集成方法.实际电路综合结果表明,和现有IP核集成相比,应用该模型进行片上系统集成,设计效率可以提高近30%,性能提高约15%.     

一种基于RIP和帧中继的网络设计

广域网和以太网是两种不同的网络技术,而小型局域网因为其业务多样性和分布离散性,使得其需要兼容不同协议的网络。提出一种基于以太网RIP路由协议和广域网的帧中继协议的网络设计,满足不同协议互通,为不同核心路由器和交换机之间配置RIP路由、静态默认路由和帧中继子接口,最终完成了该网络的布置。     

一种基于RIP和帧中继的网络设计

广域网和以太网是两种不同的网络技术,而小型局域网因为其业务多样性和分布离散性,使得其需要兼容不同协议的网络。提出一种基于以太网RIP路由协议和广域网的帧中继协议的网络设计,满足不同协议互通,为不同核心路由器和交换机之间配置RIP路由、静态默认路由和帧中继子接口,最终完成了该网络的布置。     

高速SpaceWire路由器的设计研究

SpaceWire是由欧航局所提出的高速高可靠性的航空总线标准。首先论述了基于SpaceWire标准的航空总线路由器IP核的设计与实现。SpaceWire路由器由SpaceWire接口和SpaceWire路由开关组成,文中分别介绍了这两部份的设计,并对SpaceWire路由开关的设计提出了新的架构,最后的实验结果说明了所设计的8端路由器的速度达到了 200Mb／s。     

High-speed buffer management for 40 gb/s-based photonic packet switches

We develop a method of high-speed buffer management for output-buffered photonic packet switches. The use of optical fiber delay lines is a promising solution to constructing optical buffers. The buffer manager determines packet delays in the fiber delay line buffer before the packets arrive at the buffer. We propose a buffer management method based on a parallel and pipeline processing architecture consisting of (log/sub 2/N+1) pipeline stages, where N is the number of ports of the packet switch. This is an expansion of a simple sequential scheduling used to determine the delays of arriving packets. Since the time complexity of each processor in the pipeline stages is O(1), the throughput of this buffer management is N times larger than that of the sequential scheduling method. This method can be used for buffer management of asynchronously arriving variable-length packets. We show the feasibility of a buffer manager supporting 128 /spl times/ 40 Gb/s photonic packet switches, which provide at least eight times as much throughput as the latest electronic IP routers. The proposed method for asynchronous packets overestimates the buffer occupancy to enable parallel processing. We show through simulation experiments that the degradation in the performance of the method resulting from this overestimation is quite acceptable.     

All-Optical Wavelength-Bypassing Ring Communications Networks

We introduce an all-optical WDM packet communication network that performs wavelength bypassing at the routers. Packets that arrive at a wavelength (optical cross-connect) router at designated wavelengths are switched by the router without having their headers examined. Thus, the processing element of the router is bypassed by such packets. For packet traffic that uses wavelengths that do not bypass a switch, the headers of such packets are examined to determine if this switch is the destination for the flow. If latter is the case, the packet is removed. Otherwise, the packet is switched to a pre-determined output without incurring (network internal) queueing delays. We study a ring network with routers that employ such a WDM bypassing scheme. We present methods to construct wavelength graphs that define the bypassing pattern employed by the routers to guide the traffic flows distributed at each given wavelength. Performance is measured in terms of the network throughput and the average processing path length (i.e., the average number of switches not being bypassed). For a fixed total processing capacity, we show that a WDM bypassing ring network provides a higher throughput level than that exhibited by a non-bypassing ring network, using the same value of total link capacity. By using WDM bypassing, the average processing path length (and thus the packet latency) is reduced. We study a multitude of network loading configurations, corresponding to distinct traffic matrices and client-server scenarios. Higher throughput levels are obtained for network configurations driven by non-uniform traffic matrices. The demonstrated advantages of WDM bypassing methods shown here for WDM ring networks are also applicable to more general network topological layouts.     

Performance evaluation of a new technique for IP support in a WDMoptical network: optical composite burst switching (OCBS)

The optical composite burst switching (OCBS) technique is proposed to be implemented in an all-optical backbone network to support Internet protocol (LP) traffic. The OCBS is based on two main features. First, several IP packets are assembled in a single macropacket, called burst. Second, the burst contention in an optical switch is handled by means of two techniques, the wavelength dimension and the burst-dropping (BD) technique. Different from traditional optical burst switching, where an entire burst is discarded when all of the output wavelengths are engaged at the arrival instant of the burst, a switch adopting the BD technique discards only the initial part of a burst finding all of the engaged output wavelengths while forwarding the final part of the burst, beginning at the instant in which one wavelength becomes free. The OCBS allows an increase in the switch throughput in terms of number of accepted IP packets because a burst contains a given number of IP packets. We introduce the analytical model that allows us to evaluate the effectiveness of the technique and, in particular, the obtained saving; furthermore, a sensitivity analysis of the saving, with respect to both the optical burst switch parameters and the traffic load, is carried out     

ABE: providing a low-delay service within best effort

We propose alternative best effort (ABE), a novel service for IP networks, which idea of providing low-delay at the expense of maybe less throughput. The objective is to retain the simplicity of the original Internet single-class best-effort service while providing low-delay to interactive adaptive applications. With ABE, every best effort packet is marked as either green or blue. Green packets are guaranteed a low bounded delay in every router. In exchange, green packets are more likely to be dropped (or marked using congestion notification) during periods of congestion than blue packets. For every packet, the choice of color is made by the application based on the nature of its traffic and on global traffic conditions. Typically, an interactive application with real-time deadlines, such as audio, will mark most at its packets as green, as long as the network conditions offer large enough throughput. In contrast, an application that transfers binary data such as bulk data transfer will seek to minimize overall transfer time and send blue traffic. We propose router requirements that aim at enforcing benefits for all types of traffic, namely that green traffic achieves low-delay and blue traffic receives at least as much throughput as it would in a flat (legacy) best effort network. ABE is different from differentiated or integrated services in that neither packet color can be said to receive better treatment; thus, flat rate pricing may be maintained, and there is no need for reservations or profiles. We define the ABE service, its requirements, properties, and usage. We discuss the implications of replacing the existing IP best effort service by the ABE service. We propose and analyze an implementation based on a new scheduling method called duplicate scheduling with deadlines. It supports any mixture of TCP, TCP-friendly, and non-TCP-friendly traffic     

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.     

一种太比特路由器交换核心的研究与设计

硬件可扩展性和高效的性能一直以来是高速交换核心设计中的一对矛盾。文中在总结高速交换核心关键技术之后,提出了一种基于iRGRR算法的高速交换核心,它具有硬件实现简单、可扩展性强、性能优良等特点,大大缓解了上述矛盾。该交换核心能够提供服务质量保证,支持IP分组调度。可应用于太比特路由器中。文中还简要分析了该交换核心的性能,并给出了硬件设计方案。     

Survey and taxonomy of IP address lookup algorithms

Due to the rapid growth of traffic in the Internet, backbone links of several gigabits per second are commonly deployed. To handle gigabit-per-second traffic rates, the backbone routers must be able to forward millions of packets per second on each of their ports. Fast IP address lookup in the routers, which uses the packet's destination address to determine for each packet the next hop, is therefore crucial to achieve the packet forwarding rates required. IP address lookup is difficult because it requires a longest matching prefix search. In the last couple of years, various algorithms for high-performance IP address lookup have been proposed. We present a survey of state-of-the-art IP address lookup algorithms and compare their performance in terms of lookup speed, scalability, and update overhead     

Dynamic core provisioning for quantitative differentiated services

Efficient network provisioning mechanisms that support service differentiation are essential to the realization of the Differentiated Services (DiffServ) Internet. Building on our prior work on edge provisioning, we propose a set of efficient dynamic node and core provisioning algorithms for interior nodes and core networks, respectively. The node provisioning algorithm prevents transient violations of service level agreements (SLA) by predicting the onset of service level violations based on a multiclass virtual queue measurement technique, and by automatically adjusting the service weights of weighted fair queueing schedulers at core routers. Persistent service level violations are reported to the core provisioning algorithm, which dimensions traffic aggregates at the network ingress edge. The core provisioning algorithm is designed to address the difficult problem of provisioning DiffServ traffic aggregates (i.e., rate-control can only be exerted at the root of any traffic distribution tree) by taking into account fairness issues not only across different traffic aggregates but also within the same aggregate whose packets take different routes through a core IP network. We demonstrate through analysis and simulation that the proposed dynamic provisioning model is superior to static provisioning for DiffServ in providing quantitative delay bounds with differentiated loss across per-aggregate service classes under persistent congestion and device failure conditions when observed in core networks.