共查询到19条相似文献,搜索用时 125 毫秒
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光分组在核心节点处的冲突解决问题是实现全光 组播分组交换的关键。本文提出了一种新型的解决光组播冲突的节 点结构,用于冲突解决的部分包括输出共享的网络编码模块和光纤延迟线(FDL)环 形反馈共享缓存(FDL-LSFB)模块。网络编码 模块将异或网络编码作为冲突解决方式,利用全光异或门将冲突组播进行网络编码并且改变 编码后分组波长,从而避免波长 冲突。而FDL-LSFB模块由子交换矩阵和FDL缓存组连接成环状,且冲突组 播可从任意子交换矩阵进出缓存模块, 使用少数的FDL可以提供大容量的光缓存、提高FDL利用率。针对FDL-LSFB模块冲突组播调 度问题,为减小缓存时延,设计了最小缓存长度级联控制算法(MLCBST),进而提出冲突光 组播的总调度策略。仿真结果表明,本文提出的组播节点结构和调度策略在降低丢包率(PLP)和减小缓存时延方面具有明显的效果。 相似文献
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提出了一种基于业务负载选择的光分组交换(OPS)网络的光缓存结构,根据业务负载大小灵活选择缓存方式。输出缓存光纤延迟线(FDL)采用分段式共享机制配置,输出/反馈共享缓存模块采用简并式配置,以提高有限数目FDL的利用率。分析和仿真表明,这种可选择的缓存结构可以有效降低丢包率和OPS节点需求的FDL数目。 相似文献
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研究了FDL和有限长波长转换器(LRWC)相结合的方法来解决异步变长的分组交换网中的冲突问题,对这种冲突解决方案建立了数学模型并进行了理论分析,提出了一个用于修正最佳延迟单元的公式,即在负载较大的情况下,我们要求延迟单元较小,这样可显著的降低在此交换网中的分组丢失率;对系统丢包率与负载、FDL数目和最佳延迟单元的关系进行了研究和讨论,结果表明:在同样的输入负载情况下,有限长波长转换器(LRWC)的引入可以降低缓存的数量;对延迟单元的修正可以大大降低丢包率,同时系统的性能较之单独使用FDL时有较大的改善。 相似文献
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提出了一种新型的、用于光分组交换网络的光纤缓存结构.该结构针对光分组交换网络中解决输出端口竞争需要大量光纤延迟线,从而导致核心节点造价太高的缺陷,采用光纤分段式共享的机制,充分提高光纤延迟线的利用率.仿真和分析表明这种新型结构能有效降低丢包率,并可以取得令人满意的光分组平均延时参数;随着光纤延迟矩阵规模的增大,该结构仅需增加很少数目的光纤延迟线单元便可实现核心节点的扩展;在使用的总光纤延迟线单元数目上,该结构更能体现其优越性. 相似文献
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对光分组交换中波长共享(SPC)、链路共享(SPL)和节点共享(SPN)的结构进行了理论分析,推导出三种结构的丢包率公式,并对其系统丢包率与负载、输入光纤端口数和每纤波长数的关系进行了数值计算。结果表明:在相同的波长转换器数目(没有达到极限值)时,SPN结构的丢包率低于SPL的丢包率,并且在接近极限值时,SPN结构所需要的波长转换器数目也小于SPL结构所需要的波长转换器数目。 相似文献
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Kobrinski H. Vecchi M.P. Chapuran T.E. Georges J.B. Zah C.E. Caneau C. Menocal S.G. Lin P.S.D. Gozdz A.S. Favire F.J. 《Photonics Technology Letters, IEEE》1990,2(2):139-142
The use of a three-section distributed Bragg reflector (DBR) laser to switch wavelengths rapidly and simultaneously transmit data by intensity modulation is discussed. This combination simulates the operation of a tunable transmitter in a multiwavelength packet switch. In this type of switch, each output port is tuned to receive data on a unique, fixed wavelength; packets are routed from input ports to the appropriate output ports by wavelength addressing. In each transmission cycle, the input port transmitter tunes to the wavelength associated with the intended output port and subsequently broadcasts the data packet. Limitations on various system parameters, such as the number of allowed channels, the wavelength switching times, and packet lengths (residency times), as determined by thermally-induced wavelength drifts are also discussed. The advantages of using a single device for both fast wavelength switching and direct data modulation are significant: the elimination of external modulators improves both the simplicity of the implementation and the available power budget 相似文献
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Scheduling algorithms for shared fiber-delay-line optical packet Switches-part I: the single-stage case 总被引:1,自引:0,他引:1
In all-optical packet switching, packets may arrive at an optical switch in an uncoordinated fashion. When contention occurs, fiber delay lines (FDLs) are needed to delay (buffer) the packets that have lost the contention to some future time slots for the desired output ports. There have been several optical-buffered switch architectures and FDL assignment algorithms proposed in the literature. However, most of them either have high implementation complexity or fail to schedule in advance departure time for the delayed packets. This paper studies the packet scheduling algorithms for the single-stage shared-FDL optical packet switch. Three new FDL assignment algorithms are proposed, namely sequential FDL assignment (SEFA), multicell FDL assignment (MUFA), and parallel iterative FDL assignment (PIFA) algorithms for the switch. The proposed algorithms can make FDLs and output-port reservation so as to schedule departure time for packets. Owing to FDL and/or output-port conflicts, the packets that fail to be scheduled are discarded before entering the switch so that they do not occupy any FDL resources. It is shown by simulation that with these algorithms, the optical-buffered switch can achieve a loss rate of /spl sim/10/sup -7/ even at the load of 0.9. These algorithms are extended to the three-stage Clos-Network optical packet switches in the companion paper. 相似文献
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光分组交换网络中光纤延迟线缓存技术 总被引:2,自引:2,他引:0
光分组交换网是全光网络发展的必然趋势.然而,光分组交换网络发展的瓶颈是光缓存技术.目前,在光域比较现实的还是采用光纤延迟线(FDL)作光缓存.重点研究了光纤延迟线光缓存技术,对FDL光缓存技术进行了深入的分析和归纳,并对每一种光纤延迟线光缓存调度策略的优缺点都进行了细致的分析.最后指出了光纤延迟线光缓存技术的未来研究重点和发展方向. 相似文献
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An optically transparent packet network controlled by a simple medium access circuit is presented. The system, based on frequency division multiplexing and tunable transmitters, has no internal blocking and is optically self-routing. It provides internal collision-free traffic by allowing access to the network only if the addressed channel (output port) is available. A packet denied access to the network is reflected back to its input port, which is thus informed of the packet status. Therefore, the traffic is not bogged down by acknowledgments between input and output ports. To achieve this result, each input of the network is controlled by a protection-against-collision (PAC) circuit located at a central hub. The PAC circuit uses the packet for probing the energy present in the addressed channel. The resulting signal controls an optical switch connecting the input port to the network. Thus, full optical connectivity is provided between ports controlled by electrical signals derived from simple optical power measurements 相似文献
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In all-optical packet switching, packets may arrive at an optical switch in an uncoordinated fashion. To prevent packet loss in the switch, fiber delay lines (FDLs) are used as optical buffers to store optical packets. However, assigning FDLs to the arrival packets to achieve high throughput, low delay, and low loss rate is not a trivial task. In the authors' companion paper, several efficient scheduling algorithms were proposed for single-stage shared-FDL optical packet switches (OPSs). To further enhance the switch's scalability, this work was extended to a multistage case. In this paper, two scheduling algorithms are proposed: 1) sequential FDL assignment and 2) multicell FDL assignment algorithms for a three-stage optical Clos-Network switch (OCNS). The paper shows by simulation that a three-stage OCNS with these FDL assignment algorithms can achieve satisfactory performance. 相似文献
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Since packet switches with input queueing require low-speed buffers and simple cross-bar fabrics, they potentially provide high switching capacities. In these switches, the port that is a source of a multicast session might easily get congested with the increasing popularity of this session. We propose the protocol for scheduling packets in switches with input buffers for varying popularity of different content on the Internet. Copies of a multicast packet are forwarded through the switch, so that multicasting is evenly distributed over switch ports. The performance trade-off between capacity that can be reserved and guaranteed packet delay is discussed. 相似文献
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W. Rogiest K. Laevens D. Fiems H. Bruneel 《AEUE-International Journal of Electronics and Communications》2010,64(10):953-959
Circumventing the speed bottleneck of electronic switching, novel switching approaches like optical burst switching (OBS) and optical packet switching (OPS) handle the switching of bursts (or packets) in backbone nodes optically, and include a set of fiber delay lines (FDLs) for optical buffering. While previous work acknowledges the performance difference between optical FDL buffers and electronic RAM buffers, the important role of synchronization herein has received little attention to date. 相似文献
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Scheduling Algorithms for a Slotted Packet Switch with either Fixed or Variable Length Packets 总被引:3,自引:2,他引:1
Callegati F. Cerroni W. Corazza G. Develder C. Pickavet M. Demeester P. 《Photonic Network Communications》2004,8(2):163-176
We address the problem of congestion resolution in optical packet switching (OPS). We consider a fairly generic all-optical packet switch architecture with a feedback optical buffer constituted of fiber delay lines (FDL). Two alternatives of switching granularity are addressed for a switch operating in a slotted transfer mode: switching at the slot level (i.e., fixed length packets of a single slot) or at the burst level (variable length packets that are integer multiples of the slot length). For both cases, we show that in spite of the limited queuing resources, acceptable performance in terms of packet loss can be achieved for reasonable hardware resources with an appropriate design of the time/wavelength scheduling algorithms. Depending on the switching units (slots or bursts), an adapted scheduling algorithm needs to be deployed to exploit the bandwidth and buffer resources most efficiently. 相似文献