共查询到20条相似文献,搜索用时 109 毫秒
1.
2.
3.
对于输入缓存类型的分组交换系统,调度算法是交换系统的关键技术之一,其性能直接影响着交换单元的性能。研究了几种典型的极大匹配调度算法:PIM,iSLIP,FIRM和输出串行调度算法。通过OPNET构造了一种调度算法模型,以8×8 crossbar交换结构为例,基于该模型对这几种极大匹配调度算法进行了仿真。根据仿真结果从平均调度时延等性能指标及实现复杂度方面进行了分析和比较,指出了现有算法的优缺点,并提出了进一步改进的方向,对卫星ATM/IP交换系统的研究与设计具有指导作用。 相似文献
4.
5.
文章对高速路由器交换技术中普遍采用的Crossbar交换结构的各种主要调度算法进行了分类阐述和对比分析,讨论了调度算法的基本问题,主要分析了最大匹配类算法和权重匹配类算法两种目前的主流调度算法,最后对高性能调度算法研究的最新进展进行了介绍。 相似文献
6.
7.
8.
9.
10.
11.
This paper proposes two almost all-optical packet switch architectures, called the “packing switch” and the “scheduling switch” architecture, which when combined with appropriate wait-for-reservation or tell-and-go connection and how control protocols provide lossless communication for traffic that satisfies certain smoothness properties. Both switch architectures preserve the order of packets that use a given input-output pair, and are consistent with virtual circuit switching, The scheduling switch requires 2klogT+k2 two-state elementary switches (or 2klogT+2klogk elementary switches, if a different version is used) where k is the number of inputs and T is a parameter that measures the allowed burstiness of the traffic. The packing switch requires very little processing of the packet header, and uses k2logT+klogk two-state switches. We also examine the suitability of the proposed architectures for the design of circuit switched networks. We find that the scheduling switch combines low hardware cost with little processing requirements at the nodes, and is an attractive architecture for both packet-switched and circuit-switched high-speed networks 相似文献
12.
The continuous growth in the demand for diversified quality-of-service (QoS) guarantees in broadband networks introduces new challenges in the design of packet switches that scale to large switching capacities. Packet scheduling is the most critical function involved in the provision of individual bandwidth and delay guarantees to the switched flows. Most of the scheduling techniques proposed so far assume the presence in the switch of a single contention point, residing in front of the outgoing links. Such an assumption is not consistent with the highly distributed nature of many popular architectures for scalable switches, which typically have multiple contention points, located in both ingress and egress port cards, as well as in the switching fabric. We define a distributed multilayered scheduler (DMS) to provide differentiated QoS guarantees to individual end-to-end flows in packet switches with multiple contention points. Our scheduling architecture is simple to implement, since it keeps per-flow scheduling confined within the port cards, and is suitable to support guaranteed and best-effort traffic in a wide range of QoS frameworks in both IP and ATM networks 相似文献
13.
Scheduling algorithms for optical packet fabrics 总被引:1,自引:0,他引:1
Kar K. Stiliadis D. Lakshman T.V. Tassiulas L. 《Selected Areas in Communications, IEEE Journal on》2003,21(7):1143-1155
Utilizing optical technologies to build packet fabrics for high-capacity switches and routers has several advantages in terms of scalability, power consumption, and cost. However, several technology related problems have to be overcome to be able to use such an approach. The reconfiguration times of optical crossbars are longer than those of electronic fabrics and end-to-end clock recovery in such systems add to the reconfiguration overheads. Both these problems can limit the efficiency of optical packet fabrics. In addition, existing work on input-buffered switches mostly assumes fixed size packets (referred as envelopes in this paper). When fixed size switching is used for Internet protocol networks where packets are of variable size, the incoming packets need to be fragmented to fit the fixed size envelopes. This fragmentation can lead to, possibly large loss of bandwidth and even instability. This paper addresses all of the above issues by presenting packetization and scheduling techniques that allow optical packet fabrics to be used within switches and routers. The proposed scheme aggregates multiple packets in a single envelope and when used in combination with proper scheduling algorithms, it can provide system stability as well as bandwidth and delay guarantees. As a result of the aggregation method, the reconfiguration frequency required from the optics is reduced, facilitating the use of optical technologies in implementing packet switch fabrics. 相似文献
14.
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. 相似文献
15.
The overhead associated with reconfiguring a switch fabric in optical packet switches is an important issue in relation to the packet transmission time and can adversely affect switch performance. The reconfiguration overhead increases the mean waiting time of packets and reduces throughput. The scheduling of packets must take into account the reconfiguration frequency. This work proposes an analytical model for input-buffered optical packet switches with the reconfiguration overhead and analytically finds the optimal reconfiguration frequency that minimizes the mean waiting time of packets. The analytical model is suitable for several round-robin (RR) scheduling schemes in which only non-empty virtual output queues (VOQs) are served or all VOQs are served and is used to examine the effects of the RR scheduling schemes and various network parameters on the mean waiting time of packets. Quantitative examples demonstrate that properly balancing the reconfiguration frequency can effectively reduce the mean waiting time of packets. 相似文献
16.
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
17.
Sarkar S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2004,50(12):3197-3220
The goal of this paper is to design optimal scheduling and memory management so as to minimize packet loss in input queued switches with finite input buffers. The contribution is to obtain closed-form optimal strategies that minimize packet loss in 2/spl times/2 switches with equal arrival rates for all streams. For arbitrary arrival rates, the contribution is to identify certain characteristics of the optimal strategy, and use these characteristics to design a near-optimal heuristic. A lower bound for the cost associated with packet loss for N/spl times/N switches is obtained. This lower bound is used to design a heuristic which attains near-minimum packet loss in N/spl times/N switches with arbitrary N. These policies reduce packet loss by about 25% as compared to the optimal strategy for the infinite buffer case. The framework and the policies proposed here apply to buffer-constrained wireless networks as well. 相似文献
18.
Packet-mode scheduling in input-queued cell-based switches 总被引:1,自引:0,他引:1
Ajmone Marsan M. Bianco A. Giaccone P. Leonardi E. Neri F. 《Networking, IEEE/ACM Transactions on》2002,10(5):666-678
We consider input-queued switch architectures dealing at their interfaces with variable-size packets, but internally operating on fixed-size cells. Packets are segmented into cells at input ports, transferred through the switching fabric, and reassembled at output ports. Cell transfers are controlled by a scheduling algorithm, which operates in packet-mode: all cells belonging to the same packet are transferred from inputs to outputs without interruption. We prove that input-queued switches using packet-mode scheduling can achieve 100% throughput, and we show by simulation that, depending on the packet size distribution, packet-mode scheduling may provide advantages over cell-mode scheduling. 相似文献
19.
Develder C. Stavdas A. Bianco A. Careglio D. Lnsethagen H. Gimenez J.P.F.-P. Van Caenegem R. Sygletos S. Neri F. Sole-Pareta J. Pickavet M. Le Sauze N. Demeester P. 《Lightwave Technology, Journal of》2004,22(11):2435-2451
Optical packet switching (OPS) has been proposed as a strong candidate for future metro networks. This paper assesses the viability of an OPS-based ring architecture as proposed within the research project DAVID (Data And Voice Integration on DWDM), funded by the European Commission through the Information Society Technologies (IST) framework. Its feasibility is discussed from a physical-layer point of view, and its limitations in size are explored. Through dimensioning studies, we show that the proposed OPS architecture is competitive with respect to alternative metropolitan area network (MAN) approaches, including synchronous digital hierarchy, resilient packet rings (RPR), and star-based Ethernet. Finally, the proposed OPS architectures are discussed from a logical performance point of view, and a high-quality scheduling algorithm to control the packet-switching operations in the rings is explained. 相似文献
20.
This paper considers a general parallel buffered packet switch (PBPS) architecture which is based on multiple packet switches operating independently and in parallel. A load-balancing mechanism is used at each input to distribute the traffic to the parallel switches. The buffer structure of each of the parallel packet switches is based on either a dedicated, a shared, or a buffered-crosspoint output-queued architecture. As in such PBPS multipath switches, packets may get out of order when they travel independently in parallel through these switches, a resequencing mechanism is necessary at the output side. This paper addresses the issue of evaluating the minimum resequence-queue size required for a deadlock-free lossless operation. An analytical method is presented for the exact evaluation of the worst-case resequencing delay and the worst-case resequence-queue size. The results obtained reveal their relation, and demonstrate the impact of the various system parameters on resequencing 相似文献